Towards the end of the year 2020, avian influenza (AI) or bird flu was reported from many states in India. The latest bird flu outbreak in poultry and wild birds has spanned over many states and union territories in India, from Jammu and Kashmir in the north to Kerala in the south. The states of Himachal Pradesh, Rajasthan, Madhya Pradesh, Haryana, Maharashtra, Punjab, and Kerala were particularly severely affected. Bird flu was reported among wild geese in Himachal Pradesh, crows in Madhya Pradesh and Rajasthan, and ducks in Kerala, whereas 1 lakh poultry birds died mysteriously in Haryana. Similarly, 250 crows were found dead in several districts of Rajasthan. The outbreak involved highly pathogenic viral strains H5N1 and H5N8, according to the Indian government. Ever since early 2021, states have been struggling to step up vigil and measures to control the spread of the disease.
The present outbreak of avian influenza is marked by the significant involvement and mortality of wild birds. This has necessitated for proactive monitoring of animal disease in the environment, conserving unprotected wetland habitats to curb disease spread.
Avian influenza/Bird flu
Avian influenza is a highly contagious viral disease that affects both domestic and wild birds. It occurs worldwide and is caused by Influenza Type A viruses which normally affect poultry birds. There are different strains which are more prevalent in certain areas of the world than others. The World Organisation for Animal Health (WOAH), which collaborates with the World Health Organization (WHO) and Food and Agriculture Organization (FAO), has broadly classified the viruses based on their pathogenicity. It has classified the AI viruses as low pathogenic AI (LPAI) and highly pathogenic AI (HPAI) or influenza A viruses.
The LPAI is mild and may merely cause a low egg production or other mild symptoms among chickens. The HPAI, which is severe and lethal, generally affects poultry birds such as chickens and turkeys. HPAI virus strains H5N1, H5N2, H5N8 or H8N1, H7N9 have been identified in outbreaks. Infection histories state that H5N1, H7N9 viruses pose a threat to human health as well.
Spread of AI
The Food and Agriculture Organization (FAO) states that wild birds such as geese, shorebirds and wild ducks are the natural reservoirs of AI viruses. Their migratory movement usually brings these pathogens to poultry, waterfowl, and other domestic birds through contact. The migratory birds travel long distances and the viruses are thus further spread to poultry and terrestrial birds.
Many birds carry the flu without developing sickness, and shed it in their droppings. Sometimes, birds excrete while flying leading to suspension of influenza virus through fine solid particles or liquid droplets in the atmosphere. Sometimes, the virus jumps over to mammals, such as pigs, horses, cats, and dogs. This way it spreads all over the world. The highly pathogenic avian influenza (HPAI) produces severe clinical signs of disease in birds which leads to high degree of mortality.
Moreover, AI and other zoonotic diseases are in the environment. As human activities encroach natural habitats and environments used by wild species, the risk of transmission increases.
The latest viral spread in Kerala identified over 69,000 birds, mostly ducks, stricken with H5N8 strain. Those ducks had to be culled at four infection sites to curtail further infection. According to World Health Organization (WHO), bird flu outbreaks were reported in several countries including Taiwan and Japan and a number of European countries. More than 48 lakh birds died or were culled in December 2020 all over the world.
Bird Flu Infecting Humans
For decades, bird flu outbreaks have been affecting the poultry around the world. The usual method to contain the spread of the virus is the culling of infected birds. It was only in 1996–97, the first case of human contraction of bird flu virus followed by an outbreak was witnessed in a market of Hong Kong and China. All the 18 people were affected with the H5N1 strain of the virus. Later six of them died of the disease. Since 2003, many laboratory tests have confirmed the cases of human infection of H5N1 strain that caused hundreds of deaths around 17 countries.
Though it was contained, it re-emerged after a few years in various other parts of the globe. This also led to the death of hundreds of humans especially in Southeast Asia. Movement of infected poultry and migratory birds and illegal bird trade are believed to be the causes for the spread. Some mammals such as cats and lions were also infected by the virus.
In the recent past, a one-year-old child was infected with H5N1 strain, in Laos. The infection was acquired by the child from the domestic birds of the family. According to WHO, human cases of H5N1 AI occur occasionally. It is difficult to transmit the infection from person to person. The mortality rate is about 60 per cent.
Several other strains of the virus such as H5N2 and H9N2 spread from animals to humans, thus becoming a global public health concern. Although the likelihood of infection in humans from H5N8 strain is low, it cannot be ruled out. According to the WHO, the H5N6 infection of AI has occurred among humans. In October 2020, a three-year-old girl from Guangdong, China was infected with H9N2 strain of AI.
AI viruses in poultry have a public health dimension because they cause severe disease in humans. They have the potential to mutate and can increase transmission among humans. The WHO says that human-to-human transmission is believed to have taken place in some instances as a result of prolonged close contact with the infected person. However, there is no sustained evidence to prove the case.
According to WHO, there is also no evidence that the disease can be spread to people through properly prepared and cooked poultry food. The virus is sensitive to heat and dies in cooking temperatures. About the safety concerns over eating eggs and chickens, scientists say it is safe to consume poultry products that are properly cooked at over 60–70 degree Celsius. Any temperature above this kills viruses.
Threat to Humans
The H5N1 strain of AI is severe and deadly and once transmitted to humans, leads to death in many cases. The various strains have the potential to mutate to increase transmissibility among humans. If the virus mutates and gets transmitted from person to person by altering its shape to grab human cells much more effectively, it can potentially cause a pandemic.
