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Bursali F, Touray M. The complexities of blood-feeding patterns in mosquitoes and sandflies and the burden of disease: A minireview. Vet Med Sci 2024; 10:e1580. [PMID: 39171609 PMCID: PMC11339650 DOI: 10.1002/vms3.1580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Accepted: 07/26/2024] [Indexed: 08/23/2024] Open
Abstract
Mosquitoes and sandflies exhibit a wide range of blood feeding patterns, targeting a wide range of vertebrate species, including birds, mammals, reptiles, and amphibians, for proteins vital for egg development. This broad host range increases the opportunity for them to acquire pathogens of numerous debilitating-and-fatal diseases from various animal reservoirs, playing a significant role in disease crossover between animals and humans, also known as zoonotic transmission. This review focuses on the intricate blood-feeding habits of these dipteran vectors, their sensory systems and the complex dance between host and pathogen during disease transmission. We delve into the influence of blood sources on pathogen spread by examining the insect immune response and its intricate interplay with pathogens. The remarkable sense of smell guiding them towards food sources and hosts is explored, highlighting the interplay of multiple sensory cues in their navigation. Finally, we examine the challenges in mosquito control strategies and explore innovations in this field, emphasizing the need for sustainable solutions to combat this global health threat. By understanding the biology and behaviour of these insects, we can develop more effective strategies to protect ourselves and mitigate the burden of vector-borne diseases.
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Affiliation(s)
- Fatma Bursali
- Biology Department, Faculty of ScienceAydin Adnan Menderes UniversityAydinTürkiye
| | - Mustapha Touray
- Biology Department, Faculty of ScienceAydin Adnan Menderes UniversityAydinTürkiye
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Livestock and rodents within an endemic focus of Visceral Leishmaniasis are not reservoir hosts for Leishmania donovani. PLoS Negl Trop Dis 2022; 16:e0010347. [PMID: 36264975 PMCID: PMC9624431 DOI: 10.1371/journal.pntd.0010347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 11/01/2022] [Accepted: 10/12/2022] [Indexed: 11/23/2022] Open
Abstract
Leishmaniasis on the Indian subcontinent is thought to have an anthroponotic transmission cycle. There is no direct evidence that a mammalian host other than humans can be infected with Leishmania donovani and transmit infection to the sand fly vector. The aim of the present study was to evaluate the impact of sand fly feeding on other domestic species and provide clinical evidence regarding possible non-human reservoirs through experimental sand fly feeding on cows, water buffalo goats and rodents. We performed xenodiagnosis using colonized Phlebotomus argentipes sand flies to feed on animals residing in villages with active Leishmania transmission based on current human cases. Xenodiagnoses on mammals within the endemic area were performed and blood-fed flies were analyzed for the presence of Leishmania via qPCR 48hrs after feeding. Blood samples were also collected from these mammals for qPCR and serology. Although we found evidence of Leishmania infection within some domestic mammals, they were not infectious to vector sand flies. Monitoring infection in sand flies and non-human blood meal sources in endemic villages leads to scientific proof of exposure and parasitemia in resident mammals. Lack of infectiousness of these domestic mammals to vector sand flies indicates that they likely play no role, or a very limited role in Leishmania donovani transmission to people in Bihar. Therefore, a surveillance system in the peri-/post-elimination phase of visceral leishmaniasis (VL) must monitor absence of transmission. Continued surveillance of domestic mammals in outbreak villages is necessary to ensure that a non-human reservoir is not established, including domestic mammals not present in this study, specifically dogs.
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Carvalho Cabral P, Tekade K, Stegeman SK, Olivier M, Cermakian N. The involvement of host circadian clocks in the regulation of the immune response to parasitic infections in mammals. Parasite Immunol 2021; 44:e12903. [PMID: 34964129 DOI: 10.1111/pim.12903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/21/2021] [Accepted: 12/24/2021] [Indexed: 11/29/2022]
Abstract
Circadian rhythms are recurring variations of physiology with a period of ~24 hours, generated by circadian clocks located throughout the body. Studies have shown a circadian regulation of many aspects of immunity. Immune cells have intrinsic clock mechanisms, and innate and adaptive immune responses - such as leukocyte migration, magnitude of inflammation, cytokine production and cell differentiation - are under circadian control. This circadian regulation has consequences for infections including parasitic infections. In the context of Leishmania infection, the circadian clock within host immune cells modulates the magnitude of the infection and the inflammatory response triggered by the parasite. As for malaria, rhythms within the immune system were shown to impact the developmental cycles of Plasmodium parasites within red blood cells. Further, host circadian rhythms impact infections by multicellular parasites; for example, infection with helminth Trichuris muris shows different kinetics of worm expulsion depending on time of day of infection, a variation that depends on the dendritic cell clock. Although the research on the circadian control of immunity in the context of parasitic infections is in its infancy, the research reviewed here suggests a crucial involvement of host circadian rhythms in immunity on the development and progression of parasitic infections.
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Affiliation(s)
| | - Kimaya Tekade
- Douglas Research Centre, McGill University, Montreal, QC, H4H 1R3, Canada
| | - Sophia K Stegeman
- Douglas Research Centre, McGill University, Montreal, QC, H4H 1R3, Canada
| | - Martin Olivier
- Research Institute of the McGill University Health Center, McGill University, Montreal, QC, H4A 3J1, Canada
| | - Nicolas Cermakian
- Douglas Research Centre, McGill University, Montreal, QC, H4H 1R3, Canada
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Trájer AJ. The potential impact of climate change on the seasonality of Phlebotomus neglectus, the vector of visceral leishmaniasis in the East Mediterranean region. INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 2021; 31:932-950. [PMID: 31859534 DOI: 10.1080/09603123.2019.1702150] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 12/04/2019] [Indexed: 06/10/2023]
Abstract
Phlebotomus neglectus is one of the most important vectors of visceral leishmaniasis in Southeast Europe and Asia Minor. It was aimed to study the impact of climate change on the seasonality and the range of the species for 2014-2060. In the inland areas of Asia Minor, the Balkan Peninsula and the Carpathian Basin the elongation of the activity season will reach or exceed the two months in the middle of the 21st century compared to the end of the 20th century. The most affected regions are the middle elevations of the mountainous regions and the plains of the northern distribution areas. In some areas of the southern distribution border, the season is expected to shorten. In the Apennine Peninsula, mainly the mountainous areas could be impacted notably by climate change. The results indicate the potential spread of leishmaniasis in Southeast Europe due to the increasing environmental suitability of the region.
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Deb R, Singh RP, Mishra PK, Hitchins L, Reid E, Barwa AM, Patra D, Das C, Sukla I, Srivastava AK, Raj S, Mishra S, Swain M, Mondal S, Mandal U, Foster GM, Trett A, Garrod G, McKenzie L, Ali A, Morchan K, Chaudhuri I, Roy N, Gill NK, Singh C, Agarwal N, Sharma S, Stanton MC, Hemingway J, Srikantiah S, Coleman M. Impact of IRS: Four-years of entomological surveillance of the Indian Visceral Leishmaniases elimination programme. PLoS Negl Trop Dis 2021; 15:e0009101. [PMID: 34370731 PMCID: PMC8376195 DOI: 10.1371/journal.pntd.0009101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 08/19/2021] [Accepted: 07/01/2021] [Indexed: 11/18/2022] Open
Abstract
Background In 2005, Bangladesh, India and Nepal agreed to eliminate visceral leishmaniasis (VL) as a public health problem. The approach to this was through improved case detection and treatment, and controlling transmission by the sand fly vector Phlebotomus argentipes, with indoor residual spraying (IRS) of insecticide. Initially, India applied DDT with stirrup pumps for IRS, however, this did not reduce transmission. After 2015 onwards, the pyrethroid alpha-cypermethrin was applied with compression pumps, and entomological surveillance was initiated in 2016. Methods Eight sentinel sites were established in the Indian states of Bihar, Jharkhand and West Bengal. IRS coverage was monitored by household survey, quality of insecticide application was measured by HPLC, presence and abundance of the VL vector was monitored by CDC light traps, insecticide resistance was measured with WHO diagnostic assays and case incidence was determined from the VL case register KAMIS. Results Complete treatment of houses with IRS increased across all sites from 57% in 2016 to 70% of houses in 2019, rising to >80% if partial house IRS coverage is included (except West Bengal). The quality of insecticide application has improved compared to previous studies, average doses of insecticide on filters papers ranged from 1.52 times the target dose of 25mg/m2 alpha-cypermethrin in 2019 to 1.67 times in 2018. Resistance to DDT has continued to increase, but the vector was not resistant to carbamates, organophosphates or pyrethroids. The annual and seasonal abundance of P. argentipes declined between 2016 to 2019 with an overall infection rate of 0.03%. This was associated with a decline in VL incidence for the blocks represented by the sentinel sites from 1.16 per 10,000 population in 2016 to 0.51 per 10,000 in 2019. Conclusion Through effective case detection and management reducing the infection reservoirs for P. argentipes in the human population combined with IRS keeping P. argentipes abundance and infectivity low has reduced VL transmission. This combination of effective case management and vector control has now brought India within reach of the VL elimination targets. Visceral Leishmaniasis (VL), also known as kala-azar, is a major parasitic disease in South Asia (Indian subcontinent), with 85% of the disease incidence in India. Historically VL had been controlled and almost eliminated with Indoor Residual Spraying (IRS) using dichlorodiphenyltrichloroethane (DDT). However, reinitiating this approach in 2015 failed due to high insecticide resistance in the sand fly vector and poor IRS quality, meaning that VL elimination targets were not met. To improve this the National Vector Borne Disease Control Programme changed to an effective insecticide, alpha-cypermethrin and altered the mode of application to compression pumps. Sentinel sites were established to monitor the entomological indicators, these showed the positive impact of these changes from 2016 to 2019. During this period the overall incidence of disease has decreased, and India is now on track to reach it’s target incidence for VL of less than 1/1000 people at the sub-district (block) level.
