The year 2013 marks 16 years since the H5N1 avian influenza virus, often called bird flu, was first reported, and it is getting more difficult to contain with every passing year. The virus has killed 377 people till date, and more than 150 million chickens infected or suspected to be infected with the virus have been killed in more than 60 countries.
The infection is caused by influenza virus type A, which normally infects birds and is highly contagious. The first case of human infection with highly pathogenic H5N1 avian influenza was reported in Hong Kong in 1997. In 2003, the most devastating and widespread outbreak of H5N1 to date emerged in Asia before spreading to Europe, Africa, and North America. The most obvious victim of bird flu is the multibillion-dollar poultry industry. Estimates of global losses due to outbreaks amount to hundreds of billions of dollars. [break]
The biggest threat to the poultry industry is the backlash due to customer fears. Several polls conducted in 2006 found that more than 40 percent of people thought they could get bird flu by eating poultry. Poultry sales in France fell by 30 percent following an outbreak. Consumer reaction was even more severe in Romania, which witnessed an 80 percent drop in poultry sales in May 2006.
In Italy, sales fell by 70 percent after wild swans were infected. Early in 2007, the price of chicken in Indonesia dropped by 50 percent. Similarly, after the detection of bird flu in Kathmandu Valley in the first week of July, the trade of poultry and poultry meat has come down to 5-10 percent, and about 50 percent meat sellers who used to sell only poultry meat are on the way to closure.
But does H5N1 really pose a safety risk? Continuing outbreaks of bird flu in poultry in Asia, Europe, and Africa have raised concerns about various sources of infection and risks to humans. Based on current evidence, direct contact with infected, live, or dead poultry is responsible for a majority of infections in humans. There is also concern that the virus could spread to humans through contact with contaminated poultry products.
In developed countries, meat is bought, either refrigerated or frozen, from a butcher or supermarket. In Asia, however, it is common practice to buy chickens and other live animals and slaughter them at home. As a result, Asians are more exposed to potentially disease-carrying animals, both in their homes and as they pass through the markets. Wet markets have been identified as one of the sources of H5N1 infection in humans. This raises a number of questions about food safety during an influenza outbreak.
H5N1 is sensitive to heat. Thus, it is safe to consume poultry as long as it has been cooked properly and evenly at 70°C. Consumers should also be aware of the risk of cross-contamination. Raw poultry liquids and products should never touch items that are eaten raw. People involved in the preparation of raw/frozen poultry products should thoroughly wash their hands and disinfect all utensils that contact the poultry. Hot water and soap are sufficient for this purpose. The clear message is that consumption of raw poultry ingredients poses a high risk, and should be discouraged. The virus can also be present in the tissue of frozen chicken, because low temperatures maintain the viability of the virus.
In 2004, Japan and Korea banned imports of both live and frozen poultry meat from China and Thailand following identification of the virus in frozen poultry samples. Once again, whether it is purchased fresh or frozen, the meat should be properly and thoroughly cooked.
The virus can also be found inside egg whites, egg yolks, and on the surfaces of eggs laid by infected birds, but proper cooking inactivates the virus inside the eggs. Uncooked eggs that have not been treated should not be used in food that will not be cooked, baked, or treated in any other way. There have been no reported cases or epidemiological evidence to suggest that people have been infected by consuming eggs or egg products. To eliminate shell contamination, commercial egg suppliers have to wash and disinfect the outsides of eggs with chlorine prior to breaking or packaging. When H5N1 is present in poultry, the virus can be present in meat and eggs from affected birds. It is safe, however, to consume poultry products that have been cooked thoroughly.
Another issue is that while consumers are mainly concerned about eating poultry and eggs during bird flu outbreaks, some food products are grown in agriculture and aquaculture using chicken litter as a fertilizer. Virus particles in chicken manure are inactivated after six days at 15-20°C, after 36 hours at 28-30°C, and after only 20 minutes at 56°C. It is not likely that litter from an infected poultry farm would be released several weeks after the birds have been killed or removed from the premises, and subsequently, test positive for the presence of virus. Suppliers of poultry manure should assure their customers of biosecurity measures on their farms and ensure that poultry litter is composted, properly ensiled, and dried with heat treatment. Efforts to contain the virus need to include all three stages of the food chain: the first step, the poultry farms; the intermediate step, the marketplaces; and the tertiary end of the food chain, the food processing industry and consumers.
Other than people who breed and rear birds, there are many workers such as cleaners, packers, cooks, chefs, food handlers, and other kitchen workers who come in contact with birds. People responsible for slaughtering birds must wear protective clothing. Workers cleaning and decontaminating poultry houses must also take special precautions; they are likely to have contact with contaminated feces.
Poultry growers and processors have to ensure that no dead birds are delivered to slaughterhouses. They must also adopt zero tolerance of fecal contamination of carcasses, and must dispose of tissues where the virus is most likely to reside, such as the lungs, trachea, head, and intestines.
Improved farming practices are needed to contain the spread of bird flu. These include improved biosecurity measures, quarantine for sick birds, disinfection of transport vehicles and cages, and protective clothing for farm workers. Outbreaks of bird flu have been occurring sporadically for the last 10 years, with no end in sight, imposing grave losses on the poultry industry.
Vaccination, drug treatment, and other containment efforts cannot be maximized unless the infection is detected quickly enough. Diagnosing primary bird flu infection should be of the utmost concern; early diagnosis can allow swift implementation of biosecurity, quarantine, and culling, as well as other control measures to safeguard the poultry industry. Further, bird flu outbreaks must be controlled in poultry to maintain the profitability of the poultry industry and to guarantee food security. Rapid, accurate, and easy-to-use methods that give both state-of-the-art laboratories and those with limited resources a rapid testing system are needed to prevent the spread of the disease.
The author is a Senior
Veterinary Officer
karkikedar96@gmail.com
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