It is a known fact that flu viruses are more prone to mutation because they have a segmented genome. All known strains of flu, including the seasonal flu and the pandemic flu, have jumped from birds to humans in this way.
Symptoms and Treatment of Bird Flu in Humans
The AI attacks the respiratory tract of humans and may cause severe respiratory illnesses such as pneumonia or Acute Respiratory Distress Syndrome (ARDS). Its early symptoms include fever, cough, sore throat, and sometimes abdominal pain and diarrhoea. Antiviral drugs are usually prescribed to improve the prospects of survival in humans. The union health ministry in India has advised people who work in poultry farms to use personal protective equipment (PPE) kit and follow hand hygiene. In the US, the Food and Drug Administration (FDA) had approved a vaccine for the H5N1 virus in 2007.
Bird Flu in India
India has recently emerged as a global hotspot for HPAI H5N1 as it provides critical wintering habitat for many species of migratory waterfowl and year-round habitat for several resident waterfowl species. The country lies at the heart of Central Asian Flyway (CAF). It spans over 30 countries and covers 279 populations of 182 migratory waterbird species that rely on wetlands along the flyway including the Pong Lake Wildlife Sanctuary and Ramsar site.
In India, the disease spreads mainly through migratory birds coming into India during winter months, i.e., from September–October to February–March. Another reason could be attributed to human handling through equipment (fomites) that carry the infection. The department of animal husbandry had reported 25 cases of H5N1 bird flu in poultry in 15 states from 2006 till 2015. The same strain has also been detected in crows.
Luckily bird flu viral infection in humans is not yet reported in India. There is no direct evidence which state that AI viruses was transmitted to humans via the consumption of contaminated poultry products.
Economic Impact of Bird Flu in India
India consumes around 30 crore poultry birds and around 900 crore eggs per month on average. The poultry sector of India is worth more than ` 80,000 crore, of which more than three-fourths is from the organised sector.
Around three crore farmers are engaged in the unorganised sector of poultry in backyard bird-keeping and supplying products to aggregators, who negotiate with the producers directly. India has a base of over 700 million poultry birds. According to the National Action Plan for Egg and Poultry 2022, 30 per cent of poultry consist of egg-laying birds, and 40 per cent are broilers. India exports processed poultry products such as egg powder, yolk powder, chicken products, and also pharmaceutical ingredients from the poultry sector worth hundreds of crores every year.
The actual economic cost of the current bird flu outbreak is yet to be calculated as this is an ongoing situation. There was a serious outbreak of HPAI in the year 2005–2006 in some states which was disastrous. Official data states that during that period over one million birds were culled.
The National Action Plan prescribes compensation to be given to farmers at fixed rates. The government had paid over Rs 26 crore to farmers between 2006 and 2018 on account of culling to contain spread of bird flu in India. The farmers, however, complain that compensations do not cover for their profit that they could have earned from regular business. This underscores the value of prevention to protect captive birds.
Prevention of Bird Flu in India
Implementing the management practices that incorporate biosecurity principles, personal hygiene, and cleaning and disinfection protocols, as well as cooking and processing standards are effective means of controlling the spread of the avian influenza virus.
The Department of Animal Husbandry and Dairying has set up a control room in New Delhi. This is to keep watch on the situation and to take stock on a daily basis of preventive and control measures undertaken by state authorities.
The measures suggested to the affected states to contain the disease and prevent further spread as per the National Action Plan on Avian Influenza include:
- strengthening the biosecurity of poultry farms;
- disinfection of affected areas;
- proper disposal of dead birds or carcasses;
- timely collection and submission of samples for confirmation and further surveillance;
- intensification of surveillance plan as well as the general guidelines for prevention of disease spread from affected birds to poultry and humans;
- coordination with the forest department for reporting any unusual mortality of birds; and
- a vigil on any unusual mortality amongst birds and early reporting.
The UK government had issued a legal advice making it necessary for bird keepers and poultry farmers to follow. These measures have general relevance and in India too poultry farmers can observe the following advice given by the UK government:
- housing or netting of 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.
Challenges in Controlling and Preventing Bird Flu
While the emphasis should be on monitoring multiple waterbird sites of local, national, and international importance, surveillance is complicated by the nature of the poultry-wild bird–wetlands interface.
Once the virus is introduced into a wetland, it can infect migratory or domestic birds and from there the virus can move to another area through local movements of these birds. This may then reinfect poultry or resident birds. Additionally, the virus may be picked up by predatory birds or raptors if they feed on dead or dying infected wild birds or poultry, which is beyond human control.
Attempts to eliminate wild birds near human settlements through hunting, poisoning and habitat destruction would disperse wild birds and the viruses to new areas. Hunting of wild birds and the absence of biosecurity measures bring the viruses directly to the domestic fowl.
India needs veterinary staff to conduct inspections periodically under the Prevention and Control of Infectious and Contagious Diseases in Animals Act, 2009. This will help to catch any signs of disease among birds and other animals early.
Conclusion
It is hardly possible to eradicate AI viruses because they persist in a vast reservoir of aquatic birds. Aquatic wild birds are often found in close proximity to domestic ones in many locations in India. For example, near lakes, dams, reservoirs, etc. which makes it difficult to achieve segregation.
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