Tritrichomonas foetus

Tritrichomonas foetus is a species of single-celled flagellated parasites that is known to be a pathogen of the bovine reproductive tract as well as the intestinal tract of cats. In cattle, the organism is transmitted to the female vagina and uterus from the foreskin of the bull where the parasite is known to reside. It causes infertility, and, at times, has caused spontaneous abortions in the first trimester. In the last ten years, there have been reports of Tritrichomonas foetus in the feces of young cats that have diarrhea[1] and live in households with multiple cats. Tritrichomonas foetus looks similarly to Giardia and is often misdiagnosis for it when viewed under a microscope.[2]

Tritrichomonas foetus
Scientific classification
Domain:
Eukaryota
(unranked):
Excavata
Phylum:
Metamonada
Class:
Parabasalia
Order:
Tritrichomonadida
Family:
Tritrichomonadidae
Genus:
Tritrichomonas
Species:
T. foetus
Binomial name
Tritrichomonas foetus
(Riedmueller, 1928)
Tritrichomonas foetus

Cause

Tritrichomonas foetus is the genus Tritrichomonas within the order Trichomonadida in the Kingdom Protoctista. The parasite is 5-25 µm in size and is spindle shaped with four flagella, which are whiplike projections, and an undulating or wavy membrane. Three of the flagella are found on the anterior end and approximately the same length as the body of the parasite. The fourth is on the posterior end.[3] Their movement is jerky and in a forward direction, and they also do "barrel rolls". The organisms look like small tadpoles with small tails when viewed microscopically. The parasite interacts with bacteria that normally reside in the intestinal tract by adhering to the intestinal epithelium of the host.

Cattle

Clinical signs

Bulls do not show any clinical signs of infections and can infect females at mating. In cows, there may be infertility, embryonic death and abortion, and reproductive tract infections such as pyometra.[4][5] Cows may show outward signs of infection, namely a sticky, white vaginal discharge, which may occur for up to two months after the initial infection. The disease results in abortion of the embryo, often within ten days of conception. Evidence of repeat breeding or infertility may be a sign of trichomoniasis. After the abortion of the fetus and the cow's return to a normal estrous cycle, the cow may come into estrus again, at which point it may be bred again. Eventually the cow will be able to cycle normally and carry a fetus to term. However, the irregularities after initial infection present obvious clinical signs of reproductive inconsistencies, which should be examined by a veterinarian immediately.[6] Bulls remain infected for life, but cows can successfully clear the infection, but reinfection is likely.[7]

Diagnosis

Diagnosis can be done on both males and females; however, bulls are tested more since they remain carriers. In cattle, a presumptive diagnosis can be made from the signs of infertility and geography. Diagnosis may rely on microscopic examination of vaginal or preputial smears. Complement fixation can be performed to detect parasite antibodies in vaginal secretions.[5]

Several related trichomonads may be mistaken for Tritrichomonas foetus, including: Trichomonas vaginalis, Trichomonas gallinae, and Trichomonas tenax. A study by Richard Felleisen found that identification of T. foetus using Polymerase chain reaction (PCR) resulted in a more accurate identification. The 5.8S rRNA gene of T. foetus was found to have 12 copies in the T. foetus genome. This indicated that the organism could be identified via amplification of this gene by PCR. Not only would this allow for identification of T. foetus, but also differentiation from other trichomonad species.[6] Diagnosis can also be done using the InPouch TF from a prepuce scraping sample from a bull.

Treatment and Control

Bulls can be treated in different ways. Various imidazoles have been used, but none are both safe and effective in treatment. Ipronidazole is probably most effective but, due to its low pH, frequently causes sterile abscesses at injection sites. Bulls can also remain carriers for life and can easily be susceptible to reinfection even after successful treatment. Again, keep in mind that bulls can sometimes remain carriers for life once they become infected; they are unable to clear the infection like cows can. Cows can be treated by being left alone for around three months to allow them time to shed the vaginal and uterine lining that is affected. Semen can also be treated successfully with dimetridazole and then used for artificial insemination. Commercially available vaccines (TrichGuard[8], Tricovac[9]) cannot prevent infection, but confer disease attenuation and some level of protection against complications.[10][11] In a placebo-controlled trial of TrichGuard with forty prophylactically vaccinated, T. foetus-infected beef heifers, 95% of the heifers in the active treatment group conceived, as opposed to 70% in the placebo group. 50% in the TrichGuard-group gave birth to a live calf, compared to 20% in the placebo group.[12] The most effective control method for eliminating the infection in a herd or an individual remains by culling the animal(s) and replacing them with virgin animals after positive test results. Cows can remain in the herd if given enough time to shed the infection or can be culled like bulls to allow faster turnover and assure the herd is clear of the infection.[2][3]

Transmission

There are two routes of transmission for Tritrichomonas foetus between cattle: cow-to-bull or bull-to-cow. If a bull naturally breeds an infected cow, the organism can transmit to the bull's prepuce, where the parasite likes to reside.[7]

The most common route of transmission is from bull to cow. The cow can get infected either when naturally bred to an infected bull or when receiving semen from an infected bull during artificial insemination. However, in the case of artificial insemination, while T. foetus is capable of surviving the process used to freeze semen after collection, it is usually killed by drying or high temperatures.[7]

Tritrichomonas foetus in cattle is unlikely to survive outside the host, so the only way it can successfully directly from one host to another.

