There is a parasite that lives in a cat's colon and causes chronic, foul‑smelling diarrhea — and it is routinely missed because it looks like Giardia under a microscope. This resource collects everything that is actually known about it, what has changed, and what is still unresolved — written for the person holding the cat, not the parasitologist.
Four audiences, one body of evidence. The clinical facts are identical; what changes is what you need to do next.
Why a normal fecal test means almost nothing, what to ask for instead, whether to treat at all, and what to expect.
Read the owner's path For rescues & sheltersIsolation by test and symptom status, what actually kills the organism outside the cat, and the honest cost per cat.
Open the outbreak playbook For veterinariansThe dosing history and why an older version still circulates, the neurotoxicity to watch for, and a consult summary you can print.
Read the clinical path For catteries & breedersThe population with the highest published prevalence: what to test before an introduction, what a negative really means, and what you owe a buyer.
Open the breeder's path
The organism in your cat is still called Tritrichomonas foetus by most veterinarians and
virtually every lab. In 2013 a proposal was published to give the feline organism its own species name,
Tritrichomonas blagburni, because it is genetically and biologically distinct from the
venereal parasite of cattle that shares the name.
That proposal is not universally accepted, and it is used inconsistently: the European cat-disease guidelines use the new name, other international guidance still uses the old one, and Dr. Gookin's own laboratory writes both. They are the same organism. Read the full explanation →
Approximate, and they vary by study and by test method — but each one changes a decision.
The recommended dose of ronidazole was revised downward, and the revision is more than a decade old. Much of the material owners find online still prints the superseded regimen. See the full dosing history →
The more we learn about trichomonosis in cats, the more complicated and controversial the infection has become — ranging from what we should call the organism to whether or not we should even bother trying to treat it.
