Clucking in alarm

poultry farms across north India are facing a mysterious viral disease. As many as two million birds have fallen prey to the illness and the economic loss has already mounted to more than Rs 60 crore. Even as the authorities' final diagnosis is long overdue, a chicken-and-egg controversy -- involving a major industry player and a pharmaceutical giant -- has erupted on whether or not a vaccine caused the outbreak

 
By T V Jayan
Last Updated: Saturday 04 July 2015

-- (Credit: Ruhani Kaur / CSE)poultry farms across north India are facing a mysterious viral disease. As many as two million birds have fallen prey to the illness and the economic loss has already mounted to more than Rs 60 crore. Even as the authorities' final diagnosis is long overdue, a chicken-and-egg controversy -- involving a major industry player and a pharmaceutical giant -- has erupted on whether or not a vaccine caused the outbreak.

Vinay Mahajan, a Haryana-based poultry farmer and vice-chairperson of the National Egg Coordination Committee, informed Down To Earth that the disease has spread its tentacles in major poultry belts in Punjab, Haryana, Rajasthan, Madhya Pradesh and Uttaranchal (see map: Worst-hit areas). While the official mortality rate is 5-6 per cent, farmers admit that it could actually be 10-15 per cent. The disease was first reported at a poultry farm in Haryana's Barwala district, located nearly 50 kilometres (km) from Ambala, on March 10. The density of poultry population in Barwala is 5.5 million birds per 15 square km -- the highest in north India. Not surprisingly, 0.9 million birds have succumbed to the disease in the region alone.

More than two months have elapsed since the illness was detected, but the only official response that could be elicited from the Indian Veterinary Research Institute (ivri) was that preliminary tests have yielded "a mixed reaction". This, in effect, means that more than one disease is prevalent. The Izatnagar-based institute in Uttar Pradesh is the premier poultry and livestock laboratory under the Indian Council of Agricultural Research (icar). Off the record, however, the concerned authorities have categorically stated that the illness is a mild strain of avian influenza (ai) -- a viral disease whose symptoms range from slight to severe infection. In its acute form ai can prove fatal for the domestic fowl, turkeys, guinea fowl and species such as the migratory waterfowl. Curiously, the Union government's department of animal husbandry and dairying is thinking of coining a new term to refer to the contagion: the "Barwala Conjunctivitis Syndrome".

Meanwhile, scientists are blaming the Union and state governments for not taking preventive steps expeditiously. Of utmost concern to them is the authorities' inordinate delay in notifying the disease, which could impact poultry trade drastically by delaying implementation of containment measures. How high the stakes are can be gauged from the fact that the Rs 29,000-crore Indian poultry industry is the fourth largest in the world. It covers an expansive area in terms of geographical location. Andhra Pradesh, Tamil Nadu, Haryana, Punjab and Maharashtra are the leading poultry-producing states. The country currently has an egg-laying poultry hen population of approximately 120 million, with the average daily egg production touching 95 million.

Consultants in Haryana and Punjab feel that some poultry farms, particularly in the latter state, were afflicted before Barwala's case came to light. They fear that south India, which accounts for the largest share of poultry industry in the country, could also be affected in the near future. "Egg trays are freely exchanged from one poultry belt to another. Droppings and dust on them can carry the pathogen to other states," points out a veterinary scientist.
Matter of conjecture The most noticeable symptoms in ailing birds are conjunctivitis and mild facial oedema. These are quite similar to problems associated with a commonly occurring poultry viral illness called Ranikhet disease (rd) or Newcastle disease. However, veterinary specialists maintain that the rd vaccines currently available domestically have not proved effective in this case. They assert that the infection is spreading at a much faster rate as well. A section of experts has thus inferred that the illness is not rd.

Mohinder S Oberoi, a virologist in the department of veterinary microbiology at the Ludhiana-based Punjab Agricultural University (pau), has a different view. He cites studies conducted on samples from local poultry farms to back his claim that the disease is rd. But Oberoi is at a loss to explain why the existing vaccines did not work. The Ranikhet virus is said to be stable and does not mutate easily. Incidentally, all poultry birds in the country are covered by doses of rd vaccine since the disease is considered fatal.

