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Montenegro-Quiñonez CA, Buhler C, Horstick O, Runge-Ranzinger S, Rahman KM. Efficacy and community-effectiveness of insecticide treated nets for the control of visceral leishmaniasis: A systematic review. PLoS Negl Trop Dis 2022; 16:e0010196. [PMID: 35235556 PMCID: PMC8890655 DOI: 10.1371/journal.pntd.0010196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 01/24/2022] [Indexed: 12/28/2022] Open
Abstract
Visceral leishmaniasis (VL) has been targeted for elimination from Southeast Asia (SEA). The disease has been endemic in SEA, and in other parts of the world involving both humans and animals. One of the key strategies for combating VL is controlling for the vector sandfly. There are a few vector control strategies that are currently in practice. We sought to assess the efficacy and community effectiveness of insecticide treated nets (ITNs) in controlling the burden of sandfly and the occurrence of VL among humans. We conducted a systematic review following a study protocol and the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) criteria. 6331 initial hits were retrieved from Google Scholar, Lilacs, PubMed, Science Direct, WHOlis, WHOiris and PAHOiris. 25 met the full inclusion criteria. Findings show that the insecticide impregnated bednets and the commercially treated long lasting insecticidal nets (LLINs) are effective in controlling sandflies, with mortalities as high as 75% lasting over a year; although their role in controlling VL in the community was not extensively studied, since effectiveness was usually measured with sandflies densities. Findings also show that insecticide impregnated bednets are low cost and well accepted in the community, however, early erosion of insecticides from nets could occur. Some studies also showed that killing of sandflies may not translate into reduction of VL, therefore sandfly knock down and killing data needs to be interpreted with caution. Conclusions of this review are (1) combining insecticide impregnated bednets, as targeted interventions, with another vector control measure, particularly indoor residual spraying, and in conjunction with case detection, could be the way forward to controlling VL in resource limited settings. (2) Given the current low incidence of VL in SEA, it can be difficult to further research the community effectiveness of those control measures in reducing VL. Visceral leishmaniasis (VL) is a vector borne disease endemic in Southeast Asia (SEA) and present in other regions of the world. In SEA the disease has been targeted for elimination. VL is transmitted by different species of sandflies and key strategies against VL rely on the control of the vectors. This systematic review assesses the efficacy and community effectiveness of insecticide treated nets (ITNs) in controlling sandflies and VL occurrence among humans. After a revision of 6331 initial hits, 25 studies were included in this systematic review. Main findings indicated that insecticide impregnated bednets and long-lasting insecticidal nets (LLINs) can effectively control sandflies, however, it was not possible to fully assess the role of ITNs in controlling VL transmission. Additional results showed that insecticide impregnated bednets are low cost and well accepted in the community, however early erosion of insecticides from the nets could occur. If insecticide impregnated bednets are combined with other vector control measures, such as indoor residual spraying, and together with case detection, it could be an important strategy to control VL in resource limited settings.
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Affiliation(s)
- Carlos Alberto Montenegro-Quiñonez
- Heidelberg Institute of Global Health, Research to Practice Group, Heidelberg University, Heidelberg, Germany
- Instituto de Investigaciones, Centro Universitario de Zacapa, Universidad de San Carlos de Guatemala, Zacapa, Guatemala
- * E-mail:
| | - Claudia Buhler
- Heidelberg Institute of Global Health, Research to Practice Group, Heidelberg University, Heidelberg, Germany
| | - Olaf Horstick
- Heidelberg Institute of Global Health, Research to Practice Group, Heidelberg University, Heidelberg, Germany
| | - Silvia Runge-Ranzinger
- Heidelberg Institute of Global Health, Research to Practice Group, Heidelberg University, Heidelberg, Germany
| | - Kazi Mizanur Rahman
- The University of Sydney, University Centre for Rural Health, Lismore, New South Wales, Australia
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Control of Canine Visceral Leishmaniasis: A Success Case Based on Deltamethrin 4% Collars. EPIDEMIOLGIA (BASEL, SWITZERLAND) 2021; 2:502-518. [PMID: 36417213 PMCID: PMC9620925 DOI: 10.3390/epidemiologia2040035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 09/24/2021] [Indexed: 12/14/2022]
Abstract
The effect of employing collars impregnated with deltamethrin 4% (DM4) to control canine visceral leishmaniasis (CVL) was evaluated. as were the individual factors associated with this infection. A cohort study that included household dogs was conducted between 2002 and 2006. The presence of pathognomonic signals, peridomiciliary sleep habits and breed were the main factors associated with the infection. The use of DM4 collars contributed to the reduction of CVL with an effectiveness of 66%, and the dogs' survival rate was greater than 90% at 50 months. In conclusion, the adoption of DM4 collars reduced the number of euthanized canines and in the incidence of CVL, and this reduction was sustained for one year after discontinuing the use of the collar.
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Rêgo FD, Soares RP. Lutzomyia longipalpis: an update on this sand fly vector. AN ACAD BRAS CIENC 2021; 93:e20200254. [PMID: 33950136 DOI: 10.1590/0001-37652021xxxx] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/17/2020] [Indexed: 12/13/2022] Open
Abstract
Lutzomyia longipalpis is the most important vector of Leishmania infantum, the etiological agent of visceral leishmaniasis (VL) in the New World. It is a permissive vector susceptible to infection with several Leishmania species. One of the advantages that favors the study of this sand fly is the possibility of colonization in the laboratory. For this reason, several researchers around the world use this species as a model for different subjects including biology, insecticides testing, host-parasite interaction, physiology, genetics, proteomics, molecular biology, and saliva among others. In 2003, we published our first review (Soares & Turco 2003) on this vector covering several aspects of Lu. longipalpis. This current review summarizes what has been published between 2003-2020. During this period, modern approaches were incorporated following the development of more advanced and sensitive techniques to assess this sand fly.
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Affiliation(s)
- Felipe D Rêgo
- Fundação Oswaldo Cruz (FIOCRUZ/MG), Instituto René Rachou, Avenida Augusto de Lima, 1715, Barro Preto, 30180-104 Belo Horizonte, MG, Brazil
| | - Rodrigo Pedro Soares
- Fundação Oswaldo Cruz (FIOCRUZ/MG), Instituto René Rachou, Avenida Augusto de Lima, 1715, Barro Preto, 30180-104 Belo Horizonte, MG, Brazil
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Khan W, Khan I, Ullah H, Zain SNM, Panhwar WA, Mehmood SA, Ahmed S, Siyal GB, Ahmad MS, Shah M, Rafique T, Ali N, Salim M, Hussain A. Cutaneous leishmaniasis-Awareness, knowledge and practices among general population in rural and urban areas in Malakand region, Pakistan. BRAZ J BIOL 2021; 82:e238665. [PMID: 33825759 DOI: 10.1590/1519-6984.238665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/27/2020] [Indexed: 11/22/2022] Open
Abstract
Malakand region is an endemic area for cutaneous leishmaniasis (CL). However, there are limited number of studies of this disease in Pakistan. Therefore, a study was conducted to understand the level of awareness attitude and practice among the residents of Makaland towards CL and the disease vectors. This study adopted a cross-sectional approach with a total of 400 respondents (n=93 rural and n= 307 urban). Overall, the population in Malakand region (61.2%) were well-informed in the role of sand fly in transmitting diseases, but most lack knowledge on the vector's behavior and almost a quarter (24.5%) were unable to provide knowledge on proper control measures. Alarmingly, the practice and attitudes of the general population was not satisfactory as close to half (49.8%) of the population did adopt any control method. This study calls for increase in awareness through health education campaign to reduce the risk of cutaneous leishmaniasis outbreaks in the future.
