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Grossi-Soyster EN, LaBeaud AD. Rift Valley Fever: Important Considerations for Risk Mitigation and Future Outbreaks. Trop Med Infect Dis 2020; 5:tropicalmed5020089. [PMID: 32498264 PMCID: PMC7345646 DOI: 10.3390/tropicalmed5020089] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 05/22/2020] [Accepted: 05/28/2020] [Indexed: 12/02/2022] Open
Abstract
Rift Valley fever virus (RVFV) is a zoonotic phlebovirus of the Phenuiviridae family with great opportunity for emergence in previously unaffected regions, despite its current geographical limits. Outbreaks of RVFV often infect humans or domesticated animals, such as livestock, concurrently and occur sporadically, ranging from localized outbreaks in villages to multi-country events that spread rapidly. The true burden of Rift Valley fever (RVF) is not well defined due to underreporting, misdiagnosis caused by the broad spectrum of disease presentation, and minimal access for rapid and accurate laboratory confirmation. Severe symptoms may include hemorrhagic fever, loss of vision, psychological impairment or disturbances, and organ failure. Those living in endemic areas and travelers should be aware of the potential for exposure to ongoing outbreaks or interepidemic transmission, and engage in behaviors to minimize exposure risks, as vaccinations in humans are currently unavailable and animal vaccinations are not used routinely or ubiquitously. The lack of vaccines approved for use in humans is concerning, as RVFV has proven to be highly pathogenic in naïve populations, causing severe disease in a large percent of confirmed cases, which could have considerable impact on human health.
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Rissmann M, Stoek F, Pickin MJ, Groschup MH. Mechanisms of inter-epidemic maintenance of Rift Valley fever phlebovirus. Antiviral Res 2019; 174:104692. [PMID: 31870761 DOI: 10.1016/j.antiviral.2019.104692] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 09/26/2019] [Accepted: 12/11/2019] [Indexed: 12/31/2022]
Abstract
Rift Valley fever phlebovirus (RVFV) is an arthropod-borne virus that has caused substantial epidemics throughout Africa and in the Arabian Peninsula. The virus can cause severe disease in livestock and humans and therefore the control and prevention of viral outbreaks is of utmost importance. The epidemiology of RVFV has some particular characteristics. Unexpected and significant epidemics have been observed in spatially and temporally divergent patterns across the African continent. Sudden epidemics in previously unaffected areas are followed by periods of long-term apparent absence of virus and sudden, unpredictable reoccurrence in disparate regions. Therefore, the elucidation of underlying mechanisms of viral maintenance is one of the largest gaps in the knowledge of RVFV ecology. It remains unknown whether the virus needs to be reintroduced before RVF outbreaks can occur, or if unperceived viral circulation in local vertebrates or mosquitoes is sufficient for maintenance of the virus. To gain insight into these knowledge gaps, we here review existing data that describe potential mechanisms of RVFV maintenance, as well as molecular and serological studies in endemic and non-endemic areas that provide evidence of an inter- or pre-epidemic virus presence. Basic and country-specific mechanisms of RVFV introduction into non-endemic countries are summarized and an overview of studies using mathematical modeling of RVFV persistence is given.
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Affiliation(s)
- Melanie Rissmann
- Friedrich-Loeffler-Institut, Institute of Novel and Emerging Infectious Diseases, Suedufer 10, 17489, Greifswald-Insel Riems, Germany
| | - Franziska Stoek
- Friedrich-Loeffler-Institut, Institute of Novel and Emerging Infectious Diseases, Suedufer 10, 17489, Greifswald-Insel Riems, Germany
| | - Matthew J Pickin
- Friedrich-Loeffler-Institut, Institute of Novel and Emerging Infectious Diseases, Suedufer 10, 17489, Greifswald-Insel Riems, Germany
| | - Martin H Groschup
- Friedrich-Loeffler-Institut, Institute of Novel and Emerging Infectious Diseases, Suedufer 10, 17489, Greifswald-Insel Riems, Germany.
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Rift Valley fever in animals and humans: Current perspectives. Antiviral Res 2018; 156:29-37. [PMID: 29857007 DOI: 10.1016/j.antiviral.2018.05.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/21/2018] [Accepted: 05/24/2018] [Indexed: 02/03/2023]
Abstract
Rift Valley fever (RVF) is an ecologically complex emerging arboviral disease that causes significant illness in both livestock and people. This review article is designed to assist the reader in understanding the varied aspects of RVF disease in animals and humans. The historical facets of RVF disease, including the evolution of human outbreaks, are presented and discussed. The different clinical presentations of human RVF disease and the underlying causes are then addressed. We explore the exposure and transmission potential of RVF in animals and people. In the concluding section, we discuss the historical role of RVF as a biological weapon. We conclude with an outline of the important unanswered questions for ongoing research into this important zoonotic disease.
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Olive MM, Grosbois V, Tran A, Nomenjanahary LA, Rakotoarinoro M, Andriamandimby SF, Rogier C, Heraud JM, Chevalier V. Reconstruction of Rift Valley fever transmission dynamics in Madagascar: estimation of force of infection from seroprevalence surveys using Bayesian modelling. Sci Rep 2017; 7:39870. [PMID: 28051125 PMCID: PMC5209714 DOI: 10.1038/srep39870] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 11/29/2016] [Indexed: 11/09/2022] Open
Abstract
The force of infection (FOI) is one of the key parameters describing the dynamics of transmission of vector-borne diseases. Following the occurrence of two major outbreaks of Rift Valley fever (RVF) in Madagascar in 1990-91 and 2008-09, recent studies suggest that the pattern of RVF virus (RVFV) transmission differed among the four main eco-regions (East, Highlands, North-West and South-West). Using Bayesian hierarchical models fitted to serological data from cattle of known age collected during two surveys (2008 and 2014), we estimated RVF FOI and described its variations over time and space in Madagascar. We show that the patterns of RVFV transmission strongly differed among the eco-regions. In the North-West and Highlands regions, these patterns were synchronous with a high intensity in mid-2007/mid-2008. In the East and South-West, the peaks of transmission were later, between mid-2008 and mid-2010. In the warm and humid northwestern eco-region favorable to mosquito populations, RVFV is probably transmitted all year-long at low-level during inter-epizootic period allowing its maintenance and being regularly introduced in the Highlands through ruminant trade. The RVF surveillance of animals of the northwestern region could be used as an early warning indicator of an increased risk of RVF outbreak in Madagascar.
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Affiliation(s)
- Marie-Marie Olive
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
- Institut Pasteur de Madagascar, Virology Unit, Antananarivo, Madagascar
| | - Vladimir Grosbois
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
| | - Annelise Tran
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
| | | | | | | | - Christophe Rogier
- Institut Pasteur de Madagascar, Direction, Madagascar
- Institute for Biomedical Research of the French Armed Forces (IRBA), Brétigny-Sur-Orge, France
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), Marseille, France
| | | | - Veronique Chevalier
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
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Danzetta ML, Bruno R, Sauro F, Savini L, Calistri P. Rift Valley fever trasmission dynamics described by compartmental models. Prev Vet Med 2016; 134:197-210. [PMID: 27707507 DOI: 10.1016/j.prevetmed.2016.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 08/11/2016] [Accepted: 09/10/2016] [Indexed: 11/18/2022]
Abstract
Rift Valley fever (RVF) is one of the most important zoonotic Transboundary Animal Diseases able to cross international borders and cause devastating effect on animal health and food security. Climate changes and the presence of competent vectors in the most of the current RVF-free temperate countries strongly support the inclusion of RVF virus (RVFV) among the most significant emerging viral threats for public and animal health. The transmission of RVFV is driven by complex eco-climatic factors making the epidemiology of RVF infection difficult to study and to understand. Mathematical, statistical and spatial models are often used to explain the mechanisms underlying these biological processes, providing new and effective tools to plan measures for public health protection. In this paper we performed a systematic literature review on RVF published papers with the aim of identifying and describing the most recent papers developing compartmental models for the study of RVFV transmission dynamics.
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Affiliation(s)
- Maria Luisa Danzetta
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Rossana Bruno
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Francesca Sauro
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Lara Savini
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Paolo Calistri
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy.
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Olive MM, Chevalier V, Grosbois V, Tran A, Andriamandimby SF, Durand B, Ravalohery JP, Andriamamonjy S, Rakotomanana F, Rogier C, Heraud JM. Integrated Analysis of Environment, Cattle and Human Serological Data: Risks and Mechanisms of Transmission of Rift Valley Fever in Madagascar. PLoS Negl Trop Dis 2016; 10:e0004827. [PMID: 27415438 PMCID: PMC4945045 DOI: 10.1371/journal.pntd.0004827] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 06/16/2016] [Indexed: 01/08/2023] Open
Abstract
Background Rift Valley fever (RVF) is a vector-borne disease affecting ruminants and humans. Madagascar was heavily affected by RVF in 2008–2009, with evidence of a large and heterogeneous spread of the disease. The identification of at-risk environments is essential to optimize the available resources by targeting RVF surveillance in Madagascar. Herein, the objectives of our study were: (i) to identify the environmental factors and areas favorable to RVF transmission to both cattle and human and (ii) to identify human behaviors favoring human infections in Malagasy contexts. Methodology/Principal Findings First, we characterized the environments of Malagasy communes using a Multiple Factor Analysis (MFA). Then, we analyzed cattle and human serological data collected at national level using Generalized Linear Mixed Models, with the individual serological status (cattle or human) as the response, and MFA factors, as well as other potential risk factors (cattle density, human behavior) as explanatory variables. Cattle and human seroprevalence rates were positively associated to humid environments (p<0.001). Areas with high cattle density were at risk (p<0.01; OR = 2.6). Furthermore, our analysis showed that frequent contact with raw milk contributed to explain human infection (OR = 1.6). Finally, our study highlighted the eastern-coast, western and north-western parts as high-risk areas for RVF transmission in cattle. Conclusions/Significance Our integrated approach analyzing environmental, cattle and human datasets allow us to bring new insight on RVF transmission patterns in Madagascar. The association between cattle seroprevalence, humid environments and high cattle density suggests that concomitant vectorial and direct transmissions are critical to maintain RVF enzootic transmission. Additionally, in the at-risk humid environment of the western, north-western and the eastern-coast areas, suitable to Culex and Anopheles mosquitoes, vectorial transmission probably occurs in both cattle and human. The relative contribution of vectorial or direct transmissions could be further assessed by mathematic modelling. Rift Valley fever virus (RVFV) is a pathogen that causes a vector-borne tropical disease. The disease affects ruminants and humans and severely impacts the health and economy of affected countries. Madagascar was heavily affected by Rift Valley fever (RVF) in 2008–2009, with evidence of a large and heterogeneous spread of the disease. Our study aims at identifying environmental and human-related risk factors for RVFV transmission. First, we characterized Malagasy environments according to their putative influence on RVFV mosquito density and population dynamics. Then we statistically analyzed cattle and human serological data collected at a national level with the individual serological status as response, and Malagasy environments previously characterized by climatic and landscape variables as well as other potential risk factors as explanatory variables. Our results identified humid environments of the western, north-western and eastern parts of the island as risky areas. The identification of at-risk environments is essential to focus veterinary surveillance and control of RVFV.
