Feline Heartworm Disease

If you know me, you know I wouldn't leave out cats. Well, only if it was something that truly didn't affect them.  Heartworms do, in fact, infect and AFFECT our kitties.


Here's a reminder of what happens in cats:

Cats are very different than dogs (you hear me say that a lot because cats are NOT small dogs!).  Here are some reasons:

1. The heartworm cannot complete it's life-cycle in the cat. Truly a heartworm doesn't want to be IN the cat - they'd much prefer a dog as a host.  

2. Many cats have a single to a few worms period. Dogs have MANY more (think of the heart photo from yesterday).

3. This means that our most common test - an antigen test (the in house Snap tests) - won't work reliably for our cats. Why? This test is based on an antigen produced by the uterus (yes you read that correctly) of the female heartworm. Guess what? Many cats have been found to have a single male worm or so few females that there's not enough there to get a positive.  There are tests we can send OUT to the lab that MAY help  - those detect antibodies from the cat's immune system in response to the worms.

4. Indoor cats are at risk as much as the outdoor cat. Mosquitoes do enter our homes and cats are often a nice warm relaxed blood meal for the mosquito.

5. Cats rarely have the microfilariae (baby, immature heartworms) circulating. Even if they do they seem to last a brief time. This means we can't expect to see them on a blood smear (like we often can in a dog!).

6. There is no current treatment for this in cats. 

7. In dogs the worms can live 5-7 years. In cats, on average, it's about 2 yrs.

8.  The small number of worms may seem insignificant but in the relatively small heart and vasculature of a cat, they can cause significant inflammation and tissue damage.

9. The only sign can be death. Yep. If you want to call that a sign. Often in a classic case of dog heartworm, they will cough. In cats, however, it can be  more subtle. In some cases the only sign is vomiting (which would lead us on a very large path and probably to things OTHER than HW first!)

10. Many cases of feline asthma we now think are H.A.R.D. = heartworm associated respiratory disease. It can be HARD to tell the difference between true asthma and this.

11. Guess what? Either way the goal is to reduce inflammation and in the case of HW, prevent re-infection while those worms die. So that means we put them on a steroid and a heartworm preventative. There are several approved products for cats.