1
|
Boze BGV, Markowski DM, Bennett D, Williams MG. Preparations and Activities Necessary for Aerial Mosquito Control After Hurricanes. JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION 2020; 36:90-97. [PMID: 33647138 DOI: 10.2987/19-6881.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Vector Disease Control International (VDCI) has a long history of aiding mosquito control efforts necessary for recovery after natural disasters like hurricanes and major floods. As waters associated with these events begin to recede, both nuisance and vector mosquito species surge in abundance and consequently play an increased role in public health. When these situations arise, state and county agencies implement emergency response plans and many rely on Federal Emergency Management Agency or private contractors for assistance in reducing mosquito populations that can alter arbovirus transmission cycles, cause intolerable stress, hamper reconstruction efforts, and disrupt normal community functions. Vector Disease Control International owns the largest fleet of fixed-wing aircraft dedicated specifically to mosquito control and has worked every major storm event since Hurricane Bonnie in 1998. This article describes the logistics and operations required for implementing VDCI's emergency management plan, including the relocation of equipment, adult mosquito surveillance, delivery of pesticides, assessment of efficacy, and filing of low-level waivers and congested-area plans with the Federal Aviation Administration.
Collapse
Affiliation(s)
- Broox G V Boze
- Vector Disease Control International, 1320 Brookwood Drive, Suite H, Little Rock, AR 72202
| | - Daniel M Markowski
- Vector Disease Control International, 1320 Brookwood Drive, Suite H, Little Rock, AR 72202
| | - Deborah Bennett
- Vector Disease Control International, 1320 Brookwood Drive, Suite H, Little Rock, AR 72202
| | - Malcom G Williams
- Vector Disease Control International, 1320 Brookwood Drive, Suite H, Little Rock, AR 72202
| |
Collapse
|
2
|
Poché DM, Wang HH, Grant WE. Visceral leishmaniasis on the Indian Subcontinent: Efficacy of fipronil-based cattle treatment in controlling sand fly populations is dependent on specific aspects of sand fly ecology. PLoS Negl Trop Dis 2020; 14:e0008011. [PMID: 32069283 PMCID: PMC7048295 DOI: 10.1371/journal.pntd.0008011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 02/28/2020] [Accepted: 12/22/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Visceral leishmaniasis (VL) is a deadly disease transmitted by the sand fly Phlebotomus argentipes on the Indian subcontinent, with a promising means of vector control being orally treating cattle with fipronil-based drugs. While prior research investigating the dynamic relationship between timing of fipronil-based control schemes and the seasonality of sand flies provides insights into potential of treatment on a large scale, ecological uncertainties remain. We investigated how uncertainties associated with sand fly ecology might affect our ability to assess efficacy of fipronil-based control schemes. To do this, we used a previously-described, individual-based, stochastic sand fly model to quantify how uncertainties associated with 1) the percentage of female sand flies taking blood meals from cattle, and 2) the percentage of female sand flies ovipositing in organic matter containing feces from treated cattle might impact the efficacy of fipronil-based sand fly control schemes. PRINCIPAL FINDINGS Assuming no prior knowledge of sand fly blood meal and oviposition sites, the probabilities of achieving effective sand fly population reduction with treatments performed 3, 6 and 12 times per year were ≈5-22%, ≈27-36%, and ≈46-54%, respectively. Assuming ≥50% of sand flies feed on cattle, probabilities of achieving efficacious control increased to ≈8-31%, ≈15-42%, and ≈52-65%. Assuming also that ≥50% of sand flies oviposit in cattle feces, the above probabilities increased further to ≈14-53%, ≈31-81%, and ≈89-97%. CONCLUSIONS Our assessments of the efficacy of fipronil-based cattle treatments in controlling sand fly populations depend on our assumptions regarding key aspects of sand fly ecology. Assessments are most sensitive to assumptions concerning the percentage of sand flies ovipositing in feces of treated cattle, thus emphasizing the importance of identifying sand fly oviposition sites. Our results place the evaluation of fipronil-based cattle treatment within a broader ecological context, which could aid in the planning and execution of a largescale field trial.
Collapse
Affiliation(s)
- David M. Poché
- Genesis Laboratories, Inc., Wellington, Colorado, United States of America
| | - Hsiao-Hsuan Wang
- Ecological Systems Laboratory, Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America
| | - William E. Grant
- Ecological Systems Laboratory, Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America
| |
Collapse
|
3
|
Tabbabi A, Daaboub J, Cheikh RB, Laamari A, Feriani M, Boubaker C, Jha IB, Cheikh HB. Resistance status to deltamethrin pyrethroid of Culex pipiens pipiens (Diptera: Culicidae) collected from three districts of Tunisia. Afr Health Sci 2018; 18:1182-1188. [PMID: 30766584 PMCID: PMC6354891 DOI: 10.4314/ahs.v18i4.39] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVES The aim of the present study was to determine the susceptibility status of Culex pipiens pipiens populations against deltamehtrin insecticide. METHODS Larvae of Culex pipiens pipiens were collected from three breeding places in Northern and Southern Tunisia between 2003 and 2005. Early third and late fourth instars were tested against deltamethrin pyrethroid insecticide. Cross-resistance with DDT resistance was evaluated in studied samples to estimate the role of target site insensitivity and two synergists including piperonyl butoxide (Pb) and S,S,S-tributyl phosphorotrithioate (DEF) were used to estimate the role of detoxification enzymes. RESULTS Our results revealed that the level of deltamehtrin resistance ranged from 0.67 to 31.4. We also showed the non-involvement of kdr resistance in pyrethroid resistance and no cross-resistance with DDT resistance was detected in all studied populations including the most resistant one. Synergists study on the resistant population (sample # 1) showed the involvement of CYP450 in the recorded resistance to the deltamethrin insecticide. CONCLUSION The results obtained from this study should be considered in the current control programs to combat mosquitoes in Tunisia.
