Feline Tritrichomonas foetus infection

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1 Vet Times The website for the veterinary profession Feline Tritrichomonas foetus infection Author : ANDREW SPARKES Categories : Vets Date : November 24, 2008 ANDREW SPARKES discusses dealing with an infection that could take years to leave its usually young victims TRITRICHOMONAS foetus is one of more than 15 recognised species of trichomonads (microscopic protozoan parasites). T foetus is considered the most important trichomonad in terms of the economic losses it causes it is a sexually transmitted parasite of cattle, causing infertility, abortion and endometritis. This parasite has been found all over the world, but the widespread use of artificial insemination in breeding cattle (especially dairy herds) has led to the virtual elimination of this organism from many cattle populations (including those in the UK and much of Europe). But in areas where cattle are still reared extensively (such as in parts of the USA, South America, Africa and Australia), infection rates can still be high and are reported to be more than 30 per cent in some populations (Jayawardhana, 2002; Grahn et al, 2005). A morphologically identical organism (T suis) has been identified in pigs. It commonly causes asymptomatic infection of the nasal cavity, stomach and intestine. This organism is now considered synonymous with T foetus (Lun et al, 2005). Infection in cats Reports of trichomonad-associated large bowel diarrhoea started to emerge in cats located in the USA from around Although it was initially suspected that Pentatrichomonas hominis was the organism associated with these cases, subsequent studies identified T foetus to be the 1 / 14

2 trichomonad involved (Romatowski, 2000; Levy et al, 2003). Many studies have emerged several from the USA, but from other countries too which have demonstrated that this parasite may be an important and prevalent cause of diarrhoea in cats. The first report of feline T foetus infection in the UK came from a case referred to the Animal Health Trust (Mardell and Sparkes, 2006). Pentatrichomonas has been identified in a small number of cats infected with T foetus (Gookin et al, 2007a), but there is no evidence yet that it is pathogenic in this species. In cats, T foetus infects and predominantly colonises the large intestine, but also the ileum and caecum. Histologically, the organism is mainly localised to the epithelial surface (and, occasionally, in colonic crypts), and causes an accompanying lymphoplasmacytic and neutrophilic inflammatory response. In some cases, however, the organism has been seen to invade the lamina propria or deeper layers of the colonic wall and, when this happens, a more severe inflammatory response is observed (Yaeger and Gookin, 2005). T foetus has also been isolated from the uterus of a cat with pyometra (residing in a household with other cats that had T foetus-associated colitis), which raises the possibility that this organism may also cause reproductive tract disease in cats (Dahlgren et al, 2007). Evidence is emerging that pathogenic differences exist between bovine and feline isolates of T foetus (Stockdale et al, 2007 and 2008), suggesting that different strains of the organism may be species adapted. Infection and epidemiology Infection is most commonly seen in colonies of cats and multicat households. In these situations, the organism is presumably spread between cats by close and direct contact (experimentally, infection is readily established via oral infection). It is assumed that in multicat households, the sharing of litter trays readily leads to faecal-oral infection of susceptible cats. There has been no evidence of spread from other species, or spread via food or water, but the occasional identification of T foetus in dogs with diarrhoea (Gookin et al, 2005) at least raises the possibility of organism transfer between dogs and cats. The organism is fragile in the environment, generally surviving no more than one to two hours, although it can survive for several days in moist faeces. In one study from the USA (Gookin et al, 2004), which was undertaken at a cat show, 117 cats of various ages were evaluated from 89 different catteries. This study found that 31 per cent of the cats were infected with T foetus and, similarly, 31 per cent of the catteries represented had at least one infected cat. Faecal samples were e x ami n e d for the presence of T foetus by direct microscopy, culture and PCR. Of these techniques, PCR was found to be much more sensitive 2 / 14

