Susceptibility of mosquitoes in central Taiwan to natural infections of Dirofilaria immitis.

ABSTRACT

From October 1997 to September 1998, 3085 Culex quinquefasciatus (Say) (Diptera Culicidae), 584 Cx. tritaeniorhynchus (Giles) (Diptera Culicidae), 392 Cx. annulus (Theobald) (Diptera Culicidae), 374 Aedes albopictus (Skuse) (Diptera Culicidae) and 102 Armigeres subalbatus (Coquillet) (Diptera Culicidae) were collected and examined for Dirofilaria immitis (Leidy) (Spirurida Filariidae) infection. However, only Cx. quinquefasciatus and Ae. albopictus were infected, with a prevalence of 4.28% and 3.74%, respectively. The intensity of D. immitis found in Ae. albopictus (3.43 larvae/mosquito) was higher than that found in Cx. quinquefasciatus (2.89 larvae/mosquito). After being fed with canine blood containing 7500 microfilariae (mf) per mL, Cx. quinquefasciatus ingested approximately two times as many mf as Ae. albopictus (mean of 31.73 in comparison to 16.47). However, almost three times as many third-stage infective larvae developed in Ae. albopictus as in Cx. quinquefasciatus (mean of 3.25 as compared with 1.10), with a vector efficiency index (VEI) of 19.73 and 3.47, respectively. The results showed that Cx. quinquefasciatus and Ae. albopictus served as natural vectors of D. immitis in central Taiwan. Although Ae. albopictus was more efficient for heartworm transmission, Cx. quinquefasciatus may play a more prominent role on the transmission of dirofilariasis in central Taiwan.