Smallholder pig production in northern Viet Nam

Farmer Ma Thi Puong feeds her pigs on her farm near the northern town of Meo Vac, Vietnam. Intensification of livestock farming has been found to increase the risk of zoonotic disease transmission (photo credit: ILRI/Stevie Mann).

Modern farming practices, such as intensified livestock production, as well as environmental and biodiversity changes can be linked to the new wave of zoonotic diseases, according to a new study published in the 21 May 2013 edition of the Proceedings of the National Academy of Sciences (PNAS).

Human population growth and the expansion of agriculture to meet the ever-rising demand for food have been identified as the key drivers of recent outbreaks of emerging and re-emerging zoonotic diseases.

These human behavioural changes have led to encroachment of wildlife habitats, resulting in greater interactions between people, livestock and wildlife and increased chances of spillover of potential pathogens from wildlife to livestock and, consequently, people.

“Intensive livestock farming, especially of pigs and poultry, increases the risk of disease transmission due to increased population size and density,” the study reveals.

Environmental changes arising from settlement and agriculture, including land fragmentation, deforestation and replacement of natural vegetation with crops, alter the structure of wildlife population, giving rise to new environmental conditions that favour specific hosts, vectors and pathogens.

The study was carried out in form of a systematic review by a multidisciplinary team of researchers from the International Livestock Research Institute (ILRI) and the Royal Veterinary College, University of London.

The research team sought to analyze qualitatively scientific evidence on the effect of agricultural intensification and environmental change on the risk of zoonoses transmission at the interface of humans, livestock and wildlife.

While the study has identified a clear link between the threat of zoonotic disease and the wildlife-livestock interface, it does not adequately address the complex interactions between the environmental, social and biological drivers of pathogen emergence.

For this reason, there is need to carry out local interdisciplinary studies that can come up with locally relevant solutions to tackle the threat of emerging and re-emerging zoonoses, the authors conclude.

Delia Grace, veterinary epidemiologist and food safety expert at ILRI, is among the co-authors of the study. Grace also leads the agriculture-associated diseases theme of the CGIAR Research Program on Agriculture for Nutrition and Health.

Read the full-text article

Citation: Jones BA, Grace D, Kock R, Alonso S, Rushton J, Said MY, McKeever D, Mutua F, Young J, McDermott J and Pfeiffer DU. 2013. Zoonosis emergence linked to agricultural intensification and environmental change. Proceedings of the National Academy of Sciences of the United States of America (PNAS) 110(21): 8399-8404.