Feline Trichomoniasis

Filed Under: Cats, Diseases

If your cat has been suffering from chronic large bowel diarrhea and nothing seems to be working, don’t overlook trichomoniasis as a possible cause.  Feline trichomoniasis is an infection caused by the protozoal parasite Tritrichomonas foetus.  The infection is hard to diagnose and even harder to treat. 
 
T. foetus is a single-celled obligate parasite.  The trichomonad is unable to survive desiccation but is known to survive for up to 3 days in moist feces.  This parasite has a pear-shaped body with three anterior and one posterior flagella that allow for movement. 
 
T. foetus transmission between individual cats is believed to occur through fecal-oral contact.  By sharing litter boxes, a cat may get the organism on its paws and then cleans those same paws in the grooming process, thereby ingesting the organism.  It also passed from mother to kittens.
 
Estimates of 10% in the United Kingdom and up to 31% of all cats in the United States are believed infected in densely housed conditions.  Cats in shelters and purebred catteries appear to be more commonly affected.  No breed of cat is immune to infection.
 
T. foetus primarily infects cats less than 2 years of age.  Most affected cats have a history of a chronic or relapsing diarrheaCoexisting infections with FeLV, FIV, coccidia, Giardia, or feline inflammatory bowel disease are not uncommon.  These cats may have fecal incontinence and may even dribble stool in severe cases.  The stool is loose to semiformed and is often bloody with a bad odor (malodorous) when formed.  Cats will often strain in the litter box, and develop anal or perianal inflammation.  Weight loss from the diarrhea is uncommon.  Most infected cats are in good condition since the colon is not involved in nutrient absorption but rather functions in the storage and formation of feces.  Antibiotic therapy is reported to improve the diarrhea, only to have it return once therapy is discontinued.  Often the diarrhea will resolve within 2 years of onset regardless of treatment.

Sometimes diagnosis may be made on a fresh fecal exam alone.  A direct fecal smear is the cheapest way to diagnose T. foetus, but it is also the least sensitive test for confirming an infection.  The test consists of taking fresh feces and suspending it in a drop of saline.  The slide is then observed under the microscope for the identification of the organism.  T. foetus is commonly confused with Giardia species because of their similarities in appearance within a stool sample.
 
A commercial culture test is available from Biomed Diagnostics called the InPouch TF-Feline®; this test contains a proprietary medium for the trichomonads replication while it also suppresses unwanted bacterial growth.  The pouch is inoculated with fecal material approximately the size of a grain of rice and then incubated at body temperature for 72 hours.  When the culture material is incubated at room temperature it may take as long as 12 days to observe adequate growth of the trichomonads under a light microscope. 
 
Trace amounts of the trichomonads may be detected by polymerase chain reactions, or PCR testing.   This is the most sensitive test for the detection off T. foetus but is also the most expensive.  Typically a fecal sample the size of a lima bean should be submitted.  The sample is placed in a red-topped vacutainer tube that is filled with 3 to 5 ml of 70% rubbing alcohol, and the sample should be shipped at room temperature.  These samples should never be refrigerated since the organism is extremely sensitive to cold. 
 
Currently there is no approved treatment for feline trichomoniasis.  Medications currently being used include: 

  1. Ronidazole: 30 to 50 mg/kg every 12 hours for 14 days.  Side effects include dose-related neurotoxicity.
  2. Tinidazole:  30 mg/kg every 24 hours for 14 days
  3. Concurrent use of Enrofloxacin: 5 mg every 24 hours for 21 days and Fenbendazole: at 50 mg/kg every 24 hours for 5 days. Retinal degeneration is a possible risk when enrofloxacin is given at high levels.

 Ronidazole is considered to be the most effective drug for the elimination of a T. foetus infection.  This drug is rapidly absorbed and has a long half-life (the time it takes to eliminate half of the drug from the body).  This drug predisposes some cats to exhibit neurotoxicosis.  Common signs of toxicity include lethargy, inappetance, ataxia, and seizures.  When the drug is withdrawn these symptoms generally resolve, but they may initially worsen before subsiding due to the long half-life of the drug.  In this case emergency veterinary care is necessary.  If treatment is continued in spite of neurologic signs the toxicosis could become life-threatening.  When treatment is discontinued the pet should be retested for the presence of T. foetus, for often the organism will clear in spite of a full course of treatment. 
 
Treatment is not 100% effective in all cases and there may be a reoccurrence of diarrhea after a few months when treatment is unsuccessful.  Treatment failures may occur due to insufficient dose or duration of medication, the administration of impotent drug formulation such as the 10% powder form of Ronidazole available for pigeons, the failure of the cat to consume the drug, or reinfection of the cat by an inapparent carrier within the household.  The infection with T. foetus may also be complicated by additional infectious agents or underlying conditions that may result in inadequate resolution of the diarrhea.  Despite the lack of treatment, infections may resolve in 88% of infected cats but may take up to two years for symptoms to clear.  Unfortunately 55% of these cats do remain positive when cultured for the organism and are able to transmit trichomoniasis to additional family members. 
 
Prevention is aimed at preventing transmission by providing clean litter boxes at regular intervals, no less than 2 to 3 times weekly.  It is also good to have ample litter boxes for the number of cats living together. 
 
 
References:
 
Stockdale, Heather and Byron Blagburn.  “Feline Tritrichomoniasis.”  NAVC  Clinician’s Brief.  April 2008. Pp. 9 – 11.
 
Tolbert, Mary Katherine and Jody Gookin.  “Tritrichomonas foetus:  A new Agent of Feline Diarrhea.”  Compendium:  Continuing Education for Veterinarians.  P. 374 – 381.
 
Yin, Sophia.  “T. foetus is Parasite Trickster.”  Veterinary Forum.  October 2007. Pp.  44 and 52.

Topics: parasites, protozoa

Symptoms: diarrhea

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