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Experts debunk migratory birds theory

Thursday, 1 November 2012 - 3:50pm IST | Place: Bangalore | Agency: dna

Ornithologist MB Krishna reasoned that migratory birds that have to fly thousands of kilometres to reach their destinations could not possibly be able to do so if they were infected.

The hunt for the elusive cause of the avian influenza outbreak at Central Poultry Development Organisation & Training Institute (CPDOTI) on Tuesday saw officials of animal husbandry department blaming migratory birds for carrying the virus. But ornithologists have debunked the theory despite animal husbandry officials stating that the Hesaraghatta Lake close to CPDOTI facility which attracts migratory birds was the culprit for the outbreak.

MB Krishna, ornithologist and ecologist reasoned that migratory birds that have to fly thousands of kilometres to reach their destinations could not possibly  be able to do so if they were infected. “Basically sick birds can’t fly the kind of distances which migration requires. These birds never weigh more than few kilograms; so how can they even fly across India?”

Besides, he said Hesaraghatta Lake has been dry for two years now. “So how are these migratory birds going there when there is no water?” he said.

Ornithologist, Harish Bhat, too, agreed with Krishna. He said the number of migratory birds had declined in the last five-six years.
He said Karnataka receives about five to six species of ducks from North America and Europe; Bangalore gets about four to five species of smaller birds such as warblers from Siberia. Then there are a few species of raptors like eagles and harriers from Europe. They come during the winter and leave before summer begins.

“(But) In the last five-six years, the number of birds coming to the lakes in Bangalore have greatly reduced. Now we get about three-four thousand birds during this season. But these birds are not carriers. It has been wrongly understood that they do, but the fact is such birds hardly interact with poultry as they are water- based birds. So how can they spread this disease?” he said.

Dr Sudheendra Rao NR, Research Fellow, National Brain Research Centre, Manesar, Gurgaon, who has treated influenza patients and closely connected with avian influenza-related research, said migratory birds being blamed for the outbreak should be taken with a touch of salt.

“If you look at the outbreaks across the world, you will see that majority of the cases clustered around poultry. It is true that some migratory birds (e.g Bar-headed geese) have been implicated in bringing in low pathogenic avian influenza virus to the mainlands. But we have to acknowledge that it actually is the local environment that is supporting its spread. Hence, I am not sure we can blame the migratory birds entirely for these outbreaks,” he said.

Ornithologist-ecologist Krishna said several vets he had interacted with in the wake of the outbreak had reportedly said that it was the hygiene factor within CPDOTI which had caused the virus to infect the birds by lowering their immunity systems.
“The cages in which chickens are kept in have to be properly sterilised,” he said.

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