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Affiliation(s)
- Rinki Deb
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | | | | | - Lisa Hitchins
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Emma Reid
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | | - Anna Trett
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Gala Garrod
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Laura McKenzie
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | | | | | | | - Nupur Roy
- National Vector Borne Disease Control Programme, Directorate General of Health Services, Ministry of Health and Family Welfare, Delhi, India
| | - Naresh K. Gill
- National Vector Borne Disease Control Programme, Directorate General of Health Services, Ministry of Health and Family Welfare, Delhi, India
| | | | | | | | | | - Janet Hemingway
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | | | - Michael Coleman
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- * E-mail:
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Fortunato AK, Glasser CP, Watson JA, Lu Y, Rychtář J, Taylor D. Mathematical modelling of the use of insecticide-treated nets for elimination of visceral leishmaniasis in Bihar, India. ROYAL SOCIETY OPEN SCIENCE 2021; 8:201960. [PMID: 34234949 PMCID: PMC8242840 DOI: 10.1098/rsos.201960] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 05/24/2021] [Indexed: 05/27/2023]
Abstract
Visceral leishmaniasis (VL) is a deadly neglected tropical disease caused by a parasite Leishmania donovani and spread by female sand flies Phlebotomus argentipes. There is conflicting evidence regarding the role of insecticide-treated nets (ITNs) on the prevention of VL. Numerous studies demonstrated the effectiveness of ITNs. However, KalaNet, a large trial in Nepal and India did not support those findings. The purpose of this paper is to gain insight into the situation by mathematical modelling. We expand a mathematical model of VL transmission based on the KalaNet trial and incorporate the use of ITNs explicitly into the model. One of the major contributions of this work is that we calibrate the model based on the available epidemiological data, generally independent of the KalaNet trial. We validate the model on data collected during the KalaNet trial. We conclude that in order to eliminate VL, the ITN usage would have to stay above 96%. This is higher than the 91% ITNs use at the end of the trial which may explain why the trial did not show a positive effect from ITNs. At the same time, our model indicates that asymptomatic individuals play a crucial role in VL transmission.
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Affiliation(s)
- Anna K. Fortunato
- Department of Mathematics, University of Richmond, Richmond, VA 23173, USA
| | - Casey P. Glasser
- Department of Mathematics, Virginia Tech, Blacksburg, VA 24061-1026, USA
| | - Joy A. Watson
- Department of Mathematics and Economics, Virginia State University, Petersburg, VA 23806, USA
| | - Yongjin Lu
- Department of Mathematics and Economics, Virginia State University, Petersburg, VA 23806, USA
| | - Jan Rychtář
- Department of Mathematics and Applied Mathematics, Virginia Commonwealth University, Richmond, VA 23284-2014, USA
| | - Dewey Taylor
- Department of Mathematics and Applied Mathematics, Virginia Commonwealth University, Richmond, VA 23284-2014, USA
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Priyamvada K, Bindroo J, Sharma MP, Chapman LAC, Dubey P, Mahapatra T, Hightower AW, Bern C, Srikantiah S. Visceral leishmaniasis outbreaks in Bihar: community-level investigations in the context of elimination of kala-azar as a public health problem. Parasit Vectors 2021; 14:52. [PMID: 33451361 PMCID: PMC7810196 DOI: 10.1186/s13071-020-04551-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 12/13/2020] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND With visceral leishmaniasis (VL) incidence at its lowest level since the 1960s, increasing attention has turned to early detection and investigation of outbreaks. METHODS Outbreak investigations were triggered by recognition of case clusters in the VL surveillance system established for the elimination program. Investigations included ascertainment of all VL cases by date of fever onset, household mapping and structured collection of risk factor data. RESULTS VL outbreaks were investigated in 13 villages in 10 blocks of 7 districts. Data were collected for 20,670 individuals, of whom 272 were diagnosed with VL between 2012 and 2019. Risk was significantly higher among 10-19 year-olds and adults 35 or older compared to children younger than 10 years. Outbreak confirmation triggered vector control activities and heightened surveillance. VL cases strongly clustered in tolas (hamlets within villages) in which > 66% of residents self-identified as scheduled caste or scheduled tribe (SC/ST); 79.8% of VL cases occurred in SC/ST tolas whereas only 24.2% of the population resided in them. Other significant risk factors included being an unskilled non-agricultural laborer, migration for work in a brick kiln, living in a kuccha (mud brick) house, household crowding, habitually sleeping outside or on the ground, and open defecation. CONCLUSIONS Our data highlight the importance of sensitive surveillance with triggers for case cluster detection and rapid, careful outbreak investigations to better respond to ongoing and new transmission. The strong association with SC/ST tolas suggests that efforts should focus on enhanced surveillance in these disadvantaged communities.
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Affiliation(s)
| | - Joy Bindroo
- CARE-India Solutions for Sustainable Development, Patna, India
| | | | - Lloyd A C Chapman
- Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Pushkar Dubey
- CARE-India Solutions for Sustainable Development, Patna, India
| | | | | | - Caryn Bern
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA.
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Sardar AA, Chatterjee M, Jana K, Saha P, Maji AK, Guha SK, Kundu PK. Seasonal variation of sand fly populations in Kala-azar endemic areas of the Malda district, West Bengal, India. Acta Trop 2020; 204:105358. [PMID: 31987778 DOI: 10.1016/j.actatropica.2020.105358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 01/06/2020] [Accepted: 01/23/2020] [Indexed: 01/19/2023]
Abstract
Vector control is one of the main aspects to reach the target of eliminating visceral leishmaniasis from Indian sub-continent as set by the World Health Organisation. Data on different aspects of vector like ecology, behaviour, population dynamics and their association with environmental factors are very important for formulating an effective vector control strategy. The present work was designed to study the species abundance and impact of environmental factors on population dynamics of vector P. argentipes in a visceral leishmaniasis endemic area of Malda district, West Bengal. Adult sand flies were collected using light traps and mouth aspirators from twelve kala-azar affected villages of Habibpur block of Malda district, on a monthly basis from January to December, 2018. Morphological and molecular methods were used for species identification. Population dynamics were assessed by man hour density and per night per trap collection. Data were analysed using SPSS software to determine the impact of environmental factors on vector population P. argentipes was found to the predominant species and prevalent throughout the year. A significantly higher number of sand flies were collected from cattle sheds than human dwellings and peri-domestic vegetation. A portion of the P. argentipes population was exophilic and exophagic as evidenced by their collection from peri-domestic vegetation. The highest population density was recorded during April to September. Population dynamics were mostly influenced by average temperature along humidity and rain fall. Resting behaviour of sand flies was not restricted to the lower portion of the wall but equally distributed throughout the wall and ceiling. Programme officials should consider management of outdoor populations of the sand flies and timings of indoor residual spray for chemical control purpose.
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Affiliation(s)
- Ashif Ali Sardar
- Department of Microbiology, Calcutta School of Tropical Medicine, Kolkata, West Bengal, India.
| | - Moytrey Chatterjee
- Department of Microbiology, Calcutta School of Tropical Medicine, Kolkata, West Bengal, India.
| | - Kingsuk Jana
- Department of Microbiology, Calcutta School of Tropical Medicine, Kolkata, West Bengal, India.
| | - Pabitra Saha
- Department of Microbiology, Calcutta School of Tropical Medicine, Kolkata, West Bengal, India; Department of Zoology, A. P. C. Roy Govt. College, Himachal Bihar, Matigara, Siliguri, West Bengal, India.
| | - Ardhendu Kumar Maji
- Department of Microbiology, Calcutta School of Tropical Medicine, Kolkata, West Bengal, India.
| | - Subhasish Kamal Guha
- Department of Tropical Medicine, Calcutta School of Tropical Medicine, Kolkata, West Bengal, India.
| | - Pratip Kumar Kundu
- Department of Microbiology, Calcutta School of Tropical Medicine, Kolkata, West Bengal, India.
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Salah I, Abbasi I, Warburg A, Davidovitch N, Kotler B. The spatial and temporal distribution, species composition, and host preference of phlebotomine sand flies in the Bethlehem District of Palestine. Acta Trop 2020; 203:105327. [PMID: 31899169 DOI: 10.1016/j.actatropica.2019.105327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 12/30/2019] [Accepted: 12/30/2019] [Indexed: 11/24/2022]
Abstract
In the Palestinian West Bank, leishmaniasis is emerging as a serious public health issue with incidence increasing over time, especially in the western and the northern parts. This study was aimed to evaluating the effect of altitude on sand fly density, temporal and spatial distribution, species composition, and host preference within and between three villages in the Bethlehem District. The three villages occur along an elevation cline, ranging from the disease-free area of Kisan (KIS; 732-782 m ASL), down to the endemic areas of Arab Ar-Rashaiyda (AAR; 522-568 m ASL), and Al'Azazma (AZA; 473-510 m ASL) in the Bethlehem District (southeastern West Bank). Sand flies were trapped monthly from May through October in 2013 in traps located north, south, east, and west of each village. The abundance of sand flies differed among the three villages, with Arab Ar-Rashaiyda (AAR) > Al 'Azazma (AZA) >Kisan (KIS). The sex ratio was even in AAR and AZA, and female biased in KIS. Both male and female Phlebotomus sand fly densities varied with elevation, with greatest densities found at intermediate elevations (AAR). Elevation correlated negatively with the proportion of blood-fed Phlebotomus females. Male Phlebotomus species composition differed among sites, with all the species found in this study present in AZA, while some species were absent from AAR and KIS. The host blood species engorged by P. sergenti were grouped in four categories: human (45.5%), livestock (25%), avian (19.9%), and dog (9.6%). This study provided information about the spatial and temporal distribution, age and species composition, and host preference of sand fly vectors that influence disease transmission. This information will allow us to better target sand flies, to control the disease, and to monitor risk prone areas.
