Veterinarian Q & A: Understanding Tritrichomonas foetus

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Many cat owners struggle with feline diarrhea, a common problem that can be attributed to several possible causes. The discovery of one type of large bowel diarrhea that has made its way into the feline world, Tritrichomonas foetus, is credited to the efforts of Dr. Jody Gookin, an associate professor at North Carolina State University’s College of Veterinary Medicine.

T. foetus is a flagellated, single-celled protozoa, often misdiagnosed as Giardia (and even resembles it under a microscope). It is found in pedigreed and domestic cats and resides within the colon — thriving on its warm, moist and oxygen-deprived environment. It causes colitis and chronic, foul-smelling diarrhea, known to sometimes trigger a gag reflex in humans. Surveys suggest that T. foetus infects up to 30% of all pedigreed cats.

Several years ago, Dr. Gookin discovered T. foetus after treating a cat with ongoing health problems, including diarrhea and an unusual and persistent parasite. She wondered how the two might be connected and her curiosity ultimately resulted in identifying and understanding this pesky parasite. One of the obstacles Dr. Gookin encountered was the lack of a safe and effective drug for treatment of the T. foetus infection. She and her colleagues have since focused on developing a cell-culture model for studying T. foetus and they have been screening drugs that might reduce the incidence of diarrhea.

The T. foetus infection is prevalent among cattery cats where fecal-oral transmission is suspected. Infected cats may have persistent diarrhea for up to two years and can remain infected for their lifetime. Testing for this parasite is still not routine at many veterinary clinics.

The Winn Feline Foundation (WFF), a not-for-profit organization established in 1968 that supports studies to improve cat health, emphasizes the need for continued T. foetus research. They recently honored Dr. Gookin as the recipient of the 2011 American Veterinary Medical Foundation (AVMF)/ Winn Feline Foundation Research Award, for her contributions to advancing feline research and feline health.

Tritrichomonas foetus is recognized as an important cause of diarrhea in domestic cats,” says Vicki Thayer, DVM and President-Elect of the WFF. “Dr. Jody Gookin’s research at North Carolina State University’s College of Veterinary Medicine has enhanced our knowledge of this parasite — especially its prevalence in pedigreed cats and how to better diagnose infection. The Winn Feline Foundation supports her continued research efforts where answers will be found to such questions as how to safely and effectively treat and clear Tritrichomonas foetus infections. Every cat, every day, benefits from Winn-funded research.”

We asked Dr. Gookin to help Purring Post readers better understand this perplexing infection:

Tritrichomonas foetus is well known as a venereal infection of bovines (cattle). It was first reported in cats in 1996, where it was found in the intestine and was associated with diarrhea. There is no evidence that feline T. foetus came from cattle, in fact, veterinarians don’t know how T. foetus made its way into the feline population.
T. foetus is common in pedigreed and shelter cats, with no particular breed being overly represented. No breed of cat is known to be immune to T. foetus. Based on a survey of cats at an international cat show, approximately a third of the pedigreed feline population may be infected with T. foetus. Geographically, T. foetus has been found in every country that has looked for it.
Infected cats may or may not have observable symptoms. In cats showing symptoms, T. foetus causes diarrhea, characterized by cow pie-like stools that are often gassy and malodorous. Sometimes there can be mucus or fresh blood in the stool or feces can dribble from the anus. Several breeders have commented that in symptomatic cats the stool has a very strong and unpleasant odor. Importantly, absence of diarrhea does not mean that a cat is free of infection, particularly in multi-cat households where another cat may have tested positive for T. foetus. Adult cats appear to be less inclined to develop diarrhea in response to T. foetus, but nevertheless may serve as a source of the infection for others. Cats can come down with symptoms of T. foetus infection anywhere from days to years after exposure.
The primary infection pathway is probably the litter box, where the well-timed use by two cats can transfer the parasite from the feces of one cat to the paws of another, where they later become ingested during grooming. T. foetus can live for several days in a wet stool (wet is the key word). Mutual grooming might also transfer the parasite. There is no evidence that T. foetus is sexually transmitted or that it infects the reproductive tract or mammary milk of cats.
There are three (3) ways to test for T. foetus infection:

1. Direct Fecal Smear: Fresh feces are examined in saline under a microscope for the presence of trichomonads. (Cost – cheapest; Sensitivity – poor; can detect approximately 14% of infected cats)

Be aware that T. foetus looks a lot like Giardia when examined under the microscope. If your cat has been diagnosed with Giardia and is not responding to treatment, consider the possibility that T. foetus, and not Giardia, is the actual culprit.

2. Fecal Culture: Feces are incubated in a growth medium for T. foetus. Included in this medium are antibiotics, which suppress unwanted bacterial growth. The culture is then examined microscopically for the presence of T. foetus. The only commercially available culture test kit is BioMed’s Feline InPouchTF™ test kit. (Cost – low; $5-$7 per culture pouch depending on quantity purchased. Veterinary charges for sample collection, incubation, and examination vary: Sensitivity – good; if T. foetus organisms are present their numbers will multiply in the culture over time, increasing the likelihood of their detection. Performed correctly, a fecal culture can detect approximately 55% of infected cats)

3. Polymerase chain reaction (PCR): This is a molecular biology test that is used to identify trace amounts of T. foetus DNA in the feces. (Cost – expensive; $75 per test depending on the laboratory; Sensitivity – excellent; can detect both live and dead organisms. Can detect approximately twice as many infected cats as can the fecal culture).