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Affiliation(s)
- W Khan
- University of Malakand, Laboratory of Parasitology, Department of Zoology, Lower Dir, Khyber Pakhtunkhwa, Pakistan
| | - I Khan
- Swat Medical College, Medical College, Saidu Group of Teaching Hospital, Medical Unit A, Saidu Sharif Swat, Khyber Pakhtunkhwa, Pakistan
| | - H Ullah
- University of Peshawar, Department of Zoology, Peshawar, Pakistan
| | - S N M Zain
- University of Malaya, Institute of Biological Sciences, Faculty of Science, Kuala Lumpur, Malaysia
| | - W A Panhwar
- Shah Abdul Latif University Khairpur, Department of Zoology, Miris, Sindh, Pakistan
| | - S A Mehmood
- Hazara University, Department of Zoology, Mansehra, Pakistan
| | - S Ahmed
- Hazara University, Department of Zoology, Mansehra, Pakistan
| | - G B Siyal
- Sindh University Jamshoro, Department of Zoology, Hyderabad, Pakistan
| | - M S Ahmad
- University of Swabi, Department of Zoology, Swabi, KP, Pakistan
| | - M Shah
- University of Swat, Centre for Animal Sciences & Fisheries, Swat, Pakistan
| | - T Rafique
- University of Malakand, Laboratory of Parasitology, Department of Zoology, Lower Dir, Khyber Pakhtunkhwa, Pakistan
| | - N Ali
- University of Haripur Department of Plant Breeding & Genetics, Haripur, Pakistan
| | - M Salim
- University of Haripur, Department of Forestry and Wildlife Management, Haripur, Pakistan
| | - A Hussain
- University of Haripur, Department of Forestry and Wildlife Management, Haripur, Pakistan
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Rassi Y, Ebrahimi S, Abai MR, Vatandoost H, Akhavan AA, Afshar AA. Comparative Testing of Susceptibility Levels of Phlebotomus sergenti, the Main Vector of Anthroponotic Cutaneous Leishmaniasis, to Conventional Insecticides Using Two Capture Methods in Kerman City, Southeastern Iran. J Arthropod Borne Dis 2021; 15:82-96. [PMID: 34277858 PMCID: PMC8271233 DOI: 10.18502/jad.v15i1.6488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 03/13/2021] [Indexed: 12/02/2022] Open
Abstract
Background: Collecting live sand flies from indoor sites is a major challenge for researchers in large cities due to the reluctance of families to survey their homes. This study was conducted to assess the efficacy of two methods for collecting sand flies for use in susceptibility tests in the urban area of Kerman, southeastern Iran. Methods: Sandflies were mainly collected using both baited traps and hand catch methods from outdoor and indoor sites. Susceptibility tests were separately done according to the standard World Health Organization testing protocol on Phlebotomus sergenti, including 60-minute exposure to DDT 4.0%, propoxur 0.1%, deltamethrin 0.05%, and malathion 5.0%. Results: During this research, the natural habitats and suitable indoor sites were selected to predict the density of live sand fly with perfect accuracy. The number of live Ph. sergenti caught by hand catch and baited traps methods was 42 and 361 in indoor and outdoor sites, respectively. The mortality rate of Ph. sergenti exposed to DDT 4%, deltamethrin 0.05, malathion 5%, and propoxur was 100%. Conclusion The baited traps showed a significant efficiency compared to hand catch for collecting live Ph. sergenti for use in susceptibility tests in urban areas. The Ph. sergenti collected from both indoor and outdoor sites were susceptible to all insecticides.
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Affiliation(s)
- Yavar Rassi
- Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Shahla Ebrahimi
- Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Reza Abai
- Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.,Department of Environmental Chemical Pollutants and Pesticides, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
| | - Hassan Vatandoost
- Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.,Department of Environmental Chemical Pollutants and Pesticides, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
| | - Amir Ahmad Akhavan
- Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.,Department of Environmental Chemical Pollutants and Pesticides, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
| | - Abass Aghaie Afshar
- Leishmaniasis Research Center, Kerman University of Medical Sciences, Kerman, Iran
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Gonçalves R, de Souza CF, Rontani RB, Pereira A, Farnes KB, Gorsich EE, Silva RA, Brazil RP, Hamilton JGC, Courtenay O. Community deployment of a synthetic pheromone of the sand fly Lutzomyia longipalpis co-located with insecticide reduces vector abundance in treated and neighbouring untreated houses: Implications for control of Leishmania infantum. PLoS Negl Trop Dis 2021; 15:e0009080. [PMID: 33534804 PMCID: PMC7886189 DOI: 10.1371/journal.pntd.0009080] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 02/16/2021] [Accepted: 12/17/2020] [Indexed: 01/29/2023] Open
Abstract
Background The rising incidence of visceral leishmaniasis due to Leishmania infantum requires novel methods to control transmission by the sand fly vector. Indoor residual spraying of insecticide (IRS) against these largely exophilic / exophagic vectors may not be the most effective method. A synthetic copy of the male sex-aggregation pheromone of the key vector species Lutzomyia longipalpis in the Americas, was co-located with residual pyrethroid insecticide, and tested for its effects on vector abundance, hence potential transmission, in a Brazilian community study. Methods Houses within eight defined semi-urban blocks in an endemic municipality in Brazil were randomised to synthetic pheromone + insecticide or to placebo treatments. A similar number of houses located >100m from each block were placebo treated and considered as “True Controls” (thus, analysed as three trial arms). Insecticide was sprayed on a 2.6m2 surface area of the property boundary or outbuilding wall, co-located within one metre of 50mg synthetic pheromone in controlled-release dispensers. Vector numbers captured in nearby CDC light traps were recorded at monthly intervals over 3 months post intervention. Recruited sentinel houses under True Control and pheromone + insecticide treatments were similarly monitored at 7–9 day intervals. The intervention effects were estimated by mixed effects negative binomial models compared to the True Control group. Results Dose-response field assays using 50mg of the synthetic pheromone captured a mean 4.8 (95% C.L.: 3.91, 5.80) to 6.3 (95% C.L.: 3.24, 12.11) times more vectors (female Lu. longipalpis) than using 10mg of synthetic pheromone. The intervention reduced household female vector abundance by 59% (C.L.: 48.7, 66.7%) (IRR = 0.41) estimated by the cross-sectional community study, and by 70% (C.L.: 56.7%, 78.8%) estimated by the longitudinal sentinel study. Similar reductions in male Lu. longipalpis were observed. Beneficial spill-over intervention effects were also observed at nearby untreated households with a mean reduction of 24% (95% C.L.: 0.050%, 39.8%) in female vectors. The spill-over effect in untreated houses was 44% (95% C.L.: 29.7%, 56.1%) as effective as the intervention in pheromone-treated houses. Ownership of chickens increased the intervention effects in both treated and untreated houses, attributed to the suspected synergistic attraction of the synthetic pheromone and chicken kairomones. The variation in IRR between study blocks was not associated with inter-household distances, household densities, or coverage (proportion of total households treated). Conclusions The study confirms the entomological efficacy of the lure-and-kill method to reduce the abundance of this important sand fly vector in treated and untreated homesteads. The outcomes were achieved by low coverage and using only 1–2% of the quantity of insecticide as normally required for IRS, indicating the potential cost-effectiveness of this method. Implications for programmatic deployment of this vector control method are discussed. The predominant sand fly vector of the intracellular parasite Leishmania infantum, that causes human and canine visceral leishmaniasis in the Americas, is Lutzomyia longipalpis. Vector control tools to reduce transmission are needed. A sex-aggregation pheromone released by male Lu. longipalpis attracts female conspecifics which facilitates blood-feeding and transmission. This study, conducted in Brazil, quantifies the effects of community deployment of a synthetic version of the sex-aggregation pheromone, in a controlled-release dispenser, and co-located with lethal insecticide applied to a small area of the household compound or outbuilding wall. 50mg synthetic pheromone dispensers were used since they attracted substantially more vectors than 10mg dispensers. Deploying this novel lure-and-kill method to houses in eight replicate study blocks in two suburban endemic areas, demonstrated that it reduces vector numbers at both pheromone + insecticide treated houses, and neighbouring untreated houses. The presence of chickens (a known additional attraction to blood-seeking female Lu. longipalpis) increased the beneficial effects of the intervention. The method used only 1–2% of the quantity of insecticide necessary for IRS for an average sized house. The results demonstrate the efficacy and potential cost-effectiveness of this novel lure-and-kill control method.
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Affiliation(s)
- Raquel Gonçalves
- Zeeman Institute and School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Cristian F. de Souza
- Laboratório de Doenças Parasitárias, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brazil
| | - Reila B. Rontani
- Laboratório de Doenças Parasitárias, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brazil
| | - Alisson Pereira
- Laboratório de Doenças Parasitárias, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brazil
| | - Katie B. Farnes
- Zeeman Institute and School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Erin E. Gorsich
- Zeeman Institute and School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Rafaella A. Silva
- Núcleo de Medicina Tropical, Universidade de Brasilia, Brasília, Federal District, Brazil
- Ministério da Saúde, Departamento de Imunização e Doenças Transmissíveis, Secretaria de Vigilância em Saúde, Brasília, Federal District, Brazil
| | - Reginaldo P. Brazil
- Laboratório de Doenças Parasitárias, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brazil
| | - James G. C. Hamilton
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Bailrigg, Lancaster, Lancashire, United Kingdom
- * E-mail: (JH); (OC)
| | - Orin Courtenay
- Zeeman Institute and School of Life Sciences, University of Warwick, Coventry, United Kingdom
- * E-mail: (JH); (OC)
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RÊGO FELIPED, SOARES RODRIGOPEDRO. Lutzomyia longipalpis: an update on this sand fly vector. AN ACAD BRAS CIENC 2021. [DOI: 10.1590/0001-3765202120200254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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Santamaría E, Cabrera OL, Pardo RH. Efficacy of factory-treated and dip-it-yourself long lasting insecticide-treated bednets against cutaneous leishmaniasis vectors in the sub-Andean region of Colombia: results after two years of use. Mem Inst Oswaldo Cruz 2020; 115:e190431. [PMID: 32935748 PMCID: PMC7491276 DOI: 10.1590/0074-02760190431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 08/17/2020] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Long lasting insecticide-treated nets (LLINs) may be effective for vector control of cutaneous leishmaniasis (CL). Their efficacy, however, has not been sufficiently evaluated. OBJECTIVE To evaluate the large-scale efficacy of LLINs on Lutzomyia longiflocosa entomological parameters up to two years post-intervention in the sub-Andean region of Colombia. METHODS A matched-triplet cluster-randomised study of 21 rural settlements, matched by pre-intervention L. longiflocosa indoor density was used to compare three interventions: dip it yourself (DIY) lambda-cyhalothrin LLIN, deltamethrin LLIN, and untreated nets (control). Sand fly indoor density, feeding success, and parity were recorded using CDC light trap collections at 1, 6, 12, and 24 months post-intervention. FINDINGS Both LLINs reduced significantly (74-76%) the indoor density and the proportion of fully engorged sand flies up to two years post-intervention without differences between them. Residual lethal effects of both LLINs and the use of all nets remained high throughout the two-year evaluation period. CONCLUSIONS Both LLINs demonstrated high efficacy against L. longiflocosa indoors. Therefore, the deployment of these LLINs could have a significant impact on the reduction of CL transmission in the sub-Andean region. The DIY lambda-cyhalothrin kit may be used to convert untreated nets to LLINs increasing coverage.