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Bhunia GS, Shit PK. Introduction of Visceral Leishmaniasis (Kala-azar). SPATIAL MAPPING AND MODELLING FOR KALA-AZAR DISEASE 2020. [DOI: 10.1007/978-3-030-41227-2_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Calderon-Anyosa R, Galvez-Petzoldt C, Garcia PJ, Carcamo CP. Housing Characteristics and Leishmaniasis: A Systematic Review. Am J Trop Med Hyg 2019; 99:1547-1554. [PMID: 30382013 DOI: 10.4269/ajtmh.18-0037] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Leishmaniasis is a major neglected tropical disease associated with high rates of disability and death. This disease is associated with poverty, which can be reflected in housing quality, especially in rural areas. This systematic review found that mud walls with cracks and holes, damp, and dark houses were risk factors for transmission of leishmaniasis. These characteristics create favorable conditions for sand fly breeding and resting as sand flies prefer humidity, warmth, and protection from sunlight during the day. Housing interventions might be a promising research area with a special focus on education as individual and collective protection for the effective control of leishmaniasis.
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Affiliation(s)
- Renzo Calderon-Anyosa
- Kuskaya Program, School of Public Health and Administration, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Camila Galvez-Petzoldt
- Kuskaya Program, School of Public Health and Administration, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Patricia J Garcia
- Kuskaya Program, School of Public Health and Administration, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Cesar P Carcamo
- Kuskaya Program, School of Public Health and Administration, Universidad Peruana Cayetano Heredia, Lima, Peru
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Yared S, Gebresilassie A, Abbasi I, Aklilu E, Kirstein OD, Balkew M, Brown AS, Clouse RM, Warburg A, Hailu A, Gebre-Michael T. A molecular analysis of sand fly blood meals in a visceral leishmaniasis endemic region of northwestern Ethiopia reveals a complex host-vector system. Heliyon 2019; 5:e02132. [PMID: 31384683 PMCID: PMC6661399 DOI: 10.1016/j.heliyon.2019.e02132] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 05/01/2019] [Accepted: 07/18/2019] [Indexed: 11/04/2022] Open
Abstract
Background Visceral leishmaniasis (VL, or “kala-azar”) is a major cause of disability and death, especially in East Africa. Its vectors, sand flies (Diptera: Psychodidae: Phlebotominae), are poorly controlled and guarded against in these regions, owing in part to a lack of understanding about their feeding behavior. Methods A total of 746 freshly fed female sand flies were collected in five population centers in Kafta Humera (northwestern Ethiopia), where VL is endemic. Flies were collected from habitats that ranged from inside houses to open fields, using light traps and sticky traps. Sources of sand fly blood meals were identified using enzyme-linked immunosorbent assays (ELISA) and DNA amplification with reverse-line blot analysis (PCR-RLB); 632 specimens were screened using ELISA, 408 of which had identifiable blood meals, and 114 were screened using PCR-RLB, 53 of which yielded identifications. Fly species determinations were based on morphology, and those specimens subjected to PCR-RLB were also screened for Leishmania parasites using conventional PCR to amplify the nuclear marker ITS1 (internal transcribed spacer 1) with Leishmania-specific primers. Results More than three-fourths of all sand flies collected were Phlebotomus orientalis, and the remaining portion was comprised of nine other species. Nearly two-thirds of P. orientalis specimens were collected at village peripheries. The most common blood source for all flies was donkey (33.9% of all identifications), followed by cow (24.2%), human (17.6%), dog (11.8%), and goat or sheep (8.6%); mixtures of blood meals from different sources were found in 28.2% of all flies screened. Unidentified blood meals, presumably from wildlife, not domestic animals, were significantly higher in farm fields. Leishmania parasites were not detected in any of the 114 flies screened, not surprising given an expected infection rate of 1–5 out of 1,000. Meals that included a mixture of human and cow blood were significantly more frequent relative to all cow meals than human blood meals were to non-cow meals, suggesting a zoopotentiative interaction between cows and humans in this system. Conclusions Habitat and host preferences of sand fly vectors in Kafta Humera confirmed the finding of previous reports that the main vector in the region, Phlebotomus orientalis, is a highly opportunistic feeder that prefers large animals and is most commonly found at village peripheries. These results were similar to those of a previous study conducted in a nearby region (Tahtay Adiabo), except for the role of cattle on the prevalence of human blood meals. Preliminary examinations of blood meal data from different settings point to the need for additional surveys and field experiments to understand the role of livestock on biting risks.
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Affiliation(s)
- Solomon Yared
- Department of Biology, Jigjiga University, Jigjiga, Ethiopia
| | - Araya Gebresilassie
- Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Ibrahim Abbasi
- The Kuvin Center for the Study of Infectious and Tropical Diseases, Institute for Medical Research, The Hebrew University, Israel
| | - Essayas Aklilu
- Department of Biology, Mada Walabu University, Bale-Robe, Ethiopia
| | - Oscar D Kirstein
- The Kuvin Center for the Study of Infectious and Tropical Diseases, Institute for Medical Research, The Hebrew University, Israel
| | - Meshesha Balkew
- President's Malaria Initiative (PMI) Vector Link Project, Ethiopia
| | - Adam S Brown
- Harvard University, Department of Biomedical Informatics, Boston, MA, United States
| | - Ronald M Clouse
- American Museum of Natural History, New York, NY, United States
| | - Alon Warburg
- The Kuvin Center for the Study of Infectious and Tropical Diseases, Institute for Medical Research, The Hebrew University, Israel
| | - Asrat Hailu
- Department of Microbiology, Immunology & Parasitology, School of Medicine; Addis Ababa University, Addis Ababa, Ethiopia
| | - Teshome Gebre-Michael
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
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13
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Chapman LAC, Jewell CP, Spencer SEF, Pellis L, Datta S, Chowdhury R, Bern C, Medley GF, Hollingsworth TD. The role of case proximity in transmission of visceral leishmaniasis in a highly endemic village in Bangladesh. PLoS Negl Trop Dis 2018; 12:e0006453. [PMID: 30296295 PMCID: PMC6175508 DOI: 10.1371/journal.pntd.0006453] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 04/13/2018] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Visceral leishmaniasis (VL) is characterised by a high degree of spatial clustering at all scales, and this feature remains even with successful control measures. VL is targeted for elimination as a public health problem in the Indian subcontinent by 2020, and incidence has been falling rapidly since 2011. Current control is based on early diagnosis and treatment of clinical cases, and blanket indoor residual spraying of insecticide (IRS) in endemic villages to kill the sandfly vectors. Spatially targeting active case detection and/or IRS to higher risk areas would greatly reduce costs of control, but its effectiveness as a control strategy is unknown. The effectiveness depends on two key unknowns: how quickly transmission risk decreases with distance from a VL case and how much asymptomatically infected individuals contribute to transmission. METHODOLOGY/PRINCIPAL FINDINGS To estimate these key parameters, a spatiotemporal transmission model for VL was developed and fitted to geo-located epidemiological data on 2494 individuals from a highly endemic village in Mymensingh, Bangladesh. A Bayesian inference framework that could account for the unknown infection times of the VL cases, and missing symptom onset and recovery times, was developed to perform the parameter estimation. The parameter estimates obtained suggest that, in a highly endemic setting, VL risk decreases relatively quickly with distance from a case-halving within 90m-and that VL cases contribute significantly more to transmission than asymptomatic individuals. CONCLUSIONS/SIGNIFICANCE These results suggest that spatially-targeted interventions may be effective for limiting transmission. However, the extent to which spatial transmission patterns and the asymptomatic contribution vary with VL endemicity and over time is uncertain. In any event, interventions would need to be performed promptly and in a large radius (≥300m) around a new case to reduce transmission risk.
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Affiliation(s)
- Lloyd A. C. Chapman
- Zeeman Institute, University of Warwick, Coventry, UK
- School of Life Sciences, University of Warwick, Coventry, UK
- Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Chris P. Jewell
- Centre for Health Informatics, Computing And Statistics, Lancaster University, Lancaster, UK
| | - Simon E. F. Spencer
- Zeeman Institute, University of Warwick, Coventry, UK
- Department of Statistics, University of Warwick, Coventry, UK
| | | | - Samik Datta
- Zeeman Institute, University of Warwick, Coventry, UK
- National Institute of Water and Atmospheric Research, Wellington, New Zealand
| | - Rajib Chowdhury
- National Institute of Preventive and Social Medicine (NIPSOM), Mohakhali, Dhaka, Bangladesh
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh
| | - Caryn Bern
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California, USA
| | - Graham F. Medley
- Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - T. Déirdre Hollingsworth
- Zeeman Institute, University of Warwick, Coventry, UK
- School of Life Sciences, University of Warwick, Coventry, UK
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
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Jaturas N, Vitta A, Samung Y, Apiwathnasorn C, Polseela R. Species composition and nocturnal activity of phlebotomine sand flies (Diptera: Psychodidae) inhabiting a limestone cave in Thailand. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2018; 43:52-58. [PMID: 29757516 DOI: 10.1111/jvec.12282] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 10/09/2017] [Indexed: 06/08/2023]
Abstract
We investigated the nocturnal activity of cave-dwelling sand flies at different time intervals and determined their species composition and seasonal variation. Sand flies were captured on one night each month using CDC light traps from 18:00-06:00 with the collecting bag being changed every two h between February, 2010 and January, 2011. A total of 18,709 individuals, including 10,740 males and 7,969 females, was collected. The overall ratio between male and female specimens was 1:0.74. The collected specimens included 14 species from four genera, Chinius, Idiophlebotomus, Phlebotomus, and Sergentomyia. Sergentomyia phadangensis was the most abundant species (comprising 31.9% of the collected individuals), followed by Se. anodontis (22.8%) and Ph. mascomai (18.2%). The highest number of specimens was collected in July (15.6%), followed by May (15.5%) with the peak of collection recorded at the time interval of 00:01-02:00, followed by 22:01-00:00. However, there were no significant differences observed among time intervals of sand fly collections (p=0.154). Observations of the nocturnal activity of male and female sand flies throughout the night suggest that phlebotomine sand flies show the greatest activity level after midnight.
