Dirofilaria immitis is a widespread mosquito-borne parasite that causes
dirofilariasis, a commonly diagnosed disease of dogs that is rarely
reported in cats and humans. A mosquito survey was conducted in Itacoatiara
in the State of Rio de Janeiro, from March 1995 to February 1996, using
canine, feline and human baits. A total of 3,667 mosquitoes were dissected
for D. immitis larvae, representing 19 species and 10 genera. From
those, Ae. scapularis, Ae taeniorhynchus, Cx.
quinquefasciatus, Cx. declarator, Cx. saltanensis and
Wy. bourrouli were found infected with D. immitis parasites, and
among those, only the first three harbored infective larvae. The majority
of larvae were found in the Malpighian tubules (889/936), and larval
melanization was observed in the two Aedes species. In descending
order, the best vectors were Ae. scapularis, Ae.
taeniorhynchus, and Cx. quinquefasciatus which alternate
seasonally in importance. Cx. quinquefasciatus is suggested to be a
vector to cats. The potential transmission of D. immitis parasites
by these three vectors to man is discussed.