- For both dogs and cats, clinical signs of heartworm disease may not be recognized in the early stages, as heartworms tend to accumulate gradually over a period of months and sometimes years and after repeated mosquito bites.
- In dogs, recently infected animals may exhibit no signs of the disease, while heavily infected animals may eventually show clinical signs, including mild, persistent cough, reluctance to move or exercise, tiredness after only moderate exercise, reduced appetite, and weight loss.
- Very active or working dogs can show the above clinical signs of disease with only a few worms present.
- In dogs, severe cases of the disease may lead to heart and lung failure, most often recognized by a “swollen belly” caused by accumulation of fluid in the abdomen.
- “Caval Syndrome,” a form of liver failure, is also a potential serious complication, causing dogs to become weak very rapidlyand turning their urine dark brown. This is a life-threatening situation that prompts surgical removal of the worms.
- Cats may exhibit clinical signs that are very non-specific, mimicking many other feline diseases. Chronic clinical signs include vomiting, gagging, difficulty breathing or rapid breathing, lethargy and weight loss.
- Infected cats may die acutely without allowing time for diagnosis or proper treatment.