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Affiliation(s)
- Erika Santamaría
- Instituto Nacional de Salud, Grupo de Entomología, Bogotá, Colombia
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Buckingham-Jeffery E, Hill EM, Datta S, Dilger E, Courtenay O. Spatio-temporal modelling of Leishmania infantum infection among domestic dogs: a simulation study and sensitivity analysis applied to rural Brazil. Parasit Vectors 2019; 12:215. [PMID: 31064395 PMCID: PMC6505121 DOI: 10.1186/s13071-019-3430-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 04/04/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The parasite Leishmania infantum causes zoonotic visceral leishmaniasis (VL), a potentially fatal vector-borne disease of canids and humans. Zoonotic VL poses a significant risk to public health, with regions of Latin America being particularly afflicted by the disease. Leishmania infantum parasites are transmitted between hosts during blood-feeding by infected female phlebotomine sand flies. With a principal reservoir host of L. infantum being domestic dogs, limiting prevalence in this reservoir may result in a reduced risk of infection for the human population. To this end, a primary focus of research efforts has been to understand disease transmission dynamics among dogs. One way this can be achieved is through the use of mathematical models. METHODS We have developed a stochastic, spatial, individual-based mechanistic model of L. infantum transmission in domestic dogs. The model framework was applied to a rural Brazilian village setting with parameter values informed by fieldwork and laboratory data. To ensure household and sand fly populations were realistic, we statistically fitted distributions for these entities to existing survey data. To identify the model parameters of highest importance, we performed a stochastic parameter sensitivity analysis of the prevalence of infection among dogs to the model parameters. RESULTS We computed parametric distributions for the number of humans and animals per household and a non-parametric temporal profile for sand fly abundance. The stochastic parameter sensitivity analysis determined prevalence of L. infantum infection in dogs to be most strongly affected by the sand fly associated parameters and the proportion of immigrant dogs already infected with L. infantum parasites. CONCLUSIONS Establishing the model parameters with the highest sensitivity of average L. infantum infection prevalence in dogs to their variation helps motivate future data collection efforts focusing on these elements. Moreover, the proposed mechanistic modelling framework provides a foundation that can be expanded to explore spatial patterns of zoonotic VL in humans and to assess spatially targeted interventions.
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Affiliation(s)
- Elizabeth Buckingham-Jeffery
- School of Mathematics, University of Manchester, Manchester, UK.
- Zeeman Institute: SBIDER (Systems Biology & Infectious Disease Epidemiology Research), University of Warwick, Coventry, UK.
| | - Edward M Hill
- Zeeman Institute: SBIDER (Systems Biology & Infectious Disease Epidemiology Research), University of Warwick, Coventry, UK
- Warwick Mathematics Institute, University of Warwick, Coventry, UK
| | - Samik Datta
- Population Modelling Group, National Institute of Water and Atmospheric Research, Wellington, New Zealand
- Zeeman Institute: SBIDER (Systems Biology & Infectious Disease Epidemiology Research), University of Warwick, Coventry, UK
| | - Erin Dilger
- Zeeman Institute: SBIDER (Systems Biology & Infectious Disease Epidemiology Research), University of Warwick, Coventry, UK
- School of Life Sciences, University of Warwick, Coventry, UK
| | - Orin Courtenay
- Zeeman Institute: SBIDER (Systems Biology & Infectious Disease Epidemiology Research), University of Warwick, Coventry, UK
- School of Life Sciences, University of Warwick, Coventry, UK
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Santamaria E, Marceló-Díaz C. Toxic Activity of Pyrethroids in <i>Lutzomyia longipalpis</i> (Diptera: Psychodidae) from Magdalena River Basin, Colombia. ACTA BIOLÓGICA COLOMBIANA 2019. [DOI: 10.15446/abc.v24n2.74570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The study aimed to determine the toxicity of lambda-cyhalothrin, alpha-cypermethrin, and deltamethrin in L. longipalpis, through concentration-mortality bioassays. The test here was performed following WHO guidelines, but instead of using exposure WHO recipients and impregnated papers, 250 ml Wheaton glass bottles treated with 1 ml of insecticide solution were used. Batches of ten females of L. longipalpis were exposed to five concentrations of each pyrethroid that caused between 5 and 100 % mortality in this species. After 1 h of exposure, the females were transferred to observation recipients, and mortality was recorded 24 h later. The lethal concentrations (μg/ml) that killed 50 and 95 % (LC50 and LC95) of the exposed L. longipalpis females were 0.05 and 0.86 for lambda-cyhalothrin, 0.24 and 3.62 for alpha-cypermethrin and 0.53 and 4.72 for deltamethrin. Based on the LC50 obtained, lambda-cyhalothrin is the most toxic pyrethroid for L. longipalpis, followed by alpha-cypermethrin and deltamethrin. It is expected that these data may be useful in studies on the effects of sub-lethal concentrations of the three pyrethroids on the behavior of L. longipalpis and studies on the vector susceptibility to these pyrethroids.
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González MA, Bell MJ, Bernhardt SA, Brazil RP, Dilger E, Courtenay O, Hamilton JGC. Susceptibility of wild-caught Lutzomyia longipalpis (Diptera: Psychodidae) sand flies to insecticide after an extended period of exposure in western São Paulo, Brazil. Parasit Vectors 2019; 12:110. [PMID: 30871639 PMCID: PMC6419423 DOI: 10.1186/s13071-019-3364-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Accepted: 02/26/2019] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND In Brazil, members of the sand fly species complex Lutzomyia longipalpis transmit Leishmania infantum, a protist parasite that causes visceral leishmaniasis. Male Lu. longipalpis produce a sex pheromone that is attractive to both females and males. During a cluster randomised trial, to determine the combined effect of synthetic sex-aggregation pheromone and insecticide on Le. infantum transmission Lu. longipalpis had been continuously exposed to insecticide for 30 months. The objective of this study was to determine the effect of continuous exposure to the insecticides used in the trial on the susceptibility of Lu. longipalpis population. METHODS During the trial the sand flies had been exposed to either lambda-cyhalothrin [pheromone + residual insecticide spray (PI)], deltamethrin [dog collars (DC)] or no insecticide [control (C)], for 30 months (November 2012 to April 2015). The insecticide treatment regime was kept in place for an additional 12 months (May 2015-April 2016) during this susceptibility study. Sand flies collected from the field were exposed to WHO insecticide-impregnated papers cyhalothrin (0.05%), deltamethrin (0.5%) and control (silicone oil) in a modified WHO insecticide exposure trial to determine their susceptibility. RESULTS We collected 788 Lu. longipalpis using CDC-light traps in 31 municipalities across the three trial arms. Probit analysis showed that the knockdown times (KDTs) of Lu. longipalpis collected from the lambda-cyhalothrin exposed PI-arm [KDT50: 31.1 min, confidence interval (CI): 29.6-32.6 and KDT90: 44.2 min, CI: 42.1-46.7] were longer than the KDTs from the non-insecticide-treated C-arm (KDT50: 26.3 min, CI: 25.1-27.6 and KDT90: 38.2, CI: 36.5-40.2) (no-overlapping 95% CIs). KDTs of Lu. longipalpis collected from the deltamethrin exposed DC-arm had similar values (KDT50: 13.7 min, CI: 10.1-16.2 and KDT90: 26.7 min, CI: 21.8-30.6) to those for the C-arm (KDT50: 13.5 min; CI: 12.2-14.8 and KDT90: 23.2 min, CI: 21.4-25.4) (overlapping CIs). The wild-caught unexposed Lu. longipalpis (C-arm), took approximately twice as long to knock down as laboratory-colonised specimens for both insecticides. CONCLUSIONS Our study reveals slight changes in KDT, in sand flies after prolonged exposure to lambda-cyhalothrin in the presence of pheromone. These changes are not considered to have reached the reference levels indicative of resistance in sand flies suggesting that pheromone and insecticide treatment at the level indicated in this study do not constitute a significant risk of increased insecticide resistance. Prolonged exposure to deltamethrin in dog collars did not result in changes to KDT.
