Molecular xenomonitoring of Wuchereria bancrofti infection in three different evaluation settings of lymphatic filariasis elimination programme in India.

Abstract

Background: Molecular xenomonitoring (MX) is one of the recommended post-validation surveillance tools to detect early signals of lymphatic filariasis (LF) infection. This study reports the MX results of Culex quinquefasciatus transmitted Wuchereria bancrofti in three evaluation units of different settings in India.

Methods: Female Cx. quinquefasciatus mosquitoes were collected using gravid traps from 150 households in each evaluation unit (EU). Two pools of 25 mosquitoes from each household were assayed by real time quantitative PCR for W. bancrofti DNA, and RNA by RT-PCR. The agreement between MX and transmission assessment survey (TAS) in MDA stopping decision was compared, and microfilaria (Mf) prevalence in TAS failed EU.

Results: Vector infection prevalence was 0.05% and 0.07% in the TAS cleared EUs, and 1.85% in TAS failed EU. MX corroborates with the TAS decision in all three settings. Mf prevalence was >1% in 5 sites in TAS failed EU. Infective mosquitoes were detected in TAS2 passed and TAS failed EUs. The cost of MX per pool was between USD 26.0 and 27.9 in different settings.

Conclusion: MX is a potential tool to evaluate different stages of post-MDA treatment of LF elimination programme. MX detects transmission risk areas that can be confirmed by human surveys and initiate appropriate response.