Heartworms are not transmitted directly from one cat to another nor from a dog directly to a cat. Clinical Signs One of the difficult things about diagnosing heartworms is that there are no consistent clinical signs. The most common signs are coughing and rapid breathing. However, both can be caused by several other diseases. Other common clinical signs include weight loss and vomiting , also common in other diseases.
Some cats seem to be normal, then die suddenly.
This happens due to a reaction within the lungs to the young heartworms or when dead or live heartworms enter the pulmonary arteries and obstruct the flow of blood to the lungs. There are two relatively new tests that are proving to be very helpful in diagnosing heartworms. The heartworm antibody test determines that the cat s immune system has been exposed to heartworms. A positive test may indicate that an active infection is present. Cats with late stage larvae that are not yet adults and cats with adult heartworms in places other than the heart may also test positive with the antibody test.