Internal Parasites and Deworming, Shelter and Rescue Resources
Tritrichomonas foetus in Cats
By Amy Hanson, DVM
January 13, 2023
Tritrichomonas is a protozoa parasite found in the large intestine tracts of cats. Tritrichomonas in cats causes chronic and recurrent large bowel diarrhea, often with mucus and fresh blood. This parasite is often misdiagnosed as Giardia, but it is unresponsive to most common intestinal parasite treatments. This parasite can affect any cat, but it is more commonly found in multiple-cat housing situations, such as catteries and cat shelters.
How Does a Cat get Tritrichomonas foetus?
Tritrichomonas is spread via fecal-oral route, mostly through shared contaminated litter boxes and self and mutual grooming and ingestion of contaminated feces. It can only affect other cats and does not affect dogs. There is no zoonotic potential for humans which means humans cannot get Tritrichomonas from a cat. Since cats are infected through shared resources (litter boxes, bedding, food/water bowls and mutual grooming, cats that share an environment with an infected cat should also be treated to ensure full eradication.
How Common is Tritrichomonas foetus in Cats?
(Prevalence studies have shown an global incidence of 0-81.8% infection rate in cats, with the majority being in purebred catteries)
Young cats that are under the age one year are most commonly affected, but it can affect cats of any age. Purebred cats have a higher risk of becoming infected, but also, cats housed in colony-type shelters and rescues can be at higher risk of infection. If left untreated, the diarrhea can resolve spontaneously, but some cats may be asymptomatic carriers and contribute to the spread of the disease. The protozoa do not have a true cyst stage in its life cycle; however, the parasite can live for up to seven days in moist feces at room temperature, also contributing to the spread to other cats. The severity of the diarrhea can range from subclinical to severe.
How to Know if My Cat has Tritrichomonas Foetus
Chronic diarrhea, sometimes with blood and mucus is the only clinical symptom of Tritrichomonas in cats. Some cats may be carriers and show no diarrhea.
Tritrichomonas in cats can be detected in a fresh direct smear of a stool sample, but the organisms can be difficult to find using this method and can be mistaken for Giardia in cats. Culturing of the trophozoite stage and DNA detection via polymerase chain reaction (PCR) are the more sensitive and specific ways of diagnosing this parasite. PCR can also detect the organism in those cats that are asymptomatic or have subclinical symptoms, such as occasional soft stool
Can Tritrichomonas Foetus be Cured?
If all cats in an affected environment are treated, then yes, Tritrichomonas fetus can be cured, but reinfection can occur if introducing a new cat to an established colony that is carrying the parasite.
Currently treatment for Tritrichomonas can be challenging and is still being investigated. It does not respond to antibiotics normally used to treat protozoal parasites, such as metronidazole. Ronidazole is the most effective treatment, and is only available through compounding pharmacies in the United States. Some people are concerned about using ronidazole for cats due to the potential for neurologic side effects, but this usually only occurs if ronidazole is used in high doses. Ronidazole taken as directed is usually safe and effective, although a small number of cats may have a lower tolerance to this drug and exhibit neurological symptoms. The symptoms resolve once the cat stops taking the medication. Talk to your vet about what’s best for your cat.
Prevention of feline Tritrichomonas is primarily one of good hygiene in the environment and reduction of stress. Kittens and young adult cats are most susceptible to this parasite, so preventing overcrowding, and thus increased stress, goes a long way to reducing the risk of infection. Keeping the environment, including litter boxes, transport carriers, bedding and other materials clean will also reduce the parasites in the environment. Normal disinfectants, such as Rescue disinfectant and Virkon S, are very effective at killing Tritrichomonas.
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Written by: Amy Hanson, DVM
Dr. Amy Hanson is an associate veterinarian at the Cat Clinic of Lawrence in Lawrence, Kansas. She is a 2010 graduate of Kansas State University College of Veterinary Medicine. Her special interests include felines, acupuncture and dentistry. Her hobbies include showing cats and she is a judge for the American Cat Fanciers Association (ACFA).