Collapse
|
4
|
Dickson LB, Ghozlane A, Volant S, Bouchier C, Ma L, Vega-Rúa A, Dusfour I, Jiolle D, Paupy C, Mayanja MN, Kohl A, Lutwama JJ, Duong V, Lambrechts L. Diverse laboratory colonies of Aedes aegypti harbor the same adult midgut bacterial microbiome. Parasit Vectors 2018; 11:207. [PMID: 29587819 PMCID: PMC5870067 DOI: 10.1186/s13071-018-2780-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 03/06/2018] [Indexed: 03/25/2023] Open
Abstract
Background Host-associated microbes, collectively known as the microbiota, play an important role in the biology of multicellular organisms. In mosquito vectors of human pathogens, the gut bacterial microbiota influences vectorial capacity and has become the subject of intense study. In laboratory studies of vector biology, genetic effects are often inferred from differences between geographically and genetically diverse colonies of mosquitoes that are reared in the same insectary. It is unclear, however, to what extent genetic effects can be confounded by uncontrolled differences in the microbiota composition among mosquito colonies. To address this question, we used 16S metagenomics to compare the midgut bacterial microbiome of six laboratory colonies of Aedes aegypti recently derived from wild populations representing the geographical range and genetic diversity of the species. Results We found that the diversity, abundance, and community structure of the midgut bacterial microbiome was remarkably similar among the six different colonies of Ae. aegypti, regardless of their geographical origin. We also confirmed the relatively low complexity of bacterial communities inhabiting the mosquito midgut. Conclusions Our finding that geographically diverse colonies of Ae. aegypti reared in the same insectary harbor a similar gut bacterial microbiome supports the conclusion that the gut microbiota of adult mosquitoes is environmentally determined regardless of the host genotype. Thus, uncontrolled differences in microbiota composition are unlikely to represent a significant confounding factor in genetic studies of vector biology. Electronic supplementary material The online version of this article (10.1186/s13071-018-2780-1) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Laura B Dickson
- Insect-Virus Interactions Group, Department of Genomes and Genetics, Institut Pasteur, CNRS UMR 2000, Paris, France.
| | - Amine Ghozlane
- Bioinformatics and Biostatistics Hub, C3BI, USR 3756 CNRS, Institut Pasteur, Paris, France.,Genomics Facility - Biomics Pole, CITECH, Institut Pasteur, Paris, France
| | - Stevenn Volant
- Bioinformatics and Biostatistics Hub, C3BI, USR 3756 CNRS, Institut Pasteur, Paris, France
| | | | - Laurence Ma
- Genomics Facility - Biomics Pole, CITECH, Institut Pasteur, Paris, France
| | - Anubis Vega-Rúa
- Laboratory of Medical Entomology, Environment and Health Unit, Institut Pasteur de la Guadeloupe, Guadeloupe, France
| | - Isabelle Dusfour
- Vector Control and Adaptation, Institut Pasteur de la Guyane, Vectopole Amazonien Emile Abonnenc, Cayenne, French Guiana
| | - Davy Jiolle
- MIVEGEC, IRD, CNRS, University of Montpellier, Montpellier, France.,Centre International de Recherches Médicales de Franceville, Franceville, Gabon
| | - Christophe Paupy
- MIVEGEC, IRD, CNRS, University of Montpellier, Montpellier, France.,Centre International de Recherches Médicales de Franceville, Franceville, Gabon
| | - Martin N Mayanja
- Department of Arbovirology, Uganda Virus Research Institute, Entebbe, Uganda
| | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Glasgow, UK
| | - Julius J Lutwama
- Department of Arbovirology, Uganda Virus Research Institute, Entebbe, Uganda
| | - Veasna Duong
- Virology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Louis Lambrechts
- Insect-Virus Interactions Group, Department of Genomes and Genetics, Institut Pasteur, CNRS UMR 2000, Paris, France.
| |
Collapse
|
5
|
Lord JS, Torr SJ, Auty HK, Brock PM, Byamungu M, Hargrove JW, Morrison LJ, Mramba F, Vale GA, Stanton MC. Geostatistical models using remotely-sensed data predict savanna tsetse decline across the interface between protected and unprotected areas in Serengeti, Tanzania. J Appl Ecol 2018; 55:1997-2007. [PMID: 30008483 PMCID: PMC6032868 DOI: 10.1111/1365-2664.13091] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/05/2017] [Indexed: 11/29/2022]
Abstract
Monitoring abundance is essential for vector management, but it is often only possible in a fraction of managed areas. For vector control programmes, sampling to estimate abundance is usually carried out at a local‐scale (10s km2), while interventions often extend across 100s km2. Geostatistical models have been used to interpolate between points where data are available, but this still requires costly sampling across the entire area of interest. Instead, we used geostatistical models to predict local‐scale spatial variation in the abundance of tsetse—vectors of human and animal African trypanosomes—beyond the spatial extent of data to which models were fitted, in Serengeti, Tanzania. We sampled Glossina swynnertoni and Glossina pallidipes >10 km inside the Serengeti National Park (SNP) and along four transects extending into areas where humans and livestock live. We fitted geostatistical models to data >10 km inside the SNP to produce maps of abundance for the entire region, including unprotected areas. Inside the SNP, the mean number of G. pallidipes caught per trap per day in dense woodland was 166 (± 24 SE), compared to 3 (±1) in grassland. Glossina swynnertoni was more homogenous with respective means of 15 (±3) and 15 (±8). In general, models predicted a decline in abundance from protected to unprotected areas, related to anthropogenic changes to vegetation, which was confirmed during field survey. Synthesis and applications. Our approach allows vector control managers to identify sites predicted to have relatively high tsetse abundance, and therefore to design and implement improved surveillance strategies. In East and Southern Africa, trypanosomiasis is associated with wilderness areas. Our study identified pockets of vegetation which could sustain tsetse populations in farming areas outside the Serengeti National Park. Our method will assist countries in identifying, monitoring and, if necessary, controlling tsetse in trypanosomiasis foci. This has specific application to tsetse, but the approach could also be developed for vectors of other pathogens.
