The Indian Veterinary Research Institute, Bareilly, on Thursday confirmed that avian botulism — a neuro-muscular illness caused by a toxin that is produced by a bacterial strain — was the cause of the recent mass mortality of birds, at Sambhar Salt Lake in Rajasthan. More than 18,000 carcasses of birds have been removed from the lake and its catchment area so far, raising concern among environmentalists.Laboratory tests conducted on samples of carcasses collected from the lake confirmed the nature of the disease that had afflicted the birds, backing what veterinarians in the State had said was the most likely cause. The illness, caused by a bacterium called Clostridium botulinum, affects the nervous system of birds leading to flaccid paralysis in their legs and wings, and in the neck touching the ground.More than 18,000 carcasses of birds have been removed from the lake and its catchment area so far, raising concern among environmentalists and ornithologists. The scientists at IVRI found the samples infested with maggots of third stage with a clear indication that the avian mortality had occurred over a period of time.Animal Husbandry Minister Lal Chand Kataria said the IVRI report had approved the regimen of treatment adopted for birds recovered from the lake’s shores. “The rescue centres established near the lake have treated 735 birds, of which 368 are alive and 36 have been released to their natural habitat,” he said.Located 80 km south-west of Jaipur, Sambhar Lake is India’s largest inland saline water body and has been designated as a wetland of international importance as it attracts thousands of migratory birds during winter.A Bhopal-based laboratory had earlier ruled out avian flu as the cause of death of the birds after examining the viscera. The post-mortem of two bird carcasses by a Bikaner-based research organisation had concluded that bacterium Clostridium botulinum had entered from the soil into the meat of some dead birds.The toxin produced by the bacterial strain infected the non-vegetarian birds feeding on maggot-infested carcasses, according to the experts at the College of Veterinary & Animal Sciences, Bikaner. Those species which did not feed on carcasses, such as flamingos, were not affected and only the cadaver-eating birds had died.Chief Minister Ashok Gehlot has sought the Centre’s assistance for controlling the disease and saving the birds. “The expertise rests with the Centre… we have limited resources. We expect the Union Environment and Forest Secretary to visit the lake and order an extensive scientific research to prevent the birds’ mortality in future,” he said.The species affected by the illness included shelduck, plover, common coot, black winged stilt, northern shoveler, pied avocet, mallard and crake.