Re: India - Bird Flu in Poultry/Animals Feb 5th +
Re: India - Bird Flu in Poultry/Animals Feb 5th +
Epidemic outbreaks
Though the bird flu virus in major districts in Bengal and North Bengal has been widespread, much remains to be learned about the epidemic wherein, unlike most avian flu viruses that mainly affect the respiratory tract,
A(H5N1) has been found to damage the liver and
kidneys in humans, writes Arunayan Sharma
Birds are in great danger. They are posing threat to our lives as they have been detected as carrier of the deadly virus known as Avian Influenza or Bird Flu. Although threat is mainly for the domesticated varieties of poultry chickens and ducks but can pass through wild variety of migratory birds. Avian influenza viruses have been found in many bird species, but are most often found in migratory waterfowl. Wild birds, especially waterfowl and shorebirds, have been a reason of concern for long time in poultry industry as a source for influenza infections in poultry birds. The first influenza virus was from marine birds and it was classified as subtype H5N3. Other wild birds yielding influenza viruses include various species of shorebirds, gulls, quail, pheasants, and ratites (ostrich and rhea). Bird flu is considered lethal.
With recent out break of this disease among poultry birds in various districts including Malda, North and South Dinajpur of West Bengal millions of chickens either died of infection or were put to death. The majority of waterfowl migration takes place within geographic areas. Many species other than waterfowl follow these same migratory pathways from their breeding grounds to the wintering grounds and return to the breeding grounds. Influenza virus has been found in wild birds throughout the year, but waterfowl are the only group in which these viruses are always found.
?Bird flu? is a phrase similar to ?Swine flu or ?Human flu? refers to an illness caused by many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species: Influenza ?A?virus. All subtypes (but not all strains of all subtypes) of Influenza ?A? virus are adapted to birds, which is why for many purposes avian flu virus is the Influenza ?A? virus ( ?A? does not stand for ?avian?). Adaption is non-exclusive. Being adapted towards a particular species does not preclude adaptions, or partial adaptions, towards infecting different species. In this way strains of influenza viruses are adapted to multiple species, though may be preferential towards a particular host.
In domestic birds, the indicators of disease are not diagnostic because they are highly variable and they depend on the strain of virus, bird species involved, and a variety of other factors including age and sex. Signs of disease may appear as respiratory or reproductive abnormalities. Included are such nonspecific manifestations as decreased activity, food consumption and egg production; ruffled feathers; coughing and sneezing; diarrhea; and even nervous disorders, such as tremors. Observable symbols of illness have not been described for wild birds. In domestic chickens and turkeys, certain virus subtypes like H5N2 and H7N7, respectively, are usually highly virulent and may cause up to 100 percent mortality in infected flocks. Too little is known about the impact of influenza viruses on the reproductive performance of wild birds to assess whether they are affected in the same manner as poultry.
Avian influenza viruses in wild birds cannot be effectively controlled because of the large number of virus subtypes and the high frequency of virus genetic mixing resulting in new virus subtypes. Also, virus has been recovered from water and fecal material in areas of high waterfowl use. The virus has been recovered from poultry houses more than 100 days after flock depopulation for markets. In the domestic bird industry, preventing the entry of the virus into poultry flocks is the first line of defense. Vaccines are selectively used to combat less virulent forms of this disease. Antibody present in the blood of recovered and vaccinated birds prevents virus transmission. Therefore, these birds pose little risk to other birds. Flocks are generally killed when they are infected with highly virulent viruses. In the past, the poultry industry and the wildlife conservation community have been in conflict regarding wildlife refuge development and other waterbirds habitat projects. Much remains to be learned about avian flu. Unlike most flu viruses ? which mainly affect the respiratory tract ? the A (H5N1) has been found to damage the liver and kidneys of humans. In some birds, it even attacks the central nervous system, causing the animal to flop around before it finally dies. It is feared that the virus may develop the ability to spread from person to person through close contact. That would mean going a step closer to the possibility of an epidemic. The focus has now being shifted from preventing the spread of the flu among animals to limiting the probability of human infection. This is being done through awareness initiatives like encouraging farmers to keep chickens out of their homes, wash their hands after contact with poultry and cook meat and eggs at 70 degrees and above. The pattern of human infection remains a mystery. Of those infected many were children who may have contracted the disease simply because they are closer to the ground and thus more likely to breathe in the exhalations.
