The Rajasthan government via other agencies have so far buried 18,422 bird carcasses in order to stop the spread of possible infections.
In the last 10 days, thousands of migratory birds have been found dead about 80km southwest of Jaipur at Sambhar Lake. Over 18,000 carcasses have been buried so far by officials. There has been no clear identification of the cause of their deaths. Investigations are suggesting a paralytic and frequently fatal disease, avian botulism. It is caused by the ingestion of toxins.
India’s largest inland saltwater lake, Sambhar Lake stretches across Jaipur and Nagaur districts as well as in some parts of Ajmer. With a catchment area of 5700 sq km area, the water depth fluctuates between 60cm in the dry season to 3 metres at the end of the monsoon.
Thousands of migratory birds visit the lake every year. 83 waterbird species have been recorded to visit the lake with the common birds being little grebe, great crested grebe, great white pelican, little cormorant, black stork, darter along with various species of egrets, herons, geese and plovers.
25-30 species of birds have been found dead including Brahminy duck, northern shoveller, Kentish plover, tufted duck and pied avocet. It started on November 10, when visitors to the lake found a large number of birds dead. The numbers kept increasing over the next several days. The Rajasthan government via other agencies have so far buried 18,422 bird carcasses in order to stop the spread of possible infections. 9,597 birds were disposed in Nagaur and 8,825 in Jaipur. 748 birds have also been rescued by officials out of which 400 were still alive on Wednesday.
Officials said that the number of dead birds are declining. The count of burials has reduced from a high of 3,265 to 2,696 on November 15 and November 16 to 441 by November 20. However, combing operations are still ongoing.
It hasn’t been officially confirmed but the evidence from the sites point towards avian botulism. According to a report by 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 (RAJUVAS), Bikaner, the reason for this on the basis of history, classical clinical symptoms, epidemiological functions and postmortem findings is avian botulism. The clinical signs exhibited by birds affected by the disease include dullness, depression, anorexia, flaccid paralysis in legs and wings as well as their necks touching the ground.
The government is still waiting for reports to confirm the exact cause of the birds’ death. It has reached out to eight institutions and agencies so far. Only RAJUVAS and the National Institute of High-Security Animal Diseases (NIHSAD) in Bhopal have submitted their reports on the case. Partial reports have been sent in by the Rajasthan Pollution Control Board as well as the Indian Veterinary institute situated in Bareilly.
Humans can only get affected by avian botulism, if they eat the affected birds. Bird flu was initially feared as the cause of death of the birds but NIHSAD has ruled that out.
Avian Botulism is quite common and many outbreaks of the disease have occurred in the past several years.1,17,000 in Manitoba, 1 million in Saskatchewan along with an estimated 1,00,000 birds died in Canada between the years of 1995 and 1997.
After a Division Bench of the Rajasthan High Court led by Chief Justice Indrajit Mahanty took cognisance of the deaths, the Rajasthan government listed the following likely reasons:
– Toxicity, with a new area being filled up after almost 20 years, which could create a higher concentration of salts along the edges.
– Bacteriological infection
– Higher temperature and high water levels due to a good monsoon.
– Viral infection
Sambhar lake got recognition as a wetland of international importance when it got its designation of a UNESCO Ramsar Site in the year, 1990. As per NGO Wetlands International, it has E, the worst Wetland Health Score.