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Affiliation(s)
- Marie-Marie Olive
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
- Institut Pasteur de Madagascar, Virology Unit, Antananarivo, Madagascar
- * E-mail:
| | - Véronique Chevalier
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
| | - Vladimir Grosbois
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
| | - Annelise Tran
- CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France
| | | | - Benoit Durand
- Paris-Est University, ANSES, Laboratory for Animal Health, Epidemiology Unit, Maisons-Alfort, France
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Abstract
Rift Valley fever (RVF) is a zoonotic, mosquito-borne viral disease that affects human health and causes significant losses in the livestock industry. Recent outbreaks have led to severe human infections with high mortality rates. There are many challenges to applying effective preventive and control measures, including weak infrastructure of health facilities, lack of capacity and support systems for field logistics and communication, access to global expert organizations, and insufficient information on the epidemiological and reservoir status of the RVF virus. The health systems in East African countries are underdeveloped, with gaps in adaptability to new, more accurate and rapid techniques, and well-trained staff that affect their capacity to monitor and evaluate the disease. Surveillance and response systems are inadequate in providing accurate information in a timely manner for decision making to deal with the scope of interrupting the disease transmission by applying mass animal vaccination, and other preventive measures at the early stage of an outbreak. The historical vaccines are unsuitable for use in newborn and gestating livestock, and the recent ones require a booster and annual revaccination. Future live-attenuated RVF vaccines should possess lower safety concerns regardless of the physiologic state of the animal, and provide rapid and long-term immunity after a single dose of vaccination. In the absence of an effective vaccination program, prevention and control measures must be immediately undertaken after an alert is generated. These measures include enforcing and adapting standard protocols for animal trade and movement, extensive vector control, safe disposal of infected animals, and modification of human-animal contact behavior. Directing control efforts on farmers and workers who deal with, handle, or live close to livestock, and focusing on areas with populations at high risk of an epidemic are desirable. Consideration of prevention methods as a first-line strategy against RVF is practical owing to the absence of a human vaccine, particularly under the current high environmental risks and expanding global travel and animal trade. Universal platforms are needed to support coordinated efforts; alert and response operations; exchange of expertise; and disease detection, diagnosis, control, and prevention.
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Affiliation(s)
- Yousif E Himeidan
- Vector Control Unit, Africa Technical Research Centre, Vector Health International, Arusha, Tanzania
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Gray GC, Anderson BD, LaBeaud AD, Heraud JM, Fèvre EM, Andriamandimby SF, Cook EAJ, Dahir S, de Glanville WA, Heil GL, Khan SU, Muiruri S, Olive MM, Thomas LF, Merrill HR, Merrill MLM, Richt JA. Seroepidemiological Study of Interepidemic Rift Valley Fever Virus Infection Among Persons with Intense Ruminant Exposure in Madagascar and Kenya. Am J Trop Med Hyg 2015; 93:1364-1370. [PMID: 26458775 PMCID: PMC4674260 DOI: 10.4269/ajtmh.15-0383] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2015] [Accepted: 08/16/2015] [Indexed: 12/26/2022] Open
Abstract
In this cross-sectional seroepidemiological study we sought to examine the evidence for circulation of Rift Valley fever virus (RVFV) among herders in Madagascar and Kenya. From July 2010 to June 2012, we enrolled 459 herders and 98 controls (without ruminant exposures) and studied their sera (immunoglobulin G [IgG] and IgM through enzyme-linked immunosorbent assay [ELISA] and plaque reduction neutralization test [PRNT] assays) for evidence of previous RVFV infection. Overall, 59 (12.9%) of 459 herders and 7 (7.1%) of the 98 controls were positive by the IgG ELISA assay. Of the 59 ELISA-positive herders, 23 (38.9%) were confirmed by the PRNT assay (21 from eastern Kenya). Two of the 21 PRNT-positive study subjects also had elevated IgM antibodies against RVFV suggesting recent infection. Multivariate modeling in this study revealed that being seminomadic (odds ratio [OR] = 6.4, 95% confidence interval [CI] = 2.1-15.4) was most strongly associated with antibodies against RVFV. Although we cannot know when these infections occurred, it seems likely that some interepidemic RVFV infections are occurring among herders. As there are disincentives regarding reporting RVFV outbreaks in livestock or wildlife, it may be prudent to conduct periodic, limited, active seroepidemiological surveillance for RVFV infections in herders, especially in eastern Kenya.
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Affiliation(s)
- Gregory C. Gray
- Division of Infectious Diseases, Duke Global Health Institute, Duke University, Durham, North Carolina; Nicholas School of the Environment, Duke University, Durham, North Carolina; Emerging Pathogens Institute, University of Florida, Gainesville, Florida; Division of Pediatric Infectious Diseases, Stanford University, Palo Alto, California; Virology Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar; Institute of Infection and Global Health, University of Liverpool, United Kingdom; International Livestock Research Institute, Nairobi, Kenya; Centre for Microbiology Research, Kenya Medical Research Institute, Kenya; Division of Vector Borne and Neglected Tropical Diseases, Ministry of Health, Nairobi, Kenya; Department of Environmental Sciences, Technical University of Mombasa, Mombasa, Kenya; Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
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9
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Tantely LM, Boyer S, Fontenille D. A review of mosquitoes associated with Rift Valley fever virus in Madagascar. Am J Trop Med Hyg 2015; 92:722-9. [PMID: 25732680 PMCID: PMC4385764 DOI: 10.4269/ajtmh.14-0421] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 11/24/2014] [Indexed: 11/07/2022] Open
Abstract
Rift Valley fever (RVF) is a viral zoonotic disease occurring throughout Africa, the Arabian Peninsula, and Madagascar. The disease is caused by a Phlebovirus (RVF virus [RVFV]) transmitted to vertebrate hosts through the bite of infected mosquitoes. In Madagascar, the first RVFV circulation was reported in 1979 based on detection in mosquitoes but without epidemic episode. Subsequently, two outbreaks occurred: the first along the east coast and in the central highlands in 1990 and 1991 and the most recent along the northern and eastern coasts and in the central highlands in 2008 and 2009. Despite the presence of 24 mosquitoes species potentially associated with RVFV transmission in Madagascar, little associated entomological information is available. In this review, we list the RVFV vector, Culex antennatus, as well as other taxa as candidate vector species. We discuss risk factors from an entomological perspective for the re-emergence of RVF in Madagascar.
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Affiliation(s)
- Luciano M Tantely
- Medical Entomology Unit, Institut Pasteur of Madagascar, Antananarivo, Madagascar; Institut Pasteur of Cambodia, Phnom Penh, Kingdom of Cambodia
| | - Sébastien Boyer
- Medical Entomology Unit, Institut Pasteur of Madagascar, Antananarivo, Madagascar; Institut Pasteur of Cambodia, Phnom Penh, Kingdom of Cambodia
| | - Didier Fontenille
- Medical Entomology Unit, Institut Pasteur of Madagascar, Antananarivo, Madagascar; Institut Pasteur of Cambodia, Phnom Penh, Kingdom of Cambodia
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Goutard FL, Binot A, Duboz R, Rasamoelina-Andriamanivo H, Pedrono M, Holl D, Peyre MI, Cappelle J, Chevalier V, Figuié M, Molia S, Roger FL. How to reach the poor? Surveillance in low-income countries, lessons from experiences in Cambodia and Madagascar. Prev Vet Med 2015; 120:12-26. [PMID: 25842000 DOI: 10.1016/j.prevetmed.2015.02.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 02/16/2015] [Accepted: 02/16/2015] [Indexed: 10/24/2022]
Abstract
Surveillance of animal diseases in developing countries faces many constraints. Innovative tools and methods to enhance surveillance in remote and neglected areas should be defined, assessed and applied in close connection with local farmers, national stakeholders and international agencies. The authors performed a narrative synthesis of their own publications about surveillance in Madagascar and Cambodia. They analysed the data in light of their fieldwork experiences in the two countries' very challenging environments. The burden of animal and zoonotic diseases (e.g. avian influenza, African swine fever, Newcastle disease, Rift Valley fever) is huge in both countries which are among the poorest in the world. Being poor countries implies a lack of human and financial means to ensure effective surveillance of emerging and endemic diseases. Several recent projects have shown that new approaches can be proposed and tested in the field. Several advanced participatory approaches are promising and could be part of an innovative method for improving the dialogue among different actors in a surveillance system. Thus, participatory modelling, developed for natural resources management involving local stakeholders, could be applied to health management, including surveillance. Data transmission could benefit from the large mobile-phone coverage in these countries. Ecological studies and advances in the field of livestock surveillance should guide methods for enhancing wildlife monitoring and surveillance. Under the umbrella of the One Health paradigm, and in the framework of a risk-based surveillance concept, a combination of participatory methods and modern technologies could help to overcome the constraints present in low-income countries. These unconventional approaches should be merged in order to optimise surveillance of emerging and endemic diseases in challenging environments.
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Affiliation(s)
- F L Goutard
- Cirad, AGIRs Research Unit, Montpellier, France; Kasetsart University, Bangkok, Thailand.
| | - A Binot
- Cirad, AGIRs Research Unit, Montpellier, France; Kasetsart University, Bangkok, Thailand
| | - R Duboz
- Cirad, AGIRs Research Unit, Montpellier, France; AIT, Bangkok, Thailand
| | | | - M Pedrono
- Cirad, AGIRs Research Unit, Montpellier, France; FOFIFA, Antananarivo, Madagascar
| | - D Holl
- NaVRI, Phnom Penh, Cambodia
| | - M I Peyre
- Cirad, AGIRs Research Unit, Montpellier, France; NIVR, Hanoi, Viet Nam
| | - J Cappelle
- Cirad, AGIRs Research Unit, Montpellier, France; Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - V Chevalier
- Cirad, AGIRs Research Unit, Montpellier, France
| | - M Figuié
- Cirad, MOISA Research Unit, Montpellier, France
| | - S Molia
- Cirad, AGIRs Research Unit, Montpellier, France; Institut Pasteur de Madagascar, Antananarivo, Madagascar
| | - F L Roger
- Cirad, AGIRs Research Unit, Montpellier, France; Kasetsart University, Bangkok, Thailand
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Nicolas G, Chevalier V, Tantely LM, Fontenille D, Durand B. A spatially explicit metapopulation model and cattle trade analysis suggests key determinants for the recurrent circulation of rift valley Fever virus in a pilot area of madagascar highlands. PLoS Negl Trop Dis 2014; 8:e3346. [PMID: 25474116 PMCID: PMC4256285 DOI: 10.1371/journal.pntd.0003346] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 10/14/2014] [Indexed: 11/19/2022] Open
Abstract
Rift Valley fever (RVF) is a vector-borne zoonotic disease that causes high morbidity and mortality in ruminants. In 2008-2009, a RVF outbreak affected the whole Madagascar island, including the Anjozorobe district located in Madagascar highlands. An entomological survey showed the absence of Aedes among the potential RVF virus (RVFV) vector species identified in this area, and an overall low abundance of mosquitoes due to unfavorable climatic conditions during winter. No serological nor virological sign of infection was observed in wild terrestrial mammals of the area, suggesting an absence of wild RVF virus (RVFV) reservoir. However, a three years serological and virological follow-up in cattle showed a recurrent RVFV circulation. The objective of this study was to understand the key determinants of this unexpected recurrent transmission. To achieve this goal, a spatial deterministic discrete-time metapopulation model combined with cattle trade network was designed and parameterized to reproduce the local conditions using observational data collected in the area. Three scenarios that could explain the RVFV recurrent circulation in the area were analyzed: (i) RVFV overwintering thanks to a direct transmission between cattle when viraemic cows calve, vectors being absent during the winter, (ii) a low level vector-based circulation during winter thanks to a residual vector population, without direct transmission between cattle, (iii) combination of both above mentioned mechanisms. Multi-model inference methods resulted in a model incorporating both a low level RVFV winter vector-borne transmission and a direct transmission between animals when viraemic cows calve. Predictions satisfactorily reproduced field observations, 84% of cattle infections being attributed to vector-borne transmission, and 16% to direct transmission. These results appeared robust according to the sensitivity analysis. Interweaving between agricultural works in rice fields, seasonality of vector proliferation, and cattle exchange practices could be a key element for understanding RVFV circulation in this area of Madagascar highlands.