Prognosis

The prognosis for cattle is not good. Infected bulls are advised to be culled; cows should also be culled due to easy reinfection even after clearing the initial infection. Trichomoniasis is a reportable disease in cattle, and as of now, there is no effect treatment. Prevention and smart farm practices are the only remedy. Testing should be done on any bull prior to exposing it to the herd. Limiting exposure of the herd to other cattle and limiting the introduction of open cows into the herd are good preventative practices. An estimated 42% of cows will acquire the disease if bred to an infected bull.[13]

Cat

Jody Gookin

"Dr. Gookin is nationally recognized for her expertise in gastroenterology with a special emphasis on infectious causes of feline diarrheal disease. Dr. Gookin and her colleagues are credited with identification of Tritrichomonas foetus as a previously unrecognized cause of diarrhea in domestic cats and have dedicated over 15 years of research effort into establishing the pathogenicity, means for diagnosis, worldwide significance, and an effective treatment for this infection."[14][15]

Clinical signs

In cats, Tritrichomonas foetus is characterized by diarrhea that comes and goes and may contain blood and mucus at times. The diarrhea is semi formed in a cow pie consistency. In most cases it affects cats of 12 months of age or younger and cats from rescue shelters and homes with multiple cats. Close and direct contact appears to be the mode in which the parasite is transmitted. Tritrichomonas foetus is most common in purebred felines, breeds like Bengals, Persians, etc. Since catteries tend to trade queens and studs to provide greater genetic diversity, the parasite can be spread from one cattery to another.

However, just because the cat doesn't show signs of diarrhea, it still could possibly be infected. Adult cats are less likely to develop diarrhea when infected, but they will still serve as a source of infection for other cats. Clinical signs can show up anywhere from days to years after exposure.[15]

Diagnosis

In cats, Tritrichomonas foetus can be detected by the following four methods:

  1. Direct Fecal Smear[15][2]
    1. Fresh feces are examined in saline under a microscope for the presence of trichomonads. This is the cheapest method with poor sensitivity since approximately 14% of infected cats are detected through this method.
  2. Fecal culture[2]
    1. 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.
    2. InPouch TF from a fecal sample of an infected cat is an example of this method.
    3. this is the second cheapest method at around $5-$7 per culture pouch. The sensitivity is good with approximately 55% of infected cats are detected through this method.
  3. PCR testing - A fecal sample is sent to a diagnostic laboratory for analysis. PCR testing searches the specimen for genetic evidence of the T. foetus organism. This test is the most reliable available at this time. The PCR test can take anywhere from one to three days to complete, so it is the fastest way to get results. This test can detect both living and dead organisms present in a sample.[2]
    1. This is the most expensive method at around $75 per test. The sensitivity is excellence with approximately twice as many infected cats detected through this method as fecal cultures.

Treatment and Control

One treatment that has been effective in experimentally infected cats is ronidazole. (Note “experimentally,” therefore it is unknown exactly how the treatment would act in the field.) Neurotoxicity has occurred in some cats treated with ronidazole; sign include lethargy, ataxia, seizures, etc. These side effects usually resolve when the drug is withdrawn immediately; however, if the treatment is not withdraw for a couple weeks, resulting in costly and intensive emergency veterinary care.[15]

Cats need to be monitored closely while on ronidazole. One good way to monitor if the cat suffers from the neurotoxic side effects is to engage the cat each day in a playful activity that involves coordination and agility (playing with laser point). If neurotoxicity is observed, treatment must be stopped immediately; note that neurotoxicity symptoms may continue/worsen a few days after stopping treatment before subsiding. Continuing treatment after signs of toxicity is dangerous and life-threatening to the cat.[15]

Ronidazole is currently not FDA approved in companion animals and banned for use in food-producing animals outside the United States due to human hazard. Because of this, veterinarians are advised to obtain informed consent prior to use of this drug in cats.[15] Because is not FDA approved, its usage would be considered an off-label use. Other than this drug, there is no other treatment for Tritrichomonas foetus infections in cats.

