Natural transmission of Dirofilaria immitis by Aedes vexans.

Aedes vexans mosquitoes were reared in the laboratory from field-collected fourth instar larvae. Mosquitoes were allowed to feed on dogs which were infected with Dirofilaria immitis and then the mosquitoes were housed in an environmental chamber with an ambient air temperature of approximately 26 C and a relative humidity of approximately 80%. Incandescent lighting was used to simulate daylight. On the 17th, 19th, 21st, and 28th day after their infected blood meal, the mosquitoes were allowed to feed on five microfilaria-negative dogs which had been reared in mosquito-free environments. Blood from four of the five exposed dogs became positive for microfilariae of D immitis in an average of 272 days after the feeding. The local strain of A vexans was established as a vector of canine heartworm disease in the Minneapolis-St. Paul metropolitan area.