Bats to blame for Nipah virus deaths

By Sharmilpal Kaur

NOW it is certain: Flying foxes spread the Nipah virus to pigs in the 1999 outbreak that killed 100 pig farmers in Malaysia and an abattoir worker in Singapore.

They have been conclusively identified as the villains by Dr K.B. Chua, a microbiologist and paediatrics professor at the International Medical University in Malaysia.

He presented his findings yesterday at the 10th International Congress of Infectious Diseases.

The Nipah outbreak led to more than 800,000 pigs in Malaysia being culled and Singapore banning the import of live pigs since March 1999. p> Dr Chua told The Straits Times that climate change and the El Nino weather phenomenon of 1998 caused the outbreak indirectly.

Flying foxes, or fruit bats, are natural reservoirs of the Nipah virus and are linked to a related bug, the Hendra virus, which infects cats, horses and pigs via the bats' urine.

Normally, flying foxes live deep in the jungle, feeding off succulent fruit like jambu air and mango.

But, during 1997-1998, El Nino brought drought and dry weather to the region. That led to massive forest fires and the haze that shrouded the region for months.

Referring to the drought and the haze, Dr Chua said: 'This combined effect has been shown to stop some trees from flowering.

'No flowers means no fruits, so the bats migrate to an area where there are fruits and nectar.'

The flying foxes were forced to venture out to orchards, some of which were near pig farms.

They passed the virus on to pigs via their urine, as well as their saliva in the half-eaten fruit that fell to the ground and was then eaten by the pigs.

Prof Chua said there had been no other outbreaks since then.

He said that more studies were likely to follow, including finding out in which fruit the virus survived the longest.

Pigs may not be the only conduit of the virus, he said.

Sheep and cows may also pick up the bug and spread it.

He said: 'It can affect a number of animal hosts, like cats and maybe even goats. We don't know.'