ABSTRACT
This chapter outlines the various pathological aspects of dirofilariasis. Some heartworm infections can be very mild and not develop to the status of a case of heartworm disease in which obvious clinical signs of the underlying pathology exist. The chief cause of the signs associated with heartworm disease is the development of severe arteritis of the pulmonary arteries leading to increased vascular resistance. In general, the disease process is such that most forms of pulmonary arterial pathology occur associated with inflammation and fibrosis of the intima and the arterial wall and with the perivascular areas as well. The beneficial effects of antiinflammatory and antithrombotic therapy should be assessed in an attempt to reduce the effects of inflammation on the pulmonary arteries and surrounding parenchyma and also of the effects of thromboembolism so as to reduce the extent of resultant obstructive arterial disease leading to secondary fibrosis.