There is always possible that the T. foetus infection could be resistant to Ronidazole; if this is the case, longer duration or a higher dosage of treatment will not work and will increase the chances of neurotoxicity.[15]

During treatment, the feline should be keep isolated from other cats as to prevent the spread to another cat (typically transmitted by an infected cat sharing the same litter box as other cats). The cat should be fed a veterinarian prescribed dry-food diet, preferably of high fiber content. Wet food should be avoided. A common GI diet remedy in cats (boiled chicken breast, white rice, and pumpkin) may be highly beneficial during and after treatment.

Transmission

The primary transmission route is the litter box that is shared by both infected and uninfected cats, where a 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 the act of grooming. In cats, Tritrichomonas foetus is able to live several days in wet stool. Mutual grooming may also transfer the parasite. There is no evidence that T. foetus is sexually transmitted or infects the reproductive tract or mammary glands of cats.[15]

Prognosis

The long term prognosis for cats with TF is generally good, the diarrhoea will usually resolve itself in untreated cats. However this can take many months, and cats which no longer show clinical signs can continue to shed the organism for up to two years.[16] It appears that over time the parasite dies off and the infection is remedied on its own. In some cases, the symptoms may improve over time, but the animal is likely to still be a carrier of the parasite, capable of transmitting it to another cat.

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References
  1. Gookin, Jody L.; Martha E. Stebbins; Emily Hunt; Karen Burlone; Merritt Fulton; Robin Hochel; Miriam Talaat; Matthew Poore; Michael G. Levy (2004). "Prevalence of and Risk Factors for Feline Tritrichomonas foetus and Giardia Infection". J Clin Microbiol. 42 (6): 2707–2710. doi:10.1128/JCM.42.6.2707-2710.2004. PMC 427826. PMID 15184456.
  2. Gookin, Jody. "An Owners Guide To Diagnosis and Treatment of Cats Infected with Tritrichomonas Foetus" (PDF).
  3. "Overview of Trichomoniasis in Cattle - Reproductive System". Merck Veterinary Manual. Retrieved 23 April 2019.
  4. Tritrichomonas foetus reviewed and published by WikiVet, accessed 10 October 2011.
  5. Trichomonosis - Cattle reviewed and published by WikiVet, accessed 10 October 2011.
  6. Felleisen, Richard S.J.; Natacha Lambelet; Philipp Bachmann; Jacques Nicolet; Norbert Müller; Bruno Gottstein (1998). "Detection of Tritrichomonas foetus by PCR and DNA Enzyme Immunoassay Based on rRNA Gene Unit Sequences". J Clin Microbiol. 36 (2): 513–519.
  7. Janzen, Eugene D. "Overview of Trichomoniasis in Cattle". Merck Veterinary Manual.
  8. "TRICHGUARD Product Description". bi-vetmedica.com. Boehringer Ingelheim Vetmedica, Inc. Retrieved 7 April 2020.
  9. "TRICOVAC para la inmunoprofilaxis de la trichomonosis venérea bovina, en hembras de esa especie" [TRICOVAC for the immunoprophylaxis against bovine genital trichomoniasis in female cattle]. biotandil.com.ar (in Spanish). Laboratorio Biológico de Tandil Srl. Retrieved 7 April 2020.
  10. Daly, Russ (December 2005). "Bovine Trichomoniasis". Proceedings, The Range Beef Cow Symposium XIX December 6, 7 and 8, 2005, Rapid City, South Dakota: 123–132.
  11. Vispo, P. E.; Prieto, P. N.; Stahringer, R. C. (November 2011). "Empleo de una Vacuna Comercial contra la Trichomonosis en un Rodeo Brangus Infectado Naturalmente" [Use of a commercial vaccine against trichomonosis in naturally infected Brangus cattle]. Veterinaria Argentina (in Spanish). 28 (283). Retrieved 7 April 2020.
  12. Edmondson, Misty A.; Joiner, Kellye S.; Spencer, Jennifer A.; Riddell, Kay P.; Rodning, Soren P.; Gard, Julie A.; Givens, M. Daniel (March 2017). "Impact of a killed Tritrichomonas foetus vaccine on clearance of the organism and subsequent fertility of heifers following experimental inoculation". Theriogenology. 90: 245–251. doi:10.1016/j.theriogenology.2016.09.056.
  13. https://www.addl.purdue.edu/newsletters/2000/spring/bv.shtml accessed 30 April 2014.
  14. "Profile". cvm.ncsu.edu. NC State University. Retrieved 8 April 2019.
  15. Gookin, Jody. "Dr" (PDF). An owner's guide to diagnosis and treatment of cats infected with "Tritrichomonas foetus. Nprth Carolina State University.
  16. Tritrichomonas foetus in cats
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