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Affiliation(s)
- Mikel A. González
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancashire, LA1 4YG UK
- Present Address: Departamento de Sanidad Animal, Instituto Vasco de Investigación y Desarrollo Agrario (NEIKER-Teknalia), Derio, 48160 Biscay Spain
| | - Melissa J. Bell
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancashire, LA1 4YG UK
| | | | - Reginaldo P. Brazil
- Laboratório de Doenças Parasitárias, Instituto Oswaldo Cruz, Fundaçao Oswaldo Cruz, Av. Brasil, Manguinhos, Rio de Janeiro, RJ 4365 Brazil
| | - Erin Dilger
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL UK
| | - Orin Courtenay
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL UK
| | - James G. C. Hamilton
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancashire, LA1 4YG UK
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Cabrera OL, Santamaría E, Pardo RH. Experimental hut to study the indoor behaviour and effects of insecticide-treated bednets on phlebotomine sand flies (Diptera: Psychodidae). Mem Inst Oswaldo Cruz 2018; 113:e180131. [PMID: 30043837 PMCID: PMC6052505 DOI: 10.1590/0074-02760180131] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 06/11/2018] [Indexed: 11/22/2022] Open
Abstract
INTRODUCTION Behavioural effects of insecticides on endophagic phlebotomine sand fly vectors of Leishmania are poorly understood mainly because of the lack of an experimental hut (EH) in which to study them. OBJECTIVE To build an EH to evaluate the effects of long-lasting insecticide-treated nets (LLINs) on Lutzomyia longiflocosa. METHODS The study had two phases: (1) Laboratory experiments using tunnel tests to select the traps for the EH; and (2) EH construction and evaluation of the effects of deltamethrin and lambda-cyhalothrin LLINs on L. longiflocosa females inside the EH. FINDINGS Phase 1: The horizontal-slit trap was the best trap. This trap collected the highest percentage of sand flies, and prevented them from escaping. Therefore, this trap was used in the EH. Phase 2: The main effects of LLINs on L. longiflocosa in the EH were: landing inhibition, inhibition from entering the bednet, induced exophily, and high mortality (total and inside exit traps). CONCLUSIONS The EH was effective for evaluating the effects of LLINs on endophagic sand flies. Although both types of LLINs showed high efficacy, the lambda-cyhalothrin-treated LLIN performed better. This is the first report of induced exophily in sand flies.
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Affiliation(s)
| | - Erika Santamaría
- Instituto Nacional de Salud, Grupo de Entomología, Bogotá, Colombia
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13
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Jeffries CL, Rogers ME, Walker T. Establishment of a method for Lutzomyia longipalpis sand fly embryo microinjection: The first step towards potential novel control strategies for leishmaniasis. Wellcome Open Res 2018. [DOI: 10.12688/wellcomeopenres.14555.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Leishmaniasis is a vector-borne parasitic disease transmitted by sand flies that affects 1.3 million people across 98 countries, with limited control strategies due to the lack of an available vaccine and the emergence of insecticide resistance. Novel control strategies that are being explored for mosquito-borne diseases, such as Wolbachia bacterial inhibition of pathogens and genetically modified insects (e.g. using CRISPR-Cas9 editing), rely on the ability to consistently inject embryos of the target species. Here we present a novel method to obtain and inject preblastoderm sand fly embryos of the genus Lutzomyia (Lu.) longipalpis, the principle vector of zoonotic visceral leishmaniasis in South America. The procedures required to obtain sufficiently young Lu. longipalpis colony embryos are described alongside a microinjection technique that permits rapid injection and minimal handling of small sand fly embryos post-injection. Using a strain of Wolbachia as a ‘marker’ for successful injection, our protocol produced early generation Wolbachia transinfected Lu. longipalpis lines, demonstrating its potential as the first step for use in novel applied strategies for sand fly control.
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14
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Jeffries CL, Rogers ME, Walker T. Establishment of a method for Lutzomyia longipalpis sand fly embryo microinjection: The first step towards potential novel control strategies for leishmaniasis. Wellcome Open Res 2018; 3:55. [PMID: 30175240 PMCID: PMC6107984 DOI: 10.12688/wellcomeopenres.14555.2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2018] [Indexed: 12/31/2022] Open
Abstract
Leishmaniases is a group of vector-borne parasitic diseases transmitted by sand flies that affects 1.3 million people across 98 countries, with limited control strategies due to the lack of an available vaccine and the emergence of insecticide resistance. Novel control strategies that are being explored for mosquito-borne diseases, such as
Wolbachia bacterial inhibition of pathogens and genetically modified insects (e.g. using CRISPR-Cas9 editing), rely on the ability to consistently inject eggs of the target species. Here we present a novel method to obtain and inject preblastoderm sand fly eggs of the genus
Lutzomyia (Lu.) longipalpis, the principle vector of zoonotic visceral leishmaniasis in South America. The procedures required to obtain sufficiently young
Lu. longipalpis colony eggs are described alongside a microinjection technique that permits rapid injection and minimal handling of small sand fly eggs post-injection. Using a strain of
Wolbachia as a ‘marker’ for successful injection, our protocol produced early generation
Wolbachia transinfected
Lu. longipalpis lines, demonstrating its potential as the first step for use in novel applied strategies for sand fly control.
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Affiliation(s)
- Claire L Jeffries
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Matthew E Rogers
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Thomas Walker
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
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Dynamics of American tegumentary leishmaniasis in a highly endemic region for Leishmania (Viannia) braziliensis infection in northeast Brazil. PLoS Negl Trop Dis 2017; 11:e0006015. [PMID: 29095818 PMCID: PMC5685640 DOI: 10.1371/journal.pntd.0006015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 11/14/2017] [Accepted: 10/05/2017] [Indexed: 11/19/2022] Open
Abstract
Background American Tegumentary Leishmaniasis (ATL) caused by Leishmania braziliensis is endemic in Corte de Pedra, Northeast Brazil. Most L. braziliensis infections manifest as localized cutaneous leishmaniasis (CL). Disseminated manifestations include mucosal leishmaniasis (ML), present at a low constant level for several decades, and newly emerging disseminated leishmaniasis (DL). Surprisingly, DL has recently surpassed ML in its spatial distribution. This led us to hypothesize that distinct forms of ATL might spread in different patterns through affected regions. Methodology/Principal findings We explored the incidence and geographic dispersion of the three clinical types of ATL over a span of nearly two decades in Corte de Pedra. We obtained the geographic coordinates of the homes of patients with ATL during 1992–1996, 1999–2003 and 2008–2011. The progressive dispersion of ML or DL in each time period was compared to that of CL in 2008–2011 with the Cusick and Edward’s geostatistical test. To evaluate whether ATL occurred as clusters, we compared each new case in 2008–2011 with the frequency of and distance from cases in the previous 3 to 12 months. The study revealed that DL, ML and CL actively spread within that region, but in distinct patterns. Whereas CL and DL propagated in clusters, ML occurred as sporadic cases. DL had a wider distribution than ML until 2003, but by 2011 both forms were distributed equally in Corte de Pedra. The incidence of ML fluctuated over time at a rate that was distinct from those of CL and DL. Conclusions/Significance These findings suggest that CL and DL maintain endemic levels through successive outbreaks of cases. The sporadic pattern of ML cases may reflect the long and variable latency before infected patients develop clinically detectable mucosal involvement. Intimate knowledge of the geographic distribution of leishmaniasis and how it propagates within foci of active transmission may guide approaches to disease control. American tegumentary leishmaniasis (ATL) caused by Leishmania braziliensis is characterized by lesions to the skin and/or mucosal surfaces of the oropharynx. It is widely distributed in endemic regions of northeast Brazil and has been difficult to control. Three common clinical forms of L. braziliensis infections are localized skin ulcers called cutaneous leishmaniasis (CL), mucosal leishmaniasis (ML) affecting mucosal surfaces, and disseminated leishmaniasis (DL), a recently described form with widespread skin lesions. Using GPS and epidemiologic data we explored the incidence and pattern of spread of ATL in the highly endemic region of Corte de Pedra, Brazil between 1992 and 2011. Geographic clusters of CL and DL cases were observed. In contrast, there was a sporadic non-clustered pattern of ML cases in the study area. The numbers of new cases of CL and DL presented similar fluctuation during the study period, but ML incidences were never correlated to those of CL and DL. We conclude that all forms of ATL actively spread within affected foci, but in different patterns. CL and DL cases occur in clusters suggesting active spread of causative parasite strains, whereas ML cases occurred in a sporadic pattern suggesting it may emerge due to factors such as host immunity or environmental conditions.
