Lymphatic filariasis transmission 10 years after stopping mass drug administration in the Gomoa west district of Ghana

Objectives: A survey was conducted 10 years after stopping MDA in the Gomoa West District of Ghana to assess the Wuchereria bancrofti prevalence in both human and mosquito populations. Methods: In seven communities, infection in humans was assessed using the filariasis test strip (FTS). Mosquitoes were collected once a month over six months using pyrethrum spray catches (PSC). The mosquitoes were analyzed for W. bancrofti infections, using dissection followed by poolscreening PCR. Results: FTS results showed that 2/524 (0.38%; 95% CI, 0.0%-0.9%) individuals tested positive for antigen. Dissections revealed W. bancrofti infections in 5/107 Anopheles gambiae (4.7%: 95% CI, 2.2-8.5) from one community, with three mosquitoes harboring L3 larvae (2.8%: 95% CI, 0.9-7.5). PCR analysis of 683 mosquitoes in 57 pools revealed seven positive pools from two communities. The prevalence of infected mosquitoes by PCR for the district was 3.1% (95% CI, 0.5-24.0) for An. gambiae and 2.5% (95% CI, 0.4-23.5) for all Anopheles spp. Conclusions: The infection rate in the Anopheles spp. exceeds the provisional 1% threshold suggested by WHO, indicating ongoing transmission risk ten years after stopping MDA. Further district-wide assessments are recommended to inform the scope of any interventions required in the Gomoa West district.