Zoonoses are
defined by the World Health Organisation[8] as 'diseases and
infections which are transmitted naturally between
vertebrate animals and man'. They can be transmitted
directly by contact with an animal (e.g., rabies, through a
bite), via a contaminated environment (e.g., anthrax) and
via food (e.g., campylobacteriosis) or indirectly via
vectors, such as mosquitoes or ticks (e.g., West Nile fever
and Lyme disease, respectively). The organisms causing
zoonoses include viruses, bacteria, fungi, protozoa and
other parasites, with both domestic and wild animals acting
as reservoirs for these pathogens. The diseases they cause
in humans range from mild and self-limiting (e.g. most cases
of toxoplasmosis) to fatal (e.g. Ebola haemorrhagic fever).
In the United Kingdom, food is thought to be the most common
source of zoonotic diseases[3].
The
importance of zoonotic diseases is well demonstrated by a
survey of infectious organisms which showed that, of the
1415 species known to be pathogenic to humans, 61% (868) are
zoonotic, while 75% of diseases considered to be 'emerging'
are also zoonotic[7]. It is perhaps worth noting that many
of the zoonotic agents causing disease in humans cause
little or no obvious clinical disease in their animal hosts.
As
population numbers continue to increase and new areas are
opened up for food production, both humans and their
domestic animals are more frequently exposed to diseases as
a result of encounters with "wild" animals, thus increasing
human exposure to once rare zoonotic infections. Increased
urbanisation allows faster spreading of any new disease
between populations within an area, while air travel enables
a disease to be spread worldwide within a comparatively
short space of time. The ever-increasing trade in animals
and animal products has also contributed to the spread of
zoonotic diseases[6].
Pathogens that can be transmitted between different host
species are of fundamental interest and importance from
conservation, public health and economic perspectives[2].
The recent outbreak of bovine spongiform encephalopathy (BSE)
in cattle and the consequent new variant Creutzfeldt-Jakob
disease (nvCJD) in humans well illustrates this point.
Success in the prevention and control of major zoonoses
depends on the capability to mobilise resources in different
sectors and on coordination and intersectoral approaches,
especially between national (or international) veterinary
and public health services[1]. However, a study in
Wisconsin[4] indicated not only that physicians and
veterinarians held very different views about the disease
risks from certain animals and infections agents, but also
that they communicated very little to each other about
zoonotic diseases and their prevention.
The formation of the North West Zoonoses
Group is in recognition of the importance of zoonotic
diseases and the need for extensive communication and
cooperation between human and animal health workers. The
effective surveillance, control and prevention of zoonotic
diseases is a significant challenge[5] and it is intended
that the activities of the North West Zoonoses Group will go
some way towards meeting that challenge.
[2] Cleaveland S, Laurenson MK and Taylor LH. (2001)
Diseases of humans and their domestic mammals: pathogen
characteristics, host range and the risk of emergence.
Philosophical Transactions of the Royal Society of London.
B: Biological Sciences 29; 356(1411): 991-9.
[4] Grant S
and Olsen CW (1999). Preventing zoonotic diseases in
immunocompromised persons: the role of physicians and
veterinarians. Emerging Infectious Diseases 5 (1): 159-163.
http://www.cdc.gov/ncidod/EID/vol5no1/grant.htm
[7] Taylor LH,
Latham SM and Woolhouse ME (2001). Risk factors for human
disease emergence. Philosophical Transactions of the Royal
Society of London. B: Biological Sciences 29; 356(1411):
983-9.
[8]
World Health Organisation (1959). Zoonoses: Second report of
the joint WHO/FAO Expert Committee.
