Tritrichomonas in a Cat Named Rosie


Author: Dr. Clarissa G. Noureddine, DVM, MS, MS

Lawndale Veterinary Hospital wants all pet owners to understand that their pets can develop intestinal parasite infections. That’s why we’ve picked Intestinal Parasites as our ‘Paws to Protect’ topic for July. While we do tend to see certain intestinal parasites more commonly than others, there are actually a number of parasites that can cause problems. For this week’s blog, we decided to focus on a protozoal infection that pet owners may actually not have heard as much about – Tritrichomonas foetus. Read below for our case study of the month!

Veterinarian: Dr. Crawford
Patient: Rosie Ensley
Breed: Domestic Shorthair
Age: Rosie is currently 4 years old; she was 11 months old at the time of diagnosis.
History: Rosie was adopted from the shelter in September of 2014 as a kitten. She initially struggled with upper respiratory symptoms related to a feline herpes virus infection, but she improved with treatments. Then, on March 2, 2015, the owner reported Rosie had developed diarrhea.
Physical Exam Findings: Other than the diarrhea, Rosie was doing well and feeling good.
Plan: Initially, Dr. Crawford prescribed an antibiotic for Rosie to help the suspected colitis. Although the diarrhea improved, it did not resolve. A probiotic was also added. Due to a lack of full response to those medications, Dr. Crawford recommended fecal pathogen testing. The testing was positive for an active infection with a pathogen called Tritrichomonas foetus.
Treatment: Rosie was treated with a medication called ronidazole for 14 days. A recheck fecal test for T. foetus was performed on April 30, 2015 and the results were negative for Rosie!
Explanation: Diarrhea is a symptom that can develop with a long list of diseases and conditions. Often we need to pursue a variety of diagnostic testing when an animal has persistent diarrhea. In Rosie’s case, it was a fecal pathogen test that provided us with the answer. This test looks for evidence of several different fecal pathogens, including Giardia, Clostridium sp., Salmonella, Campylobacter, Cryptosporidium, feline parvovirus, and Tritrichomonas foetus.
T. foetus is a more recently recognized pathogen in kittens. It is a single-celled anaerobic protozoa. Infection is common in shelters and catteries. Some cats who are infected with T. foetus will not display any symptoms. Others will have large bowel diarrhea causing an increased frequency of defecation, and blood may be present. The stool is often cow pie-like and may have a strong, unpleasant odor. The cats may also be gassy. Often owners may report that the cat has had diarrhea ‘since adoption’.
In a small portion of infected cats, the protozoal organism may be visualized under the microscope in a fresh fecal sample. This organism actually looks very similar to another protozoal fecal pathogen, Giardia. Rosie’s infection was diagnosed with a much more sensitive method of testing – polymerase chain reaction (PCR).
T. foetus can be difficult to treat, and ronidazole is the only antimicrobial that has convincing efficacy. Since transmission is through the contaminated feces, infected cats should be separated while undergoing treatment with prompt cleaning of soiled litter boxes. Ronidazole has a narrow margin of safety, so dosing accuracy is very important. Some cats may have a T. foetus infection that is resistant to ronidazole. Untreated cats may eventually resolve the diarrhea, but they could still be carriers.

This case is just one of many examples to emphasize the importance of prompt veterinary care and diagnostic testing when a pet has abnormal symptoms. Finally, remember that some pets may be harboring intestinal parasites without any external signs. This is why Lawndale Veterinary Hospital recommends annual fecal testing in all pets.

We are happy to report that Rosie has been doing well since her diagnosis and treatment for T. foetus!