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Avian botulism

Topics Covered:

  1. Conservation, environmental pollution and degradation, environmental impact assessment.


Avian botulism


What to study?

For Prelims: What is Avian botulism?

For Mains: The sambhar tragedy, causes and how to prevent such incidents?


Context: Avian botulism is said to be the reason behind the deaths of 18,000 birds in and around Rajasthan’s Sambhar lake.


What happened at Sambhar?

As per the report, the avian botulism in Sambhar was caused by the climate.

Fluctuating Water levels: Fluctuated throughout the year. Due to a good monsoon this year, the water level reached the lake bed after a gap of 20 years.

Favourable environment for bacteria: The good monsoon provided a favorable environment for the bacteria to spread. The bacteria needs anaerobic (absence of oxygen) conditions and does not grow in acidic conditions.

Nutrient-rich substrate: The lake also provided a nutrient-rich substrate, like areas with large amounts of decaying plant or animal materials. The monsoon brought with it a large population of crustaceans (like shrimps, crabs, and prawns), invertebrates (snails) and plankton (like algae), which are capable of hosting the bacteria for a long period of time.


What happened now?

There are two theories:

  1. The bacteria is also found in the gills and digestive tracts of healthy fish. It reproduces through spores and these spores remain dormant for years. They are resistant to temperature changes and drying. Under favourable conditions, the spores are activated. After the monsoon, when the water levels receded, there might have been an increase in salinity levels which could have led to the death of these living organisms. At this point in time, the spores could have been activated.
  2. ‘A bird-to-bird cycle’ could also have led to the tragedy. In such an event, maggots feeding on dead birds can concentrate the toxin. Birds feeding on dead birds can get affected. This was observed in Sambhar too as researchers found only insectivorous and omnivorous birds affected and not herbivores.


What need to be done?

The government should pass legislation in the Assembly to create a Sambhar Lake Development and Conservation Authority.

This authority should be handed A to Z responsibility of Sambhar Lake.

A fresh document should study why the water from four rivers, which flows into the lake, has decreased over the years. It should study the hydrology, sedimentation, the increase or decrease in depth of the lake, as well as birds, animals, their food sources, etc.


Sources: down to earth.