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→Clinical Signs
===Clinical Signs===
===Clinical Signs===
In dogs, historical findings at the time of presentation can vary. Some animals are symptomatic, or cough only occasionally. In countries where heartworm is endemic, it is sometimes routine to test for dirofilariasis at the end of the high-risk season, when weather becomes cooler<sup>3</sup>. Therefore, positive laboratory testing may be the first indication of disease<sup>1</sup>.
The onset of disease due to ''Dirofilaria immitis'' is insidious, and clinical signs are related either to a high parasite burden, or to an allergic response to the parasite<sup>2</sup>. Signs often only manifest during exercise, and so patients with a sedentary lifestyle may never show overt disease. Affected dogs most often show coughing, and dyspnoea/tachypnoea, exercise intolerance, loss of condition and syncope may also be seen. In severe cases the pulmonary vessels may rupture, leading to haemoptysis. If right-sided congestive heart failure ensues, signs can incluse jugular disension, ascites, marked exercise intolerance and hepatomegaly, possibly with a systolic murmur audible on cardiac auscultation.
The onset of disease due to ''Dirofilaria immitis'' is insidious, and clinical signs are related either to a high parasite burden, or to an allergic response to the parasite<sup>2</sup>. Signs often only manifest during exercise, and so patients with a sedentary lifestyle may never show overt disease. Affected dogs most often show coughing, and dyspnoea/tachypnoea, exercise intolerance, loss of condition and syncope may also be seen. In severe cases the pulmonary vessels may rupture, leading to haemoptysis. If right-sided congestive heart failure ensues, signs can incluse jugular disension, ascites, marked exercise intolerance and hepatomegaly, possibly with a systolic murmur audible on cardiac auscultation.
exercise intolerance, unthriftiness, dyspnea, cyanosis, hemoptysis, syncope, epistaxis, and ascites (right-sided CHF) are likely to develop. The frequency and severity of clinical signs correlate to lung pathology and level of patient activity. Signs are often not observed in sedentary dogs, even though the worm burden may be relatively high. Infected dogs experiencing a dramatic increase in activity, such as during hunting seasons, may develop overt clinical signs. Canine HW disease can be classified by physical examination, thoracic radiographs, urinalysis, and PCV.
Caval syndrome represents a severe form of heartworm
Caval syndrome represents a severe form of heartworm