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

Abstract

Objectives: Molecular xenomonitoring (MX) is a recommended post-validation surveillance tool for detecting early signs of lymphatic filariasis (LF) transmission. This study reports the MX results for Culex quinquefasciatus transmitted Wuchereria bancrofti in three evaluation units (EUs) in different settings of LF elimination in India. Methods: Female Cx. quinquefasciatus mosquitoes were collected using gravid traps from 150 households in each EU. Two pools of 25 mosquitoes from each household were assayed by real-time quantitative polymerase chain reaction for W. bancrofti DNA and RNA. The agreement between MX and the transmission assessment survey (TAS) in the mass drug administration (MDA) stopping decision was assessed. Additionally, the microfilaria (Mf) prevalence was compared in TAS-failed EU. Results: Vector infection prevalence was 0.05% and 0.07% in TAS-cleared EUs and 1.85% in TAS-failed EU. MX corroborated the TAS decision in all three settings. Mf prevalence was >1% at five sites in TAS-failed EU. Infective mosquitoes were detected in the TAS2 passed and TAS-failed EUs. The cost of MX per pool was between US $ 26.0 and 27.9 in different settings. Conclusions: MX is a potential tool for evaluating different stages of post-MDA treatment in the LF elimination program. The MX detects transmission risk areas that can be confirmed by human surveys for appropriate response.

Keywords

• Lymphatic filariasis
• Wuchereria bancrofti
• Culex quinquefasciatus
• Molecular xenomonitoring
• Transmission assessment survey
• India