A recent report by Indian Veterinary Research Institute (IVRI), bareilly on mass death of birds numbered 18,000 around sambhar lake, Rajasthan.
Avian botulism is a neurological disorder which leads to muscle contraction (Flaccid Paralysis), caused by a bacteria known as Clostridium botulinum. C. Botulinum is an anaerobic, spore forming bacteria. C. Botulinum is grouped into 7 types (Type A to G) based on the strains of Botulinum it produce. Among those strains, Type C producing bacteria is primarily responsible for the Avian Botulism. The disease is possibly transmitted through bird to bird cycle( maggot eating decaying infected birds) and/or when birds eat fish which has the strain of C. Botulinum in its gills and digestive tracts. They are commonly found in soil, river and sea water . They usually attack neurons, which leads to paralysis in their legs, wings and neck contraction. As per report, botulism affects both human and animal.
Is this phenomenon is new ?
This is not the first instance avian botulism is recorded. Around the world we can see an example of previous findings in north-east part of USA, especially in Lake Michigan in 2008 and 2012, also in Hawaii islands of northern Pacific Ocean .
Climate change and Binary fission of clostridium botulinum :
Researchers around the world found that climate change potentially outbreaks avian botulism (disease) more frequent than before. Avian botulism more likely to occur during drought and when temperature are above 21 degree Celsius. This witnesses clear conducive temperature for binary fission of bacteria and pathogens.
Avian botulism is difficult to cure in migratory or non-persistent birds due to no clear cutindications and mortality occurs over a period of time. However botulism does not affect every bird unlike avian flu .
Botulism does not affect large birds such as Flamingo and pelican. This is due to low “intensity of toxic” substance produced by bacteria botulism leaves larger birds unaffected .
Insights on sambhar lake – recent happenings:
Death of around 18,000 birds in and around India’s largest artificial lake – Sambhar lake due to Avian Botulinum is a grave concern for environmentalists. Experts say that fluctuating monsoon in Rajasthan is responsible for the outbreak of the disease. As the region saw good rainfall, the water level in the lake reached its highest (developing anaerobic condition). This anaerobic condition along with organic decaying material in the lake became a favourable condition for the reproduction of the bacteria and thereby infecting the region.
Reason for mass-die:
As per IVRI report, maggot worms feeding on dead birds can concentrate the toxin (biomagnification) and birds feeding on dead birds can get affected (birds to birds cycle). This was observed in Sambhar lake only insectivorous and omnivorous birds, not herbivores.
Carcasses of birds are being disposed of in a scientific manner to reduce the possibility of spreading any kind of infection further .
IVRI is working medical experts and research & development teams towards finding a better solution for demagnifying bacterial pathogens.
Though the climate change is inevitably the main culprit, maintaining the health of the water bodies by involving all the stakeholders, mapping the hotspots and keeping a strict vigilance over the region as a preventive measures will reduce the casualties due to outbreaks in future.
Author, Mr Gowthaman K, BE Mechanical engineer. Interested in reading books and notes