Overview of Bird Flu : Epidemic Threatens Poultry Industry Supply Chains

 

Bird Flu 

Origin and Spread of Avian Influenza Viruses

Avian influenza viruses are naturally occurring viruses found in birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them. The viruses are classified into subtypes based on two proteins on their surface, called hemagglutinin (H or H antigen) and neuraminidase (N or N antigen