First molecular detection of Dirofilaria immitis (Spirurida: Onchocercidae) infection in Aedes albopictus (Diptera: Nematocera) from Brazil

Dirofilaria immitis is a filarioid worm transmitted by culicids, with relevance to human and veterinary health. The expansion of canine dirofilariasis in regions previously considered non-endemic in Brazil highlights the need for entomological studies. This study investigated the occurrence of natural infection by D. immitis in mosquito populations in the municipalities of Magé and Duque de Caxias, state of Rio de Janeiro, Brazil. Mosquitoes were collected between August 2022 and December 2023, using CDC dry ice traps. Individuals were morphologically identified and grouped into pools for molecular genetic analyses by polymerase chain reaction, followed by DNA sequencing. A total of 427 specimens were captured, with a predominance of Culex spp., in addition to Aedes scapularis , Ae. taeniorhynchus , and Ae. albopictus . A pool of eight Ae. albopictus specimens was positive for D. immitis , representing the first documented record of natural infection by this species in Brazil. Phylogenetic analysis confirmed the molecular identity of the mosquitoes and their relationship to known strains of the parasite. The widespread distribution, opportunistic hematophagous behavior, and proximity of Ae. albopictus to human populations and domestic animals reinforce its epidemiological potential. These findings highlight the need for integrated and continuous surveillance, as well as studies on vector competence, especially in regions with favorable ecological factors. This work contributes to understanding the complexity of dirofilariasis transmission from a One Health perspective.