WASHINGTON, DC—A team of researchers from the Center for Disease Dynamics, Economics and Policy, Princeton University, the International Livestock Research Institute and the Université Libre de Bruxelles has conducted for the first time a broad assessment of antibiotic consumption in livestock around the world and predicts a startling increase in use in the next 15 years.
Global demand for animal protein is rising dramatically, and antimicrobials are used routinely in modern animal production for disease prevention and as growth promoters. In the United States antibiotic consumption in animals represents up to 80% of total antimicrobial sales.
Numerous studies have suggested links between the use of antimicrobials and antibiotic-resistant bacteria originating from livestock as well as their potential consequences for human health. Until now, however, there has been no quantitative measurement of global antimicrobial consumption by livestock—a critical component in assessing the potential consequences of widespread animal antibiotic use.
The study, “Global trends in antimicrobial use in food animals,” published today in the journal Proceedings of the National Academy of Sciences, found that worldwide antimicrobial consumption is expected to rise by a staggering 67% percent between 2010 and 2030.
Five countries—Brazil, Russia, India, China and South Africa—will experience a growth of 99% in antibiotic consumption, compared with an expected 13% growth in their human populations over the same period, according to the study authors.
Because of the incredible volume involved, this increase in antimicrobial use in animals raises serious concerns in relation to preserving antimicrobial effectiveness in the next decades.
“The invention of antibiotics was a major public health revolution of the 20th century,” said senior author Ramanan Laxminarayan, a senior research scholar in the Princeton Environmental Institute and Director of the Center for Disease Dynamics, Economics and Policy. “Their effectiveness—and the lives of millions of people around the world—are now in danger due to the increasing global problem of antibiotic resistance, which is being driven by antibiotic consumption.”
Two thirds (66%) of the global increase (67%) in antimicrobial consumption is due to the growing number of animals raised for food production. The remaining third (34%) is attributable to a shift in farming practices, with a larger proportion of animals projected to be raised in “intensive farming systems,” or factory farms.
“For about a billion poor people, livestock are essential to survival,” said Tim Robinson, Principal Scientist from the International Livestock Research Institute. “They are raising their livestock in extensive, backyard systems on the whole and do not use antibiotics as growth promoters or in disease prevention. They use them when their livestock are sick and will take a disproportionately high share of the consequences as effective drugs become more costly and less available in treating their livestock and themselves when they become sick.”
The study focused on cattle, chickens and pigs and identified the two later as the main contributors to antibiotic consumption. One key limitation in performing this first assessment was collecting and accessing enough veterinary evidence on antimicrobial consumption; the present study is based on a limited data-set of veterinary antimicrobials sales from just 32 countries, all from developed economies.
“An important limiting factor in carrying out this first inventory of antibiotic consumption in animals was the lack of ‘modelling-ready’ data on veterinary antibiotic sales in many countries,” said lead author Thomas Van Boeckel, a Fulbright research scholar in the Department of Ecology and Evolutionary Biology at Princeton.
Having reliable global data is essential for scientists and policymakers to both measure the extent of the problem and assess potential solutions.
“Sometimes these data are simply not collected because of lack of veterinary surveillance programs, but sometimes the barriers are more political and or legislative. With this work we hope to trigger a momentum and show how useful such data could be to inform the design of global concerted policies against antimicrobial resistance,” said Van Boeckel.
“Antibiotic resistance is a dangerous and growing global public health threat that isn’t showing any signs of slowing down,” said Laxminarayan. “Our findings advance our understanding of  the consequences of the rampant growth of livestock antibiotic use and its effects on human health—a crucial step towards addressing the problem of resistance.”
In addition to Laxminarayan, Robinson and Van Boeckel, the research was conducted by Bryan Grenfell, the Kathryn Briger and Sarah Fenton Professor of Ecology and Evolutionary Biology and Public Affairs at the Woodrow Wilson School; and Simon Levin, the George M. Moffett Professor of Biology and professor of ecology and evolutionary biology. In addition, two scholars from the Center for Disease Dynamics, Economics & Policy in Washington, D.C., were involved as well as Marius Gilbert from the Université Libre de Bruxelles.
The research was funded through the U.S. Department of Homeland Security; The Organization for Economic Co-operation and Development; the Bill & Melinda Gates Foundation; the RAPIDD Program; the National Institutes of Health Fogarty International Center; and the Princeton University Grand Challenges Program.
Photo courtesy of Molly Miller-Petrie.