- The avian botulism is a neuro-muscular illness caused by Botulinum (natural toxin) that is produced by a bacteria — Clostridium botulinum.
- The bacteria is commonly found in the soil, rivers, and seawater. It affects both humans and animals.
- The bacteria also need anaerobic (absence of oxygen) conditions and do not grow in acidic conditions.
- It affects the nervous system of birds, leading to paralysis in their legs and wings.
- The outbreaks of avian botulism tend to occur when average temperatures are above 21 degrees celsius, and during droughts.
There are two theories:
- 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.
- ‘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.