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Courtenay O, Peters NC, Rogers ME, Bern C. Combining epidemiology with basic biology of sand flies, parasites, and hosts to inform leishmaniasis transmission dynamics and control. PLoS Pathog 2017; 13:e1006571. [PMID: 29049371 PMCID: PMC5648254 DOI: 10.1371/journal.ppat.1006571] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Quantitation of the nonlinear heterogeneities in Leishmania parasites, sand fly vectors, and mammalian host relationships provides insights to better understand leishmanial transmission epidemiology towards improving its control. The parasite manipulates the sand fly via production of promastigote secretory gel (PSG), leading to the “blocked sand fly” phenotype, persistent feeding attempts, and feeding on multiple hosts. PSG is injected into the mammalian host with the parasite and promotes the establishment of infection. Animal models demonstrate that sand flies with the highest parasite loads and percent metacyclic promastigotes transmit more parasites with greater frequency, resulting in higher load infections that are more likely to be both symptomatic and efficient reservoirs. The existence of mammalian and sand fly “super-spreaders” provides a biological basis for the spatial and temporal clustering of clinical leishmanial disease. Sand fly blood-feeding behavior will determine the efficacies of indoor residual spraying, topical insecticides, and bed nets. Interventions need to have sufficient coverage to include transmission hot spots, especially in the absence of field tools to assess infectiousness. Interventions that reduce sand fly densities in the absence of elimination could have negative consequences, for example, by interfering with partial immunity conferred by exposure to sand fly saliva. A deeper understanding of both sand fly and host biology and behavior is essential to ensuring effectiveness of vector interventions. We review recent research that sheds light on the quantitative biology of leishmanial transmission between sand flies and mammalian hosts and use these insights to better understand transmission, the observed epidemiology of the disease, and their implications in choice of control strategy. Using animal models, we show how the parasite-induced processes manipulate sand fly blood-feeding behavior and the infectious metacyclic dose to promote host infection and to differentially regulate the onward transmission potential of individual vectors and hosts. The existence of subpopulations of mammalian and sand fly “super-spreaders” provides a biological basis for the spatial and temporal clustering of clinical leishmanial disease. While tools are unavailable to distinguish these individuals in mixed populations, blanket interventions will be necessary to ensure inclusion of transmission hot spots. Interventions that reduce sand fly densities without elimination could interfere with vector—host dynamics and conferred partial immunity to host populations.
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Affiliation(s)
- Orin Courtenay
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
- Zeeman Institute, University of Warwick, Coventry, United Kingdom
- * E-mail:
| | - Nathan C. Peters
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Matthew E. Rogers
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Caryn Bern
- Department of Epidemiology and Biostatistics, School of Medicine, University of California San Francisco, San Francisco, California, United States of America
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Rock KS, Quinnell RJ, Medley GF, Courtenay O. Progress in the Mathematical Modelling of Visceral Leishmaniasis. ADVANCES IN PARASITOLOGY 2016; 94:49-131. [PMID: 27756459 DOI: 10.1016/bs.apar.2016.08.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The leishmaniases comprise a complex of diseases characterized by clinical outcomes that range from self-limiting to chronic, and disfiguring and stigmatizing to life threatening. Diagnostic methods, treatments, and vector and reservoir control options exist, but deciding the most effective interventions requires a quantitative understanding of the population level infection and disease dynamics. The effectiveness of any set of interventions has to be determined within the context of operational conditions, including economic and political commitment. Mathematical models are the best available tools for studying quantitative systems crossing disciplinary spheres (biology, medicine, economics) within environmental and societal constraints. In 2005, the World Health Assembly and government health ministers of India, Nepal, and Bangladesh signed a Memorandum of Understanding to eliminate the life threatening form of leishmaniasis, visceral leishmaniasis (VL), on the Indian subcontinent by 2015 through a combination of early case detection, improved treatments, and vector control. The elimination target is <1 case/10,000 population at the district or subdistrict level compared to the current 20/10,000 in the regions of highest transmission. Towards this goal, this chapter focuses on mathematical models of VL, and the biology driving those models, to enable realistic predictions of the best combination of interventions. Several key issues will be discussed which have affected previous modelling of VL and the direction future modelling may take. Current understanding of the natural history of disease, immunity (and loss of immunity), and stages of infection and their durations are considered particularly for humans, and also for dogs. Asymptomatic and clinical infection are discussed in the context of their relative roles in Leishmania transmission, as well as key components of the parasite-sandfly-vector interaction and intervention strategies including diagnosis, treatment and vector control. Gaps in current biological knowledge and potential avenues to improve model structures and mathematical predictions are identified. Underpinning the marriage between biology and mathematical modelling, the content of this chapter represents the first step towards developing the next generation of models for VL.
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Affiliation(s)
- K S Rock
- University of Warwick, Coventry, United Kingdom
| | | | - G F Medley
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - O Courtenay
- University of Warwick, Coventry, United Kingdom
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18
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Salomón OD, Feliciangeli MD, Quintana MG, Afonso MMDS, Rangel EF. Lutzomyia longipalpis urbanisation and control. Mem Inst Oswaldo Cruz 2015; 110:831-46. [PMID: 26517497 PMCID: PMC4660613 DOI: 10.1590/0074-02760150207] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/01/2015] [Indexed: 11/22/2022] Open
Abstract
Since the description of Lutzomyia longipalpis by Lutz and Neiva
more than 100 years ago, much has been written in the scientific literature about
this phlebotomine species. Soares and Turco (2003) and Lainson and Rangel (2005) have
written extensive reviews focused on vector-host-parasite interactions and American
visceral leishmaniasis ecology. However, during the last two decades, the success of
Lu. longipalpis in colonising urban environments and its
simultaneous geographical spreading have led to new theoretical and operational
questions. Therefore, this review updates the general information about this species
and notes the more challenging topics regarding the new scenario of
urbanisation-spreading and its control in America. Here, we summarise the literature
on these issues and the remaining unsolved questions, which pose recommendations for
operational research.
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Affiliation(s)
| | - María Dora Feliciangeli
- Centro Nacional de Referencia de Flebótomos y Otros Vectores, Facultad de Ciencias de la Salud, Universidad de Carabobo, Maracay, Venezuela
| | | | | | - Elizabeth Ferreira Rangel
- Laboratório de Transmissores de Leishmanioses, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brasil
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Choi MY, Sanscrainte ND, Estep AS, Vander Meer RK, Becnel JJ. Identification and expression of a new member of the pyrokinin/pban gene family in the sand fly Phlebotomus papatasi. JOURNAL OF INSECT PHYSIOLOGY 2015; 79:55-62. [PMID: 26050919 DOI: 10.1016/j.jinsphys.2015.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 05/12/2015] [Accepted: 06/03/2015] [Indexed: 06/04/2023]
Abstract
The major family of neuropeptides (NPs) derived from the pk (pyrokinin)/pban (pheromone biosynthesis activating neuropeptide) gene are defined by a common FXPRL-NH2 or similar sequence at the C-termini. This family of peptides has been found in all insect groups investigated to date and is implicated in regulating various physiological functions, including pheromone biosynthesis and diapause, but other functions are still largely unknown in specific life stages. Here we identify two isoforms of pk/pban cDNA encoding the PBAN domain from the sand fly Phlebotomus papatasi. The two pk/pban isoforms have the same sequence except for a 63 nucleotide difference between the long and short forms, and contain no alternative mRNA splicing site. Two NP homologues, DASGDNGSDSQRTRPPFAPRLamide and SLPFSPRLamide are expected, however, sequence corresponding to the diapause hormone was not found in the P. papatasi pk/pban gene. The PBAN-like amino acid sequence homologue SNKYMTPRL is conserved in the gene, but there is no cleavage site for processing a functional peptide. Characterizing the expression of the isoforms in developmental stages and adults indicates that the short form is differentially transcribed depending on the life stage. The P. papatasi pk/pban gene is the only known pk/pban gene with two transcriptional isoforms and from examination of endoproteolytic cleavage sites is expected to produce fewer peptides than most of the pk/pban genes elucidated to date; only Drosophila melanogaster is simpler with a single NP detected by mass spectroscopy. A phylogenetic analysis showed P. papatasi pk/pban grouped more closely with other nematoceran flies rather than higher flies.
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Affiliation(s)
- Man-Yeon Choi
- United States Department of Agriculture, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology (CMAVE), 1600 SW 23rd Drive, Gainesville, FL 32608, USA.
| | - Neil D Sanscrainte
- United States Department of Agriculture, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology (CMAVE), 1600 SW 23rd Drive, Gainesville, FL 32608, USA
| | - Alden S Estep
- United States Department of Agriculture, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology (CMAVE), 1600 SW 23rd Drive, Gainesville, FL 32608, USA; Navy Entomology Center of Excellence, Box 43, Naval Air Station, Jacksonville, FL 32212-0043, USA
| | - Robert K Vander Meer
- United States Department of Agriculture, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology (CMAVE), 1600 SW 23rd Drive, Gainesville, FL 32608, USA
| | - James J Becnel
- United States Department of Agriculture, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology (CMAVE), 1600 SW 23rd Drive, Gainesville, FL 32608, USA.
