Evaluation of honey-baited FTA cards in combination with different mosquito traps in an area of low arbovirus prevalence

Abstract

BackgroundThe threat of mosquito-borne diseases is increasing in continental Europe as demonstrated by several autochthonous chikungunya, dengue and West Nile virus outbreaks. In Switzerland, despite the presence of competent vectors, routine surveillance of arboviruses in mosquitoes is not being carried out, mainly due to the high costs associated with the need of a constant cold chain and laborious processing of thousands of mosquitoes. An alternative approach is using honey-baited nucleic acid preserving cards (FTA cards) to collect mosquito saliva that may be analysed for arboviruses. Here, we evaluate whether FTA cards could be used to detect potentially emerging viruses in an area of low virus prevalence in combination with an effective mosquito trap.MethodsIn a field trial in southern Switzerland we measured side-by-side the efficacy of the BG-Sentinel 2, the BG-GAT and the Box gravid trap to catch Aedes and Culex mosquitoes in combination with honey-baited FTA cards during 80 trapping sessions of 48 hours. We then screened both the mosquitoes and the FTA cards for the presence of arboviruses using reverse-transcription PCR. The efficacy of the compared trap types was evaluated using generalized linear mixed models.ResultsThe Box gravid trap collected over 11 times more mosquitoes than the BG-GAT and BG-Sentinel 2 trap. On average 75.9% of the specimens fed on the honey-bait with no significant difference in feeding rates between the three trap types. From the total of 1401 collected mosquitoes, we screened 507 Aedes and 500 Culex females for the presence of arboviruses. A pool of six Cx. pipiens/Cx. torrentium mosquitoes and also the FTA card from the same Box gravid trap were positive for Usutu virus. Remarkably, only two of the six Culex mosquitoes fed on the honey-bait, emphasising the high sensitivity of the method. In addition, two Ae. albopictus collections but no FTA cards were positive for mosquito-only flaviviruses.ConclusionsBased on our results we conclude that honey-baited FTA cards, in combination with the Box gravid trap, are an effective method for arbovirus surveillance in areas of low prevalence, particularly where resources are limited for preservation and screening of individual mosquitoes.

Viromics on Honey-Baited FTA Cards as a New Tool for the Detection of Circulating Viruses in Mosquitoes

“…The detection of ISVs through metagenomics on honey-baited FTA cards provides evidence that these viruses could be transmitted within mosquitoes' expectorations, thereby contradicting previous beliefs that they could not be expelled with saliva [19]. Our findings are supported by the tissue tropism evidenced for Culex flavivirus (family Flaviviridae) and Phasi Charoen-like virus (PCLV) (genus Phasivirus, family Phenuiviridae), as they were also detected in salivary glands of Cx.…”

“…Furthermore, to improve the sensitivity and efficiency of our approach, honey-baited FTA cards could be placed inside Box gravid traps, as a recent study conducted in Switzerland demonstrated these to be the most effective traps for capturing females of different species when searching for an ovipositional site. In addition, these traps also exhibited the highest feeding success on honey-baited FTA cards [19].…”

“…Since gold-standard strategies are time-consuming, logistically complex and potentially hazardous, honey-baited Flinders Technology Associates (FTA) cards have been used as an alternative tool for arbovirus surveillance as they inactivate pathogens and preserve nucleic acids on contact, thereby simplifying the labor [12,13,16]. In previous field trials, honey-soaked FTA cards have been used in combination with molecular techniques to detect several arboviruses, such as Ross River virus (RRV), Barmah Forest virus (BFV) [13,[16][17][18] and West Nile virus strain Kunjin (WNVKUN) [13,17] in Australia, and Usutu virus (USUV) in Switzerland [19]. Moreover, while virological surveillance in mosquitoes is based mainly upon virus detection in entire mosquitoes, indicating that they might be infected, the detection of viruses expectorated within the saliva during sugar feeding and deposited directly on the FTA cards may identify infectious mosquitoes [18].…”

Epidemiology of Usutu Virus: The European Scenario

“…Subsequently, 258 human cerebrospinal fluid samples collected between 2015 and 2017 for routine clinical care in a tertiary level hospital in Geneva were tested for USUV by RT-PCR, but no samples tested positive [ 104 ]. In 2011 and 2012, USUV was found in mosquitoes from Ticino [ 105 ], and recently confirmed in the same area [ 106 ]. USUV-positive mosquito pool of Cx.pipiens / Cx.…”

Emerging Aedes-borne infections in southern Switzerland: Preparedness planning for surveillance and intervention

“…The current strategy to prevent and control Aedes-borne diseases in Canton Ticino is based on the surveillance and reports of human cases and the fight against the A e . albopictus mosquito [ 19 ]. Until now, no autochthonous cases of disease have been reported from Ticino or elsewhere in Switzerland.…”