Histolytica in cats.

Dr. Marie replied:

Hi and thanks for an interesting question. Histolytica is not something that is common in my area. In fact, I can't recall ever dealing with it.

As far as I can remember, when cats are treated for histolytica, the reason for treatment is mostly to reduce the symptoms. If Timmy doesn't have any symptoms then treatment probably would not do much.

However, I would like to do some more research for you. My main resource for finding case reports and the latest information on what other vets think about conditions like this appears to be down right now. I will probably have access after the weekend though.

At this point my answer would be to trust your vet's advice. However, give me a couple of days and I will give you a more in depth answer.

Thanks very much,
Dr. Marie

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Dr. Marie replied:

Thank you so much for your patience and waiting for my response. I now have more information for you.

Histolytica (also known as Amebiasis) is quite rare. Your cat would have ingested a cyst from contaminated food or water and now the parasite is most likely living in another form called a trophozoite in the large intestine. In some animals this can cause serious diarrhea. But, in many animals there are no symptoms.

People can definitely get histolytica. However, they can't get it from cats or dogs. Cats and dogs only pass the trophozoite life form and not the cysts. A human has to ingest the cysts in order to get infected.

I did some more research to find out what the general consensus is amongst vets as to whether or not a cat with histolytica should be treated. My research is primarily on Veterinary Information Network where almost 50,000 vets collaborate and discuss their cases. What I found is that it is extremely rare for cats to be diagnosed with histolytica! Now I don't feel so bad for not knowing more about the condition. :)

The main problem here is that no one really knows whether metronidazole (or any other medication for that matter) is really effective against Amebiasis. It might be...but it might not. And giving metronidazole to a cat is not always easy. It tends to be a very untasty pill even when compounded or made into a liquid. It's not something that cats take well.

If this were my case I would be advising you to keep an eye on Timmy. If he developed watery diarrhea then I likely would go ahead and treat with metronidazole. But otherwise, I probably would not.


I hope this has helped. Please let me know if you have further questions.

Dr. Marie.