3 (identifying 34/36 positive samples), compared with culture (20/36) and direct smear (five/36). This study also evaluated the cats for the presence of Giardia infection and found 31 per cent to be infected (by faecal ELISA), and 12 per cent of the cats were co-infected with both organisms. This study also evaluated risk factors for infection with T foetus and found a history of diarrhoea in the cattery within the previous six months. A high housing density was also significantly associated with infection. In a UK study (Gunn-Moore et al, 2007), faecal samples from 111 cats with diarrhoea submitted to a commercial diagnostic laboratory for analysis were also examined for the presence of T foetus by PCR. Although these were not samples selected from cats with just large bowel diarrhoea, 16 (14 per cent) were found to be T foetus-positive. In this study, young cats (less than a year of age) and pedigree cats were found to be significantly more likely to be infected with T foetus. In a similar study, T foetus was identified (by PCR) in six (19 per cent) out of 31 faecal samples from diarrhoeic cats in Germany and Austria (Steiner et al, 2007). In a study from France, eight out of 43 diarrhoeic cats (19 per cent) from breeding catteries were found to be T foetus-positive by a culture technique (Brigui et al, 2007). Together, these studies suggest that T foetus infection is common in cats in both the USA and Europe, and, presumably, elsewhere also. Infection is associated with clinical disease (diarrhoea) and is common in young cats from multicat households with a high population density. Clinical signs Studies have shown that this parasite mainly causes colitis (large bowel diarrhoea) with increased frequency of defecation, semi-formed to liquid faeces, sometimes with fresh blood or mucus in the faeces. With severe diarrhoea, the anus may become inflamed and painful, and the cat may become faecally incontinent. Although cats of all ages can be affected, T foetus-associated diarrhoea is most commonly seen in young cats and kittens; the majority are less than 12 months of age. Colonic biopsies from affected cats typically show mild to severe inflammatory changes, predominant l y with infiltration of lymphocytes and plasma cells a pattern commonly seen with other infectious agents and with inflamma tor y bowel disease. Although the diarrhoea may be persistent and severe, most affected cats are otherwise well, and do not show significant weight loss. In experimental infections of naïve cats, prolonged (more than 200 days) productive infection has been observed (Gookin et al, 2001), but with clinical signs of diarrhoea being shorter lived, and exacerbated by co-infection with Cryptosporidium. In one study from the USA, of 32 cats with naturally occurring trichomoniasis (Gookin et al, 1999), the median age of affected cats was nine months, and 23 (72 per cent) were less than 12 months of age. The duration of the diarrhoea 3 / 14

4 ranged from two days to three years. In another retrospective study, of 26 naturally infected cats (Foster et al, 2004), 23 had resolution of their diarrhoea after a median of nine months duration, but infection was shown to persist in many for three years or more after clinical signs of diarrhoea resolved. In general, T foetus infection appears more prevalent in young cats, and is clearly able to establish a prolonged infection. Clinical signs of large bowel diarrhoea may vary from relatively mild to very severe and, while the signs may be of limited duration in some cats, in many they will persist for months, perhaps years. Clinical signs of diarrhoea resolve long before the organism is completely eliminated from the intestinal tract and, therefore, the organism can be found in both normal and diarrhoeic cats. Clinical signs may wax and wane in affected cats, and there is evidence that antibiotic therapy may temporarily improve faecal consistency in at least some (together with reduced shedding of the organism), suggesting that there may be interplay between T foetus infection and the colonic bacterial flora. Diagnosis Diagnosis of T foetus infection is usually quite straightforward. There are three routine methods: direct microscopy, culture of the organism and PCR analysis of faeces. The availability of a specific PCR test for the diagnosis of T foetus infection provides a sensitive and specific diagnostic assay that is not dependent on the presence of live organisms for a positive result. The test can, therefore, be performed at a reference laboratory with faecal samples submitted via post. A number of commercial and university laboratories are now offering PCR diagnosis of this organism. However, because of the sensitivity of PCR as a diagnostic tool, this test may detect very low levels of the organism (or its DNA) in faeces, and the results of this test do not necessarily correlate well with the presence of clinical disease. The organism can also be cultured from faecal samples using a system developed for diagnosis in cattle. The In Pouch TF-Feline test uses a liquid culture system in a sterile plastic pouch. The pouch can be inoculated with 0.03g of faeces (less than half the size of a small pea), obtained within one to two hours from a voided sample or via a faecal loop or swab ( Figure 1 ). A swab can be rolled over the rectal mucosa for this purpose, as the organism is present on the mucosal lining. The pouches are easy and economical to use, have a 12- month shelf life and are reported to be able to detect as little as one organism in the original inoculate. The pouches are ideally incubated at 37 C for between 18 and 24 hours and then at room temperature. They can be examined microscopically (via an in-built viewing chamber) for the motile organisms every two days for 12 days. This test is considerably more sensitive than direct examination of faeces, and helpful for detecting infections where direct smears are negative. Giardia and other similar organisms will not 4 / 14

