Filarial parasite infection prevalence in field-caught mosquitoes from Connecticut, United States

Filarial nematodes are parasitic roundworms transmitted by mosquitoes that can cause morbidity and mortality for their human and animal hosts. The filariae community, specifically infection prevalence of heartworm, Dirofilaria immitis (Filarioidea: Onchocercidae) (Leidy), and its primary mosquito vector species, has not been described in Connecticut since 1977. In light of the recent invasion and establishment of an important filariasis vector, Aedes albopictus (Diptera: Culicidae) (Skuse), we used molecular-based sequencing methods to identify filarial species infecting field-caught mosquitoes in Connecticut, United States. The filarial parasites identified include D. immitis, Aproctella sp., and Setaria sp. (Filarioidea: Setariidae). The total minimum infection rate for D. immitis for all mosquito species tested in 2020 was 0.97 [0.56 to 1.56] and in 2021 was 1.48 [0.93 to 2.24]. Aedes albopictus had the highest infection prevalence compared to other species during both years. We determined a low but persistent mosquito infection prevalence for D. immitis and suggest that Ae. albopictus is likely to be the primary vector in the region. Aproctella sp. and Setaria sp. had lower burdens compared to D. immitis. Persistent mosquito infection with filarial parasites, particularly in invasive species, poses a risk to veterinary and public health.