The overall aim of this study is to gain a better understanding of the transmission dynamics of lymphatic filariasis (LF) by Culex species in East African cities and determine the role of Anopheles mosquitoes. Specifically the study will determine the magnitude and distribution of W. bancrofti transmission by Culex and Anopheles mosquito species across urban and peri-urban areas of Dar es Salaam, Zanzibar and Mombasa. It will identify climatic and local environmental factors associated with spatial and temporal distributions of LF in mosquitoes, and examine the relationship with infection rates in humans.
Currently, LF transmission in African cities is not well understood as few studies have examined the transmission dynamics of the mosquito vectors. Entomological studies in East Africa report that An. gambiae s.l, An. funestus and Cx. quinquefasciatus are key vectors in Tanzania and Kenya.
The national LF Programmers in Tanzania (mainland) and Kenya have indicated that implementation and reaching >80% treatment coverage of MDA in Dar es Salaam (and Tanga) and Mombasa is difficult, and that people continue to carry microfilaria (mf) and circulating filarial antigens (CFA) (to W. bancrofti) following multiple rounds of MDA. Recent results from Dar es Salaam (2010) suggest that 3% of Culex quinquefasciatus tested positive for W. bancrofti DNA. This implies a considerable pool of infection in the human population. In Zanzibar, the LF Programmer has shown that the LF has been eliminated in humans, however, no entomological studies have been carried across the islands to confirm the absence of infection in local vectors.
This study will provide key information to the national LF Programmers on the dynamics of urban and peri-urban mosquito vectors, and linkage with infections in humans. It will help determine whether evaluations of infection in the insect vectors reflect the infectivity in the human population and can be used as a useful, non-invasive proxy of human infection rate and a means of evaluating the success of interventions.
