Culex tritaeniorhynchus and Aedes albopictus (Diptera: Culicidae) as natural vectors of Dirofilaria immitis (Spirurida: Filariidae) in Miki City, Japan.

Natural infections with Dirofilaria immitis (Leidy) in a population of mosquitoes and dogs and its antibodies in a human population were surveyed in Miki City, a rural area of Japan, to reveal ecological features of this arthropod-borne zoönotic parasite. Microfilaremic and amicrofilaremic infection rates in 190 dogs were 52.6 and 9.0%, respectively, as determined by the hematocrit centrifuge method and the indirect fluorescent antibody test. An enzyme-linked immunosorbent assay (ELISA) test for antibodies to D. immitis showed that almost all of 917 inhabitants had antibodies in varying degrees, indicating frequent exposure of this parasite to the human population. Among the six species of wild mosquitoes sampled from 1985 through 1987 by attraction with dry ice, Culex tritaeniorhynchus Giles was the most abundant in two sites and Aedes albopictus (Skuse) in another two sites. Filarial infections were found every year in Cx. tritaeniorhynchus and Ae. albopictus collected between July and September, as examined by ELISA for detecting larval antigens in mosquito homogenate, suggesting that these species are important natural vectors in this survey area.