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Affiliation(s)
- Narong Jaturas
- Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
- Medical Science Academic Service Centre, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
| | - Apichat Vitta
- Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
- Centre of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
| | - Yudthana Samung
- Centre of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
| | - Chamnarn Apiwathnasorn
- Centre of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
- Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Raxsina Polseela
- Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
- Centre of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
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Deb RM, Stanton MC, Foster GM, Das Gupta RK, Roy N, Das P, Dhariwal AC, Coleman M. Visceral leishmaniasis cyclical trends in Bihar, India - implications for the elimination programme. Gates Open Res 2018; 2:10. [PMID: 30234191 PMCID: PMC6139379 DOI: 10.12688/gatesopenres.12793.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/14/2018] [Indexed: 11/20/2022] Open
Abstract
Background: Visceral leishmaniasis (VL) is a vector-borne disease of public health importance in India, with the highest burden of disease in the states of Bihar, Jharkhand, West Bengal and Uttar Pradesh. The disease is currently targeted for elimination (annual incidence to less than one per 10,000 population) using indoor residual spraying, active case detection and treatment. Historically the disease trend in India has been regarded as cyclical with case resurgence characteristically occurring every 15 years. Understanding this pattern is essential if the VL elimination gains are to be sustained. To better understand the cyclical trends, annual climatic indicators including rainfall, temperature and humidity over time were compared with annual VL case incidence data. Methods: Annual climate data (rainfall, average and maximum temperature and specific humidity) from 1956-2004 were used to identify potential factors influencing VL incidence. Months relevant to the VL life-cycle were identified and defined (Monsoon, Sand-fly Peak, Pre-Sand-fly Peak and Annual) for analysis. The Kruskall-Wallis test was used to determine significant difference between categorical rainfall and VL incidence, whilst univariate negative binomial regression models were used to determine predictors of disease incidence. Results: The negative binomial regression model showed statistically significant associations (p <0.05) for VL incidence and maximum temperature, and average temperature, when considering annual and pre-sand fly peak time periods. No other associations between humidity, rainfall or temperature and VL incidence were detected (all values p >0.05). Conclusion: The VL programme in Bihar has made significant progress in adopting best practices for improved treatment and vector control, with the aim to achieve VL elimination. However, open access granular programme data for indoor residual spray activities and case detection is required to fully understand the role of climate in disease transmission and potential resurgence.
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Affiliation(s)
- Rinki M Deb
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Michelle C Stanton
- Faculty of Health and Medicine, Lancaster University, Lancaster, Lancashire , LA1 4YW, UK
| | - Geraldine M Foster
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Rudra K Das Gupta
- National Vector Borne Disease Control Programme, Directorate General of Health Services, Ministry of Health and Family Welfare, Delhi, 110054, India
| | - Nupur Roy
- National Vector Borne Disease Control Programme, Directorate General of Health Services, Ministry of Health and Family Welfare, Delhi, 110054, India
| | - Pradeep Das
- Rajendra Memorial Research Institute of Medical Sciences, Patna, Bihar, India
| | - Akshay C Dhariwal
- National Vector Borne Disease Control Programme, Directorate General of Health Services, Ministry of Health and Family Welfare, Delhi, 110054, India
| | - Michael Coleman
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
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Poché DM, Garlapati RB, Mukherjee S, Torres-Poché Z, Hasker E, Rahman T, Bharti A, Tripathi VP, Prakash S, Chaubey R, Poché RM. Bionomics of Phlebotomus argentipes in villages in Bihar, India with insights into efficacy of IRS-based control measures. PLoS Negl Trop Dis 2018; 12:e0006168. [PMID: 29324760 PMCID: PMC5764230 DOI: 10.1371/journal.pntd.0006168] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 12/15/2017] [Indexed: 11/23/2022] Open
Abstract
Background Visceral leishmaniasis (VL) is a deadly vector-borne disease. Approximately 90% of Indian VL cases occur in Bihar, where the sand fly, Phlebotomus argentipes, is the principal vector. Sand fly control in Bihar consists of indoor residual spraying (IRS), the practice of spraying the inner walls of village dwellings with insecticides. Prior researchers have evaluated success of IRS-control by estimating vector abundance in village houses, but the number of sampling periods (n = 2–3) were minimal, and outdoor-resting P. argentipes were neglected. We describe a large-scale field study, performed in 24 villages within two Bihari districts, during which P. argentipes were collected biweekly over 47-weeks, in cattle enclosures, houses, and outdoors in peri-domestic vegetation. The objectives of this study were to provide updated P. argentipes ecological field data, and determine if program-initiated IRS-treatment had led to noticeable differences in vector abundance. Principal findings P. argentipes (n = 126,901) relative abundance was greatest during the summer months (June-August) when minimum temperatures were highest. P. argentipes were most frequently collected from cattle enclosures (~46% total; ~56% blood fed). Many sand flies were found to have taken blood from multiple sources, with ~81% having blood fed on humans and ~60% blood feeding on bovines. Nonparametric statistical tests were determined most appropriate for evaluating IRS-treatment. Differences in P. argentipes abundance in houses, cattle enclosures and vegetation were detected between IRS-treated and untreated villages in only ~9% of evaluation periods occurring during the peak period of human-vector exposure (June-August) and in ~8% of the total observations. No significant differences were detected between the numbers of P. argentipes collected in vegetation close to the experimental villages. Conclusion The results of this study provide updated data regarding P. argentipes seasonal abundance, spatial distribution, and host preferances, and suggest vector abundance has not significantly declined in IRS-treated villages. We suggest that IRS be supplemented with vector control strategies targeting exophagic, exophilic P. argentipes, and that disease surveillance be accompanied by rigorous vector population monitoring. Visceral leishmaniasis is a disease caused by a deadly vector-borne parasite (Leishmania donovani) transmitted to man by phlebotomine sand flies. Indoor residual spraying (IRS), performed within village dwellings, is the primary means of sand fly control performed in Bihar, India and more explicit methods of evaluating the success of control are warranted. A field-based study was conducted to collect ecological sand fly data for use in evaluating the effectiveness of IRS in reducing relative sand fly abundance. Results indicate that sand flies blood feed primarily on humans and cattle and are most frequently found within cattle enclosures. Results further suggest IRS-treatment has a limited impact on vector density. Our approach incorporates detailed evaluation of sand fly spatial distribution (cattle enclosures, houses, vegetation), seasonal fluctuations in abundance, host blood meal preferences within Bihari villages, and dates of IRS performed within treated villages. Hence, this study provides an explicit means of monitoring vector populations and evaluating control measures in Bihar.
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Affiliation(s)
- David M Poché
- Department of Vector Ecology, Genesis Laboratories, Inc., Wellington, United States of America
| | - Rajesh B Garlapati
- Department of Entomology, Genesis Laboratories India Private Limited, Patna, India
| | - Shanta Mukherjee
- Department of Entomology, Genesis Laboratories India Private Limited, Patna, India
| | - Zaria Torres-Poché
- Department of Vector Ecology, Genesis Laboratories, Inc., Wellington, United States of America
| | - Epco Hasker
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Tahfizur Rahman
- Department of Entomology, Genesis Laboratories India Private Limited, Patna, India
| | - Aakanksha Bharti
- Department of Entomology, Genesis Laboratories India Private Limited, Patna, India
| | - Vishnu P Tripathi
- Department of Entomology, Genesis Laboratories India Private Limited, Patna, India
| | - Suman Prakash
- Department of Entomology, Genesis Laboratories India Private Limited, Patna, India
| | - Rahul Chaubey
- Department of Entomology, Genesis Laboratories India Private Limited, Patna, India
| | - Richard M Poché
- Department of Vector Ecology, Genesis Laboratories, Inc., Wellington, United States of America
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17
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Jervis S, Chapman LAC, Dwivedi S, Karthick M, Das A, Le Rutte EA, Courtenay O, Medley GF, Banerjee I, Mahapatra T, Chaudhuri I, Srikantiah S, Hollingsworth TD. Variations in visceral leishmaniasis burden, mortality and the pathway to care within Bihar, India. Parasit Vectors 2017; 10:601. [PMID: 29216905 PMCID: PMC5719561 DOI: 10.1186/s13071-017-2530-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Accepted: 11/12/2017] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Visceral leishmaniasis (VL) has been targeted by the WHO for elimination as a public health problem (< 1 case/10,000 people/year) in the Indian sub-continent (ISC) by 2020. Bihar State in India, which accounts for the majority of cases in the ISC, remains a major target for this elimination effort. However, there is considerable spatial, temporal and sub-population variation in occurrence of the disease and the pathway to care, which is largely unexplored and a threat to achieving the target. METHODS Data from 6081 suspected VL patients who reported being clinically diagnosed during 2012-2013 across eight districts in Bihar were analysed. Graphical comparisons and Chi-square tests were used to determine differences in the burden of identified cases by season, district, age and sex. Log-linear regression models were fitted to onset (of symptoms)-to-diagnosis and onset-to-treatment waiting times to estimate their associations with age, sex, district and various socio-economic factors (SEFs). Logistic regression models were used to identify factors associated with mortality. RESULTS Comparisons of VL caseloads suggested an annual cycle peaking in January-March. A 17-fold variation in the burden of identified cases across districts and under-representation of young children (0-5 years) relative to age-specific populations in Bihar were observed. Women accounted for a significantly lower proportion of the reported cases than men (41 vs 59%, P < 0.0001). Age, district of residence, house wall materials, caste, treatment cost, travelling for diagnosis and the number of treatments for symptoms before diagnosis were identified as correlates of waiting times. Mortality was associated with age, district of residence, onset-to-treatment waiting time, treatment duration, cattle ownership and cost of diagnosis. CONCLUSIONS The distribution of VL in Bihar is highly heterogeneous, and reported caseloads and associated mortality vary significantly across different districts, posing different challenges to the elimination campaign. Socio-economic factors are important correlates of these differences, suggesting that elimination will require tailoring to population and sub-population circumstances.