Our approach allows vector control managers to identify sites predicted to have relatively high tsetse abundance, and therefore to design and implement improved surveillance strategies. In East and Southern Africa, trypanosomiasis is associated with wilderness areas. Our study identified pockets of vegetation which could sustain tsetse populations in farming areas outside the Serengeti National Park. Our method will assist countries in identifying, monitoring and, if necessary, controlling tsetse in trypanosomiasis foci. This has specific application to tsetse, but the approach could also be developed for vectors of other pathogens.
Collapse
Affiliation(s)
- Jennifer S Lord
- Department of Vector Biology Liverpool School of Tropical Medicine Liverpool UK
| | - Stephen J Torr
- Department of Vector Biology Liverpool School of Tropical Medicine Liverpool UK
| | | | - Paddy M Brock
- Institute of Biodiversity, Animal Health and Comparative Medicine College of Medical, Veterinary and Life Sciences University of Glasgow Glasgow UK
| | | | | | - Liam J Morrison
- Roslin Institute Royal (Dick) School of Veterinary Studies University of Edinburgh Midlothian UK
| | - Furaha Mramba
- Vector and Vector-Borne Diseases Research Institute Tanga Tanzania
| | - Glyn A Vale
- SACEMA University of Stellenbosch Stellenbosch South Africa.,Natural Resources Institute University of Greenwich Chatham UK
| | - Michelle C Stanton
- Department of Vector Biology Liverpool School of Tropical Medicine Liverpool UK
| |
Collapse
|
6
|
Mosquitoes as Arbovirus Vectors: From Species Identification to Vector Competence. PARASITOLOGY RESEARCH MONOGRAPHS 2018. [PMCID: PMC7122353 DOI: 10.1007/978-3-319-94075-5_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Mosquitoes and other arthropods transmit a large number of medically important pathogens, in particular viruses. These arthropod-borne viruses (arboviruses) include a wide variety of RNA viruses belonging to the Flaviviridae family (West Nile virus (WNV), Usutu virus (USUV), Dengue virus (DENV), Japanese encephalitis virus (JEV), Zika virus (ZIKV)), the Togaviridae family (Chikungunya virus (CHIKV)), and Bunyavirales order (Rift Valley fever virus (RVFV)) (please refer also to Table 9.1). Arboviral transmission to humans and livestock constitutes a major threat to public health and economy as illustrated by the emergence of ZIKV in the Americas, RVFV outbreaks in Africa, and the worldwide outbreaks of DENV. To answer the question if those viral pathogens also pose a risk to Europe, we need to first answer the key questions (summarized in Fig. 9.1):Who could contribute to such an outbreak? Information about mosquito species resident or imported, potential hosts and viruses able to infect vectors and hosts in Germany is needed. Where would competent mosquito species meet favorable conditions for transmission? Information on the minimum requirements for efficient replication of the virus in a given vector species and subsequent transmission is needed. How do viruses and vectors interact to facilitate transmission? Information on the vector immunity, vector physiology, vector genetics, and vector microbiomes is needed.
Collapse
|
7
|
Almeida APG, Fouque F, Launois P, Sousa CA, Silveira H. From the Laboratory to the Field: Updating Capacity Building in Medical Entomology. Trends Parasitol 2017. [PMID: 28624159 DOI: 10.1016/j.pt.2017.05.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Training and innovation in the field of medical entomology are essential to mitigate the burden of vector-borne diseases globally. However, there is a shortage of medical entomologists worldwide, and there are large discrepancies in capacity building in this field. In this article, we discuss the current situation, what is needed from the medical entomologist of today, and how we can bridge this gap.
Collapse
Affiliation(s)
- Antonio Paulo Gouveia Almeida
- GHTM/Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira, 100, 1349-008 Lisboa, Portugal; CVZ/Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
| | - Florence Fouque
- TDR/WHO - The Special Programme for Research and Training in Tropical Diseases, World Health Organization. 20, Avenue Appia, CH-1211 Geneva 27, Switzerland
| | - Pascal Launois
- TDR/WHO - The Special Programme for Research and Training in Tropical Diseases, World Health Organization. 20, Avenue Appia, CH-1211 Geneva 27, Switzerland
| | - Carla A Sousa
- GHTM/Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira, 100, 1349-008 Lisboa, Portugal
| | - Henrique Silveira
- GHTM/Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira, 100, 1349-008 Lisboa, Portugal
| |
Collapse
|
8
|
Casas J, Lazzari C, Insausti T, Launois P, Fouque F. Mapping of courses on vector biology and vector-borne diseases systems: time for a worldwide effort. Mem Inst Oswaldo Cruz 2016; 111:717-719. [PMID: 27759770 PMCID: PMC5125055 DOI: 10.1590/0074-02760160295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 08/12/2016] [Indexed: 11/23/2022] Open
Abstract
Major emergency efforts are being mounted for each vector-borne disease
epidemiological crisis anew, while knowledge about the biology of arthropods vectors
is dwindling slowly but continuously, as is the number of field entomologists. The
discrepancy between the rates of production of knowledge and its use and need for
solving crises is widening, in particular due to the highly differing time spans of
the two concurrent processes. A worldwide web based search using multiple key words
and search engines of onsite and online courses in English, Spanish, Portuguese,
French, Italian and German concerned with the biology of vectors identified over 140
courses. They are geographically and thematically scattered, the vast majority of
them are on-site, with very few courses using the latest massive open online course
(MOOC) powerfulness. Over two third of them is given in English and Western Africa is
particularity poorly represented. The taxonomic groups covered are highly unbalanced
towards mosquitoes. A worldwide unique portal to guide students of all grades and
levels of expertise, in particular those in remote locations, is badly needed. This
is the objective a new activity supported by the Special Programme for Research and
Training in Tropical Diseases (TDR).