On the other hand, there have been no cases of infection among the workers involved in culling chickens because they are taking precautions during their work.
Once the highly unstable A (H5N1) virus infects a person, it already has its effect gone through a huge number of possible combinations through random genetic recombination, a constant reshuffling of its genome that produces nonviable viral particles could, in theory, produce something terrifying. Genetic factors in distinguishing between ?human flu viruses? and ?avian flu viruses? include: PB2: (RNA polymerase): Amino acid (or residue) position 627 in the PB2 protein encoded by the PB2 RNA gene. Until H5N1, all known avian influenza viruses had a Glu at position 627, while all human influenza viruses had a lysine. HA: (hemagglutinin): Avian influenza HA bind alpha 2-3 sialic acid receptors while human influenza HA bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors. Pandemic flu viruses have some avian flu virus genes and some human flu virus genes. Both the H2N2 and H3N2 pandemic strains contained genes from avian influenza viruses. Swine were considered the original ?intermediate host? for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans.
In spite of their pandemic connection, avian influenza viruses are noninfectious for most species. When they are infectious they are usually asymptomatic, so the carrier does not have any disease from it. Thus while infected with an avian flu virus, the animal doesn?t have a ?flu?. Typically, when illness (called ?flu?) from an avian flu virus does occur, it is the result of an avian flu virus strain adapted to one species spreading to another species (usually from one bird species to another bird species). So far as is known, the most common result of this is an illness so minor as to be not worth noticing. But with the domestication of chickens and turkeys, humans have created species subtypes (domesticated poultry) that can catch an avian flu virus adapted to waterfowl and have it rapidly mutate into a form that kills in days over 90 per cent of an entire flock and spread to other flocks and kill 90 per cent of them and can only be stopped by killing every domestic bird in the area. Until H5N1 infected humans in the 1990s, this was the only reason avian flu was considered important. Since then, avian flu viruses have been intensively studied; resulting in changes in what is believed about flu pandemics, changes in poultry farming, changes in flu vaccination research, and changes in flu pandemic planning. H5N1 has evolved into a flu virus strain that infects more species than any previously known flu virus strain, is deadlier than any previously known flu virus strain, and continues to evolve becoming both more widespread and more deadly causing. The highly pathogenic Influenza A virus subtype H5N1 virus is an emerging avian influenza virus that has been causing global concern as a potential pandemic threat. It is often referred to ?bird flu? or ?avian influenza? even though it is only one subtype of avian influenza causing virus. H5N1 has killed millions of poultry in a growing number of countries throughout Asia, Europe and Africa. Health experts are concerned that the co-existence of human flu viruses and avian flu viruses (especially H5N1) will provide an opportunity for genetic material to be exchanged between species-specific viruses, possibly creating a new virulent influenza strain that is easily transmissible and lethal to humans.
Since the first H5N1 outbreak occurred in 1997, there has been an increasing number of HPAI H5N1 bird-to-human transmissions leading to clinically severe and fatal human infections. However, because there is a significant species barrier that exists between birds and humans, the virus does not easily cross over to humans, though some cases of infection are being researched to discern whether human to human transmission is occurring. Although millions of birds have become infected with the virus since its discovery, 206 humans have died from the H5N1 in twelve countries according to WHO data as of November 2007. Epidemioloigists are afraid that next time if such a virus mutates, it could pass from human to human. If this form of transmission occurs, another big pandemic could result which would be a major threat for the human society.
Wild birds can carry the viruses, but usually do not get sick from them. The H5N1 virus is endemic in much of Asia and has spread into parts of Europe and Africa. Currently, close contact with infected poultry has been the primary source for human infection. Though rare, there have been isolated reports of human-to-human transmission of the virus. Genetic studies confirm that the influenza a virus H5N1 mutates rapidly. Should it adapt to allow easy human-to-human transmission, a pandemic could ensue ? it has not done so to date. At this time, it is uncertain whether the currently circulating H5N1 virus will lead to a global disease outbreak in humans ? a pandemic. The reported symptoms of avian influenza in humans have ranged from typical influenza-like symptoms (fever, cough, sore throat, and muscle aches) to eye infections (conjunctivitis), acute respiratory distress, viral pneumonia and other severe, life-threatening complications.
