FELINE HEARTWORM DISEASE
Having just finished re-reading an article in Feline Practice, on this subject, which is a veterinary medical journal. I find myself compelled to write an overview in simple english.Not much has been said on this subject by veterinarians in my area. I always try to stay in the forefront on feline health issues. I get the feeling from the veterinarians that I have talked to on this subject that it is more of a wait and see type of protocol. You know it wasn't that long ago that we were sure that cats didn't get heartworm. It was strictly a dog disease.I had quite a few questions that I was hoping to get answers on and I did. As in any good article it also raised some points that I hadn't even considered.
Before we begin let me BRIEFLY explain Feline Heartworm Disease. It is basically has the same method of transmission and life cycle as dog heartworm. A cat must be bitten by an infected mosquito. Mosquitos are the only intermediate host. From here the parasite migrates to the heart via the blood stream. Obviously a worm boring holes and living in the heart muscle is a "bad thing", but if/when the worm(s) dies they can form a "plug" if they get stuck somewhere, this can be fatal. So, you don't want the worm in the heart but you don't want to kill it unless you can dissolve it either. Of course there is the problem of toxicity to the treatment. Surgery is the treatment of choice in cats. This can of course be fatal depending on the damaged rendered to the heart muscle by the worm(s).
Now on to what I learned and hope to pass on…… Cats have very few microfilaria (babies) in their bloodstream (usually not more than 10/ml) and They only are there for a few weeks. This means that they are very easy to miss when looking for them under a microscope. Which is one way they are looked for in dogs frequently (Knotts test). Thus different test methods should be used in cats. These tests are: a)Antigen b) Antibody c) ultrasound.
(a) Antigen test results actually depend on the sex and age of the worm!!The antigen is produced by female adult worms. Unfortunately it is not uncommon for cats to have only a single sex (male) worm infection.
(b) A positive antibody test can simply mean the cat was exposed to heartworm, not that they necessarily have it.
(c) Ultrasound had the most acurrate results of the three. But it was stated it depends on the view and that the whole heart must be viewed. or the worms can be missed.
A point I found interesting, the prevalence of this disease is much higher in dogs. It seems mosquitos like dog blood better (2-4 times). In tests (YUK) and geographical studies researchers seem to think that cats get infected 20% of the time .This could be due to which species of mosquito is prevalent in an area. That could help explain why certain states/countries are more at risk than others. It is also speculated that some cats may become immune to infection if their immune system has conquered a past challenge.
Two points were stated that frightened me. 1) That is indoor cats have died from this disease. All it takes is a nap on the balcony or an open window. 2) The tables can turn if the cat population is greater that the dog population,
(in an at risk area).
An example that was given:
Adoption agencies who are forced to place dogs in "the cat ward" due to overcrowding.
If an infected mosquito got in such a place or the dog or one of the cats was already infected….
I am in NO WAY BAD MOUHTING SHELTERS!!! I am simply stating a situation that is a possibility. One which I hadn't even considered until I read it in this article.
PLEASE DO NOT let this article sway you from adopting a pet from any type of rescue. If you live in an at risk area simply have the animal tested and discuss prevention with the vet.
So the question remains…….. Is Feline Heartworm Disease becoming more of a threat or are the numbers rising because we are looking for it with better tests???
ANSWER:
I DON'T KNOW! But what I recommend to you is, go see a Board Certified Feline Practitioner in your area when your kitty needs his/her vaccinations and ask a few questions as to what he/she has seen. Ask if they recommend a preventative???
©1999 Hui Lani
