Foraging Behavior of Anopheles Mosquitoes in Nchelenge District, Zambia

[摘要] Approximately 3.2 billion people worldwide are at risk of contracting malaria.In 2013, there were 200 million cases and close to 600,000 deaths, most of which occurred in sub-Saharan Africa and affected mainly children, denoting the disease as a major public health problem. In Nchelenge District, Zambia, there is holoendemic transmission of Plasmodium falciparum, vectored by Anopheles funestus sensu stricto and An. gambiae s.s. mosquitoes. Since 2006, the Zambian government has provided LLINs, providing approximately one net per person, and has implemented IRS campaigns in Nchelenge.Despite the use of vector control, the prevalence of malaria has not reduced, making it necessary to define and characterize the Anopheles mosquitoes involved in transmission to better develop strategies for control. Therefore, the specific aims of this study were: 1) to identify and characterize the anopheline mosquitoes and their respective roles in P. falciparum transmission both temporally and spatially, 2) to determine the extent of underestimation of Anopheles foraging behavior by standard field methods across the three southern Africa ICEMR field sites, and 3) to investigate multiple blood feeding behavior and human gender preference of human fed mosquitoes, and P. falciparum complexity of infection (COI) in infected anophelines in Nchelenge District. CDC LT and PSC trap methods were performed over three consecutive wet and dry seasons in three villages lakeside and two villages streamside, revealing An. funestus and An. gambiae as the dominant vectors.Both vectors were also highly anthropophilic.Temporally, An. funestus is the primary vector year round, whereas An. gambiae is more abundant during the wet season compared to the dry season. Spatially, during the wet season, An. funestus is the predominant vector inland and along the stream, whereas An. gambiae is the predominant vector along Lake Mweru.Additionally, the abundances of both An. funestus and An. gambiae streamside are higher than lakeside. Throughout all three collections, An. funestus had the highest transmission intensity, indicating its important role in maintaining transmission year round. When investigating the foraging behavior of malaria vectors across the three southern Africa ICEMR sites, it was found that by not including visually ;;unfed” mosquitoes in host blood meal PCR assays, the overall proportion of fed vectors is underestimated by up to 18.7%, and that this can have potential effects on the human blood index (HBI), human biting rate (HBR), and entomological inoculation rate (EIR). Finally, Anopheles mosquito foraging behavior in Nchelenge was further defined through multiple blood feeding behavior, human gender preference, and COI studies. Both An. funestus and An. gambiae displayed multiple blood feeding rates of 23.2% and 25.7% respectively, rates that are among the highest recorded in sub-Saharan Africa and lead to an underestimation of the EIR. There was a trend towards both vectors feeding on human males more so than females. Furthermore, the P. falciparum COI in infected mosquitoes was 6.4, suggesting a high transmission setting and supports the inoculation of multiple clones in a single mosquito bite in Nchelenge District. The studies described in this dissertation have provided a foundation for future entomological studies on mosquito vectors in Nchelenge District, Zambia, as well as vector control evaluation and development of effective intervention programs.

[发布机构] Johns Hopkins University

[效力级别] Zambia

[关键词] Malaria;Zambia;Anopheles;complexity of infection;multiple blood feeding;Biology