Collapse
Affiliation(s)
- Jérôme Casas
- Université de Tours, Institut de Recherche en Biologie de l'Insectes, Unité Mixte de Recherches, Centre National de la Recherche Scientifique, Tours, France
| | - Claudio Lazzari
- Université de Tours, Institut de Recherche en Biologie de l'Insectes, Unité Mixte de Recherches, Centre National de la Recherche Scientifique, Tours, France
| | - Teresita Insausti
- Université de Tours, Institut de Recherche en Biologie de l'Insectes, Unité Mixte de Recherches, Centre National de la Recherche Scientifique, Tours, France
| | - Pascal Launois
- Research and Training in Tropical Diseases, World Health Organization, Geneva, Switzerland
| | - Florence Fouque
- Research and Training in Tropical Diseases, World Health Organization, Geneva, Switzerland
| |
Collapse
|
9
|
Burns TE, Stephen C. Finding a Place for Systems-Based, Collaborative Research in Emerging Disease Research in Asia. ECOHEALTH 2015; 12:672-684. [PMID: 26582581 DOI: 10.1007/s10393-015-1072-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 09/14/2015] [Accepted: 09/27/2015] [Indexed: 06/05/2023]
Abstract
The need to adequately predict, prevent and respond to infectious diseases emerging unexpectedly from human-animal-environmental systems has driven interest in multisectoral, socio-economic, systems-based, collaborative (MSC) research approaches such as EcoHealth and One Health. Our goals were to document how MSC research has been used to address EIDs in Asia, and to explore how MSC approaches align with current priorities for EID research in Asia. We gathered priorities for EID research from the peer-reviewed and grey literature, documented organizational descriptions of MCS research approaches, and analysed a series of EID MSC projects. We found that priority areas for EID research in Asia included (1) understanding host-pathogen-environment interactions; (2) improving tools and technologies; (3) changing people's behaviour; and (4) evaluating the effectiveness of interventions. We found that the unifying characteristics of MSC research were that it was action-oriented and sought to inspire change under real-world conditions at the complex interface of human and natural systems. We suggest that MSC research can be considered a type of 'pragmatic research' and might be most useful in describing change in complex human-animal-environmental systems, accelerating research-to-action, and evaluating effectiveness of interventions in 'real world' settings.
Collapse
Affiliation(s)
- Theresa E Burns
- Centre for Coastal Health, 900 Fifth Street, Nanaimo, BC, V9R 5S5, Canada.
| | - Craig Stephen
- Canadian Wildlife Health Cooperative, Nanaimo, BC, Canada
| |
Collapse
|
10
|
Angwech H, Nyeko JHP, Opiyo EA, Okello-Onen J, Opiro R, Echodu R, Malinga GM, Njahira MN, Skilton RA. Heterogeneity in the prevalence and intensity of bovine trypanosomiasis in the districts of Amuru and Nwoya, Northern Uganda. BMC Vet Res 2015; 11:255. [PMID: 26449544 PMCID: PMC4599665 DOI: 10.1186/s12917-015-0567-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 09/30/2015] [Indexed: 11/11/2022] Open
Abstract
Background Livestock trypanosomiasis, transmitted mainly by tsetse flies of the genus Glossina is a major constraint to livestock health and productivity in the sub-Saharan Africa. Knowledge of the prevalence and intensity of trypanosomiasis is important in understanding the epidemiology of the disease. The objectives of this study were to (a) assess the prevalence and intensity of trypanosome infections in cattle, and (b) to investigate the reasons for the heterogeneity of the disease in the tsetse infested districts of Amuru and Nwoya, northern Uganda. Methods A cross-sectional study was conducted from September, 2011 to January, 2012. Blood samples were collected from 816 cattle following jugular vein puncture, and screened for trypanosomes by HCT and ITS-PCR. A Pearson chi-squared test and logistic regression analyses were performed to determine the association between location, age, sex, and prevalence of trypanosome infections. Results Out of the 816 blood samples examined, 178 (22 %) and 338 (41 %) tested positive for trypanosomiasis by HCT and ITS-PCR, respectively. Trypanosoma vivax infection accounted for 77 % of infections detected by ITS-PCR, T. congolense (16 %), T. brucei s.l (4 %) and mixed (T. vivax/ T. congolense/T.brucei) infections (3 %). The risk of trypanosome infection was significantly associated with cattle age (χ2
= 220.4, df = 3, P < 0.001). The highest proportions of infected animals were adult males (26.7 %) and the least infected were the less than one year old calves (2.0 %). In addition, the risk of trypanosome infection was significantly associated with sex (χ2 = 16.64, df = 1, P < 0.001), and males had a significantly higher prevalence of infections (26.8 %) than females (14.6 %). Conclusion Our results indicate that the prevalence and intensity of trypanosome infections are highly heterogeneous being associated with cattle age, location and sex.
Collapse
Affiliation(s)
- Harriet Angwech
- Department of Biology, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda.
| | - Jack H P Nyeko
- Department of Biology, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda.
| | - Elizabeth A Opiyo
- Department of Biology, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda.
| | - Joseph Okello-Onen
- Department of Biology, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda
| | - Robert Opiro
- Department of Biology, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda.
| | - Richard Echodu
- Department of Biology, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda.
| | - Geoffrey M Malinga
- Department of Biology, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda. .,Department of Biology, University of Eastern Finland, P. O. Box 111, 80101, Joensuu, Finland.
| | - Moses N Njahira
- Biosciences Eastern and Central Africa (BecA), International Livestock Research Institute (ILRI) - Hub, Old Naivasha Road, P.O. Box 30709- 00100, Nairobi, Kenya.
| | - Robert A Skilton
- Biosciences Eastern and Central Africa (BecA), International Livestock Research Institute (ILRI) - Hub, Old Naivasha Road, P.O. Box 30709- 00100, Nairobi, Kenya.