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Affiliation(s)
- Gaëlle Nicolas
- International Centre of Research in Agronomy for Development (CIRAD), ES Department– AGIRs Unit, Montpellier, France
- Paris-Est University, Anses, Laboratory for Animal Health, Epidemiology Unit, Maisons-Alfort, France
| | - Véronique Chevalier
- International Centre of Research in Agronomy for Development (CIRAD), ES Department– AGIRs Unit, Montpellier, France
| | | | - Didier Fontenille
- Research Institute for Development (IRD), MIVEGEC, Montpellier, France
| | - Benoît Durand
- Paris-Est University, Anses, Laboratory for Animal Health, Epidemiology Unit, Maisons-Alfort, France
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12
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Fagbo S, Coetzer JAW, Venter EH. Seroprevalence of Rift Valley fever and lumpy skin disease in African buffalo (Syncerus caffer) in the Kruger National Park and Hluhluwe-iMfolozi Park, South Africa. J S Afr Vet Assoc 2014; 85:e1-e7. [PMID: 25686252 DOI: 10.4102/jsava.v85i1.1075] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 11/06/2013] [Accepted: 11/25/2013] [Indexed: 11/01/2022] Open
Abstract
Rift Valley fever and lumpy skin disease are transboundary viral diseases endemic in Africa and some parts of the Middle East, but with increasing potential for global emergence. Wild ruminants, such as the African buffalo (Syncerus caffer), are thought to play a role in the epidemiology of these diseases. This study sought to expand the understanding of the role of buffalo in the maintenance of Rift Valley fever virus (RVFV) and lumpy skin disease virus (LSDV) by determining seroprevalence to these viruses during an inter-epidemic period. Buffaloes from the Kruger National Park (n = 138) and Hluhluwe-iMfolozi Park (n = 110) in South Africa were sampled and tested for immunoglobulin G (IgG) and neutralising antibodies against LSDV and RVFV using an indirect enzyme-linked immunosorbent assay (I-ELISA) and the serum neutralisation test (SNT). The I-ELISA for LSDV and RVFV detected IgG antibodies in 70 of 248 (28.2%) and 15 of 248 (6.1%) buffaloes, respectively. Using the SNT, LSDV and RVFV neutralising antibodies were found in 5 of 66 (7.6%) and 12 of 57 (21.1%), respectively, of samples tested. The RVFV I-ELISA and SNT results correlated well with previously reported results. Of the 12 SNT RVFV-positive sera, three (25.0%) had very high SNT titres of 1:640. Neutralising antibody titres of more than 1:80 were found in 80.0% of the positive sera tested. The LSDV SNT results did not correlate with results obtained by the I-ELISA and neutralising antibody titres detected were low, with the highest (1:20) recorded in only two buffaloes, whilst 11 buffaloes (4.4%) had evidence of co-infection with both viruses. Results obtained in this study complement other reports suggesting a role for buffaloes in the epidemiology of these diseases during inter-epidemic periods.
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Affiliation(s)
| | | | - Estelle H Venter
- Department of Veterinary Tropical Diseases, University of Pretoria.
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Himeidan YE, Kweka EJ, Mahgoub MM, El Rayah EA, Ouma JO. Recent outbreaks of rift valley Fever in East Africa and the middle East. Front Public Health 2014; 2:169. [PMID: 25340047 PMCID: PMC4186272 DOI: 10.3389/fpubh.2014.00169] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/16/2014] [Indexed: 12/16/2022] Open
Abstract
Rift Valley fever (RVF) is an important neglected, emerging, mosquito-borne disease with severe negative impact on human and animal health. Mosquitoes in the Aedes genus have been considered as the reservoir, as well as vectors, since their transovarially infected eggs withstand desiccation and larvae hatch when in contact with water. However, different mosquito species serve as epizootic/epidemic vectors of RVF, creating a complex epidemiologic pattern in East Africa. The recent RVF outbreaks in Somalia (2006–2007), Kenya (2006–2007), Tanzania (2007), and Sudan (2007–2008) showed extension to districts, which were not involved before. These outbreaks also demonstrated the changing epidemiology of the disease from being originally associated with livestock, to a seemingly highly virulent form infecting humans and causing considerably high-fatality rates. The amount of rainfall is considered to be the main factor initiating RVF outbreaks. The interaction between rainfall and local environment, i.e., type of soil, livestock, and human determine the space-time clustering of RVF outbreaks. Contact with animals or their products was the most dominant risk factor to transfer the infection to humans. Uncontrolled movement of livestock during an outbreak is responsible for introducing RVF to new areas. For example, the virus that caused the Saudi Arabia outbreak in 2000 was found to be the same strain that caused the 1997–98 outbreaks in East Africa. A strategy that involves active surveillance with effective case management and diagnosis for humans and identifying target areas for animal vaccination, restriction on animal movements outside the affected areas, identifying breeding sites, and targeted intensive mosquito control programs has been shown to succeed in limiting the effect of RVF outbreak and curb the spread of the disease from the onset.
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Affiliation(s)
- Yousif E Himeidan
- Entomology Unit, Faculty of Agriculture and Natural Resources, University of Kassala , New Halfa , Sudan ; Africa Technical Research Centre, Vector Health International , Arusha , Tanzania
| | - Eliningaya J Kweka
- Division of Livestock and Human Diseases Vector Control, Tropical Pesticides Research Institute , Arusha , Tanzania ; Department of Medical Parasitology and Entomology, Catholic University of Health and Allied Sciences , Mwanza , Tanzania
| | - Mostafa M Mahgoub
- Blue Nile National Institute for Communicable Diseases, University of Gezira , Madani , Sudan
| | - El Amin El Rayah
- Department of Zoology, University of Khartoum , Khartoum , Sudan
| | - Johnson O Ouma
- Africa Technical Research Centre, Vector Health International , Arusha , Tanzania ; Biotechnology Research Institute, Kenya Agricultural and Livestock Research Organization , Kikuyu , Kenya
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Owange NO, Ogara WO, Affognon H, Peter GB, Kasiiti J, Okuthe S, Onyango-Ouma W, Landmann T, Sang R, Mbabu M. Occurrence of rift valley fever in cattle in Ijara district, Kenya. Prev Vet Med 2014; 117:121-8. [PMID: 25217406 DOI: 10.1016/j.prevetmed.2014.08.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 08/06/2014] [Accepted: 08/12/2014] [Indexed: 11/26/2022]
Abstract
Ijara district in Kenya was one of the hotspots of rift valley fever (RVF) during the 2006/2007 outbreak which led to human and animal deaths causing huge economic and public health losses. The main constraint in the control and prevention of RVF is inadequate knowledge on its occurrence during the interepidemic period. This study was aimed at understanding the occurrence of RVF in cattle in Ijara to enable the development of improved community-based disease surveillance, prediction, control and prevention. Six herds each 700-1000 cattle were identified with participatory involvement of locals and project technical team of the project. One animal per herd was tagged with global position system (GPS) collar to enable follow up. Sero-surveys were conducted periodically to understand the herd's movement through various ecological zones and risk of exposure to RVF virus. Sixty animals less than 3 years old from each herd were randomly selected each sampling time and sero-surveyed for RVF four times (September 2012, December 2012, February 2013 and May 2013) during the study period and along the nomadic movement route. The serum samples collected were subjected to RVF inhibition ELISA test to detect if there was exposure for RVF virus (RVFV). The RVF inhibition ELISA positive samples were subjected to IgM ELISA test to determine if the exposures were current or recent (within 14 days). The result of the survey indicated that 13.1% (183/1396) of cattle sero-surveyed had RVFV antibodies by inhibition ELISA test while 1.4% (18/1396) was positive for IgM ELISA test. The highest RVFV circulation was detected after herds pass through bony forest between Lamu and Ijara and Halei forested areas. These forested areas also had the highest IgM detections. The findings indicate that even limited rainfall was able to initiate RVFV circulation in Ijara region with highest circulation detected within forested areas with potential to become epidemic if rains persist with extensive flooding. There is need to carry out regular participatory disease surveillance in domestic animals and other host systems to identify risk locations in hotspot areas and carry out community awareness and focal vaccination campaigns against RVF for preparedness, prevention and control. Additionally, monitoring of environmental conditions in risky ecological zones to detect enhanced rainfall and flooding should be prioritized for preparedness.
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Affiliation(s)
- Nelson O Owange
- University of Nairobi, Faculty of Veterinary Medicine, Department of Public Health Pharmacology and Toxicology, PO Box 29053-00625, Nairobi, Kenya; International Centre for Insect Physiology and Ecology (ICIPE), PO Box 30772-00100, Nairobi, Kenya.
| | - William O Ogara
- University of Nairobi, Faculty of Veterinary Medicine, Department of Public Health Pharmacology and Toxicology, PO Box 29053-00625, Nairobi, Kenya.
| | - Hippolyte Affognon
- International Centre for Insect Physiology and Ecology (ICIPE), PO Box 30772-00100, Nairobi, Kenya.
| | - Gathura B Peter
- University of Nairobi, Faculty of Veterinary Medicine, Department of Public Health Pharmacology and Toxicology, PO Box 29053-00625, Nairobi, Kenya.
| | - Jacqueline Kasiiti
- Ministry of Agriculture, Livestock and Fisheries, State Department of Veterinary Services, Private Bag-00625, Nairobi, Kenya.
| | - Sam Okuthe
- FAO, Emergency Centre for Transboundary Animal Diseases (ECTAD), Eastern Africa, FAO-UN, United Nations Avenue, Gigiri, Kenya.
| | - W Onyango-Ouma
- Institute of Anthropology, Gender & African Studies, University of Nairobi, PO Box 30197-00100, Nairobi, Kenya.
| | - Tobias Landmann
- International Centre for Insect Physiology and Ecology (ICIPE), PO Box 30772-00100, Nairobi, Kenya.
| | - Rosemary Sang
- International Centre for Insect Physiology and Ecology (ICIPE), PO Box 30772-00100, Nairobi, Kenya; The Center for Virus Research, Kenya Medical Research Institute, PO Box 54628, Nairobi, Kenya.
| | - Murithi Mbabu
- Ministry of Agriculture, Livestock and Fisheries, State Department of Veterinary Services, Private Bag-00625, Nairobi, Kenya.
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Jupille H, Vega-Rua A, Rougeon F, Failloux AB. Arboviruses: variations on an ancient theme. Future Virol 2014. [DOI: 10.2217/fvl.14.62] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
ABSTRACT Arboviruses utilize different strategies to complete their transmission cycle between vertebrate and invertebrate hosts. Most possess an RNA genome coupled with an RNA polymerase lacking proofreading activity and generate large populations of genetically distinct variants, permitting rapid adaptation to environmental changes. With mutation rates of between 10- 6 and 10-4 substitutions per nucleotide, arboviral genomes rapidly acquire mutations that can lead to viral emergence. Arboviruses can be described in seven families, four of which have medical importance: Togaviridae, Flaviviridae, Bunyaviridae and Reoviridae. The Togaviridae and Flaviviridae both have ssRNA genomes, while the Bunyaviridae and Reoviridae possess segmented RNA genomes. Recent epidemics caused by these arboviruses have been associated with specific mutations leading to enhanced host ranges, vector shifts and virulence.
