Avian Influenza, or “bird flu”, is a virulent and highly contagious viral disease, which occurs in poultry and other birds, and, less commonly, pigs. While all bird species are thought to be susceptible to infection, domestic poultry flocks are especially vulnerable to infections that can rapidly reach epidemic proportions.
Birds can die on the same day that symptoms first appear. Avian influenza can occasionally spread to humans and other animals, usually following direct contact with infected birds.
What are the Control Measures in Birds?
The most important control measures are rapid destruction of all infected or exposed birds, proper disposal of carcasses, and the quarantining and rigorous disinfection of farms. The virus is killed by heat (56ºC for 3 hours or 60ºC for 30 minutes) and common disinfectants, such as formalin and iodine compounds.
The virus can survive, at cool temperatures, in contaminated manure, for at least three months. In water the virus can survive for up to 4 days at 22ºC and more than 30 days at 0ºC. Restrictions on the movement of live poultry, both within and between countries, are another important control measure.
How do Outbreaks of Influenza Spread Within a Country?
- Farm to farm spread: dust and soil are contaminated by virus in bird droppings
- Airborne virus can spread the disease, causing infection when it is inhaled.
- Contaminated equipment, vehicles, feed, animals, cages or clothing – especially shoes – can carry the virus.
How does the Disease Spread from One Country to Another?
The disease can spread from country to country through international trade in live poultry. Migratory birds can carry the virus for long distances and have, in the past, been implicated in the international spread of highly pathogenic avian influenza. Migratory waterfowl – most notably wild ducks – are the natural reservoir of bird flu viruses, and these birds are also the most resistant to infection – they only develop a mild and short-lived illness.
Domestic ducks, however, are susceptible to lethal infections, as are turkeys, geese, and several other species raised on commercial or backyard farms.
Avian Flu Outbreak
In mid-December 2003, a growing number of Asian countries reported outbreaks of highly pathogenic avian influenza in chickens and ducks. Infections in several species of wild birds and in pigs were also reported.
The rapid spread of highly pathogenic avian influenza, with outbreaks occurring at the same time in several countries, was historically unprecedented and of great concern for human health as well as for agriculture.
A highly pathogenic strain of the virus –H5N1 – has jumped the species barriers causing severe disease in humans, particularly in Viet Nam and Thailand.
Signs and Symptoms in Humans
Include: fever, sore throat, cough, and, in several of the fatal cases, severe respiratory distress secondary to viral pneumonia. Previously healthy adults and children, and some with chronic medical conditions were affected.
Diagnosis
Laboratory tests for diagnosing all influenza strains of animals and humans are rapid and reliable. Rapid bedside tests for the diagnosis of human influenza are also available in some countries.
Vaccination
Effective when administered to high-risk groups, such as poultry cullers, to protect against circulating human strains and thus reduce the risk that humans at high risk of exposure to the bird virus might become infected with human and avian viruses at the same time. Such dual infections give the avian and human viruses an opportunity to exchange genes, possibly resulting in a new influenza virus subtype with pandemic potential.
Prevention and Treatment
Neuraminidase inhibitors – oseltamivir and zanimivir
These drugs have been licensed for the prevention and treatment of human influenza, and are thought to be effective regardless of the causative strain.