| |
Collapse
|
11
|
Shi L, Hu H, Ma K, Zhou D, Yu J, Zhong D, Fang F, Chang X, Hu S, Zou F, Wang W, Sun Y, Shen B, Zhang D, Ma L, Zhou G, Yan G, Zhu C. Development of Resistance to Pyrethroid in Culex pipiens pallens Population under Different Insecticide Selection Pressures. PLoS Negl Trop Dis 2015; 9:e0003928. [PMID: 26275298 PMCID: PMC4537097 DOI: 10.1371/journal.pntd.0003928] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 06/22/2015] [Indexed: 11/18/2022] Open
Abstract
Current vector control programs are largely dependent on pyrethroids, which are the most commonly used and only insecticides recommended by the World Health Organization for insecticide-treated nets (ITNs). However, the rapid spread of pyrethroid resistance worldwide compromises the effectiveness of control programs and threatens public health. Since few new insecticide classes for vector control are anticipated, limiting the development of resistance is crucial for prolonging efficacy of pyrethroids. In this study, we exposed a field-collected population of Culex pipiens pallens to different insecticide selection intensities to dynamically monitor the development of resistance. Moreover, we detected kdr mutations and three detoxification enzyme activities in order to explore the evolutionary mechanism of pyrethroid resistance. Our results revealed that the level of pyrethroid resistance was proportional to the insecticide selection pressure. The kdr and metabolic resistance both contributed to pyrethroid resistance in the Cx. pipiens pallens populations, but they had different roles under different selection pressures. We have provided important evidence for better understanding of the development and mechanisms of pyrethroid resistance which may guide future insecticide use and vector management in order to avoid or delay resistance.
Collapse
Affiliation(s)
- Linna Shi
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
- Department of Pathogenic Microorganism and Laboratory Medicine, Shaanxi University of Chinese Medicine, Shaanxi, China
| | - Hongxia Hu
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Kai Ma
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Dan Zhou
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Jing Yu
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Daibin Zhong
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, California, United States of America
| | - Fujin Fang
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Xuelian Chang
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Shengli Hu
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Feifei Zou
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Weijie Wang
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Yan Sun
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Bo Shen
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Donghui Zhang
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Lei Ma
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
| | - Guofa Zhou
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, California, United States of America
| | - Guiyun Yan
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, California, United States of America
| | - Changliang Zhu
- Department of Pathogen Biology, Nanjing Medical University, Nanjing, China
- * E-mail:
| |
Collapse
|
12
|
Spatial heterogeneity, host movement and mosquito-borne disease transmission. PLoS One 2015; 10:e0127552. [PMID: 26030769 PMCID: PMC4452543 DOI: 10.1371/journal.pone.0127552] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 04/16/2015] [Indexed: 11/19/2022] Open
Abstract
Mosquito-borne diseases are a global health priority disproportionately affecting low-income populations in tropical and sub-tropical countries. These pathogens live in mosquitoes and hosts that interact in spatially heterogeneous environments where hosts move between regions of varying transmission intensity. Although there is increasing interest in the implications of spatial processes for mosquito-borne disease dynamics, most of our understanding derives from models that assume spatially homogeneous transmission. Spatial variation in contact rates can influence transmission and the risk of epidemics, yet the interaction between spatial heterogeneity and movement of hosts remains relatively unexplored. Here we explore, analytically and through numerical simulations, how human mobility connects spatially heterogeneous mosquito populations, thereby influencing disease persistence (determined by the basic reproduction number R0), prevalence and their relationship. We show that, when local transmission rates are highly heterogeneous, R0 declines asymptotically as human mobility increases, but infection prevalence peaks at low to intermediate rates of movement and decreases asymptotically after this peak. Movement can reduce heterogeneity in exposure to mosquito biting. As a result, if biting intensity is high but uneven, infection prevalence increases with mobility despite reductions in R0. This increase in prevalence decreases with further increase in mobility because individuals do not spend enough time in high transmission patches, hence decreasing the number of new infections and overall prevalence. These results provide a better basis for understanding the interplay between spatial transmission heterogeneity and human mobility, and their combined influence on prevalence and R0.
Collapse
|
13
|
|
14
|
Harris JW, Richards SL, Anderson A. Emergency mosquito control on a selected area in eastern north Carolina after hurricane irene. ENVIRONMENTAL HEALTH INSIGHTS 2014; 8:29-33. [PMID: 25574141 PMCID: PMC4267522 DOI: 10.4137/ehi.s16001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 10/14/2014] [Accepted: 10/16/2014] [Indexed: 05/25/2023]
Abstract
Natural disasters such as hurricanes may contribute to mosquito abundance and, consequently, arbovirus transmission risk. In 2011, flooding from Hurricane Irene in eastern North Carolina (NC) resulted in increased mosquito populations that hindered recovery efforts. Budget shortfalls in NC have reduced the functionality of long-term mosquito surveillance and control programs; hence, many counties rely on the Federal Emergency Management Agency for post-disaster mosquito control. This pilot study examines mosquito abundance pre- and post-aerial insecticide spraying at eight study sites in Washington and Tyrrell Counties in rural eastern NC after Hurricane Irene. Percent change was calculated and compared for traps in areas that received aerial pesticide application and those that did not. Traps in spray zones show decreases in mosquito abundance when compared to control traps (treatment: -52.93%; control: 3.55%), although no significant differences (P = 0.286) were found in mosquito abundance between groups. Implications of reactive rather than proactive mosquito control responses are discussed.
Collapse
|
15
|
Framework for rapid assessment and adoption of new vector control tools. Trends Parasitol 2014; 30:191-204. [DOI: 10.1016/j.pt.2014.02.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Revised: 02/13/2014] [Accepted: 02/13/2014] [Indexed: 11/23/2022]
|
16
|
LORD CC, ALTO BW, ANDERSON SL, CONNELLY CR, DAY JF, RICHARDS SL, SMARTT CT, TABACHNICK WJ. Can Horton hear the whos? The importance of scale in mosquito-borne disease. JOURNAL OF MEDICAL ENTOMOLOGY 2014; 51:297-313. [PMID: 24724278 PMCID: PMC5027650 DOI: 10.1603/me11168] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The epidemiology of vector-borne pathogens is determined by mechanisms and interactions at different scales of biological organization, from individual-level cellular processes to community interactions between species and with the environment. Most research, however, focuses on one scale or level with little integration between scales or levels within scales. Understanding the interactions between levels and how they influence our perception of vector-borne pathogens is critical. Here two examples of biological scales (pathogen transmission and mosquito mortality) are presented to illustrate some of the issues of scale and to explore how processes on different levels may interact to influence mosquito-borne pathogen transmission cycles. Individual variation in survival, vector competence, and other traits affect population abundance, transmission potential, and community structure. Community structure affects interactions between individuals such as competition and predation, and thus influences the individual-level dynamics and transmission potential. Modeling is a valuable tool to assess interactions between scales and how processes at different levels can affect transmission dynamics. We expand an existing model to illustrate the types of studies needed, showing that individual-level variation in viral dose acquired or needed for infection can influence the number of infectious vectors. It is critical that interactions within and among biological scales and levels of biological organization are understood for greater understanding of pathogen transmission with the ultimate goal of improving control of vector-borne pathogens.
