| |

Dr
Andy Sparkes BVetMed PhD DipECVIM MRCVS, RCVS Specialist in
Feline Medicine
The Feline Unit, Animal Health Trust
Ellie
Mardell MA VetMB CertSAM MRCVS
The Feline Centre, University of Bristol
Kirsty
Wood BVSc MRCVS
The Feline Unit, Animal Health Trust
Dr
Danièlle Gunn-Moore
BSc,
BVM&S, PhD, MACVSc, MRCVS, RCVS Specialist in Feline Medicine
Head
of Feline Clinic, University of Edinburgh

Tritrichomonas
foetus is a microscopic single-celled flagellated protozoan
parasite that has traditionally been identified as a cause
of reproductive disease in cattle (infertility, abortion and
endometritis). This parasite has been found all over the world,
but the widespread use of artificial insemination in breeding
cattle has led to the virtual elimination of this organism
from the cattle population in many countries including the
UK and much of Europe.
Infection
in cats
There
have been a number of recent studies, mostly form the USA,
that have demonstrated that this parasite may be an important
cause of diarrhoea in cats. In cats, T foetus infects
and colonises the large intestine, and can cause prolonged
and intractable diarrhoea.
Studies
have shown that this parasite mainly causes colitis (large
bowel diarrhoea) with increased frequency of defecation, semi-formed
to liquid faeces, and sometimes fresh blood or mucus in the
faeces. With severe diarrhoea the anus may become inflamed
and painful, and in some cases the cats may develop faecal
incontinence. Although cats of all ages can be affected with
diarrhoea, it is most commonly seen in young cats and kittens,
the majority being under 12 months of age. Most of the affected
cats have come from rescue shelters and pedigree breeding
colonies. Abdominal ultrasound examination may show corrugation
of the large bowel and local lymphadenopathy. Colonic biopsies
from affected cats typically show mild to severe inflammatory
changes with predominantly infiltration of lymphocytes and
plasma cells – a pattern commonly seen with other infectious
agents and with inflammatory bowel disease. However, the parasites
may be seen in close association with the mucosa. Although
the diarrhoea may be persistent and severe, most affected
cats are otherwise well, and do not show significant weight
loss.
Infection
is most commonly seen in colonies of cats and multicat households,
where presumably the organism is spread between cats by close
and direct contact. There has been no evidence of spread from
other species, or spread via food or water. In one study,
31% of cats at a cat show in the USA were identified as being
infected with this organism, suggesting that this may be an
important, common, and previously unrecognised cause of diarrhoea
in cats.
Although
most information on T foetus infection has come
from studies of cats in the USA, we have now identified several
cases of infection in cats in England (mostly in young pedigree
cats, and all from multicat households generally with more
than one cat being affected ), and it has also been identified
in several cats in Scotland (and also in cats from Germany).
In the UK , 14-16% of faecal samples from cats with diarrhoea
are currently being found to be infected. The evidence therefore
suggests that T foetus is probably quite widespread
in cat populations, and infection is most likely where there
is a high density of cats sharing the same environment.
Diagnosis
Diagnosis
of T foetus infection is usually quite straightforward.
The organism exists in the intestine as small, motile trophozoites,
and these can be detected under the microscope. 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/mucus diluted with
some saline can be made on a microscope slide. A cover slip
can be pressed over the smear and then the slide can be examined
under x200 and x400 magnification. In most clinically affected
cats, large numbers of the small motile organisms can be seen
– they appear a little bit like microscopic tadpoles with
very short tails (!), and have an undulating membrane that
runs over the length of the body. Their movement is described
as ‘jerky, forward motion'. Examination of multiple smears
and multiple faecal samples will improve the detection of
the organism. Rectal swabs can also be examined for the organism
– a cotton swab can be inserted into the anus and rotated
over the colonic mucosa – this is then withdrawn and a smear
made on a microscope slide which is again diluted with saline
and examined as above. The organism needs to be distinguished
from Giardia , another protozoan
parasite, but with Giardia infection the trophozoites
tend to be far fewer in number, they are binucleate with a
concave ventral ‘sucker', and do not exhibit the same forward
motion as T foetus . If a cat has received recent
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.
Two
other diagnostic tests are available which are both more sensitive
and specific for this organism. Firstly, the organism can
be cultured from faecal samples using a system developed for
diagnosis in cattle. The ‘In Pouch tm TF' test (BioMed Diagnostics,
Oregon , USA ) uses a liquid culture system in a sterile plastic
pouch. The pouch can be inoculated with 0.05g of faeces (about
half the size of a small pea). The pouches are incubated at
room temperature and can be examined microscopically for the
motile organisms every two days for 12 days. This test is
more sensitive than direct examination of faeces and helpful
for detecting infections where direct smears are negative.
Giardia, and other similar organisms will not grow in this
specific culture medium. In the UK , this system is available
from Capital Diagnostics in Edinburgh (0131 535 3145).
The
other test that can be used is PCR (polymerase chain reaction)
– a sophisticated test that can detect the presence of the
genetic material of the organism. This is an extremely sensitive
test that is available in the UK from Capital Diagnostics
in Edinburgh (0131 535 3145). Alternatively, samples can be
submitted to the College of Veterinary Medicine , North Caroline
State University (USA) for this test – information on this
is available at: www.cvm.ncsu.edu/mbs/gookin_jody.htm.