Avian Influenza have been found not just in chickens and ducks, but also in teal, Canada geese, gray herons, feral pigeons as well as the black-headed gull and a peregrine falcon. Avian influenza is non-clinical viral infection of wild birds caused by a group of viruses known as type A influenzas. These viruses are maintained in wild birds by fecal-oral routes of transmission. The virus subtypes are identified and classified on the basis of two broad types of antigens, hemagglutinan (H) and neuraminidase (N); 15 H and 9 N antigens have been identified among all of the known type A influenzas. Different combinations of the two antigens appear more frequently in some groups of birds than others. In waterfowl, for example, all 9 of the neuraminidase subtypes and 14 of the 15 hemagglutinin subtypes have been found, and H6 and H3 are the predominant subtypes. In shorebirds and gulls, 10 different hemagglutinin subtypes and eight neuraminidase subtypes have been found. Many of the antigenic combinations of subtypes are unique to shorebirds. H9 and H13 are the predominate subtypes. More influenza viruses from shorebirds infect waterfowl than chickens. Hemagglutinin subtypes H5 and H7 are associated with virulence or the ability to cause severe illness and mortality in chickens and turkeys. However, two viruses with the same subtype antigens can vary in virulence for domestic birds.
Vaccines to protect humans against H5N1 viruses currently are under development. In addition, research is underway to make large quantities of vaccine more quickly. So far, research suggests that two antiviral medicines, oseltamavir (Tamiflu) and zanamavir (Relenza), may be useful treatments for H5N1 avian influenza. Some adverse reactions have been reported in children. However, H5N1 viruses are generally resistant to two other available antiviral medications, amantadine and rimantadine, so they cannot be used to. The deadly bird flu virus, which has killed millions of birds and dozens of people in East and South-East Asia, Central Asia, recently reached in West Bengal and parts of North Bengal in Malda and North and South Dinajpur district. The government of West Bengal is still discussing strategies to prepare for the virus, in case migratory birds carry it there from Asia. But in India and its sleepy poultry markets in particular, health and hygiene seem low on the priority list.
In the past years, India has checked random samples of chicken blood for H5N1, the virus that has caused havoc in other parts of Asia. But traders and farmers at and poultry retailers, are not armed with precautions. Traders shrug off fears. No disease can hurt Indians as we cook chicken in high temperatures and with hot spices no germs can survive at this temperature. Eventually, the samples are sent to Bhopal, where the High Security Animal Disease Laboratory scans them for H5N1. India set up this system a year ago when the avian flu struck South-East Asia. The Bhopal testing and diagnostic facility is only the fifth of its kind in the world, and the first in a developing country.
Every winter, birdwatchers and ornithologists eagerly await the arrival of migratory birds. In India, migratory birds come from the northern part of the globe. Such movement, however, sometimes poses the threat of disease, a phenomena that has of late assumed large proportions. Malda with its numerous big wetlands attracts large numbers of migratory birds every year. Home to various migratory birds, the district is facing the danger of bird flu. A spate of deaths, including the first possible case of human-to-human transmission, has stirred fears of a broader outbreak thus raising the chances of a human pandemic. But little can be done to stop the menace: a vaccine is yet to be made available. A recent survey by the Centre for Ecological Engineering found that poultry breeders and chicken sellers were unaware of the disease.
However, the Centre for Ecological Engineering is organising awareness programmes on this Bird Flu to the village peoples where migratory waterbirds are arrived in close proximity of their backyard poultry farming.
If avian flu starts spreading among humans, health experts warn it could lead to a disaster. The government is not equipped with proper medicines and medical teams. Birdwatchers traveling to North Bengal should be careful and take some precautions while going for waterfowl census in the wetlands. Anything unusual should be promptly should be reported immediately to the concerned authority. However, one need not unnecessarily panic. It is important not to give in to rumours ? that the chicken being sold in the local markets are not infected. It is advised to avoid chicken preparations irrespectively convinced by local poultry traders that Indian system of chicken cooking is safe for you. Prevention is better than cure.
(The author is the director of the Centre for Ecological Engineering Malda.):tiphat:
http://www.thestatesman.net/page.news.php?clid=31&theme=&usrsess=1&id=188411