Collapse
Affiliation(s)
- C. C. LORD
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - B. W. ALTO
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - S. L. ANDERSON
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - C. R. CONNELLY
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - J. F. DAY
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - S. L. RICHARDS
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - C. T. SMARTT
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - W. J. TABACHNICK
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| |
Collapse
|
17
|
Forshey BM, Stoddard ST, Halsey ES. Direct feeding on dengue patients yields new insights into human-to-mosquito dengue virus transmission. Future Virol 2013. [DOI: 10.2217/fvl.13.95] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Evaluation of: Nguyen MN, Duong TH, Trung VT et al. Host and viral features of human dengue cases shape the population of infected and infectious Aedes aegypti mosquitoes. Proc. Natl Acad. Sci. USA 110(22), 9072–9077 (2013). Dengue virus (DENV) is a mosquito-borne virus of immense and growing global health importance. Despite decades of research, many fundamental components of DENV biology remain poorly understood. The Nguyen et al. study shines new light on one such component: the relationship between DENV blood viremia and infectiousness to mosquitoes. By directly feeding mosquitoes on infected people, the authors identified the viremia levels required for mosquitoes to become infected with each of the four DENV serotypes. Based on these results, the authors then indicated that ambulatory dengue cases who did not visit a hospital had viremia levels sufficient to infect mosquitoes. In avoiding laboratory surrogates, this study has significantly improved our understanding of DENV with implications for modeling and vaccine development.
Collapse
Affiliation(s)
- Brett M Forshey
- Virology Department, US Naval Medical Research Unit No. 6, Lima, Peru
| | - Steven T Stoddard
- Department of Entomology, University of California, Davis, CA 95616, USA
| | - Eric S Halsey
- Virology Department, US Naval Medical Research Unit No. 6, Lima, Peru
| |
Collapse
|
18
|
Tabachnick WJ. Nature, nurture and evolution of intra-species variation in mosquito arbovirus transmission competence. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2013; 10:249-77. [PMID: 23343982 PMCID: PMC3564141 DOI: 10.3390/ijerph10010249] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 12/29/2012] [Accepted: 01/09/2013] [Indexed: 01/14/2023]
Abstract
Mosquitoes vary in their competence or ability to transmit arthropod-borne viruses (arboviruses). Many arboviruses cause disease in humans and animals. Identifying the environmental and genetic causes of variation in mosquito competence for arboviruses is one of the great challenges in public health. Progress identifying genetic (nature) and environmental (nurture) factors influencing mosquito competence for arboviruses is reviewed. There is great complexity in the various traits that comprise mosquito competence. The complex interactions between environmental and genetic factors controlling these traits and the factors shaping variation in Nature are largely unknown. The norms of reaction of specific genes influencing competence, their distributions in natural populations and the effects of genetic polymorphism on phenotypic variation need to be determined. Mechanisms influencing competence are not likely due to natural selection because of the direct effects of the arbovirus on mosquito fitness. More likely the traits for mosquito competence for arboviruses are the effects of adaptations for other functions of these competence mechanisms. Determining these other functions is essential to understand the evolution and distributions of competence for arboviruses. This information is needed to assess risk from mosquito-borne disease, predict new mosquito-arbovirus systems, and provide novel strategies to mitigate mosquito-borne arbovirus transmission.
Collapse
Affiliation(s)
- Walter J Tabachnick
- Florida Medical Entomology Laboratory, University of Florida, IFAS, 200 9th St. SE, Vero Beach, FL 32962, USA.
| |
Collapse
|
19
|
Tchouassi DP, Sang R, Sole CL, Bastos ADS, Mithoefer K, Torto B. Sheep skin odor improves trap captures of mosquito vectors of Rift Valley fever. PLoS Negl Trop Dis 2012; 6:e1879. [PMID: 23133687 PMCID: PMC3486883 DOI: 10.1371/journal.pntd.0001879] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Accepted: 09/12/2012] [Indexed: 11/19/2022] Open
Abstract
In recent years, the East African region has seen an increase in arboviral diseases transmitted by blood-feeding arthropods. Effective surveillance to monitor and reduce incidence of these infections requires the use of appropriate vector sampling tools. Here, trapped skin volatiles on fur from sheep, a known preferred host of mosquito vectors of Rift Valley fever virus (RVFV), were used with a standard CDC light trap to improve catches of mosquito vectors. We tested the standard CDC light trap alone (L), and baited with (a) CO2 (LC), (b) animal volatiles (LF), and (c) CO2 plus animal volatiles (LCF) in two highly endemic areas for RVF in Kenya (Marigat and Ijara districts) from March–June and September–December 2010. The incidence rate ratios (IRR) that mosquito species chose traps baited with treatments (LCF, LC and LF) instead of the control (L) were estimated. Marigat was dominated by secondary vectors and host-seeking mosquitoes were 3–4 times more likely to enter LC and LCF traps [IRR = 3.1 and IRR = 3.8 respectively] than the L only trap. The LCF trap captured a greater number of mosquitoes than the LC trap (IRR = 1.23) although the difference was not significant. Analogous results were observed at Ijara, where species were dominated by key primary and primary RVFV vectors, with 1.6-, 6.5-, and 8.5-fold increases in trap captures recorded in LF, LC and LCF baited traps respectively, relative to the control. These catches all differed significantly from those trapped in L only. Further, there was a significant increase in trap captures in LCF compared to LC (IRR = 1.63). Mosquito species composition and trap counts differed between the RVF sites. However, within each site, catches differed in abundance only and no species preferences were noted in the different baited-traps. Identifying the attractive components present in these natural odors should lead to development of an effective odor-bait trapping system for population density-monitoring and result in improved RVF surveillance especially during the inter-epidemic period. The East African region is a major epizootic center for endemic and emerging mosquito borne-arboviruses such as Rift Valley fever virus (RVFV), as evidenced by the increasing frequency and magnitude of this disease. The absence of vaccines or prophylactic drugs for most of these diseases emphasizes the need for accurate sampling of mosquito vector populations and testing for arboviruses. Accurate surveillance is crucial for early warning of potential or assessing mitigation of existing outbreaks. However, it is a challenge to sample mosquitoes in adequate numbers during the inter-epidemic periods (IEP) because this period is characterized by low mosquito population densities, sporadic transmission foci and low mosquito infection rates. Therefore more efficient tools are needed to increase capture rates so maximized virus detection probability in the mosquitoes can be achieved for assessing risk and outbreak predictions. This can be accomplished by exploiting the host-seeking behavior of adult female mosquitoes and the olfactory cues used to locate a potential host. Here, odors emanating from fur of sheep, a susceptible host for RVFV, is shown to improve trap capture rates of mosquito vectors of RVF in a standard surveillance trap. These data provide for future investigations to identify attractive components present in these natural odors, so that they can be incorporated into existing traps to serve as a population density-monitoring tool for improved arbovirus disease surveillance during IEP.
