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.