Treatment of dogs with severe heartworm disease.

Fortunately, the majority of dogs diagnosed with heartworm infection are asymptomatic (or have only mild symptoms such as intermittent cough) and go through adulticide therapy without complication. Complications occurring with heartworm infection and during its treatment most often directly reflect the pulmonary vascular and parenchymal injury inflicted by Dirofilaria immitis. Clinical signs may include exercise intolerance, frequent cough, hemoptysis, tachypnea, and dyspnea. Severe manifestations such as heart failure and caval syndrome may prove fatal. Acute hypersensitivity reactions after initiation of macrocyclic lactone preventive therapy in microfilaremic dogs or after melarsomine injection during adulticide therapy do occur, but are uncommon. This article reviews complications associated with heartworm infection.