Viral diseases such as Ebola and Middle East Respiratory Syndrome (MERS) that develop in animals but can spread to humans are an increasing threat, and too little research on them is being done, scientists warn.
Not enough has been learned about how diseases that arise in wildlife or livestock can evolve to become risks to human health, researchers at the University of Sydney in Australia say.
Only a small number of so-called zoonotic diseases, which can jump between species, have attracted almost half of all research, says researcher Dr. Siobhan Mor from the Faculty of Veterinary Science, leaving a lack of in-depth information on other animal viruses with the potential to mutate and infect humans.
Known diseases like Ebola, SARS and MERS get most of the attention – attention they deserve, certainly – but that leaves humanity in the dark about other possible threats, she says.
"We identified 10 diseases that occur at the livestock-wildlife interface, the majority of which also affect humans, and found that the majority of the research has been occurring on these [10] particular diseases since the 1960s," she explains.
"There has been a lot of research on these particular diseases, with far less on other diseases occurring."
The researchers, writing in the Proceedings of the National Academy of Sciences, say they based their findings on an analysis of nearly 15,000 scientific papers published over the last century.
As livestock production becomes more intensive in an effort to feed an ever-growing world population, animal diseases could pose a greater risk to human health, Mor says.
"We are raising animals in close proximity to wildlife because we have cleared land in order to make way for our agricultural production," she says, urging more research focusing on this increasing contact between wildlife and livestock to evaluate risks and improve responses if there is a disease epidemic.
As an example, she cites a potentially fatal virus in Australia, hendra virus or HeV, which is found in a species of fruit bat in northern and eastern Australia and can be transmitted to horses, which brings the virus into close contact with humans.
Seven people in Australia have been infected with the virus, and four of them died. Horse-to-horse transmission seems to be rare among animals kept in pastures, researchers have found, but infected horses brought into stables have spread the virus to a few animals in close contact, and from there to humans. Famers are practicing control through barriers to keep infected horses from spreading it to other horses, and management strategies that keep fruit bats away from horses.
"And we now know that bats can harbor many germs, but the research investment into wildlife disease ecology simply isn't there," she says.
In Africa, fruit bats are thought to be the natural hosts of the Ebola virus.
Sometimes new diseases are only detected after they've infected humans and only later is it determined they initially develop in animals, Mors says, giving HIV as an example.
"In the case of emerging diseases, we tend to react to large outbreaks of disease in humans, rather than preventing or managing the infection in animals, likely because we still don't know a lot about the role of these microbes in the ecology of wildlife and livestock disease," she says.
