Birds flew with flu
The good news conveyed to this writer by the director of the Bhopal-based National Institute for High Security Animal Diseases (NIHSAD), Dr DD Kulkarni, was that faecal samples of migratory birds (ruddy shelduck, mallard etc) from the Sukhna lake’s regulator-end had tested negative for avian influenza viruses.
Yet, in the same breath, Dr Kulkarni maintained that migratory birds were the prime suspects in the transmission of the virus, H5N1, leading to the death of domesticated ducks and geese at the Sukhna. I requested Dr Kulkarni to resolve this seeming contradiction.
“Migratory birds are routine carriers of flu viruses. But not all such migratory birds die or get sick from this virus and they remain silent reservoirs. Nor is it that all migratory birds are virus carriers. That said, one of the principal ways in which the virus is passed to other birds is through faeces or other discharges from the migratory bird’s body into water. But migratory birds, which are carriers, may not shed the virus through their faeces every time they defaecate. So, even though the samples we took from the lake on December 24 tested negative for viruses, it is entirely possible that these sampled birds did not exit the virus on that particular day. It is also possible that other, non-sampled migratory birds at the lake went undetected as carriers. It is likely the domesticated geese were infected with virus through faecal or other discharges from a different set of migratory birds or from birds that exited the virus on certain occasions only,” said Dr Kulkarni.
The joint director of the Jalandhar-based Regional Disease Diagnostic Laboratory, Dr Vinay Mohan, believes that the tourists’ feeding point for domesticated geese at the Sukhna lake’s entrance, where migratory birds mingled freely, was a likely point of the killer virus transmission. The three migratory bird species that intermingled with domesticated geese here — common pochard, tufted ducks and eurasian coots — are notified by the Government of India as carriers of avian flu viruses.
Origins of bird flu
How does science trace the history of avian influenza and its evolution? According to the World Organisation for Animal Health, which is the nodal authority for the global monitoring of this disease, “Influenza in birds is caused by infection with viruses of the family orthomyxoviridae placed in the genus influenzavirus A. Influenza A viruses are the only orthomyxoviruses known to naturally affect birds. Many species of birds have been shown to be susceptible to infection with influenza A viruses; aquatic birds form a major reservoir of these viruses...”
Dr Vinay Mohan traced the carrier linkages: “The virus is believed to have originated in oceanic birds, which developed high resistance to it. These oceanic birds passed it to land-based wild birds, which developed resistance also but there have been cases of the latter group suffering catastrophic mortality. Domesticated geese have lesser resistance to the virus than migratory birds. Poultry has least resistance to the virus.”
He draws attention to the synergic concept of “one health”. Dr Mohan says that many of the diseases afflicting humanity currently are originating from wild and domesticated animals/birds. “We are keeping so many pets, livestock for human use has increased, and we are engaging more with wild animals as we invade their habitat. So, such zoonotic diseases from the animal world are engaging the attention of veterinarians and human health specialists via the collaboratory concept of ‘one health’: keep animals free from disease and thereby ensure human health.”
Migratory birds are popularly associated with waterfowl, and currently with the avian flu scare. Yet, there is another wintering migrant from the more northern latitudes and one that prefers scrublands and has been observed by Chandigarh birders on a few occasions in the hinterland areas of Dera Bassi, Lalru and Chhat village. And, it is not notified as an avian flu carrier! So, rest easy! This is the short-eared owl, and one that does not always stare down hard from a safe tree perch as one normally expects owl species to do so. As the late ornithologist, Dr Salim Ali remarked, this owl was often flushed from the ground when shikaris walked up to gamebirds such as partridge and quail. This owl is so named because of its erect but barely visible ear tufts comprising feathers and resembling mammalian ears. It has a rather quaint habit, as described by Dr Ali: “...sunning itself sprawled belly to the ground with wings outspread”.
The owl hunts during parts of the day and night, gobbles rodents but also small birds and insects, and does so by swooping down on prey to seize it with sharp talons. Interestingly, the owl in its summer breeding sites lays eggs on the ground. Studies show that “eggs hatch asynchronously usually in the order of laying, so the earliest hatched have an advantage for survival”.
Since its habitat is grasslands and open country, which are under perpetual threat, the owl comes into food conflict and encounters with other raptors, such as shikras and harriers. So, next time you birders walk through scrublands dotting the tricity hinterland and under colonisation from agriculture and real estate, do tread gently and keep a sharp eye and ear for a burst and flash of this charming parliamentarian!