Wednesday, January 27, 2021
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The Hindu Explains | How serious is the bird flu outbreak in India, and how can it be contained?

The Hindu Explains | How serious is the bird flu outbreak in India, and how can it be contained?
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Does bird flu pose a threat to human beings? Why does bird flu recur? Did the major outbreaks not help form strategies?

The story so far: Avian influenza, popularly known as bird flu, has been reported from Kerala, Rajasthan, Madhya Pradesh, Himachal Pradesh, Haryana, Gujarat and Uttar Pradesh in recent weeks. During the first week of January, reports of unusual deaths of a large number of birds, including wild ones, started coming in from many States, indicating that the virus is being actively transmitted among various bird groups. The two virus types identified so far in the outbreaks — H5N1 and H5N8 — come under the category of Highly Pathogenic Avian Influenza (HPAI), which is of major concern to those keeping birds, because it leads to disease and death of fowl and causes economic havoc. H5N1 is a known threat to humans as well. The spread of the disease in a variety of birds in several geographical regions, and the seasonal movement of migratory birds, have prompted the Centre to issue an alert to States to adhere to the National Action Plan for Prevention, Control and Containment of Avian Influenza 2021. Internationally, the World Animal Health Information System in December 2020 identified outbreaks of HPAI in Taiwan, Iran, Israel, Japan, South Korea and Vietnam, a dozen European Union countries, Ukraine, Russia and the U.K., leading to a loss of over 4.8 million birds by the end of December 2020.

How serious is avian flu for bird health?

Avian Influenza (AI) is a highly contagious viral disease, affecting a variety of birds, including those connected with human consumption — chickens, ducks, turkeys, quails — as well as pet birds and wild birds. The World Organization for Animal Health, which collaborates with the World Health Organization (WHO) and the Food and Agriculture Organization (FAO), says HPAI virus strains H5N1, H5N2, H5N8, H7N8 have been identified in outbreaks, indicating active circulation. Infection histories point to H5N1 and H7N9 viruses posing a threat to human health as well.

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The FAO says wild birds act as a natural reservoir of AI viruses. Their migratory movement could bring these pathogens to poultry, waterfowl and other domestic birds through contact. HPAI produces severe clinical signs of disease in birds, causing a high degree of mortality and economic loss. The response to an outbreak is a containment strategy, which is primarily centred around removing the diseased birds through culling. Such mass destruction causes a severe impact on farmers.

In the latest viral spread, in just one instance, Kerala has already identified over 69,000 birds, mostly ducks, stricken with H5N8, to be culled at four infection sites in the Kuttanad area of Alappuzha.

What is the economic impact of bird flu?

India’s poultry sector, according to the Ministry of Agriculture and Farmers Welfare, is worth ₹80,000 crore, of which the organised sector represents 80%, and the rest is distributed among unorganised sectors, including backyard poultry-keeping which is crucial for income and nutritional security.

Also read | Centre’s Wildlife Division issues guidelines to States on containing avian flu

Exports, mainly focused on West Asia, neighbouring countries and East Asia, were valued at ₹532 crore in 2017, with an emphasis on processed products such as egg powder, yolk powder, pharma ingredients, and chicken products. Avian flu is seen as a threat to the further growth of the sector as a whole.

By the government’s estimates, there are 30 million farmers who keep backyard birds, while small and medium farmers who contribute to aggregators are crucial players in the larger ecosystem. India has a base of over 729 million poultry birds, of which 30% are layers and 40% are broilers, according to the National Action Plan for Egg and Poultry 2022. This large base shows that a serious outbreak of HPAI, as was witnessed during 2005-06 in some States, can be catastrophic. During that year, official data put the number of culled birds at over one million.

In later years, bird flu surfaced in several States, such as Manipur, Assam, West Bengal, Tripura, Bihar, and Kerala, leading to destruction of millions of birds.

Also read | Bird flu — The Bar Headed Goose and its strong link with Pong Dam Lake in Himachal

Where culling of birds is undertaken to combat bird flu, the National Action Plan prescribes compensation to be given to farmers at fixed rates. This, once again, underscores the value of prevention to protect captive birds.

