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

From October 1997 to September 1998, 3085 Culex quinquefasciatus (Say) (Dip tera: Culicidae), 584 Cx. tritaeniarhynchus (Giles) (Diptera: Culicidae), 3 92 Cx. annulus (Theobald) (Diptera: Culicidae), 374 Aedes albopictus (Skuse ) (Diptera: Culicidae) and 102 Armigeres subalbatus (Coquillet) (Diptera: C ulicidae) were collected and examined for Dirofilaria immitis (Leidy) (Spir urida: Filariidae) infection. However, only Cx. quinquefasciatus and Ae. al bopictus 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 m t, Cx. quinquefasciatus ingested approximately two times as many mf as Ae. albopictus (mean of 31.73 in comparison to 16.47). However, almost three ti mes as many third-stage infective larvae developed in lie, albopictus as in Cx. quinquefasciatus (mean of 3.25 as compared with 1.10), with a vector e fficiency index (VEI) of 19.73 and 3.47, respectively. The results showed t hat 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.