Bat caves smelled like bats. In the darkness of the caves in a cave complex west of Bangkok, Thais did their work with lanterns on their heads and hands.
Pilgrims in the temple where the caves are located prayed for small Buddha statues in one of them. The expression of the sculpted figures showed no reaction to the “plip-plop” of bat droppings that fell on his shoulders.
Bat dung collectors, also known as guano, scraped off the material to sell as fertilizer and carried sacks of it through an obstacle course made of stalactites and stalagmites.
Medical researchers, overseen by one of the world’s top bat virologists, captured animals to test for traces of the coronavirus that causes Covid-19. Scientists believe the disease originated in bats.
In front of the caves, the abbot of the Buddhist temple, known as the “Temple of Hundreds of Millions of Bats”, used a megaphone to tell visitors that the flying mammals that live there are harmless.
“Don’t worry, these bats do not carry diseases because they are insectivores,” said Abbot Phra Khru Witsuthananthakhun. “Everyone knows that when bats eat fruit, they share it with other animals like mice, and that’s how the disease spreads.”
The temple abbot rightly says that frugivorous bats (frugivores) have been linked to serious viruses that have jumped on the human population. But insectivorous bats have given humans a share of deadly diseases. Many virologists add that the horseshoe bat, an avid insect eater, may be linked to the coronavirus that causes Covid-19. And a report from a Thai national park identified a species of horseshoe bats in the caves.
The area around the caves, the Photharam district in Ratchaburi province, has its fortune to do with bats – tourists, fertilizer manufacturers, and most importantly, chiropterologists, scientists who study flying mammals.
At the center of the small and unstable local economy – some bats can vary their heart rate by 800 per minute – is the Khao Chong Phran Temple with the limestone caves where bats take shelter during the day. There are 3 million bats of ten different species in just one cave.
Almost a quarter of the world’s mammal species are bats, and their ability to fly while harboring large numbers of viruses makes them both zoological marvels and efficient vectors of disease. Infectious diseases that would have caused bats in the past few decades include coronaviruses such as Sars and Mers, as well as others such as Nipah, Hendra and Ebola.
Most of these viruses were transmitted from bats to an intermediate host, such as a civet cat or camel, before they reached humans.
Although the Covid-19 coronavirus, which became public knowledge in late 2019, is not clearly attributed to bats in southwest China’s Yunnan Province, a researcher found evidence of a virus in horseshoe bats that looks very similar to it. Cambodian horseshoe bat droppings also showed certain connections. And the same type of bat was the natural reservoir for the Sars virus.
The discovery of the possible link between horseshoe bats and Covid-19-bound coronavirus prompted Dr. Supaporn Watcharaprueksadee, deputy head of the Thailand Infectious Diseases Center and specialist in bat-borne viruses, are investigating whether bats in Thailand, not far from Yunnan and Cambodia, can share a similar viral load.
Supaporn said his team found no traces of a coronavirus similar to the one that Covid is causing in the bats at Khao Chong Phran Temple, although other coronaviruses were discovered there. Nor did she find any horseshoe bats on the site.
Tests on residents of the Khao Chong Phran area, including dung collectors who have spent decades in close proximity to bats, have also shown no evidence of antibodies to the virus.
However, the view of researchers dressed from head to toe in personal protective equipment surprised a community that relies on bats for their primary economic support.
“There is no Covid here,” said Auenjit Kaewtako, a volunteer in the district who has been coming to Khao Chong Phran Province for 40 years. “Why should we accuse bats?”
Although Thailand was the first country outside of China to confirm a case of Covid-19 – in a Chinese tourist who visited it last January – it appeared since May that it had practically strangled the local broadcast. The Thai people were generally cautious and wore masks. The country’s borders have been closed to prevent viruses from entering.
In the past few weeks, however, the coronavirus has spread across the country after it was first identified in migrant communities on the porous border with Myanmar. Thailand has not reported any local transmission cases in months, reporting hundreds of cases per day in late December and January.
Xenophobia was sharpened along with chiropractic care, fear of bats.
According to the dung collectors of Khao Chong Phran, which is not far from the border with Myanmar, the nervousness caused by bats is exaggerated. There are 17 species of these animals in the region, and only two are frugivorous, related to the spread of the disease. The rest of them eat insects, which causes the droppings to glow with iridescent residue from the insects’ wings.
“We were collecting guano from the caves before my grandfather’s generation,” said Jaew Yemcem, 65, who rested with bare feet on piles of excrement on the temple steps. “They were fine and we were fine.”
Every Saturday morning before sunrise, Khao Chong Phran allows guano gatherers, some of whom wear homemade hats to protect themselves from dripping droppings, into the caves to harvest nitrogen-rich manure. Many workers go barefoot to find a better balance on slippery floors with moisture and excrement.
After the temple has bought guano from collectors, it auctions it to farmers or middlemen, after which a handful of fertilizer gives guavas a special sweetness and papayas an impressive size.
Collectors get around $ 0.85 per bucket of guano and, with luck, can collect a dozen buckets a day.
Bats are a popular food in some Southeast Asian countries. While the tents at Khao Chong Phran Temple once sold roasted bats, residents no longer eat them because they have been designated a protected species, said Dr. Supaporn, who has been researching bats in the region for a decade.
But Prangthip Yencem, who works as a kitchen assistant at a school during the week and collects guano on Saturdays, said that while the consumption of bats is lower, it continues to persist. The bat tastes great in a variety of preparations, including sautéed with pepper and basil or fried with garlic and white pepper.
For men, bat blood with a dash of alcohol is an invigorating cocktail, she said.
Locals haven’t hunted bats since the abbot warned them about it, Prangthip said. But if a bat collides with a telephone pole and falls to the ground, who would turn down a free meal?
“People still eat bats today,” she said, “and they don’t catch Covid.”
The bat population in Photharam District has declined over the past few decades due to the urban sprawl that is consuming rural Thailand. The intensive use of pesticides also deprived bats of their food.
With fewer bats, the amount of guano being collected today is half what it was ten years ago. The presence of fewer bats disrupted pollination patterns and damaged tropical ecosystems in a similar way to the decline in bees.
Crucially, some bat virologists believe that increased bat stress can make animals more prone to symptoms of the disease, potentially increasing the likelihood of viruses invading other species.
Usually, bats can lead healthy lives with multiple viruses running through their bodies. But the artifacts of human development – tall buildings, power cables and cemented areas – can stress animals, which the organism often uses in echolocation, the emission of sound frequencies to determine their surroundings.
Phra Somnuek, now a monk in the temple, recalls that as a child the sky was dark for more than two hours at dusk and the shadows of millions of bats headed for their dinner. The herd of bats, which is still attracting tourists, is now ready in 45 minutes, he said.
“I’m afraid that one day the bats will be just a legend here,” he said. “If we lose our bats, we lose what makes us special.”
Muktita Suhartono worked together.
Translation by Luiz Roberto M. Gonçalves