Abstract
BackgroundEntomological methods may provide important tools for monitoring the transmission of filariasis in French Polynesia. In order to standardize our PCR method and refine our protocol to assess filarial infection levels in mosquitoes, we compared dissection of the vector, Aedes polynesiensis, with the poolscreening polymerase chain reaction (PS-PCR) assay.Methods(1) Mosquitoes were collected in human landing catches in five areas in Moorea island, French Polynesia. (2) A fraction of the captured mosquitoes was dissected for Wuchereria bancrofti larvae. (3) Laboratory-reared mosquitoes (uninfected as well as experimentally infected ones) were repeatedly tested to optimize a PS-PCR protocol (DNA extracts from 1–50 pooled mosquitoes were tested with an internal standardized system and primers specific for the Ssp1 repeat sequence. PCR products were analysed by gel electrophoresis). (4) Another fraction of the captured mosquitoes was assayed by PS-PCR according the optimized protocol.ResultsThe prevalence of field-mosquito infection with W. bancrofti ranged from 1 to 8 % by dissection (L1–L3) and point estimates of infection prevalence, as assayed by PS-PCR, ranged from 0.4 to 3.7 %. There was a moderately strong correlation between larval infection rates as determined by dissection and PCR.DiscussionOur results suggest that the PS-PCR assay is specific and highly sensitive for detecting parasite DNA. We obtained similar although not identical results with dissections of mosquitoes. PS-PCR appears to be adequate for testing large numbers of mosquitoes in the context of filariasis elimination programs. The role and advantages of using entomologic methods to monitor filariasis programs are discussed.
Highlights
Entomological methods may provide important tools for monitoring the transmission of filariasis in French Polynesia
Our results suggest that the poolscreening polymerase chain reaction (PS-PCR) assay is specific and highly sensitive for detecting parasite DNA
PS-PCR appears to be adequate for testing large numbers of mosquitoes in the context of filariasis elimination programs
Summary
Entomological methods may provide important tools for monitoring the transmission of filariasis in French Polynesia. In order to standardize our PCR method and refine our protocol to assess filarial infection levels in mosquitoes, we compared dissection of the vector, Aedes polynesiensis, with the poolscreening polymerase chain reaction (PS-PCR) assay. Monitoring the efficacy of filariasis elimination programs depends on careful evaluation of infection levels in the human and vector populations following the introduction of control programs. Mosquito dissection has been the gold standard for measuring infection rates and densities in the vector. The ability of PCR techniques to detect one microfilaria in pools of up to 50 mosquitoes suggests that current PCR methods could facilitate the testing of adequate numbers of mosquitoes to enable changes in transmission to be measured
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