Drinking raw date palm sap is a cherished tradition

Flickr/H G M

Scientists believe they have found a simple way to stop transmission of the deadly Nipah virus, which plagues Bangladesh every winter.

Nipah virus, a rare pathogen discovered in 1999, mainly occurs in the South Asian country, where it kills almost three-quarters of those it infects — and leaves many survivors with neurological disorders. No drugs or vaccines against the virus exist.

The theory is that the natural reservoir of this virus can be found in fruit bats. In Malaysia, bats roosting above pig sties were blamed for infecting the pigs, which then transmitted the virus to farmers.

Then in 2008, says Science, scientists "caught bats in the act". Bats lick date palm sap, collected by locals during the winter months when the sap runs sweet. Locals often drink the sap raw, which is "a game of Russian roulette".

"Getting people to stop drinking raw date palm sap is the only answer [to breaking the transmission cycle]," says Mahmudur Rahman, director of the Institute of Epidemiology, Disease Control and Research, in Bangladesh. But this could prove tough as it is a cherished tradition.

Years ago, date palm sap collectors, or gachhi, would protect the part of the palm stripped of its bark with a covering made of bamboo slats. Somewhere along the way, this practice was dropped.

In 2007, the country's International Centre for Diarrhoeal Disease Research (ICDDR,B) persuaded some gachhi to reinstate the practice — and found that the slats are effective in preventing the bats from licking the sap. As they keep the bats out, the sap is cleaner.

There are efforts to scale up such practices with the use of different materials, such as jute and plastics, and, through interventions such as community meetings and informational posters, the palm collectors are slowly accepting the practice.

But many questions about the virus remain.

Scientists are collecting blood samples from a variety of animals to see if some cases might originate from sick animals that catch the virus from the bats. Also, the virus might exist as many different forms — and some of them might infect the lungs, making it easier to transmit the virus from human to human by sneezing.