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Cats and avian flu
Cats
have been identified as one of the species which can become infected with
the H5N1 avian flu virus. Natural infection almost certainly occurs when
cats eat infected birds, and fatal infections in cats have been recorded
in Germany and Austria. In laboratory studies cats have been infected
experimentally and have transmitted the virus to other cats with which
they were in contact. Recent research, the results of which have
yet to be confirmed, indicates that in parts of south-east Asia, where
poultry have been infected with the virus, up to 20 per cent of cats have
antibodies, suggesting that many more cats become infected than become
ill. This raises the concern that cats might be a vehicle in which
the virus can become more addapted to mammals, and therefore spread readily
to man. However, there has been no evidence to date that cats have
been responsible for transmitting the virus to humans.
The simple and most effective way of avoiding cats being infected is to
keep them indoors, especially if they are known to wander and are in an
area where infected birds are known to be present. When cases of H5N!
infection occur in poultry in the UK, owners within the 3 km protection
zone should consider keeping their cats indoors as recommended by DEFRA:
'As
a precautionary approach we recommend that if you live within 3km of
a premises where avian influenza is confirmed (the protection zone)
pet owners should aim to keep their cats indoors and exercise their
dogs on a lead. This is for the protection of your animals and is not
for public health purposes. In all other areas you should continue as
normal and your pets are not at risk.'
Click
here for DEFRA's advice on avian flu and cats
Similarly,
a recent report form the European Commission Standing Committee
on the Food Chain and Animal Health says:
'Current knowledge indicates
that no H5N1 infection has ever occurred in humans due to animals other
than domestic poultry. Current knowledge suggests that the disease in
carnivores such as cats is a “cul de sac” of the infection that has
not lead to an increase in the risk posed by this virus for animal or
public health.
In areas where H5N1
has been confirmed in wild birds:
- sick or dead cats and dogs that may have had contacts with infected
birds or their carcasses should undergo veterinary inspection or post-mortem
examination. When felt necessary by the veterinarian and in accordance
with the instructions given by the veterinary authorities, further
testing should be carried out;
- contacts between domestic carnivores, particularly cats, and wild
birds should be prevented, i.e. cats should be kept indoors and dogs
should be kept on a leash or otherwise restrained, and kept under
control by the owner;
- where stray cats or dogs are found dead they should not be touched
and the veterinary authorities should be informed, so that post-mortem
examination and further testing can be performed'
The
Cat Group urges pet owners not to panic and abandon or rehome their cats
because of fears of infection with bird flu.
Background
information
This
highly pathogenic virus first appeared in chickens in Hong
Kong in 1997 and spread to people,
with six deaths being
recorded. In 2003 there were two further human deaths associated
with infection by the same subtype
of virus in southern China.
Throughout 2004, H5N1 viruses spread throughout Southeast
Asia resulting in the deaths,
or slaughter of millions of chickens and over 30 people. To date,
167 human cases have been reported. The human infections were
acquired directly from infected birds and fortunately the virus
does not appear to spread between people.
However,
a major threat from this new virus is that suddenly it might change
and cause epidemics in people. This might occur if the virus mutated
in chickens or recombined with existing human influenza viruses already in people or pigs, to
produce novel viruses that could then spread readily from person
to person, causing widespread
disease. The World Health Organisation is closely monitoring the
situation for the appearance
of any such variant viruses in people.
Other
concerns are that the H5N1 virus has been found
to cause fatal disease in domestic cats, as well as in tigers and
leopards in captivity, through the consumption
of infected poultry meat; and the virus can spread between cats.
Therefore there is a theoretical possibility that cats may be involved
in natural history of these viruses, serving as a vehicle for the
spread of the virus to other species, particularly man. Most authorities
consider this outcome to be unlikely since previously reported disease
in cats caused by avian influenza viruses have not been associated
with widespread infection, or fatalities in cats. The first recorded
natural, fatal infection of cats with an avian influenza virus was
in Korea in 1942, but the subtype of that virus is not known. Since then
there have been anecdotal accounts of natural feline infections
in Thailand in 2004 and the transmission of a current H5N1 isolate from chickens
to cats, and between cats, has been reported recently. It is considered
even more unlikely that cats could act as a ‘mixing vessel' to generate
recombinant influenza viruses, as might occur in people or pigs.
Therefore, the risk that cats might pose should be kept in perspective.
Kuiken
T, et al (2004) Avian H5N1 influenza in cats. Science 306 :241
Keawcharoen
J, et al (2004) Avian influenza H5N1 in tigers and
leopards. Emerging Infectious Diseases 10,
2189-2191 |
Question
& Answer
Question:
Can
cats bring avian flu into a household?
We
have two indoor-outdoor cats which occasionally catch rats or birds and,
of course, bring them into the house. It doesn't take much to imagine
one's cat catching and bringing into the house an infected, ill migratory
bird. How concerned should pet owners be? And what is a reasonable course
of action under such circumstances?
Answer:
The
advice from an eminent virologist and supported by DEFRA, the British
government department for the environment, food and rural affairs is:
The
facts are that cats are susceptible to the current H5N1 strains of
avian flu virus, as are garden birds. Consequently, there is a theoretical
risk that cats could introduce the virus into a household through predation,
and that people could be infected from the bird, or the cat. The risk
must be considered remote. However, in areas where bird flu has been identified
it is recommended that cats are kept indoors for their own protection.
Please
also see DEFRA's
guidance on the handling and disposing of dead garden and wild birds
The
following websites are also a useful source of information:
Advisory
Board on Cat Diseases (ABCD)
British
Veterinary Association (BVA)
Royal
Society for the Protection of Birds (RSPB)
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Tritrichomonas
foetus infection in cats
Dr Andy Sparkes BVetMed PhD
DipECVIM MRCVS
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
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 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). The evidence therefore suggests that infection 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. 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
Alternatively, from December 2005, the PCR test will also be available
in the UK from Capital Diagnostics in Edinburgh (0131 535 3145).
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 done much of the work on this infection in cats) identified that
ronidazole (an antibiotic derived from metronidazole) may have good efficacy
against T foetus infection in cats (JVIM, 2005;19;436). However,
ronidazole is not licensed for use in cats, and although it appears to
be relatively safe from limited studies*, it should be used with caution
and only with informed, signed, owner consent.
*A small number of cats have
developed neurological signs. Initial studies suggest a dose of 30-50mg/kg
once to twice daily for two weeks is capable of both resolving clinical
signs and potentially eradicating infection with T foetus. 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 and leave contact telephone number). 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) Diarrhea associated
with trichomoniasis in cats. Journal of the American Veterinary Medical
Association 215:1450-1454
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, 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, 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, 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, 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
Gookin J, Copple C, Papich M., Poore M, Levy M. Efficacy of ronidazole
in vitro and in vivo for treatment of feline Tritrichomonas foetus infection
(Abstract). Proceedings of the ACVIM, 2005, Abstract 131.
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
Gookin J, Copple C, Papich M, Poore M, Levy M (2005) Efficacy of ronidazole
in vitro and in vivo for treatment of feline Tritrichomonas foetus infection
(Abstract) . Journal of Veterinary Internal Medcine 19:436
November 2005
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.
Inherited
problems in cats
Detailed
information is published on the Feline Advisory Bureau website and
can be accessed via the link below:
http://www.fabcats.org/breeders/inherited_problems
|