Collapse
Affiliation(s)
- David P. Tchouassi
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Rosemary Sang
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
- Centre for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya
| | - Catherine L. Sole
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Armanda D. S. Bastos
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Klaus Mithoefer
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | - Baldwyn Torto
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
- * E-mail:
| |
Collapse
|
20
|
Emergence and prevalence of human vector-borne diseases in sink vector populations. PLoS One 2012; 7:e36858. [PMID: 22629337 PMCID: PMC3356347 DOI: 10.1371/journal.pone.0036858] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 04/16/2012] [Indexed: 01/04/2023] Open
Abstract
Vector-borne diseases represent a major public health concern in most tropical and subtropical areas, and an emerging threat for more developed countries. Our understanding of the ecology, evolution and control of these diseases relies predominantly on theory and data on pathogen transmission in large self-sustaining ‘source’ populations of vectors representative of highly endemic areas. However, there are numerous places where environmental conditions are less favourable to vector populations, but where immigration allows them to persist. We built an epidemiological model to investigate the dynamics of six major human vector borne-diseases in such non self-sustaining ‘sink’ vector populations. The model was parameterized through a review of the literature, and we performed extensive sensitivity analysis to look at the emergence and prevalence of the pathogen that could be encountered in these populations. Despite the low vector abundance in typical sink populations, all six human diseases were able to spread in 15–55% of cases after accidental introduction. The rate of spread was much more strongly influenced by vector longevity, immigration and feeding rates, than by transmission and virulence of the pathogen. Prevalence in humans remained lower than 5% for dengue, leishmaniasis and Japanese encephalitis, but substantially higher for diseases with longer duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were again the key factors, although their influence was lower than on pathogen emergence. Our results emphasize the need for ecology and evolution to be thought in the context of metapopulations made of a mosaic of sink and source habitats, and to design vector control program not only targeting areas of high vector density, but working at a larger spatial scale.
Collapse
|
21
|
Eastep NE, Albert RE, Anderson JR. Modulation of La Crosse Virus Infection in Aedes albopictus Mosquitoes Following Larval Exposure to Coffee Extracts. Front Physiol 2012; 3:66. [PMID: 22470349 PMCID: PMC3314198 DOI: 10.3389/fphys.2012.00066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 03/07/2012] [Indexed: 01/30/2023] Open
Abstract
The mosquito-borne La Crosse virus (LACV; Family Bunyaviridae) may cause encephalitis, primarily in children, and is distributed throughout much of the eastern United States. No antivirals or vaccines are available for LACV, or most other mosquito-borne viruses, and prevention generally relies on mosquito control. We sought to determine whether coffee extracts could interfere with LACV replication and vector mosquito development. Both regular and decaffeinated coffee demonstrated significant reductions in LACV replication in direct antiviral assays. This activity was not due to the presence of caffeine, which did not inhibit the virus life cycle. Aedes albopictus (Skuse; Diptera: Culicidae) mosquito larvae suffered near total mortality when reared in high concentrations of regular and decaffeinated coffee and in caffeine. Following larval exposure to sublethal coffee concentrations, adult A. albopictus mosquitoes had significantly reduced whole-body LACV titers 5 days post-infection, compared to larvae reared in distilled water. These results suggest that it may be possible to both control mosquito populations and alter the vector competence of mosquitoes for arthropod-borne viruses by introducing antiviral compounds into the larval habitat.
