Laboratory transmission of dog heartworm (Dirofilaria immitis) by three species of mosquitoes (diptera: culicidae) from eastern Maryland, USA

Three species of mosquitoes from eastern Maryland, USA, were tested for their ability to transmit Dirofilaria immitis (Leidy) from heartworm-positive dogs to recipient dogs with no prior exposure. Two recipient dogs and 1 uninfected control dog were allotted to each test species. Experimental mosquitoes were initially infected through feeding on a microfilaremic donor. Infection levels and larval development were observed by dissection. After a 3-wk incubation period, the mosquitoes were allowed to feed on recipient dogs. Both recipient and control dogs were tested for microfilariae during the months after exposure. Following a 6- to 10-month period, dogs were euthanized and examined for adult worms. Patent infections were produced in 4 dogs exposed to the bites of Aedes sollicitans or Aedes triseriatus, with average infection levels of 12.5 and 5.8 worms per dog, respectively. Patent infection was produced in 1 of the dogs exposed to the bites of Anopheles punctipennis. All controls were negative. All 3 test species were found to be capable of transmitting D. immitis to dogs. Under laboratory conditions, Ae. sollicitans and Ae. triseriatus were more successful at transmission than An. punctipennis.