5 grow in this culture medium, and the culture system can be used as an in clinic test. T foetus exists in the intestine as small, motile trophozoites, primarily on the mucosal surface, and these can be detected by direct microscopy. For optimum results, fresh faeces should be examined, and if any mucus has been passed with the faeces, this is the most likely place to find the organisms. Smears of faeces and/or mucus, diluted with a few drops of saline, can be made on a microscope slide. A cover slip can be pressed over the smear and then the wet preparation can be examined under x200 and x400 magnification. In many clinically affected cats, large numbers of the small motile organisms can be seen they appear a bit like microscopic tadpoles with very short tails, and have an undulating membrane that runs over the length of the body ( Figures 2 and 3 ). Their movement is described as jerky, forward motion, and they are typically 10ìm to 15ìm in length. Examination of multiple smears and multiple faecal samples will improve the detection of the organism. If fresh mucus from a voided faecal sample is not available, rather than a routine faecal smear, greater sensitivity in detection of the organism may be achieved from a rectal swab or sample of mucus obtained by rectal loop. A cotton swab moistened with sterile saline can be inserted into the rectum and rotated over the colonic mucosa this is then withdrawn and a smear made on a microscope slide, which is again mixed with one or two drops of saline and examined as described. The organism needs to be distinguished from Giardia, another protozoan parasite. With Giardia infections, the trophozoites tend to be far fewer in number and binucleate with a concave ventral sucker, and do not exhibit the same forward motion as T foetus. Additionally, unlike Giardia, T foetus does not have the ability to form cysts. If a cat has received antibiotic therapy, this can suppress the number of T foetus trophozoites shed, and can make the diagnosis more difficult. In such cases, more sensitive diagnostic techniques may be preferable. Although direct microscopy is the least sensitive of the diagnostic techniques, it is the most simple to perform. Clinical disease is generally associated with the presence of greater numbers of the organism, which improves the probability of detection via microscopy. Conversely, sub-clinical infections will be much harder to detect. None of the diagnostic tests are 100 per cent sensitive and repeat sampling may be required in some cases, together with using a very sensitive technique, such as PCR, to identify the presence of the organism. Treatment The use of a variety of different antimicrobial drugs has been reported to improve faecal consistency during therapy of infected cats, probably in part because trichomonads derive nutrients from the resident bacterial flora. Shedding of T foetus may reduce during bacterial therapy, but such antibiotic use is not recommended as it may ultimately prolong the shedding of the organism, 5 / 14

6 and does not resolve the underlying problem. The organism appears resistant to many traditionally used anti-protozoal drugs, such as fenbendazole and paromomycin. Even metronidazole appears ineffective in cats with T foetus infection, although there is uncertainty whether this relates to resistance of the organism or drug metabolism, rendering it ineffective in vivo (Gookin et al, 2006; Kather et al, 2007). Nevertheless, a related nitroimidazole ronidazole has been established to have good in-vitro and in-vivo efficacy in cats. Although ronidazole is not licensed for use in cats, in one study (Gookin et al, 2006) dosages of 10mg/kg daily for 10 days were effective in resolving diarrhoea and eliminating shedding of the organism, although recrudescence of shedding and further diarrhoea was observed after more than 80 days. Similar results were obtained following infection and treatment of SPFderived cats, but higher doses (30mg/kg to 50mg/kg twice daily for 14 days) were needed to eradicate the organism. However, neurotoxicity has been observed in cats treated with ronidazole (Rosado et al, 2007) and manifested as lethargy, inappetence, ataxia or seizures, although these signs may resolve over one to two weeks if therapy is stopped immediately. As the adverse events are likely to be dose-related, it is questionable whether the high doses of ronidazole required to eliminate infection are justified. It may be more appropriate to use a low dose (10mg/kg daily for 10 days) to treat clinical disease and reduce shedding of the organism, bearing in mind that this is unlikely to completely eliminate the organism. When used in this way, recrudescence and repeat therapy may be required, and elimination of the organism from a cattery may be difficult to achieve. Care should also be exercised in the use of ronidazole, as human toxicity concerns has led to its use in food-producing animals being banned in many countries. Careful handling of the drug is advised and, ideally, a compounding pharmacist should be used to formulate treatments for cats. As the diarrhoea does resolve over time, and is more of an inconvenience, rather than being associated with significant adverse effects in affected cats, it may not be necessary or advisable to treat all affected cats with ronidazole. Using a simple, highly digestible diet frequently results in improved faecal consistency, and this alone may allow sufficient control of clinical signs in some. Tinidazole is another nitroimidazole that shows in-vitro efficacy against T foetus, although not as good as ronidazole (Gookin et al, 2006). This drug is more widely available than ronidazole and is a licensed human antimicrobial in many countries. In one in-vivo study (Gookin et al, 2007b), tinidazole at 30mg/kg daily for 14 days was partially successful in eliminating T foetus (in two out of four infected cats) and dramatically reduced shedding of the organism in the others. Further studies are warranted with this treatment, but given that it has a much better safety profile than ronidazole, and that the doses of ronidazole required to eliminate infection carry significant toxicity risks, 6 / 14

