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About zoonoses
Zoonoses 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 many countries, food is the most common source of zoonotic diseases. 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.
Exposure
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.
Pathogens
Pathogens that can be transmitted between different host species are of fundamental interest and importance from conservation, public health and economic perspectives. The outbreak of bovine spongiform encephalopathy (BSE) in cattle in the UK 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.
However, a study in Wisconsin 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.