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Das ML, Rowland M, Austin JW, De Lazzari E, Picado A. Do Size and Insecticide Treatment Matter? Evaluation of Different Nets against Phlebotomus argentipes, the Vector of Visceral Leishmaniasis in Nepal. PLoS One 2014; 9:e114915. [PMID: 25494099 PMCID: PMC4262434 DOI: 10.1371/journal.pone.0114915] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 11/15/2014] [Indexed: 11/25/2022] Open
Abstract
In the Indian subcontinent, Leishmania donovani, the parasite causing visceral leishmaniasis (VL) is transmitted by the sand fly vector Phlebotomus argentipes. Long lasting insecticide treated nets (LN) have been postulated as alternative or complement to Indoor Residual Spraying but there are few field studies evaluating the entomological efficacy of different nets against this vector. We conducted two crossover trials in a VL endemic area in Nepal to compare the barrier effect of (1) LN with different mesh sizes (156 holes/inch2 vs 625 holes/inch2) and (2) alpha-cypermethrin treated LN and untreated nets having the same mesh size (156 holes/inch2). Each crossover trial had two arms consisting of a sequence of two different nets for 8 nights. We used 10 cattle sheds per trial. A cow placed under the net was used as bait. CDC light traps placed inside the nets were used to evaluate the number of P. argentipes crossing the net barrier. Negative binomial generalized estimating equation (GEE) population-averaged models adjusted by night and sequence were used to estimate the barrier effect of the different nets. The crossover trials conducted in a rural village in Morang district (South-eastern Nepal) demonstrated that reducing the size of the holes in treated nets (625 holes/inch2) increased the barrier effect of LN by 77% (95% confidence interval (CI): 56%-88%) compared with treated nets with larger holes (156 holes/inch2). Treating nets with alpha-cypermethrin reduced the number of P. argentipes captured inside the nets by 77% (95% CI: 27%-93%) compared with untreated nets. The effectiveness and acceptability of finer mesh pyrethroid treated LN should be tested for VL prevention in a randomized controlled trial.
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Affiliation(s)
- Murari Lal Das
- B.P. Koirala Institute of Health Sciences (BPKIHS), Dharan, Nepal
| | - Mark Rowland
- London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom
| | - James W. Austin
- BASF Corporation, Research Triangle Park, North Carolina, United States of America
| | - Elisa De Lazzari
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
| | - Albert Picado
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
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Dantas-Torres F, Otranto D. Dogs, cats, parasites, and humans in Brazil: opening the black box. Parasit Vectors 2014; 7:22. [PMID: 24423244 PMCID: PMC3914713 DOI: 10.1186/1756-3305-7-22] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 12/21/2013] [Indexed: 02/04/2023] Open
Abstract
Dogs and cats in Brazil serve as primary hosts for a considerable number of parasites, which may affect their health and wellbeing. These may include endoparasites (e.g., protozoa, cestodes, trematodes, and nematodes) and ectoparasites (i.e., fleas, lice, mites, and ticks). While some dog and cat parasites are highly host-specific (e.g., Aelurostrongylus abstrusus and Felicola subrostratus for cats, and Angiostrongylus vasorum and Trichodectes canis for dogs), others may easily switch to other hosts, including humans. In fact, several dog and cat parasites (e.g., Toxoplasma gondii, Dipylidium caninum, Ancylostoma caninum, Strongyloides stercoralis, and Toxocara canis) are important not only from a veterinary perspective but also from a medical standpoint. In addition, some of them (e.g., Lynxacarus radovskyi on cats and Rangelia vitalii in dogs) are little known to most veterinary practitioners working in Brazil. This article is a compendium on dog and cat parasites in Brazil and a call for a One Health approach towards a better management of some of these parasites, which may potentially affect humans. Practical aspects related to the diagnosis, treatment, and control of parasitic diseases of dogs and cats in Brazil are discussed.
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Affiliation(s)
- Filipe Dantas-Torres
- Department of Immunology, Aggeu Magalhães Research Centre, Oswaldo Cruz Foundation, Recife Pernambuco 50670420, Brazil.
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Bray DP, Hamilton JGC. Insecticide-impregnated netting as a potential tool for long-lasting control of the leishmaniasis vector Lutzomyia longipalpis in animal shelters. Parasit Vectors 2013; 6:133. [PMID: 23642213 PMCID: PMC3658972 DOI: 10.1186/1756-3305-6-133] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 04/30/2013] [Indexed: 11/23/2022] Open
Abstract
Background Leishmaniasis remains a serious neglected disease, with more than 350 million people potentially at risk worldwide. Control strategies often rely on spraying residual insecticides to target populations of the sand fly vectors that transmit Leishmania parasites when blood-feeding. These programmes are often difficult to sustain effectively, as sand fly resting sites must be resprayed on a regular basis. Here, we investigate whether application of insecticide-impregnated netting to a surface could act as an alternative to residual spraying for controlling the American visceral leishmaniasis vector Lutzomyia longipalpis. Methods Female L. longipalpis from our laboratory colony were exposed for 1 h to three treatments applied to plywood surfaces: 2% permethrin-impregnated netting (Olyset®), 20 mg a.i.m-2 micro-encapsulated lambda-cyhalothrin (Demand CS®) and a no-treatment control. We compared the speed at which these treatments acted, by measuring the percentage of sand flies killed both immediately after exposure to the treatment for 1 hour, as well as the number that had died 24 h after the 1 hour exposure. We repeated the experiment at 6 and 12 months following application to test the effectiveness of each treatment over time. Results When first applied, the lambda-cyhalothrin killed more sand flies in the first hour than the permethrin-impregnated netting. However, the effectiveness of the lambda-cyhalothrin diminished over time, so that there was no difference between the two treatments at 12 months. Both killed more sand flies than the control. When measured 24 h following exposure, both test treatments had killed close to 100% of sand flies when first applied, but while the lethal effect of the netting was maintained at close to 100% over 12 months, the effectiveness of the residual insecticide diminished to approximately 80% after 6 months. Conclusions The results of these initial laboratory experiments indicate that covering surfaces with insecticide impregnated netting material may provide a longer-lasting solution for killing sand flies than residual spraying. Field trials are needed to identify the feasibility of treating surfaces with netting or similar impregnated materials as part of a control program. In targeting L. longipalpis, the greatest benefits may be seen in treating animal sheds with netting, where these sand flies aggregate in large numbers, and which can be difficult to treat repeatedly by conventional spraying.
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Das M, Roy L, Picado A, Kroeger A, Rijal S, Boelaert M. Deltamethrin and permethrin residue on long-lasting insecticidal nets after 18 months of use in a visceral leishmaniasis-endemic area in Nepal. Trans R Soc Trop Med Hyg 2012; 106:230-4. [PMID: 22381627 DOI: 10.1016/j.trstmh.2012.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 01/13/2012] [Accepted: 01/13/2012] [Indexed: 12/01/2022] Open
Abstract
The insecticide residue on two types of long-lasting insecticidal nets (LLIN), Olyset Net and PermaNet 2.0, used in a visceral leishmaniasis-endemic village in eastern Nepal was quantified using HPLC. After two washes during 18 months of use the mean insecticide residues on PermaNet 2.0 and Olyset Net were 53.5 mg/m(2) (97.3% of the target dose) of deltamethrin and 911.8 mg/m(2) (91.2% of the target dose) of permethrin, respectively. These residues were close to the insecticide loads specified by the manufacturers of the two LLINs. The use of LLINs has been postulated as an alternative or complementary method to indoor residual spraying. Our results suggest that LLINs should be washed 4-5 times each year throughout their lifespan by specifically requesting villagers to wash nets on certain dates. The insecticide residue on the nets and their bioefficacy against sand fly vectors should be monitored after each wash, in various cultural settings, to assess their durability and long-term retention of the insectide.
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Affiliation(s)
- Murari Das
- BP Koirala Institute of Health Sciences, Dharan, Nepal.
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Müller GC, Schlein Y. Different methods of using attractive sugar baits (ATSB) for the control of Phlebotomus papatasi. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2011; 36 Suppl 1:S64-S70. [PMID: 21366782 DOI: 10.1111/j.1948-7134.2011.00113.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have previously shown that fermented ripe fruit is a strong attractant for several mosquito species, and when mixed with oral insecticide these attractive toxic sugar baits (ATSB) were highly effective for local mosquito control. In the present study, we compared the effects of ATSB presented in different ways on isolated populations of Phlebotomus papatasi Scopoli. Experiments were carried out in the arid habitat of the Jordan valley, Israel where the effectiveness of three methods was compared: ATSB sprayed on patches of vegetation, net fence coated with ATSB, and bait stations soaked with ATSB. Spraying ATSB reduced the population to about 5% of the control area population. Barrier ATSB coated fences, had a similar effect decreasing the population to about 12% of the concurrent catch in the control site. The effect of ATSB presented on bait stations was much smaller and compared to the control, only caused the population to be reduced to 40%. In the control areas where only food dye marker was used, the solution presented on bait stations only marked an average of 22.3% of female sand flies while spraying vegetation and using barrier fences in the two other experiments marked about 60% of the females. Our experiments show that ATSB either sprayed on the vegetation or on barrier fences is an effective means against sand flies at least in arid areas where attractive plants are scarce or absent.
