What is Tritrichomonas foetus?
(T. foetus) is a flagellated protozoan similar in size to the better known protozoan, Giardia
. T. foetus
is a parasite that can only survive in warm, moist anaerobic (without oxygen) environments such as the gastrointestinal tract or the genitourinary tract of its host.
In cats, T. foetus lives in the ileum (a portion of the small intestine) and the large intestine causing a chronic foul-smelling diarrhea. T. foetus infections are most common in circumstances where there are large numbers of cats.
T. foetus is better known to cause venereal disease in cattle herds that are naturally bred.
Which cats get T. foetus and how do they contract it?
Because of the increased density of animals, cats that originate from animal shelters or catteries are at the greatest risk of infection. Usually T. foetus infects younger cats. However, older cats may develop an infection and become asymptomatic carriers of this organism.
What are the symptoms of T. foetus infection?
Infected cats often have episodes of chronic, foul smelling diarrhea. During these episodes the diarrhea is frequent and relatively small in volume. This kind of diarrhea is characterized as 'large-bowel' diarrhea. The feces often contain mucous and sometimes fresh blood. The diarrhea is often characterized as 'cow-pie' like. The appetite is generally not affected, and cats do not exhibit weight loss. Older cats may be infected without demonstrating any symptoms although they can and do spread the infection.
How is T. foetus diagnosed?
There are four methods recognized to diagnose T. foetus:
Direct smear: In performing a direct smear, a fresh sample of fecal material is collected and examined under a microscope. Because T. foetus is an elusive organism, several samples may need to be examined.
Culture: Culturing this organism requires a specially designed culture pouch. This is a special test designed to grow T. foetus in large enough numbers to allow its identification.
PCR (Polymerase Chain Reaction): PCR is a DNA test. This test detects the DNA of T. foetus. This is a rather complex test that is usually performed at a specialized laboratory, but it is the most sensitive test.
Biopsy: Biopsy's are by far the most invasive test and are usually reserved for cases where the other diagnostic tests have been tried without success. This test requires a large sample size and some special tissue stains.
What is the treatment for T. foetus?
There is only one medication that has been used successfully to treat T. foetus: ronidazole. This medication is not labeled for use in cats and requires a prescription by a veterinarian. It is usually given for 2 weeks. Ronidazole, especially if given at too high of a dose, can be toxic to the nervous system of cats, causing loss of appetite, lethargy, incoordination, and possibly seizures.
As a result of the infection with T. foetus, the lining of the cat's large intestine will become inflamed. This inflammation usually lasts beyond the point in time when the T. foetus has been killed. What this means is that the diarrhea may continue beyond the point when the organism has been eliminated.
If a cat diagnosed with T. foetus lives in a multi-cat household, all cats will need to be tested, and treatment and temporary quarantine of other cats may be necessary.
If a cat infected with T. foetus lives in a situation where the density of cats is low, it is very likely that the diarrhea will resolve on its own within two years post infection. However, over half of these cats remain PCR positive and may serve as a source of infection for other cats.
Often the diarrhea caused by T. foetus is accompanied by another pathogenic organism such as Giardia or Cryptosporidium. When treatment of T. foetus is considered, these secondary organisms need to be treated as well; often requiring a separate medication. Unfortunately, the medications that are typically used to treat other protozoal organisms are not effective against T. foetus.
T. foetus is an emerging cause of diarrhea in cats. It is most often acquired in high-density situations such as catteries or animal shelters. Infections with T. foetus can be accompanied by other organisms. There is a treatment for T. foetus however, it requires the assistance of a veterinarian. In situations where the density of cats is low, the diarrhea may resolve without treatment within two years. Cats whose symptoms of diarrhea have resolved may become asymptomatic carriers of this organism.