Cattle: will rising numbers mean more disease?

Flickr\ILRI

[NEW DELHI] Livestock intensification in developing countries, especially in Africa and Asia, may increase the incidence of epidemics that kill both humans and animals, the Vision 2020: Leveraging Agriculture for Improving Nutrition and Health conference, was told today.

Livestock numbers are rising sharply due to both population growth — small-scale farmers depend on livestock for their livelihoods — and the rise in affluence, leading to increased demand for milk, meat and eggs.

"The increase in density leads to increased contact between humans and animals —leading to transmission of pathogens," John McDermott, deputy director general for research at the International Livestock Research Institute (ILRI), told SciDev.Net.

Over 60 per cent of human pathogens, and three-quarters of new human pathogens, are transmitted by animals, said McDermott and his co-author, Delia Grace, a veterinary and food safety researcher at the institute.

"Livestock," said McDermott, "is one of the biggest tools for poverty reduction but while the developed world has the capacity to deal with disease related to livestock-rearing, the cost makes this impossible for poor countries."

He said that livestock diseases are a double health problem since there is also the risk that human nutrition will be compromised if livestock die.

Rapid urbanisation may worsen the situation, he warned, if diseases move with humans, from rural areas to cities. Climate change, too, will force farmers to look for new grounds such as forests where they may interact with wildlife that carries pathogens.

Agricultural intensification in the developing world is typically focused on increasing food production and profitability, while the potential effects on human health remain largely ignored, they told the meeting (10−12 February).

Large-scale irrigation can also intensify the effect of disease, for example such as creating conditions to help the Rift Valley fever virus take hold in new regions, where occasional outbreaks kill hundreds of people and thousands of animals.

Per Pinstrup-Anderson, professor of food, nutrition and public policy at Cornell University, in the United States, said: "Contact between animal and human beings is the key issue here. Farmers need to be taught how to keep animals away from their living quarters".

McDermott said that countries should invest in disease surveillance and that this should include a participatory approach involving livestock-keepers because of their observational knowledge of disease.