Is molecular xenomonitoring of mosquitoes for Dirofilaria repens suitable for dirofilariosis surveillance in endemic regions?

Aleksander Masny, Rusłan Sałamatin, Wioletta Rozej-Bielicka, Elzbieta Golab

Dirofilaria repens is a parasite of animals and humans, transferred by mosquitoes. The assessment of the presence of D. repens-infected vertebrate hosts in the investigated area can be performed by xenomonitoring-detection of the parasite in blood-feeding arthropods. Our study aimed to evaluate PCR xenomonitoring of mosquitoes as a tool for dirofilariosis surveillance in Poland. We were also interested whether inter-study comparisons at the international level would be possible. Mosquitoes were collected in a single locality in Mazowsze province in Poland, in which between 12 and 20 % of dogs were infected with D. repens and autochthonous human dirofilariosis was confirmed. All captured female mosquitoes were divided into pools; alternatively, single mosquitoes were analyzed; DNA was isolated and subjected to PCR and real-time PCR for detection of D. repens. The estimations of infection rates of mosquitoes with D. repens, based on PCR results, varied from 0 to 1.57 % even between assays for detection of distinct fragments of the same marker-cytochrome oxidase subunit one gene. Polymorphisms of the DNA sequence within binding sites of the primers used in D. repens xenomonitoring assays, applied in European studies, were identified. Non-specific amplification of Setaria tundra (Nematoda: Onchocercidae) DNA occurred. Surveillance of dirofilariosis by PCR mosquito xenomonitoring is possible; however, the efficiency of the approach on territories where the prevalence of the disease among definitive hosts is lower than 12 % remains unknown. Furthermore, mosquito infection rate estimations can be PCR assay dependent, which makes inter-study comparisons difficult. The results obtained in independent European xenomonitoring studies were contradictory. International collaboration would be required to establish a standardized set of assays for sensitive and specific xenomonitoring-based dirofilariosis surveillance.