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HEALTH: Ongoing Threat of Animal-Borne Disease Looms Over Humans

Gustavo Capdevila

GENEVA, May 5 2004 (IPS) - Diseases that are associated with animals but which can be transmitted to humans – a process known as zoonosis – pose an unpredictable and growing threat that has international experts in animal and public health worried.

Francoise-Xavier Meslin, World Health Organisation (WHO) coordinator for zoonosis control, described these diseases as a serious emerging problem that affects all regions of the world.

"The current upward trend… what we have been seeing over the past 15 years, an increasing number of these problems occurring, is going to continue," he said.

The WHO expert cited other animal-based outbreaks of diseases in humans, such as SARS (severe acute respiratory syndrome) and avian flu, which have primarily affected the Asian region.

He mentioned others that "have not attracted the attention they deserve," including Ebola fever, "which is an African disease for the time being," Rift Valley fever (also known as the Hanta virus), West Nile, "which was exported recently to the United States", the Nipah virus and bovine spongiform encephalopathy, widely known as mad cow disease.

Meslin noted that SARS is considered a "potential zoonotic disease" because it has not yet been proved whether "civet cats played a role in the transmission of the disease to humans."

The SARS outbreak in 2003 was a severe blow to China, Vietnam, Hong Kong and other Asian nations to a lesser extent, and also claimed many lives in Canada.

WHO authorities said the SARS cases reported on Apr. 22 in Beijing are under control, as the origin of the transmission was the National Virology Institute in the Chinese capital, where some researchers were infected while studying the disease.

Avian flu is another problem in Asia that eludes resolution, says Dewan Sibartie, of the Paris-based World Organisation for Animal Health (OIE).

This disease is spreading at a slower pace, but every day there are reports of new cases of infected birds, said doctor Sibartie.

The first outbreak of avian flu was confirmed in Hong Kong in 1997. It was transmitted to 18 people, and six died.

The 2003 epidemic was more intense, affecting nine Asian countries. Since December, around 100 million chickens have either died from the disease or were slaughtered to prevent contagion.

Thailand reported 12 cases affecting humans, of which eight proved fatal. In Vietnam, there were 23 people affected, and 15 died.

Sibartie said the OIE is preparing health guidelines for regulating trade in birds and poultry around the world.

Experts from the OIE, WHO, and the United Nations Food and Agriculture Organisation (FAO) this week gathered in Geneva to study emerging zoonotic diseases. Their number, says Meslin, "is very, very large."

"In both the developed and the developing world, the number is increasing continuously," the WHO specialist said.

The experts from the three international institutions identified the principal causes behind the diseases, including environmental degradation, "whether linked to agricultural practises or urbanisation."

"Also the globalisation of movement, of people or goods – including animals – is a very important factor in the spread of these agents and diseases," said Meslin.

FAO representative Jan Slingenbergh said in comments to IPS that among the causes behind the expansion of these diseases, farming practices is one of the few factors that can be reformed to help fight the phenomenon.

The same cannot be said of globalisation or climate change processes, which are more complex and would require the participation of a broad array of sectors to reverse the spread of zoonotic diseases.

The three institutions recognise the difficulties they face in identifying future diseases that can spread from animals to humans – there is a constant evolution of risk factors, said the meeting’s participants.

One of the experts’ recommendations was improved coordination in medical and veterinary responses when new diseases appear.

The next step, agree the OIE, FAO and WHO, is to raise political awareness and support for public and animal health infrastructure.

Because, said Meslin, if infrastructure is not reinforced, particularly in developing countries, "the proper surveillance system will not be put into place, the proper response system will not exist."

An international network is essential to support countries in efforts to assess the risk of new zoonotic diseases, he said.