ABSTRACT
Dirofilaria immitis, as the agent of canine cardiovascular dirofilariasis, is a parasite of paramount veterinary importance. It is increasingly recognized as the cause of zoonotic infections, most frequently as the agent of human pulmonary dirofilariasis. Dirofdaria (Dirofilaria) immitis is the longest of the Dirofilaria spp. of medical and veterinary importance. Human pulmonary infections with Dirofilaria immitis and subcutaneous infections with D. tenuis, D. repens, and D. ursi are being reported with increasing frequency. Identification of Dirofilaria spp. in cross section is done primarily on the basis of structure and arrangement of the longitudinal cuticular ridges. Histochemical techniques have been used to study the distribution of acid phosphatase activity in microfilariae of D. immitis. The first, second, and early third larval stages of D. immitis are obligate parasites of mosquitoes. In addition to supporting early larval development, mosquitoes serve as vectors actively moving infective stages to susceptible vertebrates and, to the extent that their flight range allows, disseminating the parasite geographically.
