bird flu

Bird FlueAvian Influenza

• Avian influenza, more commonly known as bird flu is a contagious viral infection which can affect all species of birds. This infectious disease is caused by type A strain of the influenza virus. There are about fifteen subtypes of influenza viruses. Influenza A (H5N1) is a subtype of the Type A influenza virus

The 1918 flu pandemic killed more people than WWI

• The virus was first isolated from birds (terns) in South Africa in 1961

• Avian influenza A (H5N1) was first recognised in 1997 in Hong Kong

• During this outbreak, 18 people were affected, with six deaths and the outbreak was halted in Hong Kong by slaughter of the chickens.

• In 2003, H7N7 avian influenza affected poultry flocks in the Netherlands, leading to one human death amongst 83 affected people. The outbreak was halted by culling affected flocks.

• H5N1 has recently re-emerged in many Asian countries in slightly altered form. The disease have been confirmed among poultry in Cambodia, China, Hong Kong, Indonesia, Japan, Laos, South Korea, Thailand and Vietnam.

• Symptoms include coughing, sneezing, ruffled feathers, swelling of the skin under the eyes, blisters on the combs, swollen heads, nervous signs like depression, and diarrhea. Decreased food consumption and drops in egg production are among some of the earliest and most predictable signs of disease. In some cases, birds die rapidly without clinical signs of disease.

Symptoms

• Subtypes of the influenza A virus known as (H5N1) and (H9N2) have been known to infect humans. The symptoms of avian influenza in humans are akin to those of human influenza, fever, fatigue, malaise, myalgia, sore throat, cough and in severe cases pneumonia. Conjunctivitis is seen in some patients.

Human

Spreading

• Certain water birds act as hosts of avian influenza virus by carrying the virus in their intestinal tract and shedding it in their feces.

• Infected birds shed virus in saliva, nasal secretions and feces.

• The avian influenza virus can remain viable for long periods of time at moderate temperatures, and can survive indefinitely in frozen material. As a result, the disease can be spread through improper disposal of infected carcasses, manure, or poultry by-products.

• Transmission of Avian influenza A from birds to humans is a rare event; but it may spread to humans, when they come into contact with the droppings of infected birds

Prevention

• Infected birds shed virus in the first two weeks of infection

• No contact with newly affected and suspectable birds

• Preventing direct contact with free-flying birds and protecting domestic poultry from contact with the feces of wild birds is an important way to prevent avian influenza.

• Apart from being highly contagious, avian influenza viruses are readily transmitted from farm to farm by mechanical means, such as by contaminated equipment, vehicles, feed, cages, or clothing

•Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. In the absence of prompt control measures backed by good surveillance, the epidemic can last for years

• Any object located on an infected poultry farm must be considered contaminated and should be completely cleaned and disinfected before it is moved from that premises.

• Influenza viruses are very sensitive to most detergents and disinfectants.

• They are readily inactivated by heating and drying. However, flu viruses are well-protected from inactivation by organic material and infectious virus can be recovered from manure for up to 105 days.

• Complete removal of all organic material is part of any effective disinfection procedure.

• All buildings should be cleaned and disinfected after an infected flock is removed.

• The poultry litter should be composted before being used as manure to cultivated lands.

• Organic material should be removed followed by complete cleaning and disinfection of all surfaces. Contaminated litter and manure is problematic and should be composted to ensure that it does not spread infectious virus.

Treatment• There is no effective treatment for avian

influenza. Good husbandry, proper nutrition and broad spectrum antibiotics may reduce secondary infections

• Diagnosis of avian influenza may be made on the basis of symptoms and events leading to the disease. However, since the symptoms and course of avian influenza are similar to other diseases, laboratory diagnosis is essential.

• Recently discovered anti-viral drug, Tamiflue is considered as the only possible defense against an outbreak of human to human avian flue.

• A chemical compound called shikimic acid is the basic material for making Tamiflue drug.

• The acid is extracted from a spice named star anise, which is harvested in China, North Vietnam and neighbouring countries.

• The drug has proved effective against the lethal H5N1 strain of the bird flu. The drug will not prevent the Avian flue but it can reduce the severity of the disease.

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