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→Pathogenesis
Sequelae to heartworm infection include pulmonary thromboembolism, which can either occur due to the death and metastasis of adult worms, or due to platelet aggregation induced by the parasite. In severe cases, live nematodes can migrate to the right ventricle, right atrium and caudal vena cava. The resulting incompetence of the tricuspid valve, augmented by concurrent pulmonary hypertension, leasds to signs of right-sided heart failure. Flow of erythrocytes through the mass of parasites formed can also cause haemolysis and thus haemoglobinaemia. This combination of acute right-sided heart failure and intravascular haemolysis is referred to as "caval syndrome", which in severe cases can also be characterised by thromboembolic events and disseminated intravascular coagulation. Due to the smaller numbers of adult worms, caval syndrome is less common in cats<sup>fara</sup>.
Sequelae to heartworm infection include pulmonary thromboembolism, which can either occur due to the death and metastasis of adult worms, or due to platelet aggregation induced by the parasite. In severe cases, live nematodes can migrate to the right ventricle, right atrium and caudal vena cava. The resulting incompetence of the tricuspid valve, augmented by concurrent pulmonary hypertension, leasds to signs of right-sided heart failure. Flow of erythrocytes through the mass of parasites formed can also cause haemolysis and thus haemoglobinaemia. This combination of acute right-sided heart failure and intravascular haemolysis is referred to as "caval syndrome", which in severe cases can also be characterised by thromboembolic events and disseminated intravascular coagulation. Due to the smaller numbers of adult worms, caval syndrome is less common in cats<sup>fara</sup>.
In cats, hertwoms disease generally induces a diffuse plumonary infiltrate and signs of eosinophilis pneumonia. The death od adult worms may cause acute pulmonary embolism with severe haemorrhage and oedema of the affected lobe. Occasionally, immature nematodes cna migrate to sites other than the heart and plumonary areties, causing ectopic infection. Localisation of D. immitis has been repored in the eye, CNS, systemic arteries and subcutaneous tissues. Ectopic infections are more commonly seen in cats than in dogs, suggesting that the parasite is not well adapted to feline hosts.
In cats, heartworm disease generally causes a diffuse plumonary infiltrate and an eosinophilic pneumonia<sup>fara</sup>. Adult worms may die and embolise to the lungs, resulting in severe haemorrhage and oedema of the affected lobe. Immature nematodes have also been known to migrate to sites other than the pulmonary arteries and heart, such as the CNS, eye and subcutaneous tissues. These ectopic infections are far more common in cats than in dogs, suggesting that ''D. immitis'' is not well adapted to feline hosts.
==Signalment==
==Signalment==