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Affiliation(s)
- Henri Jupille
- Department of Virology, Arboviruses & Insect Vectors, 25 Rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Anubis Vega-Rua
- Department of Virology, Arboviruses & Insect Vectors, 25 Rue du Dr Roux, 75724 Paris Cedex 15, France
- Cellule Pasteur UPMC, Université Pierre et Marie Curie, Paris, France
| | | | - Anna-Bella Failloux
- Department of Virology, Arboviruses & Insect Vectors, 25 Rue du Dr Roux, 75724 Paris Cedex 15, France
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Sindato C, Karimuribo ED, Pfeiffer DU, Mboera LEG, Kivaria F, Dautu G, Bernard B, Paweska JT. Spatial and temporal pattern of Rift Valley fever outbreaks in Tanzania; 1930 to 2007. PLoS One 2014; 9:e88897. [PMID: 24586433 PMCID: PMC3934866 DOI: 10.1371/journal.pone.0088897] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 01/13/2014] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Rift Valley fever (RVF)-like disease was first reported in Tanzania more than eight decades ago and the last large outbreak of the disease occurred in 2006-07. This study investigates the spatial and temporal pattern of RVF outbreaks in Tanzania over the past 80 years in order to guide prevention and control strategies. MATERIALS AND METHODS A retrospective study was carried out based on disease reporting data from Tanzania at district or village level. The data were sourced from the Ministries responsible for livestock and human health, Tanzania Meteorological Agency and research institutions involved in RVF surveillance and diagnosis. The spatial distribution of outbreaks was mapped using ArcGIS 10. The space-time permutation model was applied to identify clusters of cases, and a multivariable logistic regression model was used to identify risk factors associated with the occurrence of outbreaks in the district. PRINCIPAL FINDINGS RVF outbreaks were reported between December and June in 1930, 1947, 1957, 1960, 1963, 1968, 1977-79, 1989, 1997-98 and 2006-07 in 39.2% of the districts in Tanzania. There was statistically significant spatio-temporal clustering of outbreaks. RVF occurrence was associated with the eastern Rift Valley ecosystem (OR = 6.14, CI: 1.96, 19.28), total amount of rainfall of >405.4 mm (OR = 12.36, CI: 3.06, 49.88), soil texture (clay [OR = 8.76, CI: 2.52, 30.50], and loam [OR = 8.79, CI: 2.04, 37.82]). CONCLUSION/SIGNIFICANCE RVF outbreaks were found to be distributed heterogeneously and transmission dynamics appeared to vary between areas. The sequence of outbreak waves, continuously cover more parts of the country. Whenever infection has been introduced into an area, it is likely to be involved in future outbreaks. The cases were more likely to be reported from the eastern Rift Valley than from the western Rift Valley ecosystem and from areas with clay and loam rather than sandy soil texture.
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Affiliation(s)
- Calvin Sindato
- National Institute for Medical Research, Tabora, Tanzania
- Department of Veterinary Medicine and Public Health, Sokoine University of Agriculture, Morogoro, Tanzania
- Southern Africa Centre for Infectious Disease Surveillance, Morogoro, Tanzania
| | - Esron D. Karimuribo
- Department of Veterinary Medicine and Public Health, Sokoine University of Agriculture, Morogoro, Tanzania
- Southern Africa Centre for Infectious Disease Surveillance, Morogoro, Tanzania
| | | | | | - Fredrick Kivaria
- Food and Agriculture Organization of the United Nations, Dar es Salaam, Tanzania
| | - George Dautu
- Department of Disease Control, University of Zambia, Lusaka, Zambia
| | - Bett Bernard
- International Livestock Research Institute, Nairobi, Kenya
| | - Janusz T. Paweska
- Center for Emerging and Zoonotic Diseases, National Institute for Communicable Diseases, of the National Health Laboratory Service, Sandringham, South Africa
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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Nicolas G, Durand B, Rakotoarimanana TT, Lacote S, Chevalier V, Marianneau P. A 3-year serological and virological cattle follow-up in Madagascar highlands suggests a non-classical transmission route of Rift Valley fever virus. Am J Trop Med Hyg 2013; 90:265-6. [PMID: 24366500 DOI: 10.4269/ajtmh.13-0538] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Rift Valley fever virus (RVFV) is a mosquito-borne infection of livestock and human which causes a potentially severe disease. In 2008-2009, a RVF outbreak occurred in a temperate and mountainous area located on the highlands of Madagascar. A three-year cattle follow-up (2009-2011) was conducted in a pilot area of this highland. A seroprevalence rate of 28% was estimated in 2009 and a seroconversion rate of 7% in 2009-2010. A third cross-sectional survey showed a seroconversion rate of 14% in 2010-2011. In 2011 the longitudinal study suggested a RVFV circulation during the year. In this area where vectors density is low and cattle exchanges are linked to the virus local spread, we raise hypotheses that may explain the local persistence of the virus.
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Affiliation(s)
- Gaëlle Nicolas
- International Centre for Research in Agriculture and Development (CIRAD), Montpellier, France; French Agency for Food, Environmental and Occupational Health and Safety (ANSES), Epidemiology Unit, Animal Health Laboratory, Maisons-Alfort, France; National Research Center for Rural Development ? Veterinary Department (FOFIFA-DRZV), Antananarivo, Madagascar; French Agency for Food, Environmental and Occupational Health and Safety (ANSES), Virology Unit, Laboratory of Lyon, Lyon, France
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Balenghien T, Cardinale E, Chevalier V, Elissa N, Failloux AB, Jean Jose Nipomichene TN, Nicolas G, Rakotoharinome VM, Roger M, Zumbo B. Towards a better understanding of Rift Valley fever epidemiology in the south-west of the Indian Ocean. Vet Res 2013; 44:78. [PMID: 24016237 PMCID: PMC3848763 DOI: 10.1186/1297-9716-44-78] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 08/01/2013] [Indexed: 12/31/2022] Open
Abstract
Rift Valley fever virus (Phlebovirus, Bunyaviridae) is an arbovirus causing intermittent epizootics and sporadic epidemics primarily in East Africa. Infection causes severe and often fatal illness in young sheep, goats and cattle. Domestic animals and humans can be contaminated by close contact with infectious tissues or through mosquito infectious bites. Rift Valley fever virus was historically restricted to sub-Saharan countries. The probability of Rift Valley fever emerging in virgin areas is likely to be increasing. Its geographical range has extended over the past years. As a recent example, autochthonous cases of Rift Valley fever were recorded in 2007-2008 in Mayotte in the Indian Ocean. It has been proposed that a single infected animal that enters a naive country is sufficient to initiate a major outbreak before Rift Valley fever virus would ever be detected. Unless vaccines are available and widely used to limit its expansion, Rift Valley fever will continue to be a critical issue for human and animal health in the region of the Indian Ocean.
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Affiliation(s)
| | - Eric Cardinale
- CIRAD, UMR Contrôle des maladies, F-34398 Montpellier, France
- Centre de recherche et de veille sur les maladies émergentes de l’Océan Indien (CRVOI), 2 Rue Maxime Rivière, 97490 Ste Clotilde, Ile de la Réunion, France
| | - Véronique Chevalier
- CIRAD-Département “Environnement et Sociétés”, UR AGIRs “Animal et Gestion Intégrée des Risques”, TA C-22/ E, Campus international de Baillarguet, 34398 Montpellier, Cedex 5, France
| | - Nohal Elissa
- Institut Pasteur, Unité d’Entomologie médicale, Ambatofotsikely BP 1274, Antananarivo 101, Madagascar
| | - Anna-Bella Failloux
- Institut Pasteur, Department of Virology, Arboviruses and Insect Vectors, 25–28 rue du Dr Roux, 75724 Paris, cedex 15, France
| | | | - Gaelle Nicolas
- CIRAD-Département “Environnement et Sociétés”, UR AGIRs “Animal et Gestion Intégrée des Risques”, TA C-22/ E, Campus international de Baillarguet, 34398 Montpellier, Cedex 5, France
| | - Vincent Michel Rakotoharinome
- Ministère de l’Agriculture de l’Elevage et de la Pêche, Direction de la santé animale et phytosanitaire, Ambatofotsikely, Madagascar
| | - Matthieu Roger
- CIRAD, UMR Contrôle des maladies, F-34398 Montpellier, France
| | - Betty Zumbo
- Service de lutte anti-vectorielle, Agence de Santé Océan Indien, Délégation de l’île de Mayotte, BP-410 Mamoudzou, France
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19
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Magona J, Galiwango T, Walubengo J, Mukiibi G. Rift Valley fever in Uganda: Seroprevalence and risk factor surveillance vis-à-vis mosquito vectors, anti-RVF virus IgG and RVF virus neutralizing antibodies in goats. Small Rumin Res 2013. [DOI: 10.1016/j.smallrumres.2013.05.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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20
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Schwarz NG, Girmann M, Randriamampionona N, Bialonski A, Maus D, Krefis AC, Njarasoa C, Rajanalison JF, Ramandrisoa HD, Randriarison ML, May J, Schmidt-Chanasit J, Rakotozandrindrainy R. Seroprevalence of antibodies against Chikungunya, Dengue, and Rift Valley fever viruses after febrile illness outbreak, Madagascar. Emerg Infect Dis 2013; 18:1780-6. [PMID: 23092548 PMCID: PMC3559170 DOI: 10.3201/eid1811.111036] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In October 2009, two-3 months after an outbreak of a febrile disease with joint pain on the eastern coast of Madagascar, we assessed serologic markers for chikungunya virus (CHIKV), dengue virus (DENV), and Rift Valley fever virus (RVFV) in 1,244 pregnant women at 6 locations. In 2 eastern coast towns, IgG seroprevalence against CHIKV was 45% and 23%; IgM seroprevalence was 28% and 5%. IgG seroprevalence against DENV was 17% and 11%. No anti-DENV IgM was detected. At 4 locations, 450-1,300 m high, IgG seroprevalence against CHIKV was 0%-3%, suggesting CHIKV had not spread to higher inland-altitudes. Four women had IgG against RVFV, probably antibodies from a 2008 epidemic. Most (78%) women from coastal locations with CHIKV-specific IgG reported joint pain and stiffness; 21% reported no symptoms. CHIKV infection was significantly associated with high bodyweight. The outbreak was an isolated CHIKV epidemic without relevant DENV co-transmission.
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Nicolas G, Durand B, Duboz R, Rakotondravao R, Chevalier V. Description and analysis of the cattle trade network in the Madagascar highlands: potential role in the diffusion of Rift Valley fever virus. Acta Trop 2013; 126:19-27. [PMID: 23295911 DOI: 10.1016/j.actatropica.2012.12.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 12/21/2012] [Accepted: 12/26/2012] [Indexed: 11/25/2022]
Abstract
In 2008-2009 a Rift Valley Fever (RVF) outbreak occurred in the Anjozorobe area, a temperate and mountainous area of the Madagascar highlands. The results of a serosurvey conducted in 2009 suggested recurrent circulation of RVF virus (RVFV) in this area and potential involvement of the cattle trade in RVFV circulation. The objective of this study was to describe the cattle trade network of the area and analyse the link between network structure and RVFV circulation. Five hundred and sixteen animals that tested negative in 2009 were sampled again in 2010. The 2009-2010 cattle-level seroconversion rate was estimated at 7% (95% CI: 5-10%). Trade data from 386 breeders of 48 villages were collected and analysed using social network analysis methodology, nodes being villages and ties being any movements of cattle connecting villages. The specific practice of cattle barter, known as kapsile, that involves frequent contacts between cattle of two breeders, was observed in addition to usual trade. Trade data were analysed using a logistic model, the occurrence of seroconversion at the village level being the outcome variable and the network centrality measures being the predictors. A negative association was observed between the occurrence of seroconversion in the village and introduction of cattle by trade (p=0.03), as well as the distance to the nearest water point (p=0.002). Conversely, the practice of kapsile, was a seroconversion risk factor (p=0.007). The kapsile practice may be the support for inter-village RVFV circulation whereas the trade network is probably rather implicated in the introduction of RVFV to the area from other parts of Madagascar. The negative association of the distance to the nearest water point suggests that after RVFV introduction, a substantial part of transmission may be due to vectors.