The results of pathogenicity studies carried out by the ivri's High Security Animal Disease Laboratory (hsadl) at Bhopal in Madhya Pradesh may provide some definitive answers about the infection. But these would only be announced after the director of the facility returns from leave. hsadl identifies exotic diseases in the country. For the present, experts are suggesting stop-gap solutions. A case in point is the ingenious method devised by a few consultants in Haryana to minimise damage. "We found that if the affected birds are starved for three to four days, their immunity levels go up," discloses an expert. Consequently the current mortality rate, according to him, has dropped to around 2-3 per cent.

Chance finding
A tangential issue spawned by the crisis has led some experts to draw a different conclusion. The matter pertains to a vaccine that leading drug manufacturer Ranbaxy Laboratories imports and sells in the domestic market. Pune-based Venkateshwara Hatcheries Limited, the country's largest poultry house, has levelled serious charges linking the product to the illness. Simply put, the row revolves around which came first: the virus or the vaccine?

The poultry firm alleges that the vaccine is responsible for the disease. It is said to have been used widely by farmers in Barwala, and resulted in the occurrence because it contains a hitherto unreported virulent strain. Predictably, the pharmaceutical company has issued a strong rebuttal.

Ranbaxy actually ruffled a few feathers recently, when it sent bird samples to the reputed Surrey-based Weybridge Laboratories in the uk in an attempt to clear its name. The company jumped the gun by not seeking the government's permission before despatching the specimens abroad. As per the regulations of Office International des Epizootic (oie), the global authority on animal diseases, only the secretary of the government's department of animal husbandry and dairying is authorised to take this step.

An unexpected fallout from the controversy is that the preliminary lab report has shown the disease-causing pathogen to be an ai variety called h9n2. Even scientists who do not concur with the uk lab's deduction admit that ai's symptoms overlap with those of rd. In India, the reagent of ai is available only at hsadl.

The viruses' serological identity is based on the two surface antigens present in them -- haemagglutinin (ha) and neuraminidase (na). Veterinary virologist A T Venugopal points out that the same strain was detected in ducks in certain pockets of Kerala over a decade and a half ago. Unlike some h5 and h7 viruses, mortality due to h9n2 is significantly low. At the same time, earlier studies reveal that this variety of ai can infect humans who come in contact with the infected birds. " h9n2 may indeed cause mild respiratory problems in humans," confirms Venugopal. Significantly, however, experts clarify that the consumption of infected chickens does not entail any risk.

A few years ago, the highly pathogenic h7 strain of ai wrought havoc in Pakistan. The mortality rate was as high as 80 per cent among flocks. An ai h5n1 epidemic forced Hong Kong to destroy all its poultry in 1997. Six people also died in the outbreak. The virus reared its head again in the region in February 2002. Three European countries -- Belgium, Germany and The Netherlands -- are currently reeling under a virulent attack of ai. They have restricted shipment of live poultry and eggs. Alarmingly, there are reports of human-to-human spread of the virus. The Netherlands has culled 25 million birds -- one-fourth of its total poultry population. Belgium has slaughtered 0.7 million birds and Germany has ordered the precautionary killing of 84,000 hens.

Overkill
Vaccines used for healthcare generally contain pathogens in milder quantities for generating immunity in the host body. The rapid growth of the Indian poultry industry has resulted in a sudden spurt in the manufacturing and marketing of a large number of vaccines -- a trend that has left a few members of the scientific community apprehensive. It is felt that the indiscriminate use of vaccines, which themselves contain disease-causing micro-organisms, could facilitate the entry of new pathogens into India.

Scientists at the Izatnagar-based Central Avian Research Institute (cari), another icar laboratory, warn that any country must think twice before it decides to import a live vaccine (contains a virus that is alive) -- "more so, if killed vaccines are good enough to tackle a particular disease." However, sometimes even killed vaccines contain live viruses if proper care is not taken.

"A number of new live poultry vaccines have come into the country in the past two years. They are being freely imported and promoted among poultry farmers through discounted prices and other propaganda," laments Anuradha Desai, chairperson of Venkateshwara Hatcheries.

A senior ivri scientist opines that while live vaccines can provide lasting immunity, there is an attendant risk because of likely impurities. He cites the case of an earlier polio vaccine being contaminated by a simian virus (sv40), which was a cell-transforming micro-organism. The probability of a new disease-causing strain being introduced is, therefore, very high when live vaccines are imported.

The past decade or two has seen the poultry industry emerge as a major revenue earner for the government. Yet the authorities have failed to put in place a stringent disease surveillance system for this largely privatised sector. Which is why the chickens have come home to roost.

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