Kittens and cats living in groups have an assortment of infectious diseases to contend with: upper respiratory infections, coronavirus, coccidia, to name a few. Tritrichomonas foetus is yet another infectious organism yielding diarrhea in feline patients, usually with a history of group lifestyle. This organism was previously thought to infect only cattle where it causes miscarriage and fertility problems, but recently (in 2003) T. foetus has emerged as an infectious agent for cats. Information and recommendations regarding this organism have changed in the last several years and we attempt to provide the most up to date summary of what is known and recommended for prevention and treatment of this infection.
WHAT IS TRITRICHOMONAS FOETUS ANYWAY?
The short answer is that this is a single-celled organism. The longer version is that this is a flagellate, a single-celled organism possessing lash-like structures, called “flagella,” on its “body” which wave around allowing the organism to move. Under the microscope, T. foetus is commonly mistaken for Giardia, another parasitic flagellate as they both use flagella to move around and both have pear shaped bodies.
WHAT DOES IT DO TO THE CAT?
T. foetus colonizes the lower intestine of the cat causing the mucous and sometimes bloody diarrhea that characterizes colitis. If the colon is biopsied, inflammatory cell infiltration typical of inflammatory bowel disease will be seen. The diarrhea will clear in 88% of cats within 2 years but the infection will likely persist and the cat will likely remain contagious to other cats.
Because colitis can have so many causes, it is important to keep this possible cause in mind. Chronic colitis may or may not respond to symptomatic treatment and if a specific underlying cause can be identified and treated, a long-term difficult problem can be potentially resolved permanently. Many colitis remedies will lead to temporary improvement for a Tritrichomonas-infected cat but the symptoms generally come right back after treatment ceases.
MAKING THE DIAGNOSIS
There are presently four testing methods that can be used to identify Tritrichomonas foetus in a fecal sample. It should be noted that a proper fecal sample for testing must be freshly voided (i.e. immediately retrieved from the anus with no cat litter contamination), obtained with a deeply inserted fecal loop, or flushed from the colon with a syringe. Bringing a sample from home will not be adequate. If the cat has been on antibiotics, this will interfere with testing; the cat should be off antibiotics for at least a couple of days.
Here some fecal matter is swabbed onto a microscope slide, mixed with a gentle saline solution, and examined for the presence of flagellate organisms. The feces must be immediately fresh from the rectum. The wetter and more mucous the sample, the better. Usually several slides must be examined as the organism is elusive. Standard fecal tests for parasites will not pick up this organism. Refrigeration of the sample will kill the organism and make it impossible to detect. Further, if the patient is on antibiotics the number of organisms available to detect will be greatly reduced even though most antibiotics cannot cure the infection.
While this is a relatively easy test to perform, it only has about a 14% chance of detecting a natural T. foetus infection. A more sensitive test is generally preferred.
PCR Testing (Polymerase Chain Reaction Testing)
PCR testing is a DNA test for the presence of T. foetus. A larger fecal sample is needed and the test must be done at a reference lab. Many experts prefer the pouch test because it is inexpensive and leave PCR testing for patients where the pouch test has been negative but the index of suspicion is still high. That said, most small hospitals do not have much experience identifying Tritrichomonas under the microscope so for best accuracy, a better option may be to choose the expertise of the reference laboratory. PCR testing is the most sensitive of all the test methods but is also relatively expensive. Specialized equipment is needed and only a few laboratories are qualified to run samples.
A routine colon biopsy is unlikely to find this parasite; special stains on the tissue (“immunohistochemistry”) must be requested and at least six tissue samples must be examined. This is the most invasive form of testing and would not be done right off the bat but if the patient is going to have a biopsy for chronic colitis anyway, it might be a good idea to have the pathologist look for T. foetus.
A negative test never rules out Tritrichomonas infection
In the past several different antibiotics have been reported to be effective but it turns out that this is probably an overestimate since 88% of cats will resolve their diarrhea spontaneously within 2 years. They will still be infected, or at least 57% of them will, but will have normal stool and they may relapse with stress.
The only drug that is felt to be reliable against T. foetus is ronidazole, and its use is far from straight-forward. Here is what to know:
Dr. Jody Gookin is an internationally recognized expert in the study of Tritrichomonas foetus in the cat. She has published guidelines which contain the information presented here and much more. These guidelines can be accessed at:
Page posted: 8/24/08