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Ba Y, Sall AA, Diallo D, Mondo M, Girault L, Dia I, Diallo M. Re-emergence of Rift Valley fever virus in Barkedji (Senegal, West Africa) in 2002-2003: identification of new vectors and epidemiological implications. JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION 2012; 28:170-178. [PMID: 23833896 DOI: 10.2987/12-5725.1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The Rift Valley fever virus (RVFV) is a threat that must not be neglected, as the consequences of RVFV are dramatic, both for human and animal health. This virus is a zoonotic virus that already has demonstrated a real capacity for re-emerging after long periods of silence, as observed in Barkedji (Senegal, West Africa) in 2002. In this article we present the 2nd emergence in Barkedji after the 1st manifestation in 1993, and for the 1st time the circulation of RVFV during 2 consecutive years among mosquito populations in Senegal. As part of the entomological surveillance program undertaken since 1990 to detect circulation of the RVFV in Barkedji, 108,336 mosquitoes belonging to 34 species and 5 genera were collected in 2002-2003. Aedes vexans and Culex poicilipes, previously known to be vectors of RVFV in Senegal, comprised 88.7% of the total collection. In 2002, Ae. vexans was the most abundant mosquito, followed by Cx. poicilipes; the opposite situation was observed in 2003. In 2002, 29 and 10 RVFV isolates were obtained from Cx. poicilipes (minimum infection rate [MIR] = 0.13%) and Ae. vexans (MIR = 0.02%) pools, respectively and the MIR for the 2 species were significantly different (chi2 = 34.65; df = 1, P < 0.001). In 2003, 7 RVFV strains were isolated from Cx. poicilipes (3, MIR = 0.03), Mansonia africana (2, MIR = 0.08), Ae. fowleri (1), and Ma. uniformis (1, MIR = 0.05). The 3 latter species were found to be associated with RVFV for the 1st time in Senegal. A significant decrease in MIR was observed from 2002 to 2003 (chi2 6.28; df = 1, P = 0.01) for Cx. poicilipes, the only species involved in the transmission during the 2 sampling years.
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Affiliation(s)
- Y Ba
- Institut Pasteur de Dakar, BP 220, Dakar, Senegal
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Soti V, Tran A, Degenne P, Chevalier V, Lo Seen D, Thiongane Y, Diallo M, Guégan JF, Fontenille D. Combining hydrology and mosquito population models to identify the drivers of Rift Valley fever emergence in semi-arid regions of West Africa. PLoS Negl Trop Dis 2012; 6:e1795. [PMID: 22928055 PMCID: PMC3424242 DOI: 10.1371/journal.pntd.0001795] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 07/07/2012] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Rift Valley fever (RVF) is a vector-borne viral zoonosis of increasing global importance. RVF virus (RVFV) is transmitted either through exposure to infected animals or through bites from different species of infected mosquitoes, mainly of Aedes and Culex genera. These mosquitoes are very sensitive to environmental conditions, which may determine their presence, biology, and abundance. In East Africa, RVF outbreaks are known to be closely associated with heavy rainfall events, unlike in the semi-arid regions of West Africa where the drivers of RVF emergence remain poorly understood. The assumed importance of temporary ponds and rainfall temporal distribution therefore needs to be investigated. METHODOLOGY/PRINCIPAL FINDINGS A hydrological model is combined with a mosquito population model to predict the abundance of the two main mosquito species (Aedes vexans and Culex poicilipes) involved in RVFV transmission in Senegal. The study area is an agropastoral zone located in the Ferlo Valley, characterized by a dense network of temporary water ponds which constitute mosquito breeding sites. The hydrological model uses daily rainfall as input to simulate variations of pond surface areas. The mosquito population model is mechanistic, considers both aquatic and adult stages and is driven by pond dynamics. Once validated using hydrological and entomological field data, the model was used to simulate the abundance dynamics of the two mosquito species over a 43-year period (1961-2003). We analysed the predicted dynamics of mosquito populations with regards to the years of main outbreaks. The results showed that the main RVF outbreaks occurred during years with simultaneous high abundances of both species. CONCLUSION/SIGNIFICANCE Our study provides for the first time a mechanistic insight on RVFV transmission in West Africa. It highlights the complementary roles of Aedes vexans and Culex poicilipes mosquitoes in virus transmission, and recommends the identification of rainfall patterns favourable for RVFV amplification.
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Affiliation(s)
- Valérie Soti
- CIRAD, UPR AGIRs, Montpellier, France
- CIRAD, UMR TETIS, Montpellier, France
- CIRAD, UR SCA, Montpellier, France
| | - Annelise Tran
- CIRAD, UPR AGIRs, Montpellier, France
- CIRAD, UMR TETIS, Montpellier, France
- * E-mail:
| | | | | | | | | | | | - Jean-François Guégan
- IRD, UMR MIVEGEC (IRD 224, CNRS 5290), Université de Montpellier, Montpellier, France
- EHESP, Montpellier, France
| | - Didier Fontenille
- IRD, UMR MIVEGEC (IRD 224, CNRS 5290), Université de Montpellier, Montpellier, France
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Crabtree MB, Kent Crockett RJ, Bird BH, Nichol ST, Erickson BR, Biggerstaff BJ, Horiuchi K, Miller BR. Infection and transmission of Rift Valley fever viruses lacking the NSs and/or NSm genes in mosquitoes: potential role for NSm in mosquito infection. PLoS Negl Trop Dis 2012; 6:e1639. [PMID: 22563517 PMCID: PMC3341344 DOI: 10.1371/journal.pntd.0001639] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 03/27/2012] [Indexed: 01/08/2023] Open
Abstract
Background Rift Valley fever virus is an arthropod-borne human and animal pathogen responsible for large outbreaks of acute and febrile illness throughout Africa and the Arabian Peninsula. Reverse genetics technology has been used to develop deletion mutants of the virus that lack the NSs and/or NSm virulence genes and have been shown to be stable, immunogenic and protective against Rift Valley fever virus infection in animals. We assessed the potential for these deletion mutant viruses to infect and be transmitted by Aedes mosquitoes, which are the principal vectors for maintenance of the virus in nature and emergence of virus initiating disease outbreaks, and by Culex mosquitoes which are important amplification vectors. Methodology and Principal Findings Aedes aegypti and Culex quinquefasciatus mosquitoes were fed bloodmeals containing the deletion mutant viruses. Two weeks post-exposure mosquitoes were assayed for infection, dissemination, and transmission. In Ae. aegypti, infection and transmission rates of the NSs deletion virus were similar to wild type virus while dissemination rates were significantly reduced. Infection and dissemination rates for the NSm deletion virus were lower compared to wild type. Virus lacking both NSs and NSm failed to infect Ae. aegypti. In Cx. quinquefasciatus, infection rates for viruses lacking NSm or both NSs and NSm were lower than for wild type virus. Conclusions/Significance In both species, deletion of NSm or both NSs and NSm reduced the infection and transmission potential of the virus. Deletion of both NSs and NSm resulted in the highest level of attenuation of virus replication. Deletion of NSm alone was sufficient to nearly abolish infection in Aedes aegypti mosquitoes, indicating an important role for this protein. The double deleted viruses represent an ideal vaccine profile in terms of environmental containment due to lack of ability to efficiently infect and be transmitted by mosquitoes. Rift Valley fever virus is transmitted mainly by mosquitoes and causes disease in humans and animals throughout Africa and the Arabian Peninsula. The impact of disease is large in terms of human illness and mortality, and economic impact on the livestock industry. For these reasons, and because there is a risk of this virus spreading to Europe and North America, it is important to develop a vaccine that is stable, safe and effective in preventing infection. Potential vaccine viruses have been developed through deletion of two genes (NSs and NSm) affecting virus virulence. Because this virus is normally transmitted by mosquitoes we must determine the effects of the deletions in these vaccine viruses on their ability to infect and be transmitted by mosquitoes. An optimal vaccine virus would not infect or be transmitted. The viruses were tested in two mosquito species: Aedes aegypti and Culex quinquefasciatus. Deletion of the NSm gene reduced infection of Ae. aegypti mosquitoes indicating a role for the NSm protein in mosquito infection. The virus with deletion of both NSs and NSm genes was the best vaccine candidate since it did not infect Ae. aegypti and showed reduced infection and transmission rates in Cx. quinquefasciatus.
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Affiliation(s)
- Mary B Crabtree
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America.
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An unexpected recurrent transmission of Rift Valley fever virus in cattle in a temperate and mountainous area of Madagascar. PLoS Negl Trop Dis 2011; 5:e1423. [PMID: 22206026 PMCID: PMC3243698 DOI: 10.1371/journal.pntd.0001423] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 10/24/2011] [Indexed: 11/19/2022] Open
Abstract
Rift Valley fever is an acute, zoonotic viral disease of domestic ruminants, caused by a phlebovirus (Bunyaviridae family). A large outbreak occurred in Madagascar in 2008–2009. The goal of the present study was to evaluate the point prevalence of antibodies against Rift Valley Fever Virus (RVFV) in cattle in the Anjozorobe district, located in the wet and temperate highland region of Madagascar and yet heavily affected by the disease, and analyse environmental and trade factors potentially linked to RVFV transmission. A serological study was performed in 2009 in 894 bovines. For each bovine, the following variables were recorded: age, location of the night pen, minimum distance from the pen to the nearest water point and the forest, nearest water point type, and herd replacement practices. The serological data were analyzed using a generalized linear mixed model. The overall anti-RVFV IgG seroprevalence rate was 28% [CI95% 25–31]. Age was statistically linked to prevalence (p = 10−4), being consistent with a recurrent RVFV circulation. Distance from the night pen to the nearest water point was a protective factor (p = 5.10−3), which would be compatible with a substantial part of the virus transmission being carried out by nocturnal mosquito vectors. However, water point type did not influence the risk of infection: several mosquito species are probably involved. Cattle belonging to owners who purchase animals to renew the herd were significantly more likely to have seroconverted than others (p = 0.04): cattle trade may contribute to the introduction of the virus in this area. The minimum distance of the night pen to the forest was not linked to the prevalence. This is the first evidence of a recurrent transmission of RVFV in such an ecosystem that associates a wet, temperate climate, high altitude, paddy fields, and vicinity to a dense rain forest. Persistence mechanisms need to be further investigated. Rift Valley fever (RVF) is a viral disease of domestic ruminants, which may affect humans. The RVF virus (RVFV) may be transmitted either by mosquitoes or through direct contact with vireamic body fluids or products. Until now, this disease had been described in arid, hot and irrigated or tropical areas. Performed in the year following the 2008–2009 RVFV outbreak in Madagascar, this study demonstrates for the first time a regular and intense transmission of this disease in a temperate and mountainous region.The area chosen as a pilot project shows that cattle are regularly and heavily affected in the highlands of Madagascar. Statistical analyses suggest that (i) a substantial part of the transmission is due to mosquito vectors; (ii) many mosquito species such as Culex and Anopheles, are probably involved in the transmission; (iii) cattle trade, by a regular introduction of the virus via herds coming from infected areas of the island, may explain the recurrence of the disease in this region. Further investigations are needed to understand the mechanisms of transmission of the disease, and design and implement appropriate surveillance and control measures in this area.
