What killed the thousands of migratory birds in Rajasthan?

Rajeshwari Ganesan
Rajeshwari GanesanNov 26, 2019 | 14:24

What killed the thousands of migratory birds in Rajasthan?

Avian botulism is the surficial cause that killed tens of thousands of migratory birds. Collective apathy is the underlying reason.

Residents in Jodhpur’s Khinchan village in Rajasthan were in for a shocker on November 7 when 37 demoiselle cranes were found dead in the area. However, the nightmare straight out of a horror script was yet to fall on the avian world four days later, on November 11, when close to 1,500 migratory birds of nearly 10 species were found dead 400 kilometres from Khinchan, around Sambhar Lake near Jaipur.


The numbers have been shooting up since. Until November 20, the Rajasthan government had buried 18,422 bird carcasses to prevent the spread of infection. Some reports indicate the numbers to be over 24,000. There were carcasses of at least 32 species of waterfowl including northern shoveller, Brahminy duck, pied avocet, Kentish plover and tufted duck. The deaths were reported in Jaipur, Nagaur and Ajmer districts of Rajasthan.

While the deaths initially left the officials and the ecologists flummoxed, several possible theories for the mysterious deaths soon started emerging.

One of the possible and widely accepted reasons was avian botulism.

What is avian botulism?

Avian botulism is a neuromuscular illness of waterfowl caused by a bacterial infection. A report by 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 (RAJUVAS), Bikaner says, “On the basis of history, epidemiological observations, classical clinical symptoms and postmortem findings, the most probable diagnosis is avian botulism. The clinical signs exhibited by affected birds included dullness, depression, anorexia, flaccid paralysis in legs and wings, and neck touching the ground.” A report by Indian Veterinary Research Institute, Bareilly, also endorsed the same.


A worker picks up a black-winged stilt that was one of the thousands of birds that died due to avian botulism outbreak in Sambhar Lake, Rajasthan. (Photo: PTI)

To put it simply, this deadly bacterial infection paralyses the birds, making them unable to walk, swim or fly. The birds are unable to hold up their necks, which droop. The infection releases a toxin in the body that finally kills the bird. When an infected bird dies, the maggots that feed off it become infected. These maggots are in turn consumed by additional birds, causing a massive outbreak. The cycle continues.

The Sambhar saga

Sambhar Lake is the country’s largest inland saltwater lake and is the source of around 9% of India’s salt production. Following the mass death of birds, the salt commissioner has reportedly directed Hindustan Salts Ltd (HSL), a government of India enterprise and the legal authority for salt production, to stop the dispatch of salt produced from the outbreak locations. The production has been stalled to ascertain that the salt produced is safe for human consumption.

However, Sambhar Lake is also peppered by hundreds of illegal salt mines.

In 2016, the National Green Tribunal (NGT) had instructed the state government to cancel the allotment of any more salt pans after studies showed the adverse impact of the salt industry on the ecosystem. Hundreds of these salt pans were unauthorised, to begin with.


Story of salinity

Heavy rains that lashed northern India this July reduced the salinity of the lake. However, when the water evaporated, it increased the salinity around the edges of the lake bed. The bacteria that caused the present outbreak — C. botulinum — is an anaerobic bacterium, meaning it can grow and produce toxins only in the absence of oxygen. The low-levels of warm, saline water in the lake is further estimated by ecologists to have provided an ideal location for the manifestation of botulism.

Dead birds being buried in the sand to prevent further spread of infection. (Photo: PTI)

This means that the government will have to take immediate steps to clean up and disinfect the entire Sambhar Lake — for human and avian health.

Ramsar site

Sambhar Lake was designated a UNESCO Ramsar site (recognised wetland of international importance) in 1990 as it is a key wintering area for migratory birds.

According to news reports, the environment ministry had started the process of preparing a health index of 100 major wetlands in India in August this year. The conclusive report of the findings will be released in December. Initial findings indicate that Sambhar Lake has got the lowest rating, falling in “E” category (ratings are between “A” being the best and “E” being the worst) implying that it needs "radical improvement" in the management of the ecosystems for aquatic life to survive.

Plea on deaf ears?

As of now, further assessments are being carried out at the IVRI, Wildlife Institute of India (WII) in Dehradun, Salim Ali Centre for Ornithology and Natural History (SACON) in Coimbatore and Bombay Natural History Society (BNHS) in Mumbai to understand and contain the outbreak. Rajasthan Chief Minister Ashok Gehlot has been monitoring the situation, and government officials, including the forest and health departments, are working round the clock to contain the damage.

However, Sambhar Lake is crying for a long-term, sustainable solution to survive. Will the administration be able to hear it?

Last updated: November 26, 2019 | 14:24
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