WITH a piercing cry, the wounded bat parachuted a few feet down in the sky, before plunging all the way to the ground.

As it landed in a ditch 50m away from where Dr Sohayati Abdul Rahman stood, her assistant made a dash for the creature, now wet and barely alive.

Using a syringe, Sohayati expertly drew a sample of the animal's blood from its weakening heart.

She then swabbed its mouth for saliva, sliced open the side of its lower trunk and pulled a kidney out for urine sampling.

Everything was tagged and stored while the bat was placed in a sack.
The technician standing next to Sohayati positioned himself to target another cloud of bats emerging from its roost in the evening to feed.

One was shot and, plop! it fell in a swirl into a river. Sohayati, an officer with the veterinary research institute in Ipoh, and her assistants wasted no time in repeating the process.

"I've to get the bat while it's still alive and the heart is pumping. If the bat is dead, the blood stops flowing and I can't get a sample.

"My assistants have to be efficient in retrieving the bat. We cannot manipulate the flesh too much when cutting out the kidney as the technician doesn't want us to spoil the tissues."

The veterinary research team works fast, devoting only five minutes to process each animal, so as not to keep the tech waiting for his catch of the night.

The quick action also allows the team to get as many bats sampled as possible. A three-hour outing would generally get some 30 samples.

Besides tagging along these excursions, Sohayati also does her own bat-trapping by constructing a net high up on poles.

Bats flying out from their roost would sometimes get tangled in the messy weaving of the net.

After a sample is taken, they are released back into the wild, or kept captive in the institute's quarantine station.

For four years now, bat catching has formed a major part of Sohayati's job scope in understanding the origin of the Nipah virus.

An epidemiologist, Sohayati studies the incidence and prevalence of disease in large populations and tries to detect the source and cause of epidemics of infectious disease.

Her study zeroed in on bats in Malaysia after the Nipah virus had been observed to be genetically similar to the Hendra virus in Australia, which came from fruit bats.

The local large flying fox (Pteropus vampyrus), which can weigh up to 1kg, and small flying-fox (Pteropus hypomelanus) has been identified as the natural reservoir hosts for the Nipah virus.

"This means that the virus is endemic in both the species, it's naturally there," said Sohayati.

It also means that there's no disease in the bats, even though they harbour the virus.

Sohayati managed to detect the presence of antibodies in some of the bats, signalling that they have been exposed to the virus before.

But she has never detected the virus per se in any of the 1,000 bats that she has sampled -- up until now.

The one time she found the virus present was when a bat in her captivity secreted urine which tested positive for it.

But something was absolutely baffling.

The bat had been negative for both virus and antibody for the last 11 months. And it was never exposed to bats from the wild, which could carry the virus.

This led Sohayati to hypothesise that it is possible for the Nipah virus to be "reactivated" after lying dormant in the body.

The virus could have hidden in the cells, tricking the body into thinking that it is virus-free and so, reducing the antibody in the body.

Bats which are stressed and have an active reproductive status carry a higher risk in having the virus, the study showed.

"Since the virus is endemic in bats and I found evidence that it can be reactivated, the risk of an outbreak occurring again in Malaysia or in other countries that have Pteropus bats is there."

The overlapping of the Pteropus' home range, which spreads from Australia all the way up to Pakistan, makes transborder transmission very real, Sohayati added.

Thus far, however, she has never heard of any cases of local bat hunters being infected with the virus and go on to develop encephalitis.

While the researcher has no hard evidence on whether thorough cooking can kill the virus, she said the Nipah, a RNA virus, is sensitive to heat.

"I believe the virus is destroyed after being cooked.

"We have to remember that a virus can only be transmitted when it has a chance to get contact and that the contact can cause effective transmission.

"You need to get enough viruses to the right organs in order to get infected."

So many questions, she said, have yet to be answered, especially on the reservoir status of the bats and its immune response to the disease.


BLAME IT ON FLYING FOXES

THE NIPAH virus was identified in 1999 when it caused an outbreak of neurological and respiratory disease on pig farms in Peninsular Malaysia, resulting in 105 human deaths and the culling of over a million pigs.In the early stage of the outbreak, it was mistakenly classified as Japanese Encephalitis due to the similarity in pigs being infected.

Symptoms of infection from the Malaysian outbreak were primarily encephalitic in humans and respiratory in pigs.

Patients suffered from a rapid progression of illnesses, including fever, headache, drowsiness, jerking movements and coma.

Later outbreaks elsewhere have caused respiratory illness in humans, increasing the likelihood of human-to-human transmission and indicating the existence of more dangerous strains of the virus.

The primary reservoir for the virus was identified as Pteropid fruit bats, including Pteropus vampyrus (Malayan flying fox) and Pteropus hypomelanus (Island flying fox), both of which are present in Malaysia.

The transmission of the virus from flying foxes to pigs is thought to be due to an increasing overlap between bat habitats and piggeries.

At the index farm, fruit orchards were located within the piggery, allowing the spillage of urine, faeces and partially eaten fruits onto the pigs.

There is no cure for Nipah encephalitis.