Collapse
Affiliation(s)
- Nicole E Eastep
- Radford Arbovirus and Medical Entomology Laboratory, Department of Biology, Radford University Radford, VA, USA
| | | | | |
Collapse
|
22
|
Climate-based models for understanding and forecasting dengue epidemics. PLoS Negl Trop Dis 2012; 6:e1470. [PMID: 22348154 PMCID: PMC3279338 DOI: 10.1371/journal.pntd.0001470] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 11/21/2011] [Indexed: 11/19/2022] Open
Abstract
Background Dengue dynamics are driven by complex interactions between human-hosts, mosquito-vectors and viruses that are influenced by environmental and climatic factors. The objectives of this study were to analyze and model the relationships between climate, Aedes aegypti vectors and dengue outbreaks in Noumea (New Caledonia), and to provide an early warning system. Methodology/Principal Findings Epidemiological and meteorological data were analyzed from 1971 to 2010 in Noumea. Entomological surveillance indices were available from March 2000 to December 2009. During epidemic years, the distribution of dengue cases was highly seasonal. The epidemic peak (March–April) lagged the warmest temperature by 1–2 months and was in phase with maximum precipitations, relative humidity and entomological indices. Significant inter-annual correlations were observed between the risk of outbreak and summertime temperature, precipitations or relative humidity but not ENSO. Climate-based multivariate non-linear models were developed to estimate the yearly risk of dengue outbreak in Noumea. The best explicative meteorological variables were the number of days with maximal temperature exceeding 32°C during January–February–March and the number of days with maximal relative humidity exceeding 95% during January. The best predictive variables were the maximal temperature in December and maximal relative humidity during October–November–December of the previous year. For a probability of dengue outbreak above 65% in leave-one-out cross validation, the explicative model predicted 94% of the epidemic years and 79% of the non epidemic years, and the predictive model 79% and 65%, respectively. Conclusions/Significance The epidemic dynamics of dengue in Noumea were essentially driven by climate during the last forty years. Specific conditions based on maximal temperature and relative humidity thresholds were determinant in outbreaks occurrence. Their persistence was also crucial. An operational model that will enable health authorities to anticipate the outbreak risk was successfully developed. Similar models may be developed to improve dengue management in other countries. Dengue fever is a major public health problem in the tropics and subtropics. Since no vaccine exists, understanding and predicting outbreaks remain of crucial interest. Climate influences the mosquito-vector biology and the viral transmission cycle. Its impact on dengue dynamics is of growing interest. We analyzed the epidemiology of dengue in Noumea (New Caledonia) from 1971 to 2010 and its relationships with local and remote climate conditions using an original approach combining a comparison of epidemic and non epidemic years, bivariate and multivariate analyses. We found that the occurrence of outbreaks in Noumea was strongly influenced by climate during the last forty years. Efficient models were developed to estimate the yearly risk of outbreak as a function of two meteorological variables that were contemporaneous (explicative model) or prior (predictive model) to the outbreak onset. Local threshold values of maximal temperature and relative humidity were identified. Our results provide new insights to understand the link between climate and dengue outbreaks, and have a substantial impact on dengue management in New Caledonia since the health authorities have integrated these models into their decision making process and vector control policies. This raises the possibility to provide similar early warning systems in other countries.
Collapse
|
23
|
Maciel-de-Freitas R, Lourenço-de-Oliveira R. Does targeting key-containers effectively reduce Aedes aegypti population density? Trop Med Int Health 2011; 16:965-73. [PMID: 21605290 DOI: 10.1111/j.1365-3156.2011.02797.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES The elimination of Aedes aegypti breeding sites has been broadly adopted worldwide to keep vector population density below a critical threshold. We observed the effectiveness of targeting the most productive containers on adult A. aegypti females density, which was evaluated weekly. METHODS AND RESULTS Adult mosquitoes were collected weekly over 55 weeks and pupal surveys were done in intervals of 4 months to determine container productivity and guidelines for interventions. Pupal surveys indicated that water tanks (72% of pupae in first survey) and metal drums (30.7% of pupae in second survey) were the most productive container types. We observed a dramatic but short-term decrease in weekly adult female A. aegypti density after covering 733 water tanks with nylon net. A long-term decrease in female adult population density was achieved only when we covered both water tanks and metal drums. Overall, pupae abundance and pupae standing crop diminished after netting water tanks and metal drums. Pupae per person, per hectare and per house decreased gradually between the first and the third pupal surveys, suggesting that targeting the most productive container types (water tanks and metal drums) produced a reduction in adult population density and infestation levels. CONCLUSION Overall, targeting the most productive container types caused the adult mosquito density to decrease over time, supporting the assumption that this intervention is an effective tool for dengue control. However, this effect was observed only when both water tanks and metal drums were covered, possibly due to the functional similarity between these container types, which are large, often shaded, perennial water storage containers.
Collapse
|
24
|
Quantitative genetics of Aedes aegypti vector competence for dengue viruses: towards a new paradigm? Trends Parasitol 2011; 27:111-4. [PMID: 21215699 DOI: 10.1016/j.pt.2010.12.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 12/02/2010] [Accepted: 12/03/2010] [Indexed: 01/28/2023]
Abstract
Similar to many other host-pathogen interactions, the vector competence of Aedes aegypti for dengue viruses appears to be determined by genotype-by-genotype interactions, whereby the outcome of infection depends on the specific combination of mosquito and virus genotypes. This can complicate efforts to dissect the genetic basis of vector competence in nature because it obscures mapping between genotype and phenotype and brings into question the notion of universal mosquito resistance or susceptibility. Conversely, it offers novel opportunities to better define compatible vector-pathogen associations based on integration of both vector and pathogen genomics, which should eventually improve understanding of pathogen transmission dynamics and the risk of vector-borne disease emergence.
Collapse
|
25
|
Luckhart S, Lindsay SW, James AA, Scott TW. Reframing critical needs in vector biology and management of vector-borne disease. PLoS Negl Trop Dis 2010; 4:e566. [PMID: 20186276 PMCID: PMC2826393 DOI: 10.1371/journal.pntd.0000566] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Shirley Luckhart
- Department of Medical Microbiology and Immunology, University of California at Davis, Davis, California, United States of America.
| | | | | | | |
Collapse
|
26
|
Jansen CC, Beebe NW. The dengue vector Aedes aegypti: what comes next. Microbes Infect 2010; 12:272-9. [PMID: 20096802 DOI: 10.1016/j.micinf.2009.12.011] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 12/22/2009] [Indexed: 01/01/2023]
Abstract
Aedes aegypti is the urban vector of dengue viruses worldwide. While climate influences the geographical distribution of this mosquito species, other factors also determine the suitability of the physical environment. Importantly, the close association of A. aegypti with humans and the domestic environment allows this species to persist in regions that may otherwise be unsuitable based on climatic factors alone. We highlight the need to incorporate the impact of the urban environment in attempts to model the potential distribution of A. aegypti and we briefly discuss the potential for future technology to aid management and control of this widespread vector species.
Collapse
Affiliation(s)
- Cassie C Jansen
- CSIRO Entomology, Long Pocket Laboratories, Indooroopilly, Queensland, Australia
| | | |
Collapse
|