Heartworm preventives for cats are given monthly. If your adult cat has never been on a preventive, it is generally recommended that you have him tested with an antibody and/or antigen prior to administering a heartworm preventive. However, test results can sometimes yield false positives and negatives, so it is always best to consult your veterinarian.

As often warned by vets, diagnosing and treating cats for heartworm infection can be extremely difficult, so prevention is always the key. Young kittens can usually be started on preventives without prior blood tests. Approved monthly heartworm preventatives for cats are:

1. Ivermectin (Heartgard) Given orally. Kittens can be started at 6 weeks of age. Also treats and controls two types of intestinal hookworms.

2. Milbimycine oxime (Interceptor) Given orally. Kittens can be started at 6 weeks if they weigh a minimum of 1.5 lbs. Also treats one type of hookworm.

3. Selemectin (Revolution) Applied topically on the skin. Kittens can be started at 6 weeks of age. Also controls fleas and ear mites; and treats and controls of one type of hookworm and one type of roundworm.

Select the type that is most suited to your cat´s lifestyle. Strictly indoor cats are not likely to be exposed to infection with intestinal parasites such as hookworms and roundworms, though.

If fleas are a problem, select a heartworm product with flea control, or use a flea control product in conjunction.

Flea or heartworm preventives cannot control tapeworms, which are carried by fleas. When your cat happened to ingest fleas, they can become infected and you might see small, rice–looking worms on their feces. Tapeworm infections can cause weight loss and mucous covered or loose stools.

Sharon E. Anderson, DVM

Sharon E. Anderson, DVM, answers medically-related questions, but will not attempt to diagnose or recommend specific treatments. Her advice is not meant to replace professional care. If your pet is ill, contact your veterinarian immediately.