Dr. Gookin’s laboratory was the first to design a PCR test for T. foetus and continues to be considered the authority on diagnostic testing for the infection. Information on how to collect and submit a fecal sample to Dr. Gookin’s laboratory for T. foetus PCR testing can be found at

No diagnostic tests are available that will detect infection 100% of the time. If test results are positive, the cat has T. foetus infection. If test results are negative, the cat likely does not, but still could have, T. foetus infection. Importantly, negative test results cannot be used to eliminate the possibility of this infection.

The best chance of finding T. foetus is to: 1) use the most sensitive testing method, PCR 2) consider testing repeatedly if your suspicion is high 3) only submit fecal samples that are obtained when cats are having clinical signs of diarrhea 4) make certain the cat has not received any antibiotics for at least seven (7) days prior to fecal collection 5) have your veterinarian obtain the fecal sample directly from the colon, using a fecal “loop” or saline flush technique. A video of how this technique is performed can be viewed by going to
Infected cats usually do not have their overall health adversely affected except for the presence of diarrhea. Therefore, owners of infected cats often ignore the infection since their cats maintain body and coat condition. Unfortunately, such cats remain a source of infection for others.

If left untreated, approximately ninety percent of infected cats will stop having diarrhea within two years. However, most of these cats will continue to carry the T. foetus organism, possibly for a lifetime. Single cat owners may find this outcome satisfactory if the cat remains healthy in other respects. However, if left untreated, the T. foetus infection will perpetuate within their cattery and spread to other cats and catteries when kittens are adopted or animals are transported for breeding. Although many cats will eventually resolve their diarrhea, the prolonged presence of the organisms could predispose to the development of inflammatory bowel disease later in life, but this has not yet been explored. We have also seen asymptomatic cats break with T. foetus diarrhea years after they were presumed to have spontaneously cleared the infection.

In light of the intimate association between infected cats and their human companions, the potential for zoonotic transmission should also be considered. However, only a single case of human infection with T. foetus appears in the current literature. In that particular case, the infection was present in the central nervous system of a man who was immuno-suppressed and had undergone a peripheral blood stem cell transplantation.
Repeated testing, performing tests appropriately, and appropriate efforts to isolate infected cats (to avoid transmission of the infection or re-infection) are essential to efforts in identifying all of the infected cats in a cattery.
Removing the kittens from the mother at birth is one obvious, but not recommended method. The risk of harm to kittens and mother would probably outweigh the benefits.

Another approach, which has worked on several occasions, is to place a platform (i.e. roof) over the kitten’s litter pan such that the mother is excluded but the kittens have free access. Place the mother’s litter pan out of reach of the kittens. Longhaired mothers who are symptomatic will require closer monitoring than shorthairs, as they may bring fresh feces on their coats back to the kittens. A ‘fanny wash’ should be performed to prevent this carry-back.

When the kittens are weaned and it is safe to remove the mother, begin treatment of the mother. Begin testing of the kittens if symptoms are observed, otherwise wait 14 days after separating the mother to allow for incubation of a possible infection.

At this time there is only one drug that appears to be capable of eliminating T. foetus infection in cats. The drug, Ronidazole, is an experimental drug that has a narrow margin of safety in cats. It appears that many cats that have T. foetus are also resistant to this drug. It should only be given to cats with confirmed T. foetus infection and prescribed by a veterinarian to a cat owner that is fully informed about the risks of toxicity. More detailed information about this drug can be found on our website at
It is very difficult to prove that a cat has been cured of T. foetus infection. We recommend that cats be repeatedly tested for T. foetus, either by a feces culture (most practical) or PCR, for follow-up periods of 20 or more weeks after completion of treatment.

Planning ahead for unforeseen illnesses can help make them more manageable when they occur. The CFA Pet Healthcare Plan includes coverage for Tritrichomonas foetus and other serious medical conditions, as well as preventive wellness options, to help keep your cat(s) healthy.

Are you prepared for your cat’s unexpected illnesses and injuries? The right pet healthcare plan can alleviate difficult emotional and financial decisions, while allowing you to explore a wider range of treatment options with your veterinarian. We offer several affordable plans for every budget, to significantly help manage the costs of feline veterinary care. Be prepared — plan ahead for your cat’s health and well being.

For more information on our plans and to get a no-obligation quote, visit or call us at 877.232.4441.

For more detailed information on the T. foetus infection, including videos of the parasite and how to submit samples for diagnostic testing, visit Dr. Gookin’s Web site at:

Dr. Jody Gookin holds a Ph.D. in Physiology/Biotechnology from North Carolina State University, a D.V.M. from The University of California at Davis, and a B.S. in Biology from San Diego State University. She is also a Diplomate of the American College of Veterinary Medicine (Small Animal Internal Medicine).

She emphasizes that her research would not be possible if not for the efforts of a great collaborative team of investigators including Drs. Mike Levy, Adam Birkenheuer, Mark Papich, Edward Breitschwerdt, Marty Stebbins, Michael Yeager, and Mac Law; the technical expertise of Stephen Stauffer, Maria Stone, Matthew Poore, Henry Marr, Dave Dybas, Robin Gager, and Judy Benrud; numerous veterinary students participating in research projects in the Gookin laboratory; and generous funding from the Winn Feline Foundation, Morris Animal Foundation, Fort Dodge Animal Health, Presutti Pharmaceuticals and the State of North Carolina.

To join Dr. Gookin in her fight against T. foetus infection and to make a tax-deductable contribution to STRIVE (Support for T. foetus Research Innovation and Veterinarian Education), visit her Web site at No gift is too small to help this ongoing effort.

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