Thai bat caves might offer clues to origins of disease

PHOTHARAM, Thailand — The caves reeked of bat. In the murk of the grottoes, in a cave complex west of Bangkok, Thais in headlamps and with flashlights went about their business.

Pilgrims to the temple that owns the complex prayed to Buddha figurines in one of the caves, the statues’ carved expressions betraying no reaction to the plip-plop-ploop of bat droppings falling on their shoulders.

Collectors of bat dung, or guano, scraped up the droppings to sell as fertilizer, hefting bags of manure through an obstacle course of stalactites and stalagmites.

And medical researchers, overseen by one of the world’s foremost bat virologists, trapped the winged mammals to test them for traces of the coronavirus. Scientists believe it originated in bats.

Nearly one-quarter of the world’s mammal species are bats, and their ability to fly while hosting a petri dish of viruses makes them both zoological marvels and efficient vectors of disease. Infectious diseases that are believed to have emerged from bats in recent decades include coronaviruses that cause severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome, along with other viruses such as Ebola.

Most of these viruses were transferred from bats to an intermediate host, such as a palm civet or a camel, before making their way to humans.

The coronavirus that causes COVID-19 has not

been conclusively traced to bats. But in southwestern China’s Yunnan province, a researcher found evidence in horseshoe bats of a virus that closely resembles it.

The discovery of the possible connection between horseshoe bats and the coronavirus linked to COVID-19 prompted Dr. Supaporn Watcharaprueksadee, deputy chief of the Center for Emerging Infectious Disease of Thailand and a specialist in batborne viruses, to investigate whether bats in Thailand may share a similar viral load. Thailand is not far from Yunnan and Cambodia.

Supaporn said her team has found no trace of a coronavirus similar to the one that causes COVID-19 in the bats of Khao Chong Phran Temple, although other coronaviruses have been discovered there. Nor has she found any horseshoe bats there.

Testing of human residents in and around Khao Chong Phran, including of guano collectors who have spent decades in proximity with bats, turned up no antibody evidence of the virus, either.

But in recent weeks, the coronavirus has begun spreading across the country after being identified in migrant communities working along the porous border with Myanmar. Thailand went from no cases of local transmission in months to reporting hundreds of cases a day in late December and January.

Xenophobia has spiked, along with chiroptophobia, the fear of bats.

In the view of the guano collectors of Khao Chong Phran, which is not far from the frontier with Myanmar, the anxiety caused by bats is overblown.

There are 17 species of bats in the area, and only two are fruit-eating bats tied to the spread of disease, they say. The rest consume insects, which means the bat droppings shimmer with iridescent residue from bug wings.

“Even before my grandfather’s generation, we collected guano from the caves,” said Jaew Yemcem, 65, resting on the temple grounds with her bare feet nestled in soft mounds of bat excrement. “They were fine, and we are fine.”

Adam Dean / New York Times A team of researchers catches bats as they fly at dusk out of a cave at Khao Chong Phran temple in Thailand’s Ratchaburi province in December.