Zoonoses

Zoonoses are diseases that are transferable between animals and humans. Examples include:

• Subtypes of the influenza virus such as H5N1 bird flu and H1N1 swine flu
• Campylobacter and salmonella, which cause food poisoning
• Transferable spongiform encephalopathies (variant Creuzfeldt-Jakob Disease (vCJD) in humans is acquired from cattle with Bovine Spongiform Encaphalopathy (BSE)).

Many zoonoses are associated with farmed animals. However, they may also occur in pets or wild animals. People do not necessarily catch diseases from animals by eating their meat - different diseases are transferred in different ways. Nor is the transfer one-way - people can spread diseases among animals.

Ethical argument

Sometimes, as with early concerns linking vCJD to BSE, scientific controversy surrounds the relationship between animal and human diseases. In these instances, the challenge is to make fair and sound decisions in the context of uncertainty.

Perhaps the greatest controversy, however, surrounds the relationship between farming systems and zoonotic diseases. Debate has been especially heated over bird flu and swine flu. Animal welfare groups say that the H1N1 virus originated in large-scale confined production systems, and that such systems have played a central role in the spread of H5N1. The industry and government responses have focused on the role of people in spreading H1N1, and wild birds and 'backyard' poultry farms in spreading H5N1.