7 tinidazole may prove to be an attractive alternative if it is able to resolve diarrhoea in clinically affected cats. Prognosis Current information suggests the long-term prognosis for infected cats is good, and that they will eventually overcome the infection. However, this is a slow process diarrhoea may persist for months or even years, and it appears that most infected cats continue to shed low levels of the organism in their faeces for many months or years after the resolution of the diarrhoea, and potentially even for the remainder of their life in some cases. References Dahlgren S S et al (2007). First record of natural T foetus infection of the feline uterus, JSAP 48: Foster D M et al (2004). Outcome of cats with diarrhoea and T foetus infection, JAVMA 225: Gookin J L et al (1999). Diarrhoea associated with trichomoniasis in cats, JAVMA 215: 1,450-1,454. Gookin J L et al (2001). Experimental infection of cats with T foetus, AJVR 62: 1,690-1,697. Gookin J L et al (2004). Prevalence and risk factors for feline T foetus and Giardia infection, Journal of Comparative Microbiology 42: 2,707-2,710. Gookin J L et al (2005). Molecular characterization of trichomonads from faeces of dogs with diarrhoea, Journal of Parasitology 91: Gookin J L et al (2006). Efficacy of ronidazole for treatment of feline T foetus infection, JVIM 20: Gookin J L et al (2007a). Identification of P hominis in feline faecal samples by polymerase chain reaction, Veterinary Parasitology 145: Gookin J L et al (2007b). Efficacy of tinidazole for treatment of cats experimentally infected with T foetus, AJVR 68: 1,085-1,088. Grahn R A et al (2005). An improved molecular assay for T foetus, Veterinary Parasitology 127: Gunn-Moore D A et al (2007). Prevalence of T foetus infection in cats with diarrhoea in the UK, Journal of Feline Medicine and Surgery 9: Jayawardhana G (2002). Trichomoniasis in the Northern Territory, Agnote K42, September 2002, Agdex 401/40, Northern Territory Government, Australia. Kather E J et al (2007). Determination of the in vitro susceptibility of feline T foetus to five antimicrobial agents, JVIM 21: Levy M G et al (2003). T foetus and not P hominis is the aetiologic agent of feline trichomonal diarrhoea, Journal of Parasitology 89: Lun Z-R, et al (2005). Are T foetus and T suis synonyms? Trends in Parasitology 21: / 14

8 Mardell E J and Sparkes A H (2006). Chronic diarrhoea associated with T foetus infection in a British cat, Vet Rec 158: Nora B, Henaff M and Polack B (2007). Prevalence of Tritrichomonas foetus Infection in Cats in France, World Association for the Advancement of Veterinary Parasitology Conference 2007, Ghent. Romatowski J (2000). P hominis infection in four kittens, JAVMA 216: 1,270-1,272. Rosado T W et al (2007). Neurotoxicosis in four cats receiving ronidazole, JVIM 21: Steiner J et al (2007). Identification of T foetus DNA in faeces from cats with diarrhoea from Germany and Austria, Proceedings of the American College of Veterinary Internal Medicine Annual Forum 2007, abstract 281. Stockdale H et al (2007). Experimental infection of cattle with a feline isolate of T foetus, Journal of Parasitology 93: 1,429-1,434. Stockdale H D et al (2008). Experimental infection of cats (Felis catus) with T foetus isolated from cattle, Veterinary Parasitology 154: Yaeger M J and Gookin J L (2005). Histological features associated with T foetus-associated colitis in domestic cats, Veterinary Pathology 42: / 14

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10 Figure 1. Rectal smears can be made using cotton swabs rolled over the rectal wall. Smears can be made on glass slides, and material obtained should be diluted with saline to prevent desiccat 10 / 14

11 Figure 2. Typical appearance of a large number of T foetus organisms in a faecal smear under x400 magnification. When examined, the organisms can be seen to be highly motile. 11 / 14

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14 Powered by TCPDF ( Figure 3. Appearance of an individual T foetus organism stained with Lugol s iodine. Three anterior flagellae can be seen, and an undulating membrane runs the length of the body. 14 / 14