Thousands of birds die at Indian lake

Avian botulism suspected as rescue efforts continue for survivors of outbreak

Nearly 17,500 migratory birds have died in just under two weeks at Sambhar Lake, India's largest saltwater lake, in what experts are calling one of the worst avian tragedies in recent memory in the country.

They believe the most likely cause of the mass deaths of the winged guests that arrive at the lake in the northern province of Rajasthan is a deadly and paralytic disease called avian botulism. It is caused by toxins produced by the bacterium Clostridium botulinum.

Kavita Singh, deputy conservator of forests at the Jaipur Development Authority, who is leading the provincial government's swift reaction squad, said eight agencies are working on samples to pronounce the exact cause of the deaths. "We will wait till (we hear) what they say," she said.

Strewed across the lake, which measures 230 square kilometers, the dead birds were first reported by tourists on Nov 10 to the lake authorities.

"Sambhar draws a large number of migratory birds in the winter," Singh said. The birds arrive from northern and central parts of Asia, as well as neighboring Pakistan.

Among the breeds found dead are the northern shoveler, flamingo, common coot, black-winged stilt, ruddy shelduck and ruddy turnstone.

A local group of young birdwatchers has been working with government officials to count and ferry the dead and sick birds to the rescue center, Singh said.

The Apex Centre for Animal Disease Investigation, Monitoring and Surveillance at the College of Veterinary and Animal Science under the Rajasthan University of Veterinary and Animal Sciences has cited botulism as the cause of the deaths.

"The clinical signs exhibited by affected birds included dullness, depression, anorexia, flaccid paralysis in legs and wings, and neck touching the ground," the center said in a report.

"The birds were unable to walk, swim, or take flight. There was no rise of body temperature, no nasal discharge, no respiratory distress or any other sign."

Singh said: "There were absolutely no forebodings of this. The last time mass avian deaths occurred was the bird flu outbreak in 2006."

While most of the dead birds have been buried in deep pits around the lake, 36 of the rescued birds have been released, as of Nov 20, after being treated, Singh said.

The birds were buried to stop the spread of infection, a wildlife medic attached to a zoo in Jaipur, the capital of Rajasthan, told China Daily.

Arvind Mathur, a veterinarian who has been treating some 400-odd surviving birds at the rescue center, said the other suspected cause for the mass mortality could be high sodium levels that have led to paralysis in the birds' legs. The high sodium, he said, could have been caused by illegal extractors of salt.

Fortunately, he said that native sparrows and crows as well as animals like cows and dogs have not been affected.

"The affected birds are given antibiotics, even lifesaving drugs. We are also giving them infrared therapy. Some have responded to our treatment, some have not. We have been trying our best," he said.

Last for several weeks

S. Muralidharan, senior principal scientist at Salim Ali Centre for Ornithology and Natural History, Coimbatore, said: "Avian botulism in wild water birds occurs in European countries such as England and Wales. It happens relatively frequently in India.

"A large numbers of birds are affected and die. The outbreak can last for several weeks, or even may recur.

"But, what has shocked me this time is the scale of the tragedy," said Muralidharan, adding that a mechanism in required to track to the movement and well-being of birds. While countries like the US maintain a database of all mass bird deaths, in India there is no such exercise undertaken, he said.

According to Muralidharan, although the chances of human infection are considerably low, precautionary measures must be taken. These include avoiding swimming or bathing in affected waters, or not drinking from lakes and waterways where sick and dead birds have been found.

Muralidharan does not think the mass deaths of migratory birds will lead to the restricted migration of birds. "However, it is our moral duty to see that the avian visitors spend their time happily," he said.

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