Feline Heartworm Needed

I had a bloodwork wellness panel recently done on my beautiful 6 yr. old boy, Voodoo. Everything came back fine except he tested positive for the heartworm antibody.

We have a terrible mosquito season brewing here on the East Coast, so I'm not so much surprised as I am worried. I have switched to Revolution for better broad spectrum protection against insects and parasites for all three of my kitties. Fortunately, Voodoo is not exhibiting any trademark respiratory symptoms. I've done some reading at this point and there seems to be some conflicting information about feline heartworm.

Specifically, I've read that a cat's immune system, unlike a dog's, can produce the antigen naturally as a defense in the pre-larvae stages to combat the disease. As such, heartworm disease is typically found in cats with weakened or compromised immune systems. Presence of the antigen is evidence that the cat has been bitten by an infected mosquito and has produced the antigen to fight the infection.

I know I'm not out of the woods on this one, but would be interested in what other members know and/or have experienced.

Wait... your vet suggests that you treat your infected cat with Revolution when it could possibly kill the heartworm (or two) that he has?!

I'm using Revolution instead of Frontline Plus.

It was not recommended as a course of treatment for heartworms; we are fortunately not at that stage yet.

It's generally recommended that you do not treat or do anything to kill any living heartworms in a cat. They cannot be treated as dogs are, and since there's usually 1-3 and of the same gender, they're self limiting. To kill the worms could kill the cat. Instead you treat any symptoms that pop up and wait for the heartworms to die off on their own in 2 to 3 years. The reason letting them die on their own is better is because one worm dying is less risky than two or three dying at once.

Please have it re-tested. There is some test they can do that is specifically for the heartworm. I wish I could remember what it was. Cindy tested positive once too, and it freaked me out, but once they did the other test they said she was fine.

I have my cats on Interceptor as a heartworm preventative and use Frontline Plus for fleas and ticks. Is this safe? I'm a little concerned by the discussion of killing off the heartworm may harm the cat. This isn't relevant to preventative care right?

If there's not already adult heartworms it's fine. If you've kept up on the preventative, your cats shouldn't have any to begin with.

Misty - you probably mean the antigen test? This will only tell if there's an adult female worm.
The heart can be also be checked to see if there's any enlargement.


I really suggest you all sit down and discuss this at length with your vets and just how risky even a dead worm is to a cat. If you feel they're glossing over any details, have a chat with another vet.

ETA: ..I was looking to see if revolution had any deals/discounts and following links came upon this - there's very good information about heartworms in cats here. This is a vet intended publication, thus there are technical and medical terms used, but they should be easily understandable to any reading. First parts consists of information on heartworms and on infections in cats and testing and eventually moves on to discuss treatments. You can use the menu at the top to navigate over to the pet owner resources if you need a more simplified version.