Contributions of different mosquito species to the transmission of lymphatic filariasis in central Nigeria: implications for monitoring infection by PCR in mosquito pools.

Background: Members of the Anopheles gambiae complex are important vectors of lymphatic filariasis (LF) in sub-Saharan Africa, but little is known about the relative contributions of all mosquitoes to lymphatic filariasis transmission in this area.

Methods: Over a 28 month period, mosquitoes were collected from 13 villages in Plateau and Nasarawa states in central Nigeria and dissected to determine W. bancrofti infection status. Wings and legs from a subset of the mosquitoes visually identified as A. gambiae s.l. were identified by PCR as either A. gambiae s.s. or A. arabiensis.

Results: A. gambiae s.s peaked in abundance during the rainy season while A. arabiensis predominated during drier parts of the year. Both species were found equally likely to be infected with the developing stages (L1-L3) of W. bancrofti (9.2% and 11.1%, respectively). Fewer A. funestus (1.1%, p < 0.001) were infected than A. gambiae s.l.

Conclusion: Understanding the relative contributions of morphologically indistinguishable species to LF transmission is essential if PCR is to be performed on mosquito pools. In the study area, the use of mosquito pools composed of A. gambiae sibling species would not be problematic, as both A. gambiae s.s. and A. arabiensis contribute equally to LF transmission.