Materia Medica Malaysiana

Cross-species infections to watch out for

In the not-so-distant future, more zoonoses or cross-species infections are likely to emerge. A stronger surveillance system is our only hope. KASMIAH MUSTAPHA reports.
THE battle against the Nipah virus met with success while the Severe Acute Respiratory Syndrome (SARS) and avian influenza are in remission. Monkeypox, mad cow disease and ebola have also made their presence felt in recent decades.

These are zoonoses — diseases that leap the species barrier from animals to human. They seem to emerge out of nowhere, spreading widespread fear as fatalities increase and the global medical community is forced to scramble for answers.

More could be coming. At a recent meeting, the World Health Organisation said the emergence of new diseases that were passed from animals to humans was accelerating.

It predicted that the next epidemic would be difficult to contain.

Most zoonoses or zoonotic diseases have the potential to spread beyond their region of origin and most countries are ill-equipped to counter the trend, it added.

Dr Rosemawati Ariffin, principle assistant director (zoonotic unit) at the Disease Control Division, Ministry of Health, says there could be "hundreds maybe thousands" of viruses, bacteria and parasites yet to be detected that could flare up at any moment.

"Unfortunately, due to our lifestyles and globalisation, new emerging and re-emerging diseases would no longer be isolated cases." The worrying part, says Dr Rosemawati, is that certain viruses can mutate and bring on new diseases.

"It is difficult for us to predict when an outbreak is going to happen," she adds.

Veterinary Services Department director-general Datuk Dr Hawari Hussein says zoonoses have been largely controllable in the past because the outbreaks occur only at certain areas and they could be identified.

"But it is different now because of the way we are living and moving around," he says.

He adds that although zoonoses have been in existence for a long time, recent cases which became a near-global epidemic has affected the way the world looks at these diseases.

"The fact that they can spread rapidly can cause people to panic, especially if the diseases cannot be contained in one area." According to experts, about 75 per cent of all new infectious diseases originate from animals.

The transmission of disease from animals to people depends on many factors, including the interactions that occur, the microbial agent involved and the environment.

Nipah virus, which got its name from the village where it first appeared, induces flu-like symptoms that often lead to encephalitis and coma. The virus, which killed 100 people, jumped the species barrier from fruit bats to pigs and then to humans in the deadly outbreak in Malaysia in 1999.

From November 2002 to July 2003, SARS triggered an unprecedented international health emergency.

Of the 8,098 people infected worldwide, 774 died from the disease.

Scientists believe the virus was passed to humans from civet cats and other mongoose-like animals that were sold in live food markets in southern China.

Experts says there are several factors that contribute to the increase in cross-species infections.

One is the growing world population as humans venture into previously undisturbed parts of the world and encounter new animals and their indigenous pathogens.

Exotic animal trade — as pets and food — is also the reason for the increased number of zoonoses.

The global movement of these animals has created what some experts say is a "viral traffic" or "microbial traffic", which encourages the shift of viruses and parasites to humans.

Dr Rosemawati says that efforts to contain diseases must involve cooperation from other countries, especially the country from which the disease originated.

"They should alert the world and take the necessary precautions if there are any known or unknown diseases emerging in their country. Prompt action will help other countries set up their surveillance system immediately," she says.

Unless the source and transmission of a disease is known, the only thing that health agencies can do is strengthen their surveillance system.

"We managed to contain the SARS outbreak because we identified the cause of transmission and quickly implemented the surveillance system." To counter the possibility of new emerging diseases, the Disease Control Division has implemented a syndromic approach in which doctors help alert the Health Ministry.

"We will then take the appropriate precautions. We are more prepared now as we have strengthened our surveillance system," she adds.

The Veterinary Services Department has also extended its monitoring and surveillance system. Previously it focused only on the point of entry and abattoir aspects. Since Nipah, however, it has implemented the farm-to-table concept.

"We will inspect livestock farms including the management, feeding and transfer of animals from farms to abattoir. We have also implemented more guidelines for livestock farmers," says Dr Hawari.