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Evaluation of ivermectin mass drug administration for malaria transmission control across different West African environments.

Alout H, Krajacich BJ, Meyers JI, Grubaugh ND, Brackney DE, Kobylinski KC, Diclaro JW, Bolay FK, Fakoli LS, Diabaté A, Dabiré RK, Bougma RW, Foy BD - Malar. J. (2014)

Bottom Line: This study examines the degree and duration of mosquitocidal effects resulting from single MDAs conducted in three different West African countries, and the subsequent reductions in parity and Plasmodium sporozoite rates.The effect of MDA was then analysed against the time relative to the MDA, the distributed drugs and environmental variables.Anopheles gambiae survivorship was reduced by 33.9% for one week following MDA and parity rates were significantly reduced for more than two weeks after the MDAs.

View Article: PubMed Central - PubMed

Affiliation: Arthropod-borne and Infectious Diseases Laboratory, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA. haoues.alout@colostate.edu.

ABSTRACT

Background: Mass drug administration (MDA) of ivermectin to humans for control and elimination of filarial parasites can kill biting malaria vectors and lead to Plasmodium transmission reduction. This study examines the degree and duration of mosquitocidal effects resulting from single MDAs conducted in three different West African countries, and the subsequent reductions in parity and Plasmodium sporozoite rates.

Methods: Indoor-resting, blood-fed and outdoor host-seeking Anopheles spp. were captured on days surrounding MDAs from 2008-2013 in Senegalese, Liberian and Burkinabé villages. Mortality was assessed on a portion of the indoor collection, and parity status was determined on host-seeking mosquitoes. The effect of MDA was then analysed against the time relative to the MDA, the distributed drugs and environmental variables.

Results: Anopheles gambiae survivorship was reduced by 33.9% for one week following MDA and parity rates were significantly reduced for more than two weeks after the MDAs. Sporozoite rates were significantly reduced by >77% for two weeks following the MDAs in treatment villages despite occurring in the middle of intense transmission seasons. These observed effects were consistent across three different West African transmission dynamics.

Conclusions: These data provide a comprehensive and crucial evidence base for the significant reduction in malaria transmission following single ivermectin MDAs across diverse field sites. Despite the limited duration of transmission reduction, these results support the hypothesis that repeated MDAs with optimal timing could help sustainably control malaria as well as filarial transmission.

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Related in: MedlinePlus

Study sites outlined on maps showing the spatial distribution of thePlasmodium falciparumentomological inoculation rate (PfEIR) in Africa (panel A), Burkina Faso (B), Senegal (C) and Liberia (D) in 2010. Red squares represent the location of the sampled villages. Data are available at Malaria Atlas Project[13].
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Fig1: Study sites outlined on maps showing the spatial distribution of thePlasmodium falciparumentomological inoculation rate (PfEIR) in Africa (panel A), Burkina Faso (B), Senegal (C) and Liberia (D) in 2010. Red squares represent the location of the sampled villages. Data are available at Malaria Atlas Project[13].

Mentions: Ivermectin is an endectocide that has been extensively used alone for decades for the control of onchocerciasis, or in combination with albendazole for the elimination of lymphatic filariasis. Currently, more than 300 million individuals living in areas endemic for filarial infections are treated each year in mass drug administration (MDA) campaigns[7]. The drug has an excellent safety profile in humans and can be lethal to mosquitoes when they feed on treated humans. Ivermectin MDA addresses specific malERA recommendations including: a) a different mode of action from current insecticides; b) it targets all biting vectors, regardless of their ecology and feeding behaviour; and, c) it may be integrated into existing strategies to simultaneously control malaria, filariasis and other neglected tropical diseases[8]. The mosquitocidal effect of ivermectin MDA has been demonstrated on several Anopheles species from field trials[9, 10]. However, subsequent effects on vector population age-structure has only been modelled[11], and effects on vector infection rates with Plasmodium have only been measured for a limited duration in one setting[12]. Repeated MDAs with ivermectin have been proposed as a complementary Plasmodium transmission control tool[10] but several knowledge gaps need to be filled in order to fully evaluate this strategy. Here, the effects of single ivermectin MDAs were comprehensively analysed across different years and in three West African countries with distinct malaria transmission dynamics: Senegal, Liberia and Burkina Faso (Figure 1, Table 1). The degree and duration of effects on mosquito survival, parity rate and the proportion of sporozoite-infected vectors before and after single ivermectin MDAs in treatment villages, and in pair-matched, untreated villages, were assessed, taking into account several biotic (species, exophily) and abiotic (environmental) factors.Figure 1


Evaluation of ivermectin mass drug administration for malaria transmission control across different West African environments.