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 – in one study of infected
cats, resolution of the diarrhoea took an average of 9 months,
with occasional cats having diarrhoea persisting for more
than two years, while in others it resolved after two months.
It appears that most infected cats continue to shed low levels
of the organism in their faeces for many months after the
resolution of the diarrhoea.
Treatment
Most
studies on treatment of T foetus infection in cats
have been unrewarding. The organism is resistant to most traditionally
used anti-protozoal drugs such as fenbendazole and metronidazole.
The use of a variety of different antimicrobial drugs has
been reported to improve faecal consistency during therapy
of infected cats, possibly because of interaction between
T foetus and the bacteria normally present in the
intestine. However, such antibiotic use is not recommended
as it may ultimately prolong the shedding of the organism,
and does not resolve the underlying problem.
A
recent study by Dr Jody Gookin at the North Carolina State
University (who has performed most of the work on this infection
in cats) identified that ronidazole (an antibiotic similar
but not the same as metronidazole) may have good efficacy
against T. foetus infection in cats (JVIM, 2006;20;536).
From limited studies its use appears to be relatively safe
in cats, although a small number of patients have developed
neurological signs e.g. twitching and seizures, which have
resolved on stopping the drug. (The neurological signs are
similar to those seen in some kittens, or cats with liver
disease, when they are given standard or high doses of metronidazole).
However, ronidazole is not licensed for use in cats; it should
only be used with caution and with informed, signed, owner
consent. Initial studies suggested that a dose of 30-50mg/kg
once to twice daily for two weeks is capable of both resolving
clinical signs and potentially eradicating the T. foetus.
However, keeping to the lower end of the dose is advisable
(30mg/kg), as is reducing it even further for young kittens,
or cats with hepatopathy; (10mg/kg once to twice daily for
two weeks). The bitterness of the powder means that it must
be placed in capsules prior to administration.
Ronidazole
is commonly used to treat trichomoniasis in birds (e.g. pigeons).
However, care should be exercised in the use of ronidazole,
as there are very few studies of its use in cats, and long-term
studies in other species have suggested some potential toxicity
concerns. (In many countries its use in food-producing animals
has been banned to minimise human exposure). Careful handling
of the drug is therefore advised; and vets should seek further
information before considering treatment ( Danielle.Gunn-Moore@ed.ac.uk
). As the diarrhoea does resolve over time, and is often
more of an inconvenience 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.
References
and further reading
Foster DM,
Gookin JL, Poore MF, Stebbins ME, Levy MG (2004) Outcome
of cats with diarrhoea and Tritrichomonas foetus
infection. Journal of the American Veterinary
Medical Association 225:888-892
Gookin JL,
Breitschwerdt EB, Levy MG, Gager RB (1999) Diarrhoea
associated with trichomoniasis in cats. Journal
of the American Veterinary Medical Association 215
:1450-1454
Gookin JL,
Birkenheuer AJ, Breitschwerdt EB, Levy MG (2002) Single-tube
nested PCR for detection of Tritrichomonas foetus
in feline faeces. Journal of Clinical Microbiology
40:4126-4130
Gookin JL,
Copple CN, Papich MG, Poore MW, Stauffer SH, Birkenheuer
AJ, Twedt DC, Levy M (2006) Efficacy of ronidazole for
treatment of feline Tritrichomonas foetus
infection. Journal of Veterinary Internal Medicine
20:536-543
Gookin JL,
Copple CN, Papich MG, Poore MW, Stauffer SH, Birkenheuer
AJ, Twedt DC, Levy M. Efficacy of ronidazole for treatment
of feline Tritrichomonas foetus infection.
JVIM, 2006 20:536-543
Gookin JL,
Foster DM, Poore MF, Stebbins ME, Levy MG (2003b) Use
of a commercially available culture system for diagnosis
of Tritrichomonas foetus infection in cats.
Journal of the American Veterinary Medical Association
222:1376-1379
Gookin JL,
Levy MG, Law JM, Papich MG, Poore MF, Breitschwerdt
EB (2001) Experimental infection of cats with Tritrichomonas
foetus. American Journal of Veterinary Research
62:1690-1697
Gookin JL,
Stebbins ME, Adams E, Burlone K, Fulton M, Hochel R,
Talaat M, Poore M, Levy MG (2003a) Prevalence and risk
of T foetus infection in cattery cats (Abstract).
Journal of Veterinary Internal Medicine 17:380
Gookin JL,
Stebbins ME, Hunt E, Bulone K, Fulton M, Hochel R, Talaat
M, Poore M, Levy MG (2004) Prevalence and risk factors
for feline Tritrichomonas foetus and Giardia
infection. Journal of Clinical Microbiology
42:2707-2710
Levy MG, Gookin
JL, Poore M, Birkenheuer AJ, Dykstra MJ, Litaker RW
(2003) Tritrichomonas foetus and not Pentatrichomonas
hominis is the etiologic agent of feline trichomonal
diarrhoea. Journal of Parasitology 89:99-104
Mardell EJ,
Sparkes AH. Chronic diarrhoea associated with Tritrichomanas
foetus infection in a British cat. Veterinary
Record (In press)
Romatowski
J (2000) Pentatrichomonas hominis infection
in four kittens. Journal of the American Veterinary
Medical Association 216:1270-1272
Updated November 2006
 |
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 desiccation.
|
 |
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.
|
 |
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.
|
|