Tritrichomonas blagburni (formerly T. foetus) is a frustrating cause of diarrhea in cats. This parasite causes chronic diarrhea that will most often ultimately resolve on its own, but it can take months (or longer). During that time, most cats are largely healthy but with very messy feces (and they’re infectious). Some cats do feel sick, and can have a range of problems such as abdominal pain, vomiting, weight loss and complications from having a constantly diarrhea-stained rear end, or from straining. So while many cats may seem fine, we’d rather treat them, both for the cat and to reduce transmission risks.

There are no licensed treatments for this disease, and no drugs that are licensed for use in cats for other diseases are effective. Traditionally, we’ve treated these cats with a drug called ronidazole, which was obtained from compounding pharmacies (a valid approach when there’s no approved product). However, there’s currently a global issue with access to the base drug, so it’s no longer accessible in most areas.

Tinidazole is plan B in these cases, but it’s not great for a few reasons. The drug has not been well studied and doesn’t seem to work as well as ronidazole. It probably helps infected cats, but is far from a preferred option. However, we are now also have problems accessing tinidazole (and I haven’t been able to find a source in Canada).

Are there any other options? I’ve wondered about using secnidazole, and would consider it. We know nothing about efficacy (or safety), which is a significant concern, but it could be an option in some countries where a human oral version is available… which does not include Canada, so we have to keep moving down the options.

Most often, we end up trying to manage these cases with diet to try to minimize diarrhea and keep things tolerable until the cat ultimately gets rid of the parasite on its own. Sometimes, the diarrhea is pretty bad though, so we’d really like to try something more in those cats in particular.

That leaves the bottom of the barrel option, pradofloxacin, a fluoroquinolone antibiotic. It’s a higher-tier antibiotic so I really hate considering it for this disease, but some infected cats are pretty miserable, so we have to consider it in severe cases. Efficacy data are lacking, so it’s more of a “this might work, you could try it if you really need to” situation, than something based on even preliminary data. If cats are sick enough and not responding to dietary management, I’m okay with that. The treatment duration that’s typically used is 7 days; if there’s not a good response after 7 days, I wouldn’t extend it, at that point we’d just have to accept that we’ll need to wait it out for that patient.

Are there any ways to get ronidazole?

The internet is an interesting place. You can find pretty much anything somewhere, but it’s very much buyer beware. Whether anything you order is actually ronidazole (and at the stated concentration) is always going to be in question. There are also legal issues with importing drugs. As veterinarians, we are able to get permission to import drugs on an emergency release basis. However, that system is focused on licensed drugs that are available in other countries but not here in Canada. It’s not meant for accessing unapproved drugs and compounded drugs. We were able to get permission to import antivirals for the treatment of FIP in cats, but that took some time, the drugs came from a well established company, and due diligence was done on that company as part of the review process. Importing from an established compounder that has clear quality control procedures and testing is different than buying a drug from some random company that provides no information (at least not in English or French). I’d be interested in exploring some of these products more to see if we can get enough information to pitch an Emergency Drug Release request, but I haven’t been able to find anything that would give me confidence to make such a request yet.

So, the answer to the common “how can I treat this cat with tritrich?” question is still currently ”feel free to call around and see if any pharmacies have been able to get ronidazole. If not, and they can’t get tinidazole (or maybe secnidazole) either, try dietary management. If that doesn’t work, consider a course of pradofloxacin. If that doesn’t work, you have to try to wait it out for now.”

I don’t like the “see what happens, it will hopefully get better soon” approach, but that’s unfortunately where we sometimes end up.