Stemming the spread of animal-to-human diseases

Deforestation of the Amazon forest in the Anapu region, northern Brazil. Land openings bring humans, livestock and wildlife closer together, raising the risk of transmission of zoonotic diseases. - AFP

Scientists screen wildlife for diseases that can be transmitted to humans.

LAND-USE change – such as when forests are converted into agricultural land or when urban areas move into pristine or rural sites – are often discussed from the aspect of carbon emissions.

What is less understood is how land-use change can result in the emergence of zoonotic diseases (ailments which are transmitted from wildlife to people or livestock).

Scientific field work is now being carried out locally to better understand how land transformation can trigger the occurrence of such diseases. For this scheme, US-based organisation EcoHealth Alliance is working with the Health Ministry, Wildlife and National Parks Department, Veterinary Services Department, Sabah Wildlife Department and Sabah Health Department. They will check wildlife for diseases, improve laboratory and surveillance capacity, and integrate wildlife disease surveillance into public health infrastructure.

These are done to create an early warning system for potential zoonotic disease spill-over into domestic animals and humans, through the USAID Emerging Pandemic Threats’ Predict programme that was launched in 2010. EcoHealth Alliance works to protect global health by preventing the outbreak of emerging diseases and safeguard ecosystems by promoting conservation.

It is leading the USAID Infectious Disease Emergence and Economics of Altered Landscapes Project (launched in 2013) which is constructing a model to examine the severity of outbreaks as well as calculate the expected damages under different land-use change scenarios.

The Predict programme was established to identify emerging diseases that can threaten humans and livestock. EcoHealth Alliance Malaysia project co-ordinator Tom Hughes says research shows that nearly 60% of human pathogens recorded since 1940 were caused by zoonotic pathogens, and more than 70% of these were caused by pathogens with a wildlife origin.

“What is perhaps not widely known is that most zoonoses emerge as a result of human actions, such as altering a landscape, that results in increased contact between wildlife and human or livestock,” says Hughes.

He cites the example of the Nipah virus which caused a respiratory and neurological disease outbreak in 1998 in Kampung Sungai Nipah, Negri Sembilan. It infected 265 people, mostly pig farm workers, and 40% of them died. Pigs had been the intermediate host for the virus that is carried by flying foxes. Agricultural conversion (planting fruit trees between pig pens) had resulted in flying foxes feeding in the farm. Intensive farming activities allowed the disease to persist and infect humans.

“Predict’s effort in Malaysia is supported by growing appreciation for the ‘one health’ concept, that is, if we want to have healthy people, we need to have healthy wildlife and livestock. These viruses matter because there are huge economic costs involved. A country’s expenses could run into billions when dealing with an outbreak. There is also impact on trade and travel. This is why there is a real, urgent need for prevention measures against any possible outbreak,” says Hughes.

Case in point: the Nipah virus led to estimated losses of between US$550mil and US$650mil for South-East Asia in 1998 when more than a million pigs were culled and resources had to be invested to control the crisis.

Researchers from Sabah Wildlife Department's wildlife health unit collecting tissue samples from a Cantor's roundleaf bat to check for potential zoonotic diseases. – Ecohealth Alliance

The Predict project is currently active in Peninsular Malaysia and Sabah. Wildlife samples have been collected for research and inspection – more than 11,000 specimens from 1,000 animals in Sabah, and over 15,000 specimens from around 1,000 animals in Peninsular Malaysia. In addition to this, Perhilitan’s own sampling consist of 4,900 specimens from more than 720 animals. To date, over 8,300 samples from more than 3,200 animals have been screened for 24 viral families, exposing 44 novel viruses and 26 known viruses.

“Ultimately, Predict Malaysia aims to find out what humans are doing to allow these viruses to spill over. We hope to integrate wildlife disease surveillance into public health infrastructure to create an early warning system in detecting potential zoonotic diseases in domestic animals and humans, while helping to prevent larger outbreaks.

“In Sabah last year, we conducted capacity-building and training sessions for participants across different government departments on aspects such as animal capture, sampling safety as well as sample handling and storage, among others. An improved lab, the Wildlife Health, Genetic and Forensic Laboratory, is also in place. It is equipped to store samples, as well as run extractions and analysis on biological samples for genetic research, forensic investigations and disease surveillance such as that under the Deep Forest project.”

The Deep Forest Project in Sabah studies the impact of land-use change on wildlife diversity and their viral diversity, by sampling species that have the most contact with humans and likely to carry a virus that could infect them.

Hughes says 43% of past emerging infectious diseases are attributable to land-use and agricultural changes, including extractive industries.

“The question now is how much land should be converted and how quickly so, to minimise the risk of an outbreak. This is what the USAID Infectious Disease Emergence and Economics of Altered Landscapes Project aims to determine.

“The global economy could suffer a liability between US$10bil and US$40bil (RM32bil to RM128bil) over the next 10 years just to arrest disease outbreaks from land-use change.” Plans are currently afoot to launch a Development and Health Research Unit based at University Malaysia Sabah, to disseminate findings, tool kits and handbooks about the effects of land-use change.

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