Sambhar bird death: Mortality pattern indicates Avian botulism, says report

JAIPUR: Bikaner-based microbiologist Dr A K Kataria, who conducted the post-mortem examination of birds that died at Sambhar Lake , concluded in his report that "mortality pattern, epidemiological parameters and classical clinical symptoms" indicated that the cause of death of over 8,000 birds was 'Avian botulism' - a serious neuro-muscular illness caused by a toxin produced by bacterium Clostridium botulinum.

The report, prepared by Kataria of Apex Centre for Animal Disease Investigation, Monitoring and Surveillance, College of Veterinary and Animal Sciences, RAJUVAS, along with Dr Rohitash Dadhich, Dr Sandeep Kumar Sharma and Dr Madan Mohan Mali, stated, "On the basis of history, epidemiological observations, classical clinical symptoms and post-mortem findings, the most probable diagnosis is Avian botulism."

"During the visit, data was collected regarding the start of arrival of migratory birds, possible time of onset, pattern and duration of disease, age and species of affected birds, any treatment given and response to treatment and any other observation made. The birds were examined for their clinical symptoms and samples (nasal and oral swabs) were collected from sick animals for analysis. Post-mortem examination of two available fresh carcasses was carried out and tissue samples were collected for histopathological examination. Additionally water samples was taken from lake for bacteriological analysis," read the report.

"The mortality pattern, epidemiological parameters, classical clinical symptoms, availability of the carcasses and post-mortem findings are sufficient to tell me that the cause of deaths of the birds is Avian botluism. It is caused by a toxin that is produced by an anaerobic bacteria called clostridium botulinum. It remains in the soil for years together and feeds on protein/muscles. From the soil, it goes into the meat of the dead animal and grows there. When it multiplies, it produces toxins, called botulinum toxin. This toxin is very fatal and potent. One gram of toxin is able to kill 5 lakh adult cattle heads," Kataria told TOI adding that this was the first time this phenomenon has been observed in the state.

"So, when non-vegeterian birds feed on maggot-infested carcasses, the toxin in the muscles reaches the body of the healthy animals. It reaches their nerves and lead to paralysis of the birds. Everything depends on the amount of toxin consumed by the bird . But, flamingoes, which do not feed on maggots or meat, are not dying. Only, cadaver eating birds are dying," he added.

The report stated, "During the visit, information was collected from attending veterinarians and the general public about the disease. According to locals, they first saw several hundred carcases 5-6 days ago from the day of our visit. The veterinarians reported that there was no response to any treatment given to sick birds. The death of the affected birds was seen over a variable period of time. The mortality rate increased with passage of time and till the day of visit thousands of birds of all ages but of some specific species succumbed. Some species which do not feed on carcases were not affected at all."