Alout H, Krajacich BJ, Meyers JI, Grubaugh ND, Brackney DE, Kobylinski KC, Diclaro JW, Bolay FK, Fakoli LS, Diabaté A, Dabiré RK, Bougma RW, Foy BD - Malar. J. (2014)

Study sites outlined on maps showing the spatial distribution of thePlasmodium falciparumentomological inoculation rate (PfEIR) in Africa (panel A), Burkina Faso (B), Senegal (C) and Liberia (D) in 2010. Red squares represent the location of the sampled villages. Data are available at Malaria Atlas Project[13].
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4226880&req=5

Fig1: Study sites outlined on maps showing the spatial distribution of thePlasmodium falciparumentomological inoculation rate (PfEIR) in Africa (panel A), Burkina Faso (B), Senegal (C) and Liberia (D) in 2010. Red squares represent the location of the sampled villages. Data are available at Malaria Atlas Project[13].
Mentions: Ivermectin is an endectocide that has been extensively used alone for decades for the control of onchocerciasis, or in combination with albendazole for the elimination of lymphatic filariasis. Currently, more than 300 million individuals living in areas endemic for filarial infections are treated each year in mass drug administration (MDA) campaigns[7]. The drug has an excellent safety profile in humans and can be lethal to mosquitoes when they feed on treated humans. Ivermectin MDA addresses specific malERA recommendations including: a) a different mode of action from current insecticides; b) it targets all biting vectors, regardless of their ecology and feeding behaviour; and, c) it may be integrated into existing strategies to simultaneously control malaria, filariasis and other neglected tropical diseases[8]. The mosquitocidal effect of ivermectin MDA has been demonstrated on several Anopheles species from field trials[9, 10]. However, subsequent effects on vector population age-structure has only been modelled[11], and effects on vector infection rates with Plasmodium have only been measured for a limited duration in one setting[12]. Repeated MDAs with ivermectin have been proposed as a complementary Plasmodium transmission control tool[10] but several knowledge gaps need to be filled in order to fully evaluate this strategy. Here, the effects of single ivermectin MDAs were comprehensively analysed across different years and in three West African countries with distinct malaria transmission dynamics: Senegal, Liberia and Burkina Faso (Figure 1, Table 1). The degree and duration of effects on mosquito survival, parity rate and the proportion of sporozoite-infected vectors before and after single ivermectin MDAs in treatment villages, and in pair-matched, untreated villages, were assessed, taking into account several biotic (species, exophily) and abiotic (environmental) factors.Figure 1

Bottom Line: This study examines the degree and duration of mosquitocidal effects resulting from single MDAs conducted in three different West African countries, and the subsequent reductions in parity and Plasmodium sporozoite rates.The effect of MDA was then analysed against the time relative to the MDA, the distributed drugs and environmental variables.Anopheles gambiae survivorship was reduced by 33.9% for one week following MDA and parity rates were significantly reduced for more than two weeks after the MDAs.

View Article: PubMed Central - PubMed

Affiliation: Arthropod-borne and Infectious Diseases Laboratory, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA. haoues.alout@colostate.edu.

ABSTRACT

Background: Mass drug administration (MDA) of ivermectin to humans for control and elimination of filarial parasites can kill biting malaria vectors and lead to Plasmodium transmission reduction. This study examines the degree and duration of mosquitocidal effects resulting from single MDAs conducted in three different West African countries, and the subsequent reductions in parity and Plasmodium sporozoite rates.

Methods: Indoor-resting, blood-fed and outdoor host-seeking Anopheles spp. were captured on days surrounding MDAs from 2008-2013 in Senegalese, Liberian and Burkinabé villages. Mortality was assessed on a portion of the indoor collection, and parity status was determined on host-seeking mosquitoes. The effect of MDA was then analysed against the time relative to the MDA, the distributed drugs and environmental variables.

Results: Anopheles gambiae survivorship was reduced by 33.9% for one week following MDA and parity rates were significantly reduced for more than two weeks after the MDAs. Sporozoite rates were significantly reduced by >77% for two weeks following the MDAs in treatment villages despite occurring in the middle of intense transmission seasons. These observed effects were consistent across three different West African transmission dynamics.

Conclusions: These data provide a comprehensive and crucial evidence base for the significant reduction in malaria transmission following single ivermectin MDAs across diverse field sites. Despite the limited duration of transmission reduction, these results support the hypothesis that repeated MDAs with optimal timing could help sustainably control malaria as well as filarial transmission.

Show MeSH
Related in: MedlinePlus