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Affiliation(s)
- Sarah Jervis
- School of Life Sciences, University of Warwick, Gibbet Hill Campus, Coventry, CV4 7AL, UK.
| | - Lloyd A C Chapman
- School of Life Sciences, University of Warwick, Gibbet Hill Campus, Coventry, CV4 7AL, UK.
| | - Shweta Dwivedi
- CARE India Solutions for Sustainable Development, Patna, Bihar, India
| | - Morchan Karthick
- CARE India Solutions for Sustainable Development, Patna, Bihar, India
| | - Aritra Das
- CARE India Solutions for Sustainable Development, Patna, Bihar, India
| | - Epke A Le Rutte
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000, CA, Rotterdam, The Netherlands
| | - Orin Courtenay
- School of Life Sciences, University of Warwick, Gibbet Hill Campus, Coventry, CV4 7AL, UK
| | - Graham F Medley
- London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | | | - Tanmay Mahapatra
- CARE India Solutions for Sustainable Development, Patna, Bihar, India
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DebRoy S, Prosper O, Mishoe A, Mubayi A. Challenges in modeling complexity of neglected tropical diseases: a review of dynamics of visceral leishmaniasis in resource limited settings. Emerg Themes Epidemiol 2017; 14:10. [PMID: 28936226 PMCID: PMC5604165 DOI: 10.1186/s12982-017-0065-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 08/30/2017] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVES Neglected tropical diseases (NTD), account for a large proportion of the global disease burden, and their control faces several challenges including diminishing human and financial resources for those distressed from such diseases. Visceral leishmaniasis (VL), the second-largest parasitic killer (after malaria) and an NTD affects poor populations and causes considerable cost to the affected individuals. Mathematical models can serve as a critical and cost-effective tool for understanding VL dynamics, however, complex array of socio-economic factors affecting its dynamics need to be identified and appropriately incorporated within a dynamical modeling framework. This study reviews literature on vector-borne diseases and collects challenges and successes related to the modeling of transmission dynamics of VL. Possible ways of creating a comprehensive mathematical model is also discussed. METHODS Published literature in three categories are reviewed: (i) identifying non-traditional but critical mechanisms for VL transmission in resource limited regions, (ii) mathematical models used for dynamics of Leishmaniasis and other related vector borne infectious diseases and (iii) examples of modeling that have the potential to capture identified mechanisms of VL to study its dynamics. RESULTS This review suggests that VL elimination have not been achieved yet because existing transmission dynamics models for VL fails to capture relevant local socio-economic risk factors. This study identifies critical risk factors of VL and distribute them in six categories (atmosphere, access, availability, awareness, adherence, and accedence). The study also suggests novel quantitative models, parts of it are borrowed from other non-neglected diseases, for incorporating these factors and using them to understand VL dynamics and evaluating control programs for achieving VL elimination in a resource-limited environment. CONCLUSIONS Controlling VL is expensive for local communities in endemic countries where individuals remain in the vicious cycle of disease and poverty. Smarter public investment in control programs would not only decrease the VL disease burden but will also help to alleviate poverty. However, dynamical models are necessary to evaluate intervention strategies to formulate a cost-effective optimal policy for eradication of VL.
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Affiliation(s)
- Swati DebRoy
- Department of Mathematics and Computational Science, University of South Carolina, Beaufort, SC USA
| | - Olivia Prosper
- Department of Mathematics, University of Kentucky, Lexington, KY USA
| | - Austin Mishoe
- Department of Mathematics and Computational Science, University of South Carolina, Beaufort, SC USA
| | - Anuj Mubayi
- Simon A. Levin-Mathematical Computational and Modeling Science Center, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ USA
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Tiwary P, Singh SK, Kushwaha AK, Rowton E, Sacks D, Singh OP, Sundar S, Lawyer P. Establishing, Expanding, and Certifying a Closed Colony of Phlebotomus argentipes (Diptera: Psychodidae) for Xenodiagnostic Studies at the Kala Azar Medical Research Center, Muzaffarpur, Bihar, India. JOURNAL OF MEDICAL ENTOMOLOGY 2017; 54:1129-1139. [PMID: 28525618 PMCID: PMC5850120 DOI: 10.1093/jme/tjx099] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Indexed: 05/26/2023]
Abstract
This pilot project was preliminary and essential to a larger effort to define the ability of certain human-subject groups across the infection spectrum to serve as reservoirs of Leishmania donovani infection to sand flies in areas of anthroponotic transmission such as in Bihar state, India. This is possible only via xenodiagnosis of well-defined subject groups using live vector sand flies. The objective was to establish at the Kala Azar Medical Research Center (KAMRC), Muzaffarpur, Bihar, India, a self-sustaining colony of Phlebotomus argentipes (Annandale & Brunneti), closed to infusion with wild-caught material and certified safe for human xenodiagnosis. Prior to this endeavor, no laboratory colony of this vector existed in India meeting the stringent biosafety requirements of this human-use study. From March through mid-December, 2015, over 68,000 sand flies were collected in human dwellings and cattle sheds using CDC-type light traps over 254 nights. Blood-fed and gravid P. argentipes females were selected and placed individually in isoline-rearing vials for oviposition, and >2,500 egg clutches were harvested. Progeny were reared according to standard methods, providing a continuous critical mass of F1 males and females to stimulate social feeding behavior. With construction of a large feeding cage and use of a custom-made rabbit restrainer, the desired level of blood-feeding on restrained rabbits was achieved to make the colony self-sustaining and expand it to working level. Once self-sustaining, the colony was closed to infusion with wild-caught material and certified free of specific human pathogens.
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Affiliation(s)
- Puja Tiwary
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India (; ; ; )
| | | | - Anurag Kumar Kushwaha
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India (; ; ; )
| | - Edgar Rowton
- Entomologist, Walter Reed Army Institute of Research, Silver Spring, MD ()
| | - David Sacks
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD (; )
| | - Om Prakash Singh
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India (; ; ; )
| | - Shyam Sundar
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India (; ; ; )
| | - Phillip Lawyer
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD (; )
- Monte L. Bean Life Science Museum, Brigham Young University, Provo, UT
- Corresponding author, e-mail:
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Aklilu E, Gebresilassie A, Yared S, Kindu M, Tekie H, Balkew M, Warburg A, Hailu A, Gebre-Michael T. Comparative study on the nocturnal activity of phlebotomine sand flies in a highland and lowland foci of visceral leishmaniasis in north-western Ethiopia with special reference to Phlebotomus orientalis. Parasit Vectors 2017; 10:393. [PMID: 28830569 PMCID: PMC5568301 DOI: 10.1186/s13071-017-2339-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 08/17/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Leishmania donovani, the causative agent of visceral leishmaniasis (VL), is most probably vectored by Phlebotomus orientalis in north-western Ethiopia. The aim of this study was to determine and compare the nocturnal activity patterns of Ph. orientalis in VL endemic foci of Libo-Kemkem (highland) and Metema (lowland) districts of north-western Ethiopia. METHODS Sampling of sand flies was conducted bimonthly from January-May 2012 in the highland and from March-June 2013 in the lowland. Sand flies were sampled using two CDC light traps placed in compounds occupied by both cattle and humans. Sampling of sand flies started at 18:00 h and ended at 06:00 h. Every hour, a cage was replaced by another cage. RESULTS In total, 9479 nocturnally active sand flies were collected from both study areas. Six Phlebotomus species (Ph. orientalis, Ph. duboscqi, Ph. papatasi, Ph. bergeroti, Ph. rodhaini and Ph. martini) and several Sergentomyia spp. were identified. In both areas, of the six Phlebotomus spp., Ph. orientalis was the preponderate. In the highland, the hourly activity pattern of Ph. orientalis females was higher before midnight with a peak in density between 22:00-23:00 h, whereas in the lowland after midnight between 03:00-04:00 h. CONCLUSIONS The present study showed that Ph. orientalis females exhibited different nocturnal activity patterns with a peak in the early part of the night in the highland and in the latter part of the night in the lowland areas. As the risk of acquiring L. donovani infections vary in the two areas, appropriate control strategies should be developed according to the activity of Ph. orientalis in the respective areas.
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Affiliation(s)
- Esayas Aklilu
- Department of Biology, Mada Walabu University, Bale-Robe, Ethiopia.
| | | | - Solomon Yared
- Department of Biology, Jigjiga University, Jigjiga, Ethiopia
| | - Mizan Kindu
- Department of Microbiology and Parasitology, Mada Walabu University, Bale-Robe, Ethiopia
| | - Habte Tekie
- Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Meshesha Balkew
- Aklilu Lemma Institutes of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Alon Warburg
- Faculty of Medicine, The Hebrew University, Hadassah Medical School, Jerusalem, Israel
| | - Asrat Hailu
- Department of Microbiology, Immunology and Parasitology, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Teshome Gebre-Michael
- Aklilu Lemma Institutes of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
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Mandal R, Das P, Kumar V, Kesari S. Spatial Distribution of Phlebotomus argentipes (Diptera: Psychodidae) in Eastern India, a Case Study Evaluating Multispatial Resolution Remotely Sensed Environmental Evidence and Microclimatic Data. JOURNAL OF MEDICAL ENTOMOLOGY 2017; 54:844-853. [PMID: 28399209 DOI: 10.1093/jme/tjw232] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Indexed: 06/07/2023]
Abstract
Remote sensing, a powerful tool for analyzing landscape factors, is being used to explore the spatial ecology of vectors of several diseases. This study aims to explore the role of buffer size in identification and quantification of geo-environmental factors from multispatial resolution satellite data and its application along with microclimatic data to kala-azar vector abundance modeling.Sand fly abundance and microclimatic data were collected from 210 sample sites during the premonsoon and postmonsoon season of 2014 from Muzaffarpur district of Bihar (India). Linear imaging self-scanning sensor (LISS-III; 23.5 m) and advanced wide field sensor (AWiFS; 56 m) imageries were used for generating environmental variables at 300- and 500-m buffer zones. Four analytical models of sand fly density were developed and evaluated for predictive accuracy.A total of 33 geo-environmental and four microclimatic variables were tested for the prediction of sand fly density, of which the best four were maximum temperature, relative humidity, Euclidean nearest-neighbor distance of settlement area to mixed bush-grass land, and surface water body. Predictive accuracy of the LISS-III models was found to be higher than AWiFS models at all buffer sizes.The results show that geo-environmental parameters and microclimatic data are the best predictors for sand fly density modeling. Buffer sizes play an important role in identifying the explanatory variables. Model parameters may be useful in identifying predisposing factors of sand fly habitat suitability at the micro level.
