Heartworm Testing for Cats

The Feline Heartworm Antibody Test

The feline heartworm antibody test tells us if a cat has any heartworms present in the body. These heartworms can be present anywhere in the body not just in the lungs or heart. This is because the heartworm is a parasite of the dog and the cat is considered an aberrant host. When a heartworm is in the cat it may be anywhere including the abdomen, the brain, the lungs or the heart. This is because a heartworm in a cat is “lost” and is using a map of the dog to find its way. So the feline heartworm antibody test is just a screening test to see if infected mosquitoes have bitten the cat.

What do you do when the Antibody Test is Positive?

Cats that test positive for heartworm antibodies have been exposed to heartworms. A positive test does not necessarily mean that the cat has heartworm disease. Heartworm disease is present when the heartworm larvae have migrated to the heart and lungs and developed into adult heartworms. Once an antibody test is found positive a cat should be tested with an ELISA test.

Why do we learn from an ELISA test?

The feline heartworm ELISA antigen test determines if adult female heartworms are present in the cat’s heart. If the ELSIA test is positive adult females are present in the cat’s heart. If the antibody test is positive and the ELISA test is negative there could be young females or adult male heartworms in the lungs or heart. (A negative antibody and a negative ELISA test confirm that that has been no heartworm infection.)

My pet is positive for the Antibody test but Negative for the ELISA test why are we doing radiographs?

If the antibody test is positive and the ELISA test is negative there could be young females or adult male heartworms in the lungs or heart. A radiograph of the chest will determine if the lungs or the major blood vessels of the lungs are infected by heartworms.

Can you see my cat’s heartworms on Ultrasound?

Heartworms show up very well on ultrasound. Their bodies look like an “equals sign” or a donut moving with the blood flow. A cat is relatively small compared to a 12 inch heartworm and ultrasound is often a very accurate way to see the heartworms. Ultrasound is the way we determine if heartworm surgery is the best way to treat cats for heartworm infection.