We only recommend testing when we think the cat has heartworm. Routine testing is typically not done, probably because there's no treatment for it once the cat has adult heartworms. They don't have microfilaria, which is the baby warm circulating in the blood, so all heartworm preventatives are safe for them. We recommend prevention in cats. In a symptomatic cat, a sick cat, and we suspect heartworms, then we’re probably going to get an x-ray, we screen for antibodies. And do the ELISA antigen test as well.

Typically, if we suspect a cat has heartworm, we will recommend a test just like in a dog. Most of the time, it comes out negative because, once again, that test tests for adult heartworms, which it's not usually adult heartworm that causes a problem in a cat. There aren't tests out there for immature stages. We sometimes test for antibodies. However, though they can develop antibodies a couple of months after infection, they are very transient. They go away really quickly, so we have a short window to catch them. That only means exposure and not necessarily that the cat is continuing to be infected as well. We will often look at x-rays, and we can see changes in the lungs that are highly suspicious of heartworm.

Heartworm tends to cause asthma-like symptoms, so the cat can't breathe. They're not perfusing, so they're very panicked. Some of their tissues may be a little painful because they're not perfusing, the pins and needles, perhaps, but I’m not sure.

Weight loss, open mouth breathing, coughing and labored breathing, and often vomiting. Cats tend to vomit with many different diseases. Cats develop symptoms much earlier than dogs because the immature stages arrive in the lungs earlier than in dogs. Dog symptoms are more geared towards adult worms being present. It's the immature stages, the earlier stages, that cause problems in a cat. Sometimes a few worms will make it to adulthood, and that's not a good scenario when that happens.

Cats that roam and are outside more are a little more at risk of becoming infected with heartworm. It's much less than the risk of a dog. Even so, because heartworm disease is invariably fatal for a cat if it reaches maturity, prevention is paramount.

The heartworm cycle in a cat is when a mosquito bites the cat and injects a baby worm into the cat’s skin. These worms then migrate through the skin into the bloodstream, and they arrive at the lungs, and that's when all the damage is done. Months later, when the worms start arriving at the lungs, the cat develops an intense inflammatory reaction to destroy these worms before they continue to mature. The cat has these asthma-like symptoms—coughing, open mouth breathing, vomiting, and labored breathing in general.