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Affiliation(s)
- Rakesh Mandal
- Department of Vector Biology and Control, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Agamkuan, Patna 800 007, Bihar, India
| | - Pradeep Das
- Department of Vector Biology and Control, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Agamkuan, Patna 800 007, Bihar, India
| | - Vijay Kumar
- Department of Vector Biology and Control, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Agamkuan, Patna 800 007, Bihar, India
| | - Shreekant Kesari
- Department of Vector Biology and Control, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Agamkuan, Patna 800 007, Bihar, India
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Hussaini N, Lubuma JMS, Barley K, Gumel AB. Mathematical analysis of a model for AVL-HIV co-endemicity. Math Biosci 2015; 271:80-95. [PMID: 26596715 DOI: 10.1016/j.mbs.2015.10.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 10/07/2015] [Accepted: 10/08/2015] [Indexed: 10/22/2022]
Abstract
A model for the transmission dynamics of Anthroponotic Visceral Leishmaniasis (AVL) and human immunodeficiency virus (HIV) in a population is developed and used to assess the impact of the spread of each disease on the overall transmission dynamics. As for other vector-borne disease models, the AVL component of the model undergoes backward bifurcation when the associated reproduction number of the AVL-only sub-model (denoted by RL) is less than unity. Uncertainty and sensitivity analyzes of the model, using data relevant to the dynamics of the two diseases in Ethiopia, show that the top three parameters that drive the AVL infection (with respect to the associated response function, RL) are the average number of times a sandfly bites humans per unit time (σV), carrying capacity of vectors (KV) and transmission probability from infected humans to susceptible sandflies (β2). The distribution of RL is RL∈[0.06,3.94] with a mean of RL=1.08. Furthermore, the top three parameters that affect HIV dynamics (with respect to the response function RH) are the transmission rate of HIV (βH), HIV-induced death rate (δH), and the modification parameter for the increase in infectiousness of AIDS individuals in comparison to HIV infected without clinical symptoms of AIDS (ωH). The distribution of RH is RH∈[0.88,2.79] with a mean of RH=1.46. The dominant parameters that affect the dynamics of the full VL-HIV model (with respect to the associated reproduction number, RLH, as the response function) are the transmission rate of HIV (βH), the average number of times a sandfly bites humans per unit time (σV), and HIV-induced death rate (δH) (the distribution of RLH is RLH∈[0.88,3.94] with a mean of RLH=1.64). Numerical simulations of the model show that the two diseases co-exist (with AVL dominating, but not driving HIV to extinction) whenever the reproduction number of each disease exceeds unity. It is shown that AVL can invade a population at HIV-endemic state if a certain threshold quantity, known as invasion reproduction number, exceeds unity.
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Affiliation(s)
- N Hussaini
- Department of Mathematics and Applied Mathematics, University of Pretoria, Pretoria 0002, South Africa; Department of Mathematical Sciences, Bayero University Kano, P.M.B. 3011, Kano, Nigeria
| | - J M-S Lubuma
- Department of Mathematics and Applied Mathematics, University of Pretoria, Pretoria 0002, South Africa
| | - K Barley
- Simon A. Levin Mathematical, Computational and Modeling Sciences Center, Arizona State University, Tempe, AZ, 85287 USA
| | - A B Gumel
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, USA; Extraordinary Professor, Department of Mathematics and Applied Mathematics, University of Pretoria, Pretoria 0002, South Africa.
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DDT-based indoor residual spraying suboptimal for visceral leishmaniasis elimination in India. Proc Natl Acad Sci U S A 2015; 112:8573-8. [PMID: 26124110 DOI: 10.1073/pnas.1507782112] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Indoor residual spraying (IRS) is used to control visceral leishmaniasis (VL) in India, but it is poorly quality assured. Quality assurance was performed in eight VL endemic districts in Bihar State, India, in 2014. Residual dichlorodiphenyltrichloroethane (DDT) was sampled from walls using Bostik tape discs, and DDT concentrations [grams of active ingredient per square meter (g ai/m(2))] were determined using HPLC. Pre-IRS surveys were performed in three districts, and post-IRS surveys were performed in eight districts. A 20% threshold above and below the target spray of 1.0 g ai/m(2) was defined as "in range." The entomological assessments were made in four districts in IRS and non-IRS villages. Vector densities were measured: pre-IRS and 1 and 3 mo post-IRS. Insecticide susceptibility to 4% DDT and 0.05% deltamethrin WHO-impregnated papers was determined with wild-caught sand flies. The majority (329 of 360, 91.3%) of pre-IRS samples had residual DDT concentrations of <0.1 g ai/m(2). The mean residual concentration of DDT post-IRS was 0.37 g ai/m(2); 84.9% of walls were undersprayed, 7.4% were sprayed in range, and 7.6% were oversprayed. The abundance of sand flies in IRS and non-IRS villages was significantly different at 1 mo post-IRS only. Sand flies were highly resistant to DDT but susceptible to deltamethrin. The Stockholm Convention, ratified by India in 2006, calls for the complete phasing out of DDT as soon as practical, with limited use in the interim where no viable IRS alternatives exist. Given the poor quality of the DDT-based IRS, ready availability of pyrethroids, and susceptibility profile of Indian sand flies, the continued use of DDT in this IRS program is questionable.
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Picado A, Ostyn B, Rijal S, Sundar S, Singh SP, Chappuis F, Das ML, Khanal B, Gidwani K, Hasker E, Dujardin JC, Vanlerberghe V, Menten J, Coosemans M, Boelaert M. Long-lasting insecticidal nets to prevent visceral leishmaniasis in the Indian subcontinent; methodological lessons learned from a cluster randomised controlled trial. PLoS Negl Trop Dis 2015; 9:e0003597. [PMID: 25856238 PMCID: PMC4391877 DOI: 10.1371/journal.pntd.0003597] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Affiliation(s)
- Albert Picado
- ISGlobal, Barcelona Center for International Health Research (CRESIB), Hospital Clínic—Universitat de Barcelona, Barcelona, Spain
| | - Bart Ostyn
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Suman Rijal
- Department of Medicine, B. P. Koirala Institute of Health Sciences, Dharan, Nepal
| | - Shyam Sundar
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Shri Prakash Singh
- Department of Community Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - François Chappuis
- Division of Tropical and Humanitarian Medicine, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Murari Lal Das
- Department of Microbiology, B. P. Koirala Institute of Health Sciences, Dharan, Nepal
| | - Basudha Khanal
- Department of Microbiology, B. P. Koirala Institute of Health Sciences, Dharan, Nepal
| | - Kamlesh Gidwani
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Epco Hasker
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Jean Claude Dujardin
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Veerle Vanlerberghe
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Joris Menten
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Marc Coosemans
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Marleen Boelaert
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
- * E-mail:
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Model-based investigations of different vector-related intervention strategies to eliminate visceral leishmaniasis on the Indian subcontinent. PLoS Negl Trop Dis 2014; 8:e2810. [PMID: 24762676 PMCID: PMC3998939 DOI: 10.1371/journal.pntd.0002810] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 03/10/2014] [Indexed: 01/19/2023] Open
Abstract
The elimination of infectious diseases requires reducing transmission below a certain threshold. The Visceral Leishmaniasis (VL) Elimination Initiative in Southeast Asia aims to reduce the annual VL incidence rate below 1 case per 10,000 inhabitants in endemic areas by 2015 via a combination of case management and vector control. Using a previously developed VL transmission model, we investigated transmission thresholds dependent on measures reducing the sand fly density either by killing sand flies (e.g., indoor residual spraying and long-lasting insecticidal nets) or by destroying breeding sites (e.g., environmental management). Model simulations suggest that elimination of VL is possible if the sand fly density can be reduced by 67% through killing sand flies, or if the number of breeding sites can be reduced by more than 79% through measures of environmental management. These results were compared to data from two recent cluster randomised controlled trials conducted in India, Nepal and Bangladesh showing a 72% reduction in sand fly density after indoor residual spraying, a 44% and 25% reduction through the use of long-lasting insecticidal nets and a 42% reduction after environmental management. Based on model predictions, we identified the parameters within the transmission cycle of VL that predominantly determine the prospects of intervention success. We suggest further research to refine model-based predictions into the elimination of VL. Visceral leishmaniasis is suspected to be the second largest parasitic killer in the world after malaria. On the Indian subcontinent, the vector-borne disease is caused by the protozoan flagellate Leishmania donovani and transmitted by the sand fly Phlebotomus argentipes. The regional elimination programme has suggested as a target line to reduce the annual incidence below 1 case in 10,000 by 2015. Using a previously developed mathematical model, we investigated to what extent the sand fly population must be controlled to achieve elimination. These calculated thresholds were compared to data from two recent trials conducted in India, Nepal and Bangladesh to evaluate the efficacy of different vector control measures. Our results indicate that elimination should be feasible because the evaluated effect of indoor residual spraying exceeds the threshold. However, emerging insecticide resistance may compromise the effectiveness of this measure. The observed effects of long lasting insecticidal nets and environmental management do not seem to be sufficient to reach either threshold. Integrated vector management based on indoor residual spraying combined with long lasting insecticidal nets and more effective environmental management may allow overcoming the limitations of the current vector control methods and should also prevent re-emergence of the infection after local extinction.
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Tiwary P, Kumar D, Mishra M, Singh RP, Rai M, Sundar S. Seasonal variation in the prevalence of sand flies infected with Leishmania donovani. PLoS One 2013; 8:e61370. [PMID: 23585896 PMCID: PMC3621828 DOI: 10.1371/journal.pone.0061370] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 03/11/2013] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Visceral Leishmaniasis (VL) is a life threatening neglected infectious disease in the Indian subcontinent, transmitted by the bite of female sand flies. Estimation of the infectivity in the vector population, collected in different seasons, may be useful to better understanding the transmission dynamics of VL as well as to plan vector control measures. METHODOLOGY We collected sand flies from highly endemic regions of Bihar state, India for one year over three seasons. The species of the sand flies were confirmed by species-specific PCR-RFLP. Leishmania donovani infection was investigated in 1397 female Phlebotomus argentipes using PCR, targeting the Leishmania specific minicircle of the kDNA region. Further, the parasitic load in the infected sand flies was measured using quantitative PCR. CONCLUSION Though sand flies were most abundant in the rainy season, the highest rate of infection was detected in the winter season with 2.84% sand flies infected followed by the summer and rainy seasons respectively. This study can help in vector elimination programmes and to reduce disease transmission.
