From UPSC perspective, the following things are important :
Prelims level : Avian Botulism
Mains level : Conservation of migratory birds in India
On November 10, visitors at Sambhar Lake, India’s largest inland saltwater lake located about 80 km southwest of Jaipur, spotted a very large number of dead birds.
Why and how did these birds die?
- Nearly 10 days into the tragedy, the government is yet to determine the cause of the deaths.
- The investigation so far points to Avian Botulism — a paralytic, frequently fatal disease caused by the ingestion of toxins — as a possible cause.
- This has not, however, been officially confirmed.
- After studying bird samples and on the basis of history, epidemiological observations, classical clinical symptoms and post-mortem 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.
- 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.
Other possible reasons
- After a Division Bench of the Rajasthan High Court took cognizance of the bird deaths, the Rajasthan government listed four likely reasons.
- Viral infection
- Toxicity, as new area has been filled up after almost 20 years, and there could be higher concentration of salts along the edges
- Bacteriological infection
- Higher temperature and high water levels due to good monsoon might have led to an increase in intra-species and inter-species competition for resources.
- The weaker individuals, exhausted from the long journey, perhaps were unable to compete, and may have succumbed to stress emanating from the shortage of food, susceptibility to disease/pollutants/toxins and other habitat-related factors in the wintering grounds.
- In such an eventuality, it is expected that with fall of temperature and lowering of water levels, the incidence of such mortality will go down.