The Guardian has a good report today on the very important, but often neglected, connection between livestock in agriculture and human health.
Scientists call it zoonosis, but you can think of it as where HIV, cholera, avian flu, plague and many other (in fact, most) human diseases come from.
Though this natural evolutionary tendency for infectious bugs to move from infecting animals to humans (and vise versa) often happens in the wild, many experts think poor agricultural hygiene methods used in the developing world means it is happening with greater frequency on farms.
Says The Guardian:
A new human disease emerges around every four months, usually after jumping from animals. Many of these infections are minor and of interest only to microbiologists. But as intensive agricultural production expands and populations push into uninhabited areas, epidemics of devastating diseases, like Sars and HIV, which started out as animal pathogens, are likely to become more common.