ABSTRACT
Heart worm is a major potentially life-threatening disease of dogs in Thailand, spread through mosquito biting. Because of Thailand is located in tropical zone, mosquitoes proliferate easily. All dogs living in a heavily populated mosquito area are at risk. It is possible that most dogs in endemic foci could be at risk for heartworm new infection and reinfection every year. Dogs may not show signs of illness until the disease is severe. Through surveys, the high prevalence of Dirofilaria immitis infection has been shown be evident in the stray and pet dogs. Humans are accidental and deadend hosts of dirofilariae because adults worms do not reach maturity in the heart. Most infective larvae injected into humans are thought to perish; therefore, infected individuals usually are not microfilaremic. Human disease is amicrofilaremic; although, because human disease is an accidental event, only one degenerate immature larva or young adult worm usually is isolated from an ectopic position of the body. Human infection presents with either subcutaneous nodules or lung parenchymal disease that may be asymptomatic. The significance of infection in humans is that pulmonary lesions and some subcutaneous lesions are commonly labeled malignant tumors, requiring invasive investigation and surgery before a correct diagnosis is made. The interruption of the transmission cycle and the reduction of mosquitos’ population play an important role in the controlling of dirofilariasis. More over, a final line of defense for this disease is the prevention of mosquito bites in both human beings and animals.