Comparative Vector Efficiency of Two Prevalent Mosquito Species for Dog Heartworm in North Carolina

The dog heartworm, Dirofilaria immitis (Leidy) (Spirurida: Onchocercidae), is a devastating parasite of domestic and wild canines vectored by a multitude of mosquito species. Although many species are implicated as vectors, not all contribute equally to disease transmission, with demonstrated variation in vector efficiency between and within species. We investigated the vector efficiency of mosquitoes derived from wild-caught North Carolina populations of two known heartworm vectors: a native species, Aedes triseriatus (Say) (Diptera: Culicidae), and an invasive species, Aedes albopictus (Skuse). We compared the parasite developmental times within the mosquito, mosquito longevity and fecundity, and the vector efficiency index between the two species. We found that the tested composite North Carolina population of Ae. triseriatus was an efficient vector of D. immitis under laboratory conditions, whereas the local composite population of Ae. albopictus was a competent but relatively poor vector. Compared with Ae. triseriatus, Ae. albopictus showed a longer time for parasite development, lower infection rates, and lower vector efficiency. Additionally, Ae. albopictus was the sole species to exhibit significant parasite-induced mortality. These results are in contrast to prior studies of populations of Ae. albopictus from locations outside of North Carolina, which have implicated the species as a highly competent heartworm vector. The variation seen for different strains of the same species emphasizes the heritable nature of D. immitis vector competence and highlights the need for local infection studies for accurate transmission risk assessment in a particular locale.