Avian influenza strain sparks concern

ByJayashree Nandi, New Delhi
May 05, 2023 04:47 AM IST

Avian influenza: The outbreak has raised concerns recently due to its devastating impact on endangered wild birds and mammals.

India has reported 1 positive case, in a non-domestic species so far, a black heron, of highly pathogenic influenza subtype A (HPAI) H5N1 (avian influenza) variant that is ravaging wildlife in several parts of the world.

Veterinarians take a sample for avian influenza from chickens in Indonesia. (AFP)
Veterinarians take a sample for avian influenza from chickens in Indonesia. (AFP)

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The outbreak has raised concerns recently due to its devastating impact on endangered wild birds and mammals.

Out of 1500 samples received by the Department of Animal Husbandry this year, only 1 non-domestic bird tested positive for the highly virulent virus. But, considering India’s rich biodiversity, the detection of the infection is still a matter of concern.

There have already been 2-3 outbreaks in Kerala and Jharkhand among domestic birds this year which had to be contained by mass culling, according to officials. Outbreaks were reported from Thiruvalla in the kuttanad belt among ducks in January; AND among poultry farms in Ranchi and Bokaro in Jharkhand in March. Over 400 chicken died in a period of five days at the government poultry farm located in Lohanchal, in Bokaro according to news reports from Jharkhand.

“India is not new to avian flu. We have been detecting outbreaks since 2006. But, there are two issues of concern with the current global outbreak—the speed of its spread and the fact that it is infecting mammals. But we do not need to panic. Covid has taught us how important detection and surveillance is. It is continuously being done. We have a clear protocol in place on how to handle outbreaks. One of the reference labs of World Organisation for Animal Health is in India which is the National Institute of High Security Animal Diseases (NIHSAD). It is a state-of-the-art facility and has been detecting these cases,” said Abhijit Mitra, Animal Husbandry Commissioner, Department of Animal Husbandry & Dairying.

“Only one case of a non-domestic bird has tested positive for HPAI so far. However, we cannot be complacent,” he added.

From 2021 to 2022, Europe and North America have observed their largest and most extended epidemic of avian influenza with unusual persistence of the virus in wild bird populations. A broader range of wild bird species continue to be infected globally which has significant ecological consequences and has caused mass die offs in some species, the World Health Organisation said in a rapid risk assessment released last year.

“There was an outbreak in Kerala and Jharkhand this year. The infection can affect migratory bird species. There is no vaccine for it. The only way to curb is through active detection and culling. In some mutations the virulence is very high as is the case this year globally. In a flock of birds, even if 2-3 birds are infected, they will have to be culled. Ducks and poultry are particularly susceptible. There are low pathogenicity infections also which have impacted birds in the past,” said Aniket Sanyal, Director, ICAR-NIHSAD, Bhopal.

“The mutations normally follow a global pattern. So the dominant strain globally is likely to be here (India) also,” added Mitra.

The most recent wave of infection spread began in October 2021, and to date thousands of outbreaks have been recorded worldwide. Events have been mainly in North America (56%) and Europe (34%). Massive mortalities were reported in seabirds, aquatic birds, and raptors, and there are also reports of infections in wild mammals such as foxes, otters, and seals, which is relatively unusual for H5 strains. Although the current outbreaks have been linked to a low number of human infections, involving mild symptoms, all H5N1 strains pose zoonotic risks, the World Organisation for Animal Health said.

Avian influenza is a disease caused by Influenza A virus (AIV). AIV can infect birds and mammals, including humans, and is transmitted effectively through respiratory aerosols, faeces and bodily fluids, whether directly (host-to-host proximity) or indirectly (contaminated water or objects).

WOAH recommends that If there is evidence of unusual sickness and/or deaths of wild birds (especially aquatic birds and raptors) or mammals (especially carnivores), local animal health and wildlife conservation authorities should be notified immediately to ensure that appropriate investigation is conducted. There is no benefit to be gained in attempting to control the virus in wild birds and mammals through culling or habitat destruction. Instead, measures should be taken to improve monitoring, surveillance, and biosecurity especially in areas of congregation of aquatic birds and raptors such as breeding colonies, roosts, migratory stopover sites, shared foraging grounds and where these birds may come in contact with poultry.

The majority of the influenza A(H5N1) HPAI characterized genetically since 2020 related to these outbreaks are belonging to the clade, WHO said.

Sporadic cases reported among humans are usually not very severe and are limited to those with exposure to infected poultry.

Read here: ‘Sars-Cov-2, influenza B Victoria behind surge in respiratory illnesses’

“There have not been mass deaths like in the Sambhar lake in 2021. But even if the infection were affecting birds in the wild we may not know. Its very difficult to detect such deaths in the wilderness. Congregating birds such as ducks are at great risk,” said Asad R Rahmani, veteran ornithologist.

“The next pandemic has already begun. To use a more accurate term, a panzootic — a widespread outbreak of disease among nonhuman animals — is underway. To appreciate this catastrophe, we’ve got to move the focus off humans, at least for a bit. H5N1 is devastating the world’s birds. Eagles are dropping dead, as are great horned owls and peregrine falcons and pelicans,” wrote David Quammen, science writer in New York Times on April 23.

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