by
Dr. David Obendorf, BVSc (Hons), B(An)Sc, PhD (Melbourne) Chairperson,
Wildlife Advisory Committee, Australian Member of the Scientific
Advisory Board to the International Animal Health Body, (OIE)
Paris (Office des Internationale Epizootes), Wildlife Pathologist
with over 20 years experience in the parasites & diseases
of Australian native fauna.
Kangaroos
and wallabies can harbour a wide range of parasitic, bacterial,
fungal and viral diseases and the majority of infections are
unapparent (i.e. animals appear normal). Even meat inspection
procedures are unlikely to detect some infections unless gross
lesions are detected or routine samples are taken for microbiological
and pathological testing.
Worldwide,
it is recognised that so-called ‘game meats’ are a source of
these infections for hunters, processors and consumers, especially
when care is not taken while eviscerating and handling the carcasses
or when the meat from these animals is served undercooked or
raw. Trichinosis, cysticercosis and toxoplasmosis are examples
of parasitic zoonoses (i.e. diseases transmissible from animals
to humans).
In
Australia, Toxoplasmosis and the bacterial disease, Salmonellosis
are two infections with public health significance directly
related to the handling, processing and consumption of kangaroo
meat. The October issue of Womans’ Day (1995) reported that
a food-borne outbreak of toxoplasmosis caused acute clinical
illnesses in 12 humans and one case of congenital chorio-retinitis
(inflammation of the eye tissues) in a new born baby. The mother
of the affected baby together with the 12 other people had attended
a Christmas function at which rare kangaroo medallions were
served. A thorough epidemiological investigation concluded that
the most likely ‘risk food’ was the kangaroo meat.
Even
‘new’ human diseases have been shown to have origins in Australian
game meat. In 1993 the first confirmed human case of Pseudotrichinosis
was diagnosed. The medical investigators concluded that the
patient became infected in Tasmania through eating meat, most
probably derived from a wild animal. Subsequent research conducted
at the University of Tasmania showed that about 2% of Tasmanians
surveyed had antibodies to this muscle-encysting nematode.
Professor
John Goldsmid, Lecturer in Microbiology at the University of
Tasmania expressed his scientific concerns about the lack of
research into a range of diseases and parasites transmissible
between Tasmanian native animals and humans.
Australia
has no dedicated research or diagnostic facility to investigate
wildlife diseases. Detections of new diseases are handled on
an ad hoc basis by government or university laboratories.
Possums
trapped overnight in wire cages (comparable to that described
in the brush possum code) show that cage distress and attempts
to escape causes muscle damage comparable to capture-stress
myopathy of deer.
Tasmania
is the only State of Australia listed by the WHO as having endemic
trichinosis in its wildlife. The Tasmanian Department responsible
for permitting a game meat industry denied there was a public
health risk associated with the harvesting and processing of
Tasmanian possum. Tasmanian wildlife harbour parasitic diseases
which are serious infections in humans.
A
recent scientific report of the International Health Organisation,
the Office Internationale des Epizootes warns that wild animal
meats which are raw, undercooked, dried or cold-smoked are potentially
infectious to animal or humans that consume them.
The
incidence of Toxoplasma abortions and infertility is amongst
the highest in Australia. Free ranging wallabies, pademelons,
bandicoots and wombats are regularly killed by this infection
and surveys show a high percentage of wallabies harbour this
infection.
The
concern is that chefs and food raconteurs recommend cooking
methods which would not kill this parasite.
A
newly identified worm thought to be derived from marsupials
was found to be responsible for acute illness in two humans.
Like Trichinella they invade muscles. The worms are thought
to belong to a class of nematodes known as Muscpiceoids. In
wallabies and possums these nematodes live in several tissues
of the body and can invade muscles.
In
his paper to the University of Tasmania (1997 114 ), Professor
John Goldsmid said, "Kliks (1983) identified the aetiological
agents of human infectious diseases as "heirloom"
or "souvenir" species, depending on their evolutionary
association with humans. Amongst the most important of the souvenir
species are the zoonotic infections, infecting humans as a result
of animal-human contact of some kind and varying from companionable
contact to utilisation of animals as a food source.
In
the last 25 or so years, of 35 new or newly recognised infections
in humans, 20 (57%) have been zoonotic in origin - some trivial,
some devastating to both the individual and the community.
With
the increase in the numbers of immunocompromised people in the
community resulting from medical treatment or as a result of
the spread of AIDS, the problem of zoonotic infections will
continue and there seems little doubt that the likely source
for many of these new human infections in Australia will be
the native animal population.
People
who eat undercooked wallaby or kangaroo meat could be at risk
of infection by a newly-discovered animal parasite, Australian
doctors have warned.
The
parasite was found in a Tasmanian man who suffered from inexplicable
and severe muscle weakness over a number of years. He was known
to consume large quantities of game. ("Parasite Risk to
Game Eaters" November 7, 1997 Animal Pharmacology No. 384)
Laboratory
tests suggests that the parasite is a new species of microscopic
worm. It may also have been responsible for a similar infection
in a New Zealand woman who had eaten wallaby meat while visiting
Tasmania.
"The
cases highlight the risks of eating wild game, the
parasites of which are poorly understood compared with
those of livestock.
More
studies are needed to identify disease agents in
these animals and to elucidate the role of native animal
species in the transmission of diseases
to humans."
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