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Affiliation(s)
- Puja Tiwary
- Infectious Disease Research Laboratory, Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
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Bhunia GS, Chatterjee N, Kumar V, Siddiqui NA, Mandal R, Das P, Kesari S. Delimitation of kala-azar risk areas in the district of Vaishali in Bihar (India) using a geo-environmental approach. Mem Inst Oswaldo Cruz 2012; 107:609-20. [DOI: 10.1590/s0074-02762012000500007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 04/12/2012] [Indexed: 11/22/2022] Open
Affiliation(s)
| | | | - Vijay Kumar
- Rajendra Memorial Research Institute of Medical Sciences, India
| | | | - Rakesh Mandal
- Rajendra Memorial Research Institute of Medical Sciences, India
| | - Pradeep Das
- Rajendra Memorial Research Institute of Medical Sciences, India
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Gidwani K, Picado A, Rijal S, Singh SP, Roy L, Volfova V, Andersen EW, Uranw S, Ostyn B, Sudarshan M, Chakravarty J, Volf P, Sundar S, Boelaert M, Rogers ME. Serological markers of sand fly exposure to evaluate insecticidal nets against visceral leishmaniasis in India and Nepal: a cluster-randomized trial. PLoS Negl Trop Dis 2011; 5:e1296. [PMID: 21931871 PMCID: PMC3172194 DOI: 10.1371/journal.pntd.0001296] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 07/16/2011] [Indexed: 12/02/2022] Open
Abstract
Background Visceral leishmaniasis is the world' second largest vector-borne parasitic killer and a neglected tropical disease, prevalent in poor communities. Long-lasting insecticidal nets (LNs) are a low cost proven vector intervention method for malaria control; however, their effectiveness against visceral leishmaniasis (VL) is unknown. This study quantified the effect of LNs on exposure to the sand fly vector of VL in India and Nepal during a two year community intervention trial. Methods As part of a paired-cluster randomized controlled clinical trial in VL-endemic regions of India and Nepal we tested the effect of LNs on sand fly biting by measuring the antibody response of subjects to the saliva of Leishmania donovani vector Phlebotomus argentipes and the sympatric (non-vector) Phlebotomus papatasi. Fifteen to 20 individuals above 15 years of age from 26 VL endemic clusters were asked to provide a blood sample at baseline, 12 and 24 months post-intervention. Results A total of 305 individuals were included in the study, 68 participants provided two blood samples and 237 gave three samples. A random effect linear regression model showed that cluster-wide distribution of LNs reduced exposure to P. argentipes by 12% at 12 months (effect 0.88; 95% CI 0.83–0.94) and 9% at 24 months (effect 0.91; 95% CI 0.80–1.02) in the intervention group compared to control adjusting for baseline values and pair. Similar results were obtained for P. papatasi. Conclusions This trial provides evidence that LNs have a limited effect on sand fly exposure in VL endemic communities in India and Nepal and supports the use of sand fly saliva antibodies as a marker to evaluate vector control interventions. Visceral leishmaniasis (VL), also known as kala azar, is one of the major public health concerns of the Indian subcontinent, caused by Leishmania donovani transmitted by the bite of the sand fly Phlebotomus argentipes. To date, Indoor Residual Spraying (IRS) campaigns have been unable to control the disease. This makes Long-lasting insecticidal nets (LNs) an attractive alternative or complement to IRS. Therefore, it is important to assess the extent that LNs reduce bites from P. argentipes. When female sand flies bite they require their saliva to efficiently bloodfeed. For humans and animals alike, the host' immune response against components of sand fly saliva can be used as a marker of exposure to the vector. Here we describe how comprehensive coverage of LNs in trial communities over two years reduced antibody levels to the saliva of P. argentipes and P. papatasi (a man-biting sand fly that co-exists with P. argentipes but does not transmit VL) sand flies by 9–12% compared to communities without LNs. Our results demonstrate that the large-scale distribution of LNs did not confer significant additional protection against sand fly bites in VL-endemic regions of India and Nepal and questions the indoor transmission of L. donovani in these regions.
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Affiliation(s)
| | - Albert Picado
- London School of Hygiene and Tropical Medicine, London, United Kingdom
- Institute of Tropical Medicine, Antwerp, Belgium
| | - Suman Rijal
- BP Koirala Institute of Health Sciences, Dharan, Nepal
| | | | - Lalita Roy
- BP Koirala Institute of Health Sciences, Dharan, Nepal
| | | | - Elisabeth Wreford Andersen
- London School of Hygiene and Tropical Medicine, London, United Kingdom
- University of Copenhagen, Copenhagen, Denmark
| | | | - Bart Ostyn
- Institute of Tropical Medicine, Antwerp, Belgium
| | | | | | - Petr Volf
- Charles University, Prague, Czech Republic
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Chowdhury R, Dotson E, Blackstock AJ, McClintock S, Maheswary NP, Faria S, Islam S, Akter T, Kroeger A, Akhter S, Bern C. Comparison of insecticide-treated nets and indoor residual spraying to control the vector of visceral leishmaniasis in Mymensingh District, Bangladesh. Am J Trop Med Hyg 2011; 84:662-7. [PMID: 21540372 DOI: 10.4269/ajtmh.2011.10-0682] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Integrated vector management is a pillar of the South Asian visceral leishmaniasis (VL) elimination program, but the best approach remains a matter of debate. Sand fly seasonality was determined in 40 houses sampled monthly. The impact of interventions on Phlebotomus argentipes density was tested from 2006-2007 in a cluster-randomized trial with four arms: indoor residual spraying (IRS), insecticide-treated nets (ITNs), environmental management (EVM), and no intervention. Phlebotomus argentipes density peaked in March with the highest proportion of gravid females in May. The EVM (mud plastering of wall and floor cracks) showed no impact. The IRS and ITNs were associated with a 70-80% decrease in male and female P. argentipes density up to 5 months post intervention. Vector density rebounded by 11 months post-IRS, whereas ITN-treated households continued to show significantly lower density compared with households without intervention. Our data suggest that both IRS and ITNs may help to improve VL control in Bangladesh.
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Affiliation(s)
- Rajib Chowdhury
- Regional Office for South-East Asia, World Health Organization, New Delhi, India.
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Visceral leishmaniasis in Muzaffarpur district, Bihar, India from 1990 to 2008. PLoS One 2011; 6:e14751. [PMID: 21394195 PMCID: PMC3048857 DOI: 10.1371/journal.pone.0014751] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Accepted: 02/06/2011] [Indexed: 11/21/2022] Open
Abstract
Background Visceral Leishmaniasis (VL) is a vector-borne disease transmitted by Phlebotomus argentipes. To understand the VL seasonality, annual and monthly variations of VL incidence and its relationship to meteorological variables, the numbers of VL cases reported in Muzaffarpur district, Bihar, India from 1990 to 2008 were studied. Methods Annual VL incidence per 10,000 and the total number of annual VL cases reported at block Community Health Centres (CHC), Public Hospitals or Non-Governmental Organisations (NGO) and the number of VL cases per month from 2000 to 2008 as well as the monthly average of cases for 2000–08, 2000–04 and 2005–08 periods along with the monthly averages of temperature, rainfall and relative humidity were plotted. VL Standardised Incidence Ratios per block were computed for the periods of 1990–1993, 1994–1998, 1999–2004 and 2005–2008 and month wise from 2002 to 2008. A negative binomial regression model was used to evaluate the association between meteorological variables and the number of VL cases per month from 2000 to 2008. Results A total of 68,358 VL cases were reported in Muzaffarpur district from 1990 to 2008, ranging from 1,2481 in 1992 to 1,161 in 2001. The blocks with the highest number of cases shifted from East (1990–98) to West (1999–2008). Monthly averages of cases ranged from 149 to 309, highest peak in March–April and another one in July. Monthly VL incidence was associated positively to rainfall and negatively to relative humidity and the numbers of VL cases in the previous month. Interpretation The number of cases reported to the public health sector allowed the describing of the spatial distribution and temporal variations in the Muzaffarpur from 1990 to 2008. However, to assess the actual VL burden, as well as the efficacy of the control measures applied in the district, reporting from private practices and NGOs should be encouraged.
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Bern C, Courtenay O, Alvar J. Of cattle, sand flies and men: a systematic review of risk factor analyses for South Asian visceral leishmaniasis and implications for elimination. PLoS Negl Trop Dis 2010; 4:e599. [PMID: 20161727 PMCID: PMC2817719 DOI: 10.1371/journal.pntd.0000599] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Accepted: 12/16/2009] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Studies performed over the past decade have identified fairly consistent epidemiological patterns of risk factors for visceral leishmaniasis (VL) in the Indian subcontinent. METHODS AND PRINCIPAL FINDINGS To inform the current regional VL elimination effort and identify key gaps in knowledge, we performed a systematic review of the literature, with a special emphasis on data regarding the role of cattle because primary risk factor studies have yielded apparently contradictory results. Because humans form the sole infection reservoir, clustering of kala-azar cases is a prominent epidemiological feature, both at the household level and on a larger scale. Subclinical infection also tends to show clustering around kala-azar cases. Within villages, areas become saturated over a period of several years; kala-azar incidence then decreases while neighboring areas see increases. More recently, post kala-azar dermal leishmaniasis (PKDL) cases have followed kala-azar peaks. Mud walls, palpable dampness in houses, and peri-domestic vegetation may increase infection risk through enhanced density and prolonged survival of the sand fly vector. Bed net use, sleeping on a cot and indoor residual spraying are generally associated with decreased risk. Poor micronutrient status increases the risk of progression to kala-azar. The presence of cattle is associated with increased risk in some studies and decreased risk in others, reflecting the complexity of the effect of bovines on sand fly abundance, aggregation, feeding behavior and leishmanial infection rates. Poverty is an overarching theme, interacting with individual risk factors on multiple levels. CONCLUSIONS Carefully designed demonstration projects, taking into account the complex web of interconnected risk factors, are needed to provide direct proof of principle for elimination and to identify the most effective maintenance activities to prevent a rapid resurgence when interventions are scaled back. More effective, short-course treatment regimens for PKDL are urgently needed to enable the elimination initiative to succeed.
