The susceptibility of the mosquitoes Aedes notoscriptus and Culex annulirostris to infection with dog heartworm Dirofilaria immitis and their vector efficiency.

The mosquitoes Aedes notoscriptus (Skuse) and Culex annulirostris Skuse were fed on a dog infected with Dirofilaria immitis (Leidy) and a blood parasite count of approximately 5000 microfilaria per ml. Cx annulirostris ingested almost 4 times as much blood and almost 4 times as many microfilariae as Ae.notoscriptus (mean 26.0 compared to 6.6). Attrition of the filarial numbers occurred primarily within the midgut during the first 24 h following ingestion and was greater in Cx annulirostris than Ae.notoscriptus. Aedes notoscriptus sustained development of almost 8 times as many third-stage infective larvae as Cx annulirostris (mean of 3.8 compared to 0.5), and thus had a vector efficiency index of 57.6 compared to 1.9 for Cx annulirostris. In a series of investigations Ae.notoscriptus has now been shown to be an important vector for dog heartworm in southern Australia and may be a significant factor in the apparent burgeoning of the disease.