For a good part of this month, the muddy shoreline of the Sambhar Lake looked like a battlefield. There were disembodied wings and feathers scattered around, frantic footprints on the soil.
These were the remains of thousands of birds, many of them migratory, which mysteriously died on the shores of India’s largest inland saline lake in Rajasthan a fortnight ago.
Scientists were initially at a loss to explain the deaths. Now, it has been found that the birds were infected by avian botulism, a serious neuro-muscular illness caused by a toxin produced by the bacterium Clostridium botulinum. Birds from some 25 species have been affected so far, including water birds such as stilts, shovelers and sandpipers, gulls, terns, and also bee-eaters and kites.
Good sign first
Things appeared to be going well for the Sambhar Lake this monsoon, as it was replenished by copious amounts of rain. When it is brimming, the lake spreads over an area of 190 sq. km. Algae and bacteria lend the water a distinct hue and sustain the ecology that supports the many species of migratory birds that fly here, supplying them with ample zooplankton, phytoplankton and crustaceans.
Most notably, thousands of flamingos congregate here each year.
Sambhar Lake is best known for the thousands of flamingos that migrate here every year.
Sambhar has been designated a Ramsar site — a wetland designated to be of international importance — because of the staggering diversity of birds it attracts, even though some parts of the lake are used for salt production.
It was early this month that villagers and birdwatchers began to notice decomposed carcasses on the shores. The news soon hit the headlines. Until the middle of last week, more than 18,000 birds had been found dead in and around the lake.
The condition of the carcasses indicated that the deaths had occurred over a period of time. State forest officials and vets found limb and wing paralysis among the birds that were still alive. They were unable to walk, swim, or fly, or even hold up their heads — but there was no increase in body temperature and no respiratory distress.
“We had never seen anything like this before. It was all very mysterious; everyone was baffled,” said Jaipur-based birder Sudhir Garg.
While the sick birds were shifted to a rescue centre in Phulera town, the carcasses were collected in tractor-trolleys and buried in deep pits with limestone to prevent the spread of any infection.
The animal husbandry team sent samples to the Wildlife Institute of India in Dehradun, Indian Veterinary Research Institute in Bareilly, and Salim Ali Centre for Ornithology and Natural History in Coimbatore. Water samples were also sent to the Rajasthan State Pollution Control Board to test for contamination. A Bhopal-based laboratory ruled out avian flu as the cause of death after examining the viscera.
Ripple effect
Then, an initial post-mortem on two carcasses by a Bikaner-based research organisation found avian botulism. One theory, advanced by microbiologist A.K. Kataria of the College of Veterinary & Animal Sciences, Bikaner, had been that the bacteria could have been transferred from the carcasses to carrion-feeding birds. Then, on Thursday, the Indian Veterinary Research Institute confirmed that avian botulism was indeed responsible for the mass deaths.
A vet attends to a sick bird.
Sixty members of the civil defence team have started a combing operation inside the lake with boats, and a 17-member team of the State Disaster Response Force has pitched in with equipment.
Local people have been particularly perturbed. Gauri Shankar Sharma, a priest at the nearby Shakambari temple, said he saw hundreds of birds dropping dead from the temple’s roof. Ratan Lal, 76, of Naika Ki Dhani village, said he had never before seen birds dying on this scale.
Environmentalist and honorary secretary of Tourism & Wildlife Society of India, Harsh Vardhan, visited the lake and said, “Since migratory birds will soon be arriving for winter, the forest department should intiate a plan of action.”
The Rajasthan High Court, having taken suo motu cognisance of the deaths, had asked the State government to explain the steps being taken. Meanwhile, the incident has finally pushed the State government to make the Wetland Authority operational, to conserve water bodies and protect their flora and fauna.
Chief Minister Ashok Gehlot has sought the Centre’s assistance to control the disease. “We have limited resources. We expect the Union Environment and Forest Secretary to visit the lake and undertake extensive research to prevent such epidemics in future,” he said.