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Affiliation(s)
- Günter C Müller
- Department of Microbiology and Molecular Genetics, IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Faculty of Medicine, Hebrew University, Jerusalem, Israel
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Picado A, Singh SP, Rijal S, Sundar S, Ostyn B, Chappuis F, Uranw S, Gidwani K, Khanal B, Rai M, Paudel IS, Das ML, Kumar R, Srivastava P, Dujardin JC, Vanlerberghe V, Andersen EW, Davies CR, Boelaert M. Longlasting insecticidal nets for prevention of Leishmania donovani infection in India and Nepal: paired cluster randomised trial. BMJ 2010; 341:c6760. [PMID: 21190965 PMCID: PMC3011370 DOI: 10.1136/bmj.c6760] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE To test the effectiveness of large scale distribution of longlasting nets treated with insecticide in reducing the incidence of visceral leishmaniasis in India and Nepal. DESIGN Paired cluster randomised controlled trial designed to detect a 50% reduction in incidence of Leishmania donovani infection. SETTING Villages in Muzaffarpur district in India and Saptari, Sunsari, and Morang districts in Nepal. PARTICIPANTS 13 intervention and 13 control clusters. 12 691 people were included in the analysis of the main outcome (infection), and 19 810 were enrolled for the secondary (disease) end point. INTERVENTION Longlasting insecticidal nets (treated with deltamethrin) were distributed in the intervention clusters in December 2006. MAIN OUTCOME MEASURES Infection was determined by direct agglutination test at 12 and 24 months after the intervention in those who had negative results (titre <1:1600) at baseline. The effect estimate was computed as the geometric mean of the risk ratios for seroconversion for each cluster pair (net/no net), with its 95% confidence interval. Formal tests of effect of no intervention were obtained with a paired t test. RESULTS There was no significant difference in the risk of seroconversion over 24 months in intervention (5.4%; 347/6372) compared with control (5.5%; 345/6319 people) clusters (risk ratio 0.90, 95% confidence interval 0.49 to 1.65) nor in the risk of clinical visceral leishmaniasis (0.99, 0.46 to 1.40). Adjustment for covariates did not alter these conclusions. CONCLUSIONS There is no evidence that large scale distribution of longlasting insecticidal nets provides additional protection against visceral leishmaniasis compared with existing control practice in the Indian subcontinent. The observed effect was small and not significant, though the confidence intervals did not exclude a 50% change in either direction. TRIAL REGISTRATION Clinical Trials NCT 2005-015374.
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Affiliation(s)
- Albert Picado
- London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
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Santini MS, Salomón OD, Acardi SA, Sandoval EA, Tartaglino L. Lutzomyia longipalpis behavior and control at an urban visceral leishmaniasis focus in Argentina. Rev Inst Med Trop Sao Paulo 2010; 52:187-91. [DOI: 10.1590/s0036-46652010000400004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Accepted: 06/11/2010] [Indexed: 11/22/2022] Open
Abstract
During the earlier stages of visceral leishmaniasis transmission in Posadas City, Misiones, both the night activity and attraction to humans of Lutzomyia longipalpis were assessed, in order to provide preliminary recommendations. The impact of peridomestic deltamethrin spraying performed by local officials was also evaluated. Although Lu. longipalpis were found in traps located over a dog the entire night, 90% of the females were captured from 20.30h to 1.30h, and only landed on a human when he was at a distance of 1.5 m from the dog. Peridomestic spraying of deltamethrin (25 mg/m²) reduced the sand fly capture up to seven days post-intervention without dispersion in the border of the sprayed areas. These results support the recommendations about time-space focus of the protection measures: first half of the night, in the backyard, with pets and domestic animals kept at least 5 m from humans. The deltamethrin as it was used did not seem very effective in this scenario; neither did the eventual use of bed nets, at least in adults, due to the place/hour of sand fly higher activity. This study strengthens the need for a multidisciplinary approach to develop prevention strategies based both on biological and anthropological studies.
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Affiliation(s)
- Maria Soledad Santini
- Argentina, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
| | - Oscar Daniel Salomón
- Argentina, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
| | - Soraya Alejandra Acardi
- Universidad Nacional de Misiones, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
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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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Das ML, Roy L, Rijal S, Paudel IS, Picado A, Kroeger A, Petzold M, Davies C, Boelaert M. Comparative study of kala-azar vector control measures in eastern Nepal. Acta Trop 2010; 113:162-6. [PMID: 19879851 DOI: 10.1016/j.actatropica.2009.10.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2009] [Revised: 10/21/2009] [Accepted: 10/22/2009] [Indexed: 11/19/2022]
Abstract
This study was conducted to explore the most effective vector control tool among indoor residual spraying (IRS), long lasting insecticidal nets (LLINs) and ecological vector management (EVM) as a part of the regional visceral leishmaniasis elimination initiative. Alpha-cypermethrin as IRS, PermaNet as LLINs and plastering the inner walls of houses with lime as EVM were the interventions. One baseline and three follow-up entomological surveys were carried out in all arms using CDC miniature light traps (LT) and mouth aspirators. Comparisons were made between intervention arms and control arms with pre-intervention and post-intervention vector densities. Light traps were found more efficient in the collection of Phlebotomus argentipes in comparison with aspiration. Vector densities were significantly low in both IRS arm (p=0.009 in LT and p<0.001 in aspirator collections) and LLIN arm (p=0.019 in LT and p=0.023 in aspirator collections) in comparison with control arm. However, in EVM arm, there was no significant difference in P. argentipes sand fly density in comparison with control arm (p=0.785) in LT collections in follow-up surveys. Hence, IRS was found most effective control measure to decrease vector density. LLINs were also found effective and can be considered as a promising alternative vector control tool in VL elimination initiative.
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Affiliation(s)
- M L Das
- Department of Microbiology, B.P. Koirala Institute of Health Sciences, Dharan, Nepal.
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Romero GAS, Boelaert M. Control of visceral leishmaniasis in latin america-a systematic review. PLoS Negl Trop Dis 2010; 4:e584. [PMID: 20098726 PMCID: PMC2808217 DOI: 10.1371/journal.pntd.0000584] [Citation(s) in RCA: 238] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 12/01/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND While three countries in South Asia decided to eliminate anthroponotic visceral leishmaniasis (VL) by 2015, its control in other regions seems fraught with difficulties. Is there a scope for more effective VL control in the Americas where transmission is zoonotic? We reviewed the evidence on VL control strategies in Latin America-diagnosis, treatment, veterinary interventions, vector control-with respect to entomological and clinical outcomes. METHODOLOGY/PRINCIPAL FINDINGS We searched the electronic databases of MEDLINE, LILACS, and the Cochrane Central Register of Controlled Trials, from 1960 to November 2008 and references of selected articles. Intervention trials as well as observational studies that evaluated control strategies of VL in the Americas were included. While the use of rapid diagnostic tests for VL diagnosis seems well established, there is a striking lack of evidence from clinical trials for drug therapy and few well designed intervention studies for control of vectors or canine reservoirs. CONCLUSION Elimination of zoonotic VL in the Americas does not seem a realistic goal at this point given the lack of political commitment, gaps in scientific knowledge, and the weakness of case management and surveillance systems. Research priorities and current strategies should be reviewed with the aim of achieving better VL control.
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Affiliation(s)
- Gustavo A S Romero
- Núcleo de Medicina Tropical, Faculdade de Medicina, Universidade de Brasília, Brasília, Distrito Federal, Brazil.
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Abstract
Zoonotic visceral leishmaniasis (ZVL) caused by Leishmania infantum is an important disease of humans and dogs. Here we review aspects of the transmission and control of ZVL. Whilst there is clear evidence that ZVL is maintained by sandfly transmission, transmission may also occur by non-sandfly routes, such as congenital and sexual transmission. Dogs are the only confirmed primary reservoir of infection. Meta-analysis of dog studies confirms that infectiousness is higher in symptomatic infection; infectiousness is also higher in European than South American studies. A high prevalence of infection has been reported from an increasing number of domestic and wild mammals; updated host ranges are provided. The crab-eating fox Cerdocyon thous, opossums Didelphis spp., domestic cat Felis cattus, black rat Rattus rattus and humans can infect sandflies, but confirmation of these hosts as primary or secondary reservoirs requires further xenodiagnosis studies at the population level. Thus the putative sylvatic reservoir(s) of ZVL remains unknown. Review of intervention studies examining the effectiveness of current control methods highlights the lack of randomized controlled trials of both dog culling and residual insecticide spraying. Topical insecticides (deltamethrin-impregnated collars and pour-ons) have been shown to provide a high level of individual protection to treated dogs, but further community-level studies are needed.
