Then begin entering right side of heart and take several hundred days to mature. Up to 60 worms - circulatory difficulty. 100 or more worms - Blockage of pulmonary artery and right side of heart. Interference with the heart valves. Right side of the heart becomes dilated and enlarged.
Blood backs up in the liver and other parts of the body.
General congestion and degeneration. Dogs fatigue easily, cough, and appear unthrifty. Diagnosis is by finding of microfilariae in the blood.