Avian botulism is a serious neuro-muscular illness caused by a toxin produced by the bacterium Clostridium botulinum. Avian botulism typically results in paralysis – with the infected birds exhibiting unusual behaviour. For example, water birds may not be able to hold their head up and as a result, often drown. Gulls can often walk, but not fly. Other birds may drag one or both wings, exhibiting poor posture while standing. In general, outbreaks of avian botulism occur only when a variety of ecological factors occur concurrently. This typically involves warmer water temperatures, oxygen deprivation in water, and higher levels of bacterial substrate in the form of decaying plants, algae or animal materials.
In Rajasthan
According to the IVRI report, the outbreak at Sambhar was caused by the climate. The neurotoxin production may have been triggered by warm weather, it said. Further, water levels were fluctuating throughout the year. Due to a good monsoon this year, the water level reached the lake bed after a gap of 20 years. The monsoon might have provided a favourable environment for the bacteria to spread. The monsoon also brought with it a large population of crustaceans (such as shrimps, crabs and prawns), invertebrates (snails) and plankton (such as algae). These organisms are capable of hosting the bacteria for a long period of time.
Transmission
Avian botulism is not contagious: it is not spread directly from bird to bird. But it can spread to birds through their consumption of maggots infected with the bacteria. When an infected bird dies, the maggots that feed off it become infected themselves. These maggots are in turn consumed by other birds, thus getting infected. This was observed in Sambhar too as researchers found only insectivorous and omnivorous birds affected and not herbivores.
Treatment
The sick birds are receiving supportive treatments as there is no cure for avian botulism. A bird ICU has been set up. They are administrated antibiotics, multivitamins, eye drops, fluid and oxygen as well as nutritious feed.
Picture Credit : Google
