Two summers ago, we had quite a scare: Allie developed a croupy, dry cough and
when examined, our veterinarian advised us to get her tested for heartworms. It was the first we'd ever heard that a cat might be susceptible to this parasite.
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| Allie gave us quote a scare a few years ago! |
Not only that, but we were informed that their practice treated more cats with heartworms in 2011-2012 than they did dogs.
Each summer since, we've felt this to be a critical message to pass along - especially here in the midwest.
And if my experience outside yesterday evening was any indication, we're in for another mosquito-infested summer in our neck of the woods.
So we decided to ask Dr. Sara Huber of Leawood Plaza Animal Hospital to help us understand the symptoms, risks and preventive care for heartworms in cats.
Heartworm in Cats, Part 1
A Tonk's Tale: Hasn't heartworm traditionally been a dog disease?
Dr. Sara Huber: Yes. But though we typically think of dogs as the host of heartworms, the life cycle also can be completed in cats. Infection rates are usually 10-20% that of dogs in endemic regions.
Several studies have shown that heartworm infection rate in cats is actually greater than that for FIV and FeLV!
ATT: That is one
scary statistic. We heard that it can take a while for heartworms to manifest in a cat...?
Dr. Huber: That's true. Here's how it works: an infected mosquito bites a cat and larvae migrate through the subcutaneous and vascular tissue.
Once they enter the bloodstream, the larvae are brought to the pulmonary arteries and into the lungs (3-4 months post infection). Only a small amount of heartworms mature to the adult stage. These are able to reproduce around 7-8 months post infection (1-2 months longer than in dogs).
The disease in cats is split into three stages. The first stage is associated with the arrival of the juvenile worms in the pulmonary arteries and they develop an acute inflammatory reaction. This stage is followed by a symptom free period where the host immune response is suppressed and the worms are maturing.
When the worms die, an intense inflammatory response develops with sudden death reported in 10-20% of cats (stage 2). If they survive this stage, they go onto stage 3 which is permanent lung injury and chronic respiratory disease.
ATT: This is something we did not know about - but it makes such sense, given that the parasite takes up residency in the cat - sometimes for years. Are there any signs we can watch for?
Dr. Huber: Sometimes yes, sometimes no. Owners may notice a variety of clinical signs including chronic cough, sudden difficulty breathing, vomiting, lethargy, etc. Vomiting and coughing are common clinical signs in heartworm infected cats and when seen together should be a red flag for the veterinarian.
Asthmatic-like signs are common 3-4 months after infection. But unfortunately, sometimes the only clinical sign the owners see is severe respiratory distress or sudden death. (I know this is scary to hear, but don't worry! Its preventable!!)
ATT: Is there a conclusive test that exists to diagnose this?
Dr. Huber: Confirming a diagnosis often requires a combination of tests. The testing is hard to explain in non-veterinary language. Tests for antigen and antibody, when used together, improves the probability of making a correct diagnosis. Simply put, talk to your veterinarian about which blood test(s) are best to confirm the disease if it is suspected.
Thoracic radiography and/or echocardiography are very useful in conjunction with blood tests, though radiographic changes consistent with heartworm disease are only seen in about half the cats suspected to have the disease.
Echocardiography can be very useful in determining the severity of damage from the disease but is very operator dependent and should be done by a specialist skilled in this trade.
We thank Dr. Huber for her time and insight into this scary but preventable disease!
Next week:
Treatment and Complications
for Heartworm in Cats
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Don't Forget!
Winners will be announced this Friday.
