A new global study mapping human-animal diseases like tuberculosis (TB) and Rift Valley fever finds that an "unlucky" 13 zoonoses are responsible for 2.4 billion cases of human illness and 2.2 million deaths per year. The vast majority occur in low- and middle-income countries.
The report, which was conducted by the International Livestock Research Institute (ILRI), the Institute of Zoology (UK) and the Hanoi School of Public Health in Viet Nam, maps poverty, livestock-keeping and the diseases humans get from animals, and presents a ‘Top 20’ list of geographical hotspots.
"From cyst-causing tapeworms to avian flu, zoonoses present a major threat to human and animal health," said Delia Grace, a veterinary epidemiologist and food safety expert with ILRI in Kenya and lead author of the study. "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 one billion poor livestock keepers."
"Exploding global demand for livestock products is likely to fuel the spread of a wide range of human-animal infectious diseases," Grace added.
According to the study, Ethiopia, Nigeria and Tanzania in Africa, as well as India in Asia, have the highest zoonotic disease burdens, with widespread illness and death. Meanwhile, the northeastern United States, Western Europe (especially the United Kingdom), Brazil and parts of Southeast Asia may be hotspots of "emerging zoonoses"—those that are newly infecting humans, are newly virulent, or have newly become drug resistant. The study examined the likely impacts of livestock intensification and climate change on the 13 zoonotic diseases currently causing the greatest harm to the world's poor.
The report, Mapping of Poverty and Likely Zoonoses Hotspots, was developed with support from the United Kingdom's Department for International Development (DFID). The goal of the research was to identify areas where better control of zoonotic diseases would most benefit poor people. It also updates a map of emerging disease events published in the science journal Nature in 2008 by Jones et al.
Remarkably, some 60 per cent of all human diseases and 75 per cent of all emerging infectious diseases are zoonotic. Among the high-priority zoonoses studied here are "endemic zoonoses," such as brucellosis, which cause the vast majority of illness and death in poor countries; "epidemic zoonoses," which typically occur as outbreaks, such as anthrax and Rift Valley fever; and the relatively rare "emerging zoonoses," such as bird flu, a few of which, like HIV/AIDS, spread to cause global cataclysms. While zoonoses can be transmitted to people by either wild or domesticated animals, most human infections are acquired from the world's 24 billion livestock, including pigs, poultry, cattle, goats, sheep and camels.
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