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.