Detection of potential transmission foci of lymphatic filariasis using molecular xenomonitoring in Huahine, French Polynesia.

BACKGROUND

In French Polynesia, substantial progress has been achieved in eliminating lymphatic filariasis (LF) caused by Wuchereria bancrofti var. pacifica, a parasite transmitted by the mosquito vector Aedes polynesiensis. However, despite multiple rounds of Mass Drug Administration (MDA), LF transmission persists on some islands, underscoring the need for robust surveillance to evaluate transmission risks and identify potential transmission foci.

METHODOLOGY/PRINCIPAL FINDINGS: An extensive entomological survey combined with a Molecular Xenomonitoring (MX) study was conducted on Huahine Island in the Leeward Islands (Society Islands), where new LF cases continue to be reported. Adult mosquitoes were collected from 420 sampling points across 28 Primary Sampling Units (PSUs) to map mosquito species distribution and estimate infection prevalence in mosquitoes. Among the 5508 female mosquitoes collected, Ae. polynesiensis was the predominant species (74%), widely distributed across the island and particularly abundant in some PSUs. Other species included Aedes aegypti (20%) and Culex quinquefasciatus (4%). Mosquito pools from species of the genera Aedes and Culex were tested for the presence of W. bancrofti using real-time PCR. Positive pools were detected in 13 PSUs, involving both vector and non-vector Aedes species, Ae. polynesiensis (63.6%) and Ae. aegypti (36.4%). Estimated infection prevalence in mosquitoes was higher in Ae. aegypti (1.1%) than in Ae. polynesiensis (0.53%), likely reflecting the differences in species abundance and host preferences. Several potential transmission foci were identified, primarily concentrated in the northern part of the island.

CONCLUSIONS/SIGNIFICANCE: Our study demonstrates the effectiveness of MX using female Aedes mosquitoes in identifying potential transmission foci and detecting the presence of LF cases in the vicinity on the island of Huahine. This approach constitutes a valuable tool for post-MDA surveillance in Pacific Islands, where Aedes mosquitoes are key vectors for W. bancrofti, and will effectively inform the targeted implementation of control interventions, including innovative vector control strategies.