Diseases from livestock and other animals are infecting humans at a higher rate than ever, causing at least 2.5 billion illnesses and 2.7 million human deaths per year, according to a new study.
The vast majority of these illnesses and deaths are caused by the 13 worst of these zoonoses — infectious diseases that can be transmitted from one species to another — including tuberculosis, anthrax and hepatitis E. The number of cases of these diseases has grown along with the rise in global demand for livestock products, especially in poverty-stricken countries. Ironically, raising livestock is seen as an avenue out of poverty for people in many poorer countries.
"From cyst-causing tapeworms to avian flu, zoonoses present a major threat to human and animal health," Delia Grace, a veterinary epidemiologist and food safety expert with ILRI in Kenya and lead author of the study, said in a prepared release. "Targeting the diseases in the hardest hit countries is crucial to protecting global health as well as to reducing severe levels of poverty and illness among the world's 1 billion poor livestock keepers."
The study, published July 2 under the title Mapping of Poverty and Likely Zoonoses Hotspots, was conducted by the International Livestock Research Institute (ILRI), the Institute of Zoology (U.K.) and the Hanoi School of Public Health in Vietnam support from the United Kingdom's Department for International Development.
The study found that Ethiopia, Nigeria, Tanzania and India have the highest levels of poverty-stricken livestock keepers as well as the highest zoonotic disease burdens, at least according to government reports, which are not always as detailed as they should be. "We found massive underreporting of zoonoses and animal diseases in general in poor countries," Grace said. "In sub-Saharan Africa, for example, 99.9 percent of livestock losses do not appear in official disease reports."
But richer Western countries also face zoonoses threats. The study found that the northeastern United States, Western Europe, Brazil and parts of Southeast Asia have the potential to become hotpots of what they called "emerging zoonoses": diseases that are either newly infecting humans, more virulent than previously seen, or have become drug-resistant. Commodity farming, where animals are bred and raised in more concentrated spaces, is seen as increasing the risk of disease spread, according to the ILRI.
The ILRI says that the risks of zoonoses do not outweigh the value of livestock, as livestock provide poor households with up to half of their income and as much as a third of their protein. But proper management of diseases will be essential to maintaining both the productivity of these animals and the health of the humans who depend on them. "Increased demand [for livestock] will continue over the coming decades, driven by rising populations and incomes, urbanization and changing diets in emerging economies," said Steve Staal, deputy director general-research at ILRI. "Greater access to global and regional meat markets could move millions of poor livestock keepers out of poverty if they can effectively participate in meeting that rising demand." He warns that all diseases "confound their greatest efforts to escape poverty and hunger."
The results of the study will now be used to target efforts to alleviate diseases and poverty. "These findings allow us to focus on the hotspots of zoonoses and poverty, within which we should be able to make a difference," Grace said.