A study into the locations on the planet where diseases cross between animals and humans has picked out Ethiopia as the epicentre of zoonoses.
The report, which was put together by the International Livestock Research Institute, the UK Institute of Zoology and the Hanoi School of Public Health, concludes that the highest rates of human-animal disease transfer occur in Ethiopia, Nigeria, Tanzania and India. Most human infections are acquired from the world's 24 billion livestock, including pigs, poultry, cattle, goats, sheep and camels.
Diseases that transfer between species are known as a zoonose, and the process is known as zoonosis. Tuberculosis, Bird Flu and Rift Valley fever are well-known zoonoses, and a mere 13 of them are responsible for 2.2 million human deaths and 2.4 million illnesses each year.
"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."
The survey covered more than ten million people, six million animals and 6,000 food and environment samples.
The worst offender? Diarrheal disease. At least a third of cases of this affliction can be attributed to zoonotic causes, making it the biggest zoonotic threat to public health. Tuberculosis, both human and bovine (both of which can affect both cattle and humans), is another massive problem -- in 2010 more than 12 million people suffered from it globally, a number which is thought to be significantly underreported.
While Africa contains most of the worst locations for zoonosis right now, the northeastern US, western Europe (and particularly the UK), Brazil and parts of southeast Asia are expected to become hotspots for "emerging zoonoses" -- diseases that are newly affecting humans, or newly virulent. These include diseases like BSE and Lyme disease, though few people tend to die of these diseases in these areas, likely due to good reporting and healthcare available.
The report also considered how climate change and livestock intensification may affect the results of the study in the future -- concluding that livestock density is associated more with disease "event emergence" than with overall disease burdens. Also, areas predicted to gain increased rainfall and flooding are expected to be at increased risk of zoonoses.
"These findings allow us to focus on the hotspots of zoonoses and poverty, within which we should be able to make a difference," said Grace.