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Affiliation(s)
- Caryn Bern
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
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Picado A, Das ML, Kumar V, Kesari S, Dinesh DS, Roy L, Rijal S, Das P, Rowland M, Sundar S, Coosemans M, Boelaert M, Davies CR. Effect of village-wide use of long-lasting insecticidal nets on visceral Leishmaniasis vectors in India and Nepal: a cluster randomized trial. PLoS Negl Trop Dis 2010; 4:e587. [PMID: 20126269 PMCID: PMC2811172 DOI: 10.1371/journal.pntd.0000587] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 12/07/2009] [Indexed: 11/30/2022] Open
Abstract
Background Visceral leishmaniasis (VL) control in the Indian subcontinent is currently based on case detection and treatment, and on vector control using indoor residual spraying (IRS). The use of long-lasting insecticidal nets (LN) has been postulated as an alternative or complement to IRS. Here we tested the impact of comprehensive distribution of LN on the density of Phlebotomus argentipes in VL-endemic villages. Methods A cluster-randomized controlled trial with household P. argentipes density as outcome was designed. Twelve clusters from an ongoing LN clinical trial—three intervention and three control clusters in both India and Nepal—were selected on the basis of accessibility and VL incidence. Ten houses per cluster selected on the basis of high pre-intervention P. argentipes density were monitored monthly for 12 months after distribution of LN using CDC light traps (LT) and mouth aspiration methods. Ten cattle sheds per cluster were also monitored by aspiration. Findings A random effect linear regression model showed that the cluster-wide distribution of LNs significantly reduced the P. argentipes density/house by 24.9% (95% CI 1.80%–42.5%) as measured by means of LTs. Interpretation The ongoing clinical trial, designed to measure the impact of LNs on VL incidence, will confirm whether LNs should be adopted as a control strategy in the regional VL elimination programs. The entomological evidence described here provides some evidence that LNs could be usefully deployed as part of the VL control program. Trial registration ClinicalTrials.gov CT-2005-015374 Visceral leishmaniasis (VL) is a vector-borne disease causing at least 60,000 deaths each year amongst an estimated half million cases, and until recently there have been no significant initiatives to reduce this burden. However, in 2005, the governments of India, Bangladesh and Nepal signed a memorandum of understanding at the World Health Assembly in Geneva for the elimination of the disease by 2015. In the absence of an effective vaccine, the program will rely on the active detection and prompt treatment of cases throughout the endemic region, combined with a recurrent indoor residual spraying (IRS) of all villages at risk. Vector control programs based on IRS are notorious for failing to maintain comprehensive spray coverage over time owing to logistical problems and lack of compliance by householders. Long-lasting insecticidal nets (LNs) have been postulated as an alternative or complement to IRS. Here we describe how comprehensive coverage of LN in trial communities reduced the indoor density of sand flies by 25% compared to communities without LNs. This provides an indication that LNs could be usefully deployed as a component of the VL control program in the Indian subcontinent.
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Affiliation(s)
- Albert Picado
- London School of Hygiene and Tropical Medicine, London, United Kingdom
- * E-mail:
| | - Murari L. Das
- B. P. Koirala Institute of Health Sciences, Dharan, Nepal
| | - Vijay Kumar
- Rajendra Memorial Research Institute of Medical Sciences, Patna, India
| | - Shreekant Kesari
- Rajendra Memorial Research Institute of Medical Sciences, Patna, India
| | - Diwakar S. Dinesh
- Rajendra Memorial Research Institute of Medical Sciences, Patna, India
| | - Lalita Roy
- B. P. Koirala Institute of Health Sciences, Dharan, Nepal
| | - Suman Rijal
- B. P. Koirala Institute of Health Sciences, Dharan, Nepal
| | - Pradeep Das
- Rajendra Memorial Research Institute of Medical Sciences, Patna, India
| | - Mark Rowland
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | - Marc Coosemans
- Prince Leopold Institute of Tropical Medicine, Antwerp, Belgium
| | | | - Clive R. Davies
- London School of Hygiene and Tropical Medicine, London, United Kingdom
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Emergence periodicity of Phlebotomus argentipes annandale and brunetti (Diptera: psychodidae): A laboratory study. J Parasit Dis 2009; 33:23-7. [PMID: 23129884 DOI: 10.1007/s12639-009-0003-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 12/03/2009] [Indexed: 10/19/2022] Open
Abstract
Phlebotomus argentipes Annandale and Brunetti (Diptera: Psychodidae) is the vector for visceral leishmaniasis in India. The aspects of its biology such as feeding and man vector contact are associated with emergence periodicity of the adult. Hence, the present study was made to find out the actual emergence period of P. argentipes. Wild caught P. argentipes were confined in the rearing pots inside laboratory. The newly emerged adults were collected at hourly intervals and released in to separate polythene bags and were held at 4°C till death. Sand flies were segregated sex-wise after the death under a microscope. The emergence of adult was observed throughout the day. However, the male preferred dawn emergence and the female the dusk. Two peaks of emergence were found in a day; first one in the morning (0900h) and the second one in the evening (1800h). The ratio of both sexes was found to be about equal. The emergence of adult was found to be 77% out of total eggs laid, which was completed within 7-10 days from the 1st day of emergence under laboratory conditions (25°C to 31°C and 70% to 75% relative humidity). This study has important bearings to find out the actual time for personal protection against biting of sand flies to prevent the transmission of Kala-azar.
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Ostyn B, Vanlerberghe V, Picado A, Dinesh DS, Sundar S, Chappuis F, Rijal S, Dujardin JC, Coosemans M, Boelaert M, Davies C. Vector control by insecticide-treated nets in the fight against visceral leishmaniasis in the Indian subcontinent, what is the evidence? Trop Med Int Health 2008; 13:1073-85. [PMID: 18564350 DOI: 10.1111/j.1365-3156.2008.02110.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Visceral leishmaniasis (VL) is a deadly vector-borne disease that causes an estimated 500 000 new cases a year. In India, Nepal and Bangladesh, VL is caused by Leishmania donovani, which is transmitted from man to man by the sandfly Phlebotomus argentipes. In 2005, these three countries signed a memorandum of understanding to eliminate VL from the region. Integrated vector management is one of the pillars of this elimination strategy, alongside early case detection and treatment. We reviewed the evidence of effectiveness of different vector control methods, to examine the potential role of insecticide treated bednets (ITNs). Indoor residual spraying has shown poor impact for various reasons and resistance to DDT is emerging in Bihar. Environmental management performed poorly compared to insecticide based methods. ITNs could give individual protection but this still needs to be proven in randomized trials. Given the constraints of indoor residual spraying, it is worthwhile to further explore the use of ITNs, in particular long lasting ITNs, as an additional tool in the VL elimination initiative.
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Affiliation(s)
- Bart Ostyn
- Institute of Tropical Medicine, Antwerp, Belgium.
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Dinesh DS, Das P, Picado A, Davies C, Speybroeck N, Ostyn B, Boelaert M, Coosemans M. Long-lasting insecticidal nets fail at household level to reduce abundance of sandfly vector Phlebotomus argentipes in treated houses in Bihar (India). Trop Med Int Health 2008; 13:953-8. [PMID: 18482197 DOI: 10.1111/j.1365-3156.2008.02096.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To determine whether the use of long-lasting insecticidal nets (LLINS) at household level are effective in reducing the abundance of Phlebotomus argentipes, vector of anthroponotic visceral leishmaniasis in India, Nepal and Bangladesh. METHODS The impact of two long-lasting nets (Olyset and PermaNet) on indoor sandfly abundance was evaluated in selected houses of three endemic hamlets in Bihar (India). It was assumed that most sandflies breed inside the houses and that LLINs would progressively reduce the indoor density during the reproduction season. A campaign of indoor spraying with dichloro-diphenyl-trichloroethane (DDT) interfered with the trial but did not affect the sandfly population. Results Only the density of males of P. argentipes was significantly reduced by both the LLINs but not the females. CONCLUSIONS These findings suggest that most female sandflies are coming from outside and that LLINs do not reduce their entry rate.
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Affiliation(s)
- Diwakar S Dinesh
- Rajendra Memorial Research Institute of Medical Sciences, Indian Council of Medical Research, Agamkuan Patna, India
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Guernaoui S, Boussaa S, Pesson B, Boumezzough A. Nocturnal activity of phlebotomine sandflies (Diptera: Psychodidae) in a cutaneous leishmaniasis focus in Chichaoua, Morocco. Parasitol Res 2005; 98:184-8. [PMID: 16323026 DOI: 10.1007/s00436-005-0032-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Accepted: 09/20/2005] [Indexed: 10/25/2022]
Abstract
The nocturnal activity of phlebotomine sandflies (Diptera: Psychodidae) was studied "at an epidemic focus" on human cutaneous leishmaniasis due to Leishmania tropica Wright in Chichaoua province, in Morocco. Sandflies were collected using light and sticky-paper traps changed at 2-h intervals, inside and around houses, in August and October 2004. Overall, 633 sandflies, belonging to six species of Phlebotomus and three of Sergentomyia, were collected. Sandfly activity was nocturnal and higher at twilight. Several activity patterns were observed according to the species. Phlebotomus (Paraphlebotomus) sergenti Parrot, 1917, the suspected vector of L. tropica in this focus, was caught during each collection performed from 1900 to 0500 hours, the numbers of species caught peaked at 1900-2100 hours. There were seasonal variations of the nocturnal activity, which could be related to the variations in temperature and relative humidity.
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Affiliation(s)
- S Guernaoui
- UR Geodes, Institut de Recherche pour le Développement, Bondy, France.
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