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Mycoplasma is an unusual organism infecting the red blood cells. For one thing, clindamycin and interferon are not effective against this organism so ask your veterinarian if you need to continue these medications. It's also very difficult to diagnose as the tests are not very accurate but does cause anemia, so it's consistent with your cat's other test results. Doxycycline is the most common treatment and is available from any pharmacy but only in tablet form, so it's often compounded into a liquid. This medication is given orally so either needs to be put in his mouth with a dropper or mixed in his food if he'll eat it. Otherwise, you may need to either bring him in to your veterinarian's office to administer the medications or have a pet sitter who can give the medication come to your house. Severely affected cats should also be put on Prednisolone and may require a blood transfusion. If your cat hasn't recently been tested for Feline Leukemia and Feline Immunodeficiency Virus (FIV), it should be done now as Mycoplasma is more common in cats that have these diseases.

Drew Weigner, DVM, ABVP
The Cat Doctor
Board Certified in Feline Practice

Hi Dr Weigner,

I'm a bit confused. May I ask you a question about Mycoplasma?

I've listened to vet talks about "Mycoplasma felis" which I thought was a respiratory form of mycoplasma. My own cat tested positive for it on an IDEXX URI panel, though my cat is not sick and my vet (and Dr Richard Ford of NC State, whom I asked about it) felt that it is likely just a part of my cat's natural flora. But I know that Dr Lappin at Colorado State feels that in some cats, Mycoplasma felis is a primary cause of upper respiratory disease.

Then, I've heard talks about Mycoplasma haemofelis (formerly called Haemobartonella felis) which is a parasite that attacks the red blood cells and can cause anemia.

I know that both are "mycoplasmas" ... which are unique in that they do not have a cell wall of their own. But are Mycoplasma felis and Mycoplasma haemofelis two different strains ... or are they the same thing that is found in different parts of the cat?

I thought that they were distinctly different (which may be a wrong assumption on my part). But it is interesting that in the post above, Piggy was initially taken to the vet's for upper respiratory disease ... and then found to be anemic with Mycoplasma haemofelis. So, is it the same mycoplasma that is causing both the anemia and also the upper respiratory infection? Or, did Piggy have the bad luck of being co-infected by two different types of mycoplasma (one attacking the blood cells and one in the respiratory tract). Or, is it possible that the URI is caused by something else?

I'm confused by the relationship of Mycoplasma felis to Mycoplasma haemofelis. Are they the same or different?

I've heard Dr Lappin also recommend Doxycyline for Mycoplasma ... whether Mycoplasma felis or Mycoplasma haemofelis. So, it does seem like the best treatment for either or both. Dr Lappin also recommends Doxycycline for a number of other bacterial causes of upper respiratory infection ... so, I think it would be good to use even if there are other co-infections involved. Do you agree, or am I misunderstanding something?

One other question. I've also read elsewhere (Veterinary Partner website) that Prednisone is used for severe Mycoplasma haemofelis to suppress the immune response. But what happens if one factor of the URI is Herpesvirus? I've also heard that steroids can cause Herpes to get much worse since it suppresses the immune system which is needed to control the Herpes. Given the seriousness of the Mycoplasma haemofelis, do you give the Pred and then deal with the Herpes if it gets worse (i.e. if Herpes is involved)? I know that veterinary medicine is an "art" and it can be tricky to balance multiple co-infections or diseases.

Thanks for helping me to learn.

Stephanie in Montreal