The Filarial Genome Network The Filarial Genome NetworkDirofilaria immitis, the dog heart worm, causes a common zoonotic filarial infection. It is endemic to tropical, subtropical, and warm temperate regions of the world (including the south western United States).
Adult worms reside in the right ventricle and pulmonary artery of the dog while the unsheathed microfilariae circulate in the blood. Once ingested by the appropriate mosquito vector the microfilariae undergo development into infective larvae which can be transmitted to both dogs and humans. Development of the larvae into adult worms takes about 180 days in dogs. The worms never reach full maturity in humans.
Most humans infected with D. immitis are asymptomatic. Coin sized lesions can be found in the lungs during radiological examinations. These nodules result from an immune response to the dead or dying worms which are either necrotic or in the processes of being calcified.