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Genetic evidence for Rift Valley fever outbreaks in Madagascar resulting from virus introductions from the East African mainland rather than enzootic maintenance. J Virol 2011; 85:6162-7. [PMID: 21507967 DOI: 10.1128/jvi.00335-11] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rift Valley fever virus (RVFV), a mosquito-borne phlebovirus, has been detected in Madagascar since 1979, with occasional outbreaks. In 2008 to 2009, a large RVFV outbreak was detected in Malagasy livestock and humans during two successive rainy seasons. To determine whether cases were due to enzootic maintenance of the virus within Madagascar or to importation from the East African mainland, nine RVFV whole genomic sequences were generated for viruses from the 1991 and 2008 Malagasy outbreaks. Bayesian coalescent analyses of available whole S, M, and L segment sequences were used to estimate the time to the most recent common ancestor for the RVFVs. The 1979 Madagascar isolate shared a common ancestor with strains on the mainland around 1972. The 1991 Madagascar isolates were in a clade distinct from that of the 1979 isolate and shared a common ancestor around 1987. Finally, the 2008 Madagascar viruses were embedded within a large clade of RVFVs from the 2006-2007 outbreak in East Africa and shared a common ancestor around 2003 to 2004. These results suggest that the most recent Madagascar outbreak was caused by a virus likely arriving in the country some time between 2003 and 2008 and that this outbreak may be an extension of the 2006-2007 East African outbreak. Clustering of the Malagasy sequences into subclades indicates that the viruses have continued to evolve during their short-term circulation within the country. These data are consistent with the notion that RVFV outbreaks in Madagascar result not from emergence from enzootic cycles within the country but from recurrent virus introductions from the East African mainland.
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Jeanmaire EM, Rabenarivahiny R, Biarmann M, Rabibisoa L, Ravaomanana F, Randriamparany T, Andriamandimby SF, Diaw CS, Fenozara P, de La Rocque S, Reynes JM. Prevalence of Rift Valley fever infection in ruminants in Madagascar after the 2008 outbreak. Vector Borne Zoonotic Dis 2011; 11:395-402. [PMID: 21395414 DOI: 10.1089/vbz.2009.0249] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A Rift Valley fever (RVF) outbreak occurred in Madagascar from January to May 2008. The objectives of this study were (1) to assess the current and past circulation of RVF virus (RVFV) in livestock in Madagascar and (2) to evaluate the extent and magnitude of the 2008 RVF outbreak in livestock. The results of a country-wide serosurvey conducted in August 2008 on small and large ruminants are reported here. The study included 3437 cattle and 989 small ruminants (227 sheep and 762 goats) sampled in 30 of the 111 Malagasy districts, selected to be representative of the different ecozones and livestock density areas. Sera of animals were tested for the detection of immunoglobulins M (IgM) and G (IgG) against RVFV using commercial enzyme-linked immunosorbent assays kits. Recent infections (presence of IgM against RVFV) were detected in only 9 cattle (0.3% [0.1-0.4]) and 33 small ruminant (3.3% [2.2-4.5]) samples. Past infections (presence of IgG and absence of IgM against RVFV) were detected in 887 cattle (25.8% [24.3-27.3]) and 244 small ruminant (24.7% [22.0-27.4]) samples. Past infections were detected in all sampled sites. All ecozones were affected. In the southern and northwestern areas, the prevalence of cattle showing evidence of past infection with RVFV increased with the age of the animals. Our results suggest that there has been country-wide circulation of RVFV in 2008 in Madagascar, including in parts of the country where no clinical illness, either in animals or in humans, was reported. The data also suggest that the southern and northwestern areas may be endemic for RVFV, and that the virus may spread when ecological conditions are favorable for its amplification.
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Affiliation(s)
- Elisabeth Marie Jeanmaire
- Food and Agriculture Organization of the United Nations, Emergency Coordination and Rehabilitation Unit, Antananarivo, Madagascar.
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Rakotoarivelo RA, Andrianasolo R, Razafimahefa SH, Randremandranto Razafimbelo NS, Randria MJD. [Severe presentations of Rift Valley Fever in Madagascar]. Med Mal Infect 2011; 41:318-21. [PMID: 21295426 DOI: 10.1016/j.medmal.2010.12.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 11/19/2010] [Accepted: 12/27/2010] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The authors describe clinical and epidemiologic characteristics of severe presentations of Rift valley fever (RVF) during the 2008 epidemic in Madagascar. METHODOLOGY The diagnosis was confirmed by RVF virus polymerase chain reaction (PCR), or detection of specifics antibodies by Elisa. RESULTS Sixteen cases of severe RVF were recorded. The sex-ratio was 7/1 and median age was 32 years (20/59 years). The risk factors of infection were: contact with infected animals or their meat (n=8), and travelling to a risk area (n=2). Hemorrhagic, neurological, and ocular manifestations were observed respectively in 87.5%, 43.8% and 6.3% of cases. All patients who died (n=4) presented with a hemorrhagic form of the disease. CONCLUSION The hemorrhagic form was the most frequent presentation of RVF and was responsible for a high level of mortality. Epidemiologic surveillance must be implemented.
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Affiliation(s)
- R A Rakotoarivelo
- Service des maladies infectieuses, hôpital Joseph-Raseta, CHU d'Antananarivo, 101, Antananarivo, Madagascar.
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Krida G, Diancourt L, Bouattour A, Rhim A, Chermiti B, Failloux AB. [Assessment of the risk of introduction to Tunisia of the Rift Valley fever virus by the mosquito Culex pipiens]. ACTA ACUST UNITED AC 2010; 104:250-9. [PMID: 21184293 DOI: 10.1007/s13149-010-0122-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 10/19/2010] [Indexed: 12/27/2022]
Abstract
The mosquito Culex pipiens has been involved as vector of the West Nile virus in Tunisia. Its bio-ecological characteristics in combination with some environmental factors have favoured the emergence of this virus in a West-Nile free zone. This leads to question about the potential risk of introducing another arbovirus, the Rift Valley fever (RVF) virus, in Tunisia from neighbouring countries where RVF circulates. In this study, we have evaluated the vector competence of different populations of Cx. pipiens towards two strains of RVF virus, the virulent ZH548 and the avirulent Clone 13 by experimental infections and the genetic differentiation of these populations of Cx. pipiens using four microsatellite loci. We found disseminated infection rates ranging from 0% to 14.7% and a high genetic differentiation among populations without any geographical pattern (no isolation by distance). Thus, although Cx. pipiens is able to sustain an amplification of RVF virus, viral dissemination through mosquito dispersal would be unlikely. However, as RVF is an emerging disease transmitted by several other potential mosquito species (e.g. Ochlerotatus caspius), attention should be maintained to survey livestock and mosquitoes in Tunisia.
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Affiliation(s)
- G Krida
- Institut Pasteur de Tunis, service d'entomologie médicale, Tunis Belvédère, Tunisie
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Ratovonjato J, Olive MM, Tantely LM, Andrianaivolambo L, Tata E, Razainirina J, Jeanmaire E, Reynes JM, Elissa N. Detection, isolation, and genetic characterization of Rift Valley fever virus from Anopheles (Anopheles) coustani, Anopheles (Anopheles) squamosus, and Culex (Culex) antennatus of the Haute Matsiatra region, Madagascar. Vector Borne Zoonotic Dis 2010; 11:753-9. [PMID: 21028960 DOI: 10.1089/vbz.2010.0031] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Following veterinary alerts of Rift Valley fever (RVF) in the districts of Fianarantsoa I and II in November 2008 and in the district of Ambalavao in April 2009, entomological and virological investigations were carried out to identify the mosquito species that could act as RVF virus (RVFV) vectors in the region. A total of 12,785 adult mosquitoes belonging to 5 genera and 21 species were collected. After identification, mosquitoes were pooled by species, sex, and female status (fed or unfed) and then stored at -80°C. Of 319 pools of unfed monospecific female mosquito tested by real-time RT-polymerase chain reaction, RVFV was detected in 1 pool of Anopheles coustani, 5 pools of An. squamosus, and 2 pools of Culex antennatus mosquitoes. The virus was isolated in mosquito cell lines from two of the five Real Time-RT-polymerase chain reaction (real time-RT-PCR) positive pools of An. squamosus mosquitoes. From the eight RVFV strains detected, partial S, M, and L genome segments sequences were obtained. The phylogenetic analysis of these sequences showed that the strains circulating in mosquitoes were genetically close to those that circulated in livestock and humans during RVF outbreaks in 2008 and 2009. This study, therefore, provides strong evidence that An. squamosus, An. coustani, and Cx. antennatus could play a role as vectors of the RVFV during the disease outbreaks in 2008-2009. Bioecological, genetic, and RVF transmission studies on these three mosquito species are needed to address this question and thus improve prevention and control of future RVF outbreaks in Madagascar, where these species are present.
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Affiliation(s)
- Jocelyn Ratovonjato
- Unité d'Entomologie Médicale, Institut Pasteur de Madagascar, Antananarivo, Madagascar.
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Sang R, Kioko E, Lutomiah J, Warigia M, Ochieng C, O'Guinn M, Lee JS, Koka H, Godsey M, Hoel D, Hanafi H, Miller B, Schnabel D, Breiman RF, Richardson J. Rift Valley fever virus epidemic in Kenya, 2006/2007: the entomologic investigations. Am J Trop Med Hyg 2010; 83:28-37. [PMID: 20682903 DOI: 10.4269/ajtmh.2010.09-0319] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In December 2006, Rift Valley fever (RVF) was diagnosed in humans in Garissa Hospital, Kenya and an outbreak reported affecting 11 districts. Entomologic surveillance was performed in four districts to determine the epidemic/epizootic vectors of RVF virus (RVFV). Approximately 297,000 mosquitoes were collected, 164,626 identified to species, 72,058 sorted into 3,003 pools and tested for RVFV by reverse transcription-polymerase chain reaction. Seventy-seven pools representing 10 species tested positive for RVFV, including Aedes mcintoshi/circumluteolus (26 pools), Aedes ochraceus (23 pools), Mansonia uniformis (15 pools); Culex poicilipes, Culex bitaeniorhynchus (3 pools each); Anopheles squamosus, Mansonia africana (2 pools each); Culex quinquefasciatus, Culex univittatus, Aedes pembaensis (1 pool each). Positive Ae. pembaensis, Cx. univittatus, and Cx. bitaeniorhynchus was a first time observation. Species composition, densities, and infection varied among districts supporting hypothesis that different mosquito species serve as epizootic/epidemic vectors of RVFV in diverse ecologies, creating a complex epidemiologic pattern in East Africa.
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Affiliation(s)
- Rosemary Sang
- Arbovirology/Hemorrhagic Fevers Laboratory, Centre for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya.
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Rift Valley fever virus seroprevalence in human rural populations of Gabon. PLoS Negl Trop Dis 2010; 4:e763. [PMID: 20668541 PMCID: PMC2910672 DOI: 10.1371/journal.pntd.0000763] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 06/14/2010] [Indexed: 11/21/2022] Open
Abstract
Background Rift Valley fever (RVF) is a mosquito-borne viral zoonosis caused by a phlebovirus and transmitted by Aedes mosquitoes. Humans can also be infected through direct contact with blood (aerosols) or tissues (placenta, stillborn) of infected animals. Although severe clinical cases can be observed, infection with RVF virus (RVFV) in humans is, in most cases, asymptomatic or causes a febrile illness without serious symptoms. In small ruminants RVFV mainly causes abortion and neonatal death. The distribution of RVFV has been well documented in many African countries, particularly in the north (Egypt, Sudan), east (Kenya, Tanzania, Somalia), west (Senegal, Mauritania) and south (South Africa), but also in the Indian Ocean (Madagascar, Mayotte) and the Arabian Peninsula. In contrast, the prevalence of RVFV has rarely been investigated in central African countries. Methodology/Principal Findings We therefore conducted a large serological survey of rural populations in Gabon, involving 4,323 individuals from 212 randomly selected villages (10.3% of all Gabonese villages). RVFV-specific IgG was found in a total of 145 individuals (3.3%) suggesting the wide circulation of Rift Valley fever virus in Gabon. The seroprevalence was significantly higher in the lakes region than in forest and savannas zones, with respective rates of 8.3%, 2.9% and 2.2%. In the lakes region, RVFV-specific IgG was significantly more prevalent in males than in females (respectively 12.8% and 3.8%) and the seroprevalence increased gradually with age in males but not in females. Conclusions/Significance Although RVFV was suggested to circulate at a relatively high level in Gabon, no outbreaks or even isolated cases have been documented in the country. The higher prevalence in the lakes region is likely to be driven by specific ecologic conditions favorable to certain mosquito vector species. Males may be more at risk of infection than females because they spend more time farming and hunting outside the villages, where they may be more exposed to mosquito bites and infected animals. Further investigations are needed to determine the putative sylvan cycle of RVFV, including the mosquito species and the reservoir role of wild animals in the viral maintenance cycle. Rift Valley fever (RVF) is a disease transmitted by a mosquito bite (Aedes). Humans can also be infected through direct contact with blood (aerosols) or tissues (placenta, stillborn) of infected animals. Although severe clinical cases can be observed, infection with RVF virus (RVFV) in humans in most cases causes a febrile illness without serious symptoms. In small ruminants RVFV mainly causes abortion and neonatal death. RVFV distribution has been poorly investigated in Central Africa. We conducted a large scale serological survey of RVF antibodies in rural populations in Gabon, involving 4,323 individuals from 212 randomly selected villages. The results showed an overall RVFV prevalence of 3.3%, with values of 2.9% in the forested zones, 2.2% in savannas and 8.3% in the lakes region. These findings strongly suggest for the first time the wide circulation of Rift valley fever virus in Gabon and the possible existence of a sylvan cycle of RVF virus in this country. The serological higher prevalence in the lake region suggests that this region is likely to have particular ecological conditions, especially mosquito vector species, favoring the circulation of this virus. In Gabon, human cases of RVF may occur but are either misdiagnosed or not reported.