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Courtenay O, Kovacic V, Gomes PAF, Garcez LM, Quinnell RJ. A long-lasting topical deltamethrin treatment to protect dogs against visceral leishmaniasis. MEDICAL AND VETERINARY ENTOMOLOGY 2009; 23:245-256. [PMID: 19712155 DOI: 10.1111/j.1365-2915.2009.00815.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
To develop long-lasting, topical pour-on insecticides for dogs to control zoonotic visceral leishmaniasis, two deltamethrin-based formulations (emulsifiable concentrate [EC] and suspension concentrate [SC]) were tested for their efficacy against the phlebotomine sandfly Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae), vector of Leishmania infantum Nicolle (Kinetoplastida: Trypanosomatidae). The entomological outcomes tested were anti-feeding effect (proportion of female sandflies unfed), lethal effect (24-h female sandfly mortality) and these two effects combined, and the insecticide persistence time at 50% (residual activity, RA50) and 80% (RA80) efficacy. On initial application, the proportions of female flies that demonstrated anti-feeding activity or were killed were similar for both formulations, at 0.93 (95% confidence interval [CI] 0.856-0.977) vs. 0.81 (95% CI 0.763-0.858) (anti-feeding) and 0.86 (95% CI 0.787-0.920) vs. 0.76 (95% CI 0.698-0.817) (24-h mortality) for EC and SC, respectively. The RA(50) rates for anti-feeding and mortality caused by the EC formulation were 4.7 months (95% CI 4.18-5.84) and 2.5 months (95% CI 2.25-2.90), respectively, compared with 1.1 months (95% CI 0.96-1.15) and 0.6 months (95% CI 0.50-0.61), respectively, for the SC formulation. The RA(50) for the combined anti-feeding and mortality effects of EC was 5.2 months (95% CI 4.73-5.96), compared with only 0.9 months (95% CI 0.85-1.00) for the SC formulation. The four- to six-fold superior residual activity of the EC formulation was attributed to the addition of a solvent-soluble resin in the formulation which improved fur adhesion and acted as a reservoir for the slow release of the active ingredient. These results identify the potential of such a low-cost formulation to reduce the inter-intervention interval to 5-6 months, similar to that recommended for deltamethrin-impregnated dog collars or for re-impregnation of conventional bednets, both of which are currently used to combat Leishmania transmission. Finally, a novel bioassay was developed in which sandflies were exposed to fur from treated dogs, revealing no detectable tolerance (24-h mortality) in wild-caught sandflies to the insecticide formulations up to 8 months after the initiation of communitywide application of the insecticides to dogs.
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Affiliation(s)
- O Courtenay
- Populations and Disease Research Group, Department of Biological Sciences, University of Warwick, Coventry, UK.
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Faiman R, Cuño R, Warburg A. Control of phlebotomine sand flies with vertical fine-mesh nets. JOURNAL OF MEDICAL ENTOMOLOGY 2009; 46:820-831. [PMID: 19645284 DOI: 10.1603/033.046.0412] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Insecticide-treated vertical net barriers were used to intercept foraging sand flies. Two different nets were draped on fenced enclosures (10 by 10 m; 2 m high) in the central Jordan Valley. One enclosure was draped with a deltamethrin-impregnated net (PermaNet, 225 holes/in2). The holes of this net are sufficiently large to allow sand flies to pass through but not without coming in close contact with the mesh. The other enclosure was covered with SpiderNet+ (1,240 holes/in2) and sprayed with beta-cyfluthrin. Sand flies were captured inside and outside the enclosures before and after draping with the nets using CO2-baited CDC traps or CDC light traps. Both barrier types exhibited > 90% efficacy in blocking sand flies from entering the enclosures (P < 0.01). The Spider-Net+ exhibited high efficiency even before being sprayed with insecticide because the small mesh size physically prevented flies from passing through. In Ma'ale Adumim, a 60-m-long, 2-m-high PermaNet barrier was erected to intercept sand flies approaching houses from their natural habitats. Sand flies were monitored on all sides of the barrier using CO2-baited CDC traps or CDC light traps. Results showed a 60% reduction in the mean number of sand flies trapped behind the net compared with the untreated areas adjacent to it (P < 0.05). Integrated vector control campaigns for reducing the burden of sand fly bites should consider vertical fine-mesh nets to reduce the numbers of sand flies arriving at inhabited areas.
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Affiliation(s)
- R Faiman
- Department of Parasitology, The Kuvin Centre for the Study of Infectious and Tropical Diseases, The Institute for Medical Research Israel Canada, The Hebrew University, Hadassah Medical School, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
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Schaffer WM, Bronnikova TV. Controlling malaria: competition, seasonality and 'slingshotting' transgenic mosquitoes into natural populations. JOURNAL OF BIOLOGICAL DYNAMICS 2009; 3:286-304. [PMID: 22880835 DOI: 10.1080/17513750802582621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Forty years after the World Health Organization abandoned its eradication campaign, malaria remains a public health problem of the first magnitude with worldwide infection rates on the order of 300 million souls. The present paper reviews potential control strategies from the viewpoint of mathematical epidemiology. Following MacDonald and others, we argue in Section 1 that the use of imagicides, i.e., killing, or at least repelling, adult mosquitoes, is inherently the most effective way of combating the pandemic. In Section 2, we model competition between wild-type (WT) and plasmodium-resistant, genetically modified (GM) mosquitoes. Under the assumptions of inherent cost and prevalence-dependant benefit to transgenics, GM introduction can never eradicate malaria save by stochastic extinction of WTs. Moreover, alternative interventions that reduce prevalence have the undesirable consequence of reducing the likelihood of successful GM introduction. Section 3 considers the possibility of using seasonal fluctuations in mosquito abundance and disease prevalence to 'slingshot' GM mosquitoes into natural populations. By introducing GM mosquitoes when natural populations are about to expand, one can 'piggyback' on the yearly cycle. Importantly, this effect is only significant when transgene cost is small, in which case the non-trivial equilibrium is a focus (damped oscillations), and piggybacking is amplified by the system's inherent tendency to oscillate. By way of contrast, when transgene cost is large, the equilibrium is a node and no such amplification is obtained.
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Affiliation(s)
- W M Schaffer
- Department of Ecology and Evolutionary Biology, The University of Arizona, AZ, USA.
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Sirak-Wizeman M, Faiman R, Al-Jawabreh A, Warburg A. Control of phlebotomine sandflies in confined spaces using diffusible repellents and insecticides. MEDICAL AND VETERINARY ENTOMOLOGY 2008; 22:405-412. [PMID: 19120969 DOI: 10.1111/j.1365-2915.2008.00762.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The control of phlebotomine sandflies (Diptera: Psychodidae), the vectors of leishmaniasis, is directed mostly against adults as larvae develop in unknown or inaccessible habitats. In the current study we tested geraniol, a natural plant-derived product, as a space repellent and the synthetic pyrethroid prallethrin as a diffusible insecticide. Geraniol was dispersed in the air using diffusers with an electric fan and prallethrin was evaporated using electrically heated evaporators. Both substances were tested in inhabited bedrooms and in tents. Geraniol failed to effect significant reductions in the numbers of either Phlebotomus papatasi Scopoli in rooms or Phlebotomus sergenti Parrot in tents. In laboratory experiments, geraniol proved ineffective in preventing sandflies from feeding. By contrast, prallethrin was highly effective in reducing the number of sandflies in rooms as well as in tents. Exposure of sandflies to prallethrin in laboratory experiments caused 97% mortality rates. Both prallethrin and, to a lesser extent, geraniol reduced the number of Culex mosquitoes captured in tents. Electric liquid-vaporizers with 1.5% prallethrin are highly effective in protecting people from sandfly bites in confined spaces and may be useful in combating cutaneous leishmaniasis.
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Affiliation(s)
- M Sirak-Wizeman
- Department of Parasitology, Kuvin Center for the Study of Tropical and Infectious Diseases, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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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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Das ML, Singh SP, Vanlerberghe V, Rijal S, Rai M, Karki P, Sundar S, Boelaert M. Population preference of net texture prior to bed net trial in Kala-Azar-endemic areas. PLoS Negl Trop Dis 2007; 1:e100. [PMID: 18160976 PMCID: PMC2154387 DOI: 10.1371/journal.pntd.0000100] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2007] [Accepted: 09/06/2007] [Indexed: 11/18/2022] Open
Abstract
Prior to a community-based efficacy trial of long-lasting insecticidal nets (LLINs) in the prevention of visceral leishmaniasis (VL; also called kala-azar), a pilot study on preference of tools was held in endemic areas of India and Nepal in September 2005.LLINs made of polyester and polyethylene were distributed to 60 participants, who used the nets sequentially for 7 d. Acceptability and preference were evaluated via indirect indicators through questionnaires at three defined time points before and after use of the LLINs and through focus group discussions (FGDs). In the latter, preferences for color and size were also assessed. Untreated bed nets were owned by 87% of the households prior to the study. All users liked textures of both LLIN types after 7 d of use, but had a slight preference for those made of polyester if they were to recommend a LLIN to relatives or friends (p<0.05), mainly because of their relatively greater softness in comparison to polyethylene LLINs. Users reported that both net types reduced mosquito bites and number of insects, including sand fly (bhusana; genus Phlebotomus), inside the house. Side effects were minor and disappeared quickly.The large-scale intervention trial considered the preferences of the study population to decide on the best tool of intervention--light-blue, rectangular, polyester LLINs of different sizes.
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Affiliation(s)
- Murari L. Das
- BP Koirala Institute of Health Sciences, Dharan, Nepal
| | - Shri P. Singh
- Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | | | - Suman Rijal
- BP Koirala Institute of Health Sciences, Dharan, Nepal
| | - Madhukar Rai
- Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Prahlad Karki
- BP Koirala Institute of Health Sciences, Dharan, Nepal
| | - Shyam Sundar
- Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
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