Development of an urban molecular xenomonitoring system for lymphatic filariasis in the Recife Metropolitan Region, Brazil

Abstract

IntroductionMolecular xenomonitoring (MX)—pathogen detection in the mosquito rather than human—is a promising tool for lymphatic filariasis (LF) surveillance. In the Recife Metropolitan Region (RMR), the last LF focus in Brazil, Culex quinquefasciatus mosquitoes have been implicated in transmitting Wuchereria bancrofti parasites. This paper presents findings on the ideal mosquito collection method, mosquito dispersion, W. bancrofti infection in mosquitoes and W. bancrofti antigen in humans to aid MX development.MethodsExperiments occurred within two densely populated urban areas of Olinda, RMR, in July and August 2015. U.S. Centers for Disease Control and Prevention (CDC) light traps were compared to battery-powered aspirators as collection methods, and mosquito dispersion was measured by mosquito mark release recapture (MMRR). Female Cx. quinquefasciatus were tested by PCR for W. bancrofti infection, and study area residents were screened by rapid tests for W. bancrofti antigen.ResultsAspirators caught 2.6 times more total Cx. quinquefasciatus, including 38 times more blood-fed and 5 times more gravid stages, than CDC light traps. They also collected 123 times more Aedes aegypti. Of the 9,644 marked mosquitoes released, only ten (0.01%) were recaptured, nine of which were < 50m (34.8m median, 85.4m maximum) from the release point. Of 9,169 unmarked mosquitoes captured in the MMR, 38.3% were unfed, 48.8% blood-fed, 5.5% semi-gravid, and 7.3% gravid. PCR on 182 pools (1,556 mosquitoes) found no evidence of W. bancrofti infection in Cx. quinquefasciatus. Rapid tests on 110 of 111 eligible residents were all negative for W. bancrofti antigen.ConclusionsAspirators were more effective than CDC light traps at capturing Ae. aegypti and all but unfed stages of Cx. quinquefasciatus. Female Cx. quinquefasciatus traveled short (< 86m) distances in this urban area. Lack of evidence for W. bancrofti infection in mosquitoes and antigen in humans in these fine-scale studies does not indicate that LF transmission has ceased in the RMR. A MX surveillance system should consider vector-specific collection methods, mosquito dispersion, and spatial scale but also local context, environmental factors such as sanitation, and host factors such as infection prevalence and treatment history.

<p>Mapping and monitoring for a lymphatic filariasis elimination program: a systematic review</p>

“…If the area is endemic for other NTDs as well, an integrated mapping approach would be cost effective as well as feasible. For example in India, if an area is prone for dengue, chikungunya and LF, serological or MX surveys with appropriate test kits/devices with good sampling designs can be used to carry out integrated mapping of these diseases at the same time sharing the man-power and other resources 144. However, to include this as a part of a national program, a substantial investment has to be made in providing the infrastructure and training to personnel to carry out serological and MX surveys for the NTDs prevalent in the area.…”

No evidence of Zika, dengue, or chikungunya virus infection in field-caught mosquitoes from the Recife Metropolitan Region, Brazil, 2015

“…Between them and accounting for a 100 m buffer zone, the two study sites covered a combined area of approximately 0.4 km 2 containing approximately 5,514 residents, which was roughly equivalent to 1% of the territorial area and 1% of the population of Olinda, RMR ( Figure 1) 27 . As previously described, the mosquitoes used in this study were captured from two studies to optimise an urban MX system for LF and arboviruses: a collection method comparison (CMC) to determine the ideal mosquito capture method and a mosquito mark release recapture (MMRR) study to determine mean and maximum mosquito dispersion 36 . Mosquito collection occurred between July 22 and August 21, 2015, coinciding with the end of the rainy season and associated peak in mosquito abundance.…”

“…Detailed information on the study design and methods by which mosquitoes were collected have been described elsewhere 36 . Briefly, houses were selected for participation from satellite images and geographic information systems (GIS) software of ArcGIS 10.2 (ESRI 2014.…”

“…In 2015, a three-year MX project on LF commenced in order to aid LF elimination activities in the RMR 36 . The MX project was designed to provide detailed entomological data in an LF endemic area subjected to MDA and explore human and mosquito infection transmission dynamics over a small geographic area, to be scaled up in future, in order to inform a larger MX surveillance system.…”

Molecular xenomonitoring as a post-MDA surveillance tool for global programme to eliminate lymphatic filariasis: Field validation in an evaluation unit in India

“…Various collection methods have been employed and tested for their efficiency to capture different vector species: gravid traps [8,19,[23][24][25][26][27], CDC light traps and battery powered aspirators for Cx. quinquefasciatus [28], AGT, a variant of OviART & pyrethrum spray method for Anopheles gambiae [13,29,30], and BG sentinel traps for Aedes polynesiensis [12]. MX technique is shown to be more efficient and sensitive in detecting parasite DNA than Mf-testing in humans [26,31] and assessing the residual or renewed foci of infection after several rounds of MDA [8,12,19,21,26,[31][32][33][34][35].…”