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Andriamandimby SF, Randrianarivo-Solofoniaina AE, Jeanmaire EM, Ravololomanana L, Razafimanantsoa LT, Rakotojoelinandrasana T, Razainirina J, Hoffmann J, Ravalohery JP, Rafisandratantsoa JT, Rollin PE, Reynes JM. Rift Valley fever during rainy seasons, Madagascar, 2008 and 2009. Emerg Infect Dis 2010; 16:963-70. [PMID: 20507747 PMCID: PMC3086256 DOI: 10.3201/eid1606.091266] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
During 2 successive rainy seasons, January 2008 through May 2008 and November 2008 through March 2009, Rift Valley fever virus (RVFV) caused outbreaks in Madagascar. Human and animal infections were confirmed on the northern and southern coasts and in the central highlands. Analysis of partial sequences from RVFV strains showed that all were similar to the strains circulating in Kenya during 2006-2007. A national cross-sectional serologic survey among slaughterhouse workers at high risk showed that RVFV circulation during the 2008 outbreaks included all of the Malagasy regions and that the virus has circulated in at least 92 of Madagascar's 111 districts. To better predict and respond to RVF outbreaks in Madagascar, further epidemiologic studies are needed, such as RVFV complete genome analysis, ruminant movement mapping, and surveillance implementation.
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Morrill JC, Ikegami T, Yoshikawa-Iwata N, Lokugamage N, Won S, Terasaki K, Zamoto-Niikura A, Peters CJ, Makino S. Rapid accumulation of virulent rift valley Fever virus in mice from an attenuated virus carrying a single nucleotide substitution in the m RNA. PLoS One 2010; 5:e9986. [PMID: 20376320 PMCID: PMC2848673 DOI: 10.1371/journal.pone.0009986] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Accepted: 03/10/2010] [Indexed: 12/17/2022] Open
Abstract
Background Rift Valley fever virus (RVFV), a member of the genus Phlebovirus within the family Bunyaviridae, is a negative-stranded RNA virus with a tripartite genome. RVFV is transmitted by mosquitoes and causes fever and severe hemorrhagic illness among humans, while in livestock it causes fever and high abortion rates. Methodology/Principal Findings Sequence analysis showed that a wild-type RVFV ZH501 preparation consisted of two major viral subpopulations, with a single nucleotide heterogeneity at nucleotide 847 of M segment (M847); one had a G residue at M847 encoding glycine in a major viral envelope Gn protein, while the other carried A residue encoding glutamic acid at the corresponding site. Two ZH501-derived viruses, rZH501-M847-G and rZH501-M847-A, carried identical genomic sequences, except that the former and the latter had G and A, respectively, at M847 were recovered by using a reverse genetics system. Intraperitoneal inoculation of rZH501-M847-A into mice caused a rapid and efficient viral accumulation in the sera, livers, spleens, kidneys and brains, and killed most of the mice within 8 days, whereas rZH501-M847-G caused low viremia titers, did not replicate as efficiently as did rZH501-M847-A in these organs, and had attenuated virulence to mice. Remarkably, as early as 2 days postinfection with rZH501-M847-G, the viruses carrying A at M847 emerged and became the major virus population thereafter, while replicating viruses retained the input A residue at M847 in rZH501-M847-A-infected mice. Conclusions/Significance These data demonstrated that the single nucleotide substitution in the Gn protein substantially affected the RVFV mouse virulence and that a virus population carrying the virulent viral genotype quickly emerged and became the major viral population within a few days in mice that were inoculated with the attenuated virus.
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Affiliation(s)
- John C. Morrill
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Tetsuro Ikegami
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Department of Pathology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Naoko Yoshikawa-Iwata
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Nandadeva Lokugamage
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Sungyong Won
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Kaori Terasaki
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Aya Zamoto-Niikura
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - C. J. Peters
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Department of Pathology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- * E-mail: (CJP); (SM)
| | - Shinji Makino
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- * E-mail: (CJP); (SM)
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Bouloy M, Flick R. Reverse genetics technology for Rift Valley fever virus: current and future applications for the development of therapeutics and vaccines. Antiviral Res 2009; 84:101-18. [PMID: 19682499 PMCID: PMC2801414 DOI: 10.1016/j.antiviral.2009.08.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 07/22/2009] [Accepted: 08/06/2009] [Indexed: 11/30/2022]
Abstract
The advent of reverse genetics technology has revolutionized the study of RNA viruses, making it possible to manipulate their genomes and evaluate the effects of these changes on their biology and pathogenesis. The fundamental insights gleaned from reverse genetics-based studies over the last several years provide a new momentum for the development of designed therapies for the control and prevention of these viral pathogens. This review summarizes the successes and stumbling blocks in the development of reverse genetics technologies for Rift Valley fever virus and their application to the further dissection of its pathogenesis and the design of new therapeutics and safe and effective vaccines.
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Affiliation(s)
- Michele Bouloy
- Institut Pasteur, Unité de Génétique Moléculaire des Bunyavirus, 25 rue du Dr Roux, 75724 Paris Cedex, France
| | - Ramon Flick
- BioProtection Systems Corporation, 2901 South Loop Drive, Suite 3360, Ames, IA 50010-8646, USA
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36
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Cêtre-Sossah C, Billecocq A, Lancelot R, Defernez C, Favre J, Bouloy M, Martinez D, Albina E. Evaluation of a commercial competitive ELISA for the detection of antibodies to Rift Valley fever virus in sera of domestic ruminants in France. Prev Vet Med 2009; 90:146-9. [PMID: 19394096 DOI: 10.1016/j.prevetmed.2009.03.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 03/16/2009] [Accepted: 03/18/2009] [Indexed: 11/17/2022]
Abstract
This paper describes the sensitivity and specificity of a commercial competitive ELISA for the detection of antibodies to Rift Valley fever virus (RVFV) from sera of French domestic ruminants. Field samples were collected from mainland France for the known-negative sera (cattle=191, goats=119, sheep=192) and from ruminants of a French overseas territory (Mayotte) for the known-positive sera. A cut-off value of 43% was determined for all species, achieving a sensitivity and specificity of 100% and a concordance of 100% with the species-specific threshold recommended by the manufacturer. Our results demonstrate that this ELISA may be a suitable diagnostic tool for disease surveillance programmes and import/export veterinary certification of French cattle, goats and sheep.
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Ikegami T, Narayanan K, Won S, Kamitani W, Peters CJ, Makino S. Rift Valley fever virus NSs protein promotes post-transcriptional downregulation of protein kinase PKR and inhibits eIF2alpha phosphorylation. PLoS Pathog 2009; 5:e1000287. [PMID: 19197350 PMCID: PMC2629125 DOI: 10.1371/journal.ppat.1000287] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Accepted: 01/08/2009] [Indexed: 12/18/2022] Open
Abstract
Rift Valley fever virus (RVFV) (genus Phlebovirus, family Bunyaviridae) is a negative-stranded RNA virus with a tripartite genome. RVFV is transmitted by mosquitoes and causes fever and severe hemorrhagic illness among humans, and fever and high rates of abortions in livestock. A nonstructural RVFV NSs protein inhibits the transcription of host mRNAs, including interferon-β mRNA, and is a major virulence factor. The present study explored a novel function of the RVFV NSs protein by testing the replication of RVFV lacking the NSs gene in the presence of actinomycin D (ActD) or α-amanitin, both of which served as a surrogate of the host mRNA synthesis suppression function of the NSs. In the presence of the host-transcriptional inhibitors, the replication of RVFV lacking the NSs protein, but not that carrying NSs, induced double-stranded RNA-dependent protein kinase (PKR)–mediated eukaryotic initiation factor (eIF)2α phosphorylation, leading to the suppression of host and viral protein translation. RVFV NSs promoted post-transcriptional downregulation of PKR early in the course of the infection and suppressed the phosphorylated eIF2α accumulation. These data suggested that a combination of RVFV replication and NSs-induced host transcriptional suppression induces PKR-mediated eIF2α phosphorylation, while the NSs facilitates efficient viral translation by downregulating PKR and inhibiting PKR-mediated eIF2α phosphorylation. Thus, the two distinct functions of the NSs, i.e., the suppression of host transcription, including that of type I interferon mRNAs, and the downregulation of PKR, work together to prevent host innate antiviral functions, allowing efficient replication and survival of RVFV in infected mammalian hosts. The mosquito-borne bunyavirus Rift Valley fever virus (RVFV) devastates both humans and domestic animals; it causes abortions in ruminants and complications such as hemorrhage, encephalitis, or retinal vasculitis in humans. A major RVFV virulence factor, NSs, disables host cell mRNA synthesis. Here we describe our new evidence that showed NSs working in a second way; in addition to inhibiting host cell transcription, NSs kept translation active in infected cells. It is well-established that activated protein kinase PKR phosphorylates a translation factor, eIF2α, and then this phosphorylated eIF2α suppresses translation. We found that NSs decreased PKR abundance and prevented eIF2α phosphorylation in infected cells, allowing efficient viral translation and replication. In contrast, when cells were infected with an RVFV mutant lacking NSs in the presence of transcriptional inhibitors that mimic the transcription inhibition function of NSs, the PKR reduction did not occur and phoshorylated eIF2α was accumulated, resulting in the inhibition of virus gene expression and replication. Thus, NSs functions in two ways to help RVFV replicate in mammalian hosts: its newly identified PKR downregulation function secures efficient viral translation, and its host transcription inhibition function suppresses the expression of host innate antiviral functions.
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Affiliation(s)
- Tetsuro Ikegami
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Department of Pathology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Sealy Center for Vaccine Development, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- * E-mail: (TI); (SM)
| | - Krishna Narayanan
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Sungyong Won
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Wataru Kamitani
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - C. J. Peters
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Department of Pathology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Sealy Center for Vaccine Development, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Shinji Makino
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Sealy Center for Vaccine Development, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, The University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- * E-mail: (TI); (SM)
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Clements ACA, Pfeiffer DU, Martin V, Pittliglio C, Best N, Thiongane Y. Spatial risk assessment of Rift Valley fever in Senegal. Vector Borne Zoonotic Dis 2007; 7:203-16. [PMID: 17627440 DOI: 10.1089/vbz.2006.0600] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Rift Valley fever (RVF) is broadening its geographic range and is increasingly becoming a disease of global importance with potentially severe consequences for human and animal health. We conducted a spatial risk assessment of RVF in Senegal using serologic data from 16,738 animals in 211 locations. Bayesian spatial regression models were developed with interpolated seasonal rainfall, land surface temperature, distance to perennial water bodies, and time of year entered as fixed-effect variables. Average total monthly rainfall during December-February was the most important spatial predictor of risk of positive RVF serologic status. Maps derived from the models highlighted the lower Senegal River basin and the southern border regions of Senegal as high-risk areas. These risk maps are suitable for use in planning improved sentinel surveillance systems in Senegal, although further data collection is required in large areas of Senegal to better define the spatial distribution of RVF.
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Affiliation(s)
- Archie C A Clements
- Epidemiology Division, Department of Veterinary Clinical Sciences, Royal Veterinary College, Hatfield, Hertfordshire, United Kingdom.
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39
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Bird BH, Bawiec DA, Ksiazek TG, Shoemaker TR, Nichol ST. Highly sensitive and broadly reactive quantitative reverse transcription-PCR assay for high-throughput detection of Rift Valley fever virus. J Clin Microbiol 2007; 45:3506-13. [PMID: 17804663 PMCID: PMC2168471 DOI: 10.1128/jcm.00936-07] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rift Valley fever (RVF) virus is a mosquito-borne virus associated with large-scale epizootics/epidemics throughout Africa and the Arabian peninsula. Virus infection can result in economically disastrous "abortion storms" and high newborn mortality in livestock. Human infections result in a flu-like illness, with 1 to 2% of patients developing severe complications, including encephalitis or hemorrhagic fever with high fatality rates. There is a critical need for a highly sensitive and specific molecular diagnostic assay capable of detecting the natural genetic spectrum of RVF viruses. We report here the establishment of a pan-RVF virus quantitative real-time reverse transcription-PCR assay with high analytical sensitivity (approximately 5 RNA copies of in vitro-transcribed RNA/reaction or approximately 0.1 PFU of infectious virus/reaction) and efficiency (standard curve slope = -3.66). Based on the alignments of the complete genome sequences of 40 ecologically and biologically diverse virus isolates collected over 56 years (1944 to 2000), the primer and probe annealing sites targeted in this assay are known to be located in highly conserved genomic regions. The performance of this assay relative to serologic assays is illustrated by testing of known RVF case materials obtained during the Saudi Arabia outbreak in 2000. Furthermore, analysis of acute-phase blood samples collected from human patients (25 nonfatal, 8 fatal) during that outbreak revealed that patient viremia at time of presentation at hospital may be a useful prognostic tool in determining patient outcome.
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Affiliation(s)
- Brian H Bird
- Special Pathogens Branch, Division of Viral and Rickettsial Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
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40
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Ikegami T, Won S, Peters CJ, Makino S. Characterization of Rift Valley fever virus transcriptional terminations. J Virol 2007; 81:8421-38. [PMID: 17537856 PMCID: PMC1951372 DOI: 10.1128/jvi.02641-06] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rift Valley fever virus (RVFV) (genus Phlebovirus, family Bunyaviridae) has a tripartite negative-strand genome and causes a mosquito-borne disease among humans and livestock in sub-Saharan African and Arabian Peninsula countries. Phlebovirus L, M, and N mRNAs are synthesized from the virus-sense RNA segments, while NSs mRNA is transcribed from the anti-virus-sense S segment. The present study determined the 3' termini of all RVFV mRNAs. The 3' termini of N and NSs mRNAs were mapped within the S-segment intergenic region and were complementary to each other by 30 to 60 nucleotides. The termini of M and L mRNAs were mapped within 122 to 107 nucleotides and 16 to 41 nucleotides, respectively, from the 5' ends of their templates. Viral RNA elements that control phlebovirus transcriptional terminations are largely unknown. Our studies suggested the importance of a pentanucleotide sequence, CGUCG, for N, NSs, and M mRNA transcription terminations. Homopolymeric tracts of C sequences, which were located upstream of the pentanucleotide sequence, promoted N and M mRNA terminations. Likewise, the homopolymeric tracts of G sequences that are found upstream of the pentanucleotide sequence promoted NSs mRNA termination. The L-segment 5'-untranslated region (L-5' UTR) had neither the pentanucleotide sequence nor homopolymeric sequences, yet replacement of the S-segment intergenic region with the L-5' UTR exerted N mRNA termination in an infectious virus. The L-5' UTR contained two 13-nucleotide-long complete complementary sequences, and their sequence complementarities were important for L mRNA termination. A computer-mediated RNA secondary structure analysis further suggested that RNA secondary structures formed by the sections of the two 13-nucleotide-long sequences and by the sequence between them may have a role in L mRNA termination. Our data demonstrated that viral RNA elements that govern L mRNA termination differed from those that regulate mRNA terminations in the M and S segments.
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Affiliation(s)
- Tetsuro Ikegami
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1019, USA.
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41
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Bird BH, Khristova ML, Rollin PE, Ksiazek TG, Nichol ST. Complete genome analysis of 33 ecologically and biologically diverse Rift Valley fever virus strains reveals widespread virus movement and low genetic diversity due to recent common ancestry. J Virol 2007; 81:2805-16. [PMID: 17192303 PMCID: PMC1865992 DOI: 10.1128/jvi.02095-06] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Accepted: 12/18/2006] [Indexed: 11/20/2022] Open
Abstract
Rift Valley fever (RVF) virus is a mosquito-borne RNA virus responsible for large explosive outbreaks of acute febrile disease in humans and livestock in Africa with significant mortality and economic impact. The successful high-throughput generation of the complete genome sequence was achieved for 33 diverse RVF virus strains collected from throughout Africa and Saudi Arabia from 1944 to 2000, including strains differing in pathogenicity in disease models. While several distinct virus genetic lineages were determined, which approximately correlate with geographic origin, multiple exceptions indicative of long-distance virus movement have been found. Virus strains isolated within an epidemic (e.g., Mauritania, 1987, or Egypt, 1977 to 1978) exhibit little diversity, while those in enzootic settings (e.g., 1970s Zimbabwe) can be highly diverse. In addition, the large Saudi Arabian RVF outbreak in 2000 appears to have involved virus introduction from East Africa, based on the close ancestral relationship of a 1998 East African virus. Virus genetic diversity was low (approximately 5%) and primarily involved accumulation of mutations at an average of 2.9 x 10(-4) substitutions/site/year, although some evidence of RNA segment reassortment was found. Bayesian analysis of current RVF virus genetic diversity places the most recent common ancestor of these viruses in the late 1800s, the colonial period in Africa, a time of dramatic changes in agricultural practices and introduction of nonindigenous livestock breeds. In addition to insights into the evolution and ecology of RVF virus, these genomic data also provide a foundation for the design of molecular detection assays and prototype vaccines useful in combating this important disease.
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Affiliation(s)
- Brian H Bird
- Special Pathogens Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road MS G-14, Atlanta, GA 30329, USA
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Sall AA, Zanotto PM, Sene OK, Zeller HG, Digoutte JP, Thiongane Y, Bouloy M. Genetic reassortment of Rift Valley fever virus in nature. J Virol 1999; 73:8196-200. [PMID: 10482570 PMCID: PMC112837 DOI: 10.1128/jvi.73.10.8196-8200.1999] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/1999] [Accepted: 07/15/1999] [Indexed: 11/20/2022] Open
Abstract
Rift Valley fever virus (RVFV), a phlebovirus of the Bunyaviridae family, is an arthropod-borne virus which emerges periodically throughout Africa, emphasizing that it poses a major threat for animal and human populations. To assess the genetic variability of RVFV, several isolates from diverse localities of Africa were investigated by means of reverse transcription-PCR followed by direct sequencing of a region of the small (S), medium (M), and large (L) genomic segments. Phylogenetic analysis showed the existence of three major lineages corresponding to geographic variants from West Africa, Egypt, and Central-East Africa. However, incongruences detected between the L, M, and S phylogenies suggested that genetic exchange via reassortment occurred between strains from different lineages. This hypothesis, depicted by parallel phylogenies, was further confirmed by statistical tests. Our findings, which strongly suggest exchanges between strains from areas of endemicity in West and East Africa, strengthen the potential existence of a sylvatic cycle in the tropical rain forest. This also emphasizes the risk of generating uncontrolled chimeric viruses by using live attenuated vaccines in areas of endemicity.
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Affiliation(s)
- A A Sall
- Institut Pasteur de Dakar, Dakar, Senegal
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43
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Pittman PR, Liu CT, Cannon TL, Makuch RS, Mangiafico JA, Gibbs PH, Peters CJ. Immunogenicity of an inactivated Rift Valley fever vaccine in humans: a 12-year experience. Vaccine 1999; 18:181-9. [PMID: 10501248 DOI: 10.1016/s0264-410x(99)00218-2] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Rift Valley fever (RVF) virus causes serious and fatal disease in animals and man. To protect personnel who work with RVF virus in the laboratory, or troops who may be exposed to this virus, the US Army successfully developed an improved version of inactivated RVF vaccine, TSI-GSD-200. From early 1986 to late 1997, 598 at-risk workers at the US Army Medical Research Institute of Infectious Diseases (USAMRIID) were vaccinated as part of an occupational safety and health program. The subjects of this study received three subcutaneous doses (0, 7 and 28 days) of 0.5 ml of TSI-GSD-200. A total of 540 vaccinees (90.3%) initially responded (group A) with an 80% plaque-reduction neutralization antibody titer (PRNT80) of > or =1:40; whereas 58 subjects (9.7%) were initial nonresponders (group B) failing to achieve this titer. Volunteers who either failed to respond or who achieved a titer of > or =1:40 but whose titer waned below 1:40 were boosted 1-4 times with the same vaccine. Among 247 group A subjects who received the first recall injection, 242 (98%) were successfully boosted, achieving a PRNT80 > or =1:40. Thirty-three of 44 (75%) initial nonresponders were converted to responder status after the first booster, which is a lower rate than that of group A (P < 0.001). After the primary series and the first booster, Kaplan-Meier analysis showed 50% probability of group A members maintaining a titer of > or =1:40 for approximately eight years; whereas group B had a 50% probability of maintaining a titer for only 204 days. Group A immune response rates to boosts 1-4 ranged from 87 to 100% with geometric mean titers (GMTs) ranging from 80 to 916. Boosts 1-4 immune response rates of group B volunteers ranged from 67 to 79% with GMTs ranging from 90 to 177. Minor side effects to TSI-GSD-200 were noted in 2.7% of all vaccinees after primaries and 3.5% of all vaccinees who had primaries and up to four boosters. We conclude that the use of TSI-GSD-200 is safe and provides good long-term immunity in humans when the primary series and one boost are administered.
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Affiliation(s)
- P R Pittman
- Division of Medicine, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, USA
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44
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Sall AA, Zanotto PM, Vialat P, Sène OK, Bouloy M. Molecular epidemiology and emergence of Rift Valley fever. Mem Inst Oswaldo Cruz 1998; 93:609-14. [PMID: 9830526 DOI: 10.1590/s0074-02761998000500009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rift Valley fever (RVF) is a mosquito-borne viral disease which manifested itself during recent epidemics and revealed its significant potential of emergence. Studies on molecular epidemiology undertaken to better understand the factors leading to RVF emergence, have confirmed the mode of circulation of the virus and highlighted probable risks and obstacles for prevention and control. As for several other viral agents, molecular epidemiology is becoming a useful tool in the study of the emergence of RVF as a serious infectious disease.
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Affiliation(s)
- A A Sall
- Institut Pasteur de Dakar, Senegal.
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