Combined intensive agriculture and environmental change identified in expanding disease outbreaks
Business Wire 31 May 11;
NEW YORK--(BUSINESS WIRE)--In a study released today, scientists reveal the factors behind the emergence of the deadly Nipah virus in Malaysia and Singapore in 1998, which caused more than 100 fatalities and cost hundreds of millions of dollars in economic losses. In this paper published today in Interface, a journal of the Royal Society, scientists describe two different stages of a deadly disease outbreak and a missed opportunity for early detection and prevention.
Nipah virus is carried by a species of fruit bat commonly known as the Malaysian flying fox. In 1998, it spread to pig and human populations. This five-year study examined the two factors previously thought to cause the Nipah outbreak: agricultural intensification and climate change. The analysis rules out the role of climate change and instead suggests that repeated disease ‘spillover’ from bats resulted from the close relationship between pig farming and mango production.
Between the 1970s and the 1990s, pig and mango production tripled in Malaysia. Mango trees were typically planted near pig enclosures, attracting fruit bats to the area. As bats fed and roosted in the trees, nearby livestock became infected with Nipah virus, which eventually spread to farm laborers.
“Our work shows that repeated spillover of Nipah virus from bats into a very structured, intensive piggery led to the emergence of this disease,” said Dr. Peter Daszak, senior author of the paper and president of EcoHealth Alliance. “This is yet another case of an emerging disease caused by human activity, and puts the focus on us to change the way we mix agriculture and the environment for a healthier planet.”
Nipah virus – like HIV/AIDS, SARS, Ebola, West Nile virus, and three-quarters of newly emerging diseases – is “zoonotic” and originated in other animals. This is one of the first times scientists have gone back to an outbreak of a new lethal disease to find out exactly what happened.
“Identifying the causes behind zoonotic disease emergence is the first step towards preventing large outbreaks,” said Dr. Juliet Pulliam, lead author on the paper. “We now have empirical evidence to support a previously hypothetical mechanism of disease emergence.”
The study involved collaborators in five countries, including ecologists, veterinarians, physicians, and mathematicians. “This is a great example of how bringing together multidisciplinary teams helps us get to the underlying cause of a complex issue,” said Dr. Jonathan Epstein, associate vice president of EcoHealth Alliance. “It’s an essential approach to understanding and stopping emerging pandemic threats.” The work also points to new ways to deal with the growing pandemic threat.
“What’s really tantalizing about our analysis is that people had a two-year window from the first case to the big outbreak to intervene, close down the pig farms, and prevent this disease,” said Dr. Daszak. “Returning to the outbreak site and doing this work could help us stop the next pandemic even before it emerges.”