Does bird flu pose a threat to human beings?

The WHO, in its literature on avian influenza, states that humans can be infected with virus subtypes H5N1, H7N9 and H9N2. In a recent instance of human infection, a one-year-old was confirmed to have H5N1 in Lao PDR, thought to have been acquired from backyard birds kept by the family. Infection in other birds in the region was also confirmed. On the H5N1 virus, the WHO says, “Human cases of H5N1 avian influenza occur occasionally, but it is difficult to transmit the infection from person to person. When people do become infected, the mortality rate is about 60%.”

The global health body records that since 2003, there have been 862 laboratory-confirmed cases of human infection with H5N1, and 455 deaths have been reported from 17 countries.

Also read | Duck farmers in Kerala in deep trouble due to bird flu outbreak, seek govt. help

On the H5N8 strain, the consensus is that human infection cannot be ruled out, although the likelihood is low. However, H5N6 infection, of a related clade (a descendant type) has occurred among humans, the WHO says. One case of the H9N2 strain, in a three-year old girl, was reported last October from Guangdong, China. It was mildly symptomatic and was detected during routine surveillance for Influenza-like illness.

AI viruses in poultry have a public health dimension because they cause severe disease in humans and “have the potential to mutate to increase transmissibility among humans”, the WHO adds. This calls for pandemic preparedness. Human-to-human transmission is believed to have taken place in some instances as a result of close or prolonged contact, but “there has been no sustained human-to-human transmission identified”.

Why does bird flu recur? Did the major outbreaks not help form strategies?

It is impossible to eradicate influenza viruses because they persist in a vast reservoir of aquatic birds. The answer to why there are periodic outbreaks that spread to domestic environments may lie in local bird-keeping conditions. After the unprecedented outbreak in 2006 in Asia, when as many as 258 cases of bird flu in humans had been reported till November 13 of that year, experts who met at an international conference in New Delhi under the aegis of WHO felt that continuous growth in poultry farming under poor sanitary conditions was sustaining the virus, with multiple susceptible species living in the same area. This underscores the importance of prevention and surveillance.

The Delhi Declaration passed at the summit resolved on a common framework for countries to build local strategies, but it did not lay emphasis on preserving the natural environment, which is key to helping wild birds move safely in an unspoilt habitat and stop transmission of viruses to domestic fowl, which threatens humans with infections and a potential pandemic due to mutating viruses.

What steps can be taken to minimise risk to domestic birds?

Governments lay down biosecurity measures to keep domestic birds safe from transmission by wild or migratory birds and prevent local spread. The protocol involves active surveillance of bird areas to identify emerging outbreaks. On the other hand, it is wrong and counterproductive, the FAO cautions, to attempt elimination of wild birds near human settlements through hunting, poisoning, and habitat destruction. Such activity disperses wild birds, and the viruses, to new areas. Moreover, hunting of wild birds and the absence of biosecurity measures bring the viruses directly to domestic fowl.

In the wake of an outbreak in 2020, the U.K. issued advice making it legally necessary for bird-keepers in that country to house them in such a manner that they do not come into contact with wild birds. The measures, which have general relevance to farmers everywhere, include housing or netting all captive birds, cleansing and disinfecting clothing, footwear and vehicles, reduction of people’s movement in the farm bird areas to reduce contamination, eliminating or reducing contact between captive and wild birds, particularly through feed and water storage, and cleansing and disinfecting production areas. The U.K. uses a checklist approach to help farmers with best practices.

In India, the Central government requires veterinary staff to conduct inspections periodically under the Prevention and Control of Infectious and Contagious Diseases in Animals Act, 2009, to catch any signs of disease among birds and other animals early. However, aquatic wild birds are often found in close proximity to domestic ones in many locations in India, near lakes, dams and reservoirs, making it difficult to achieve segregation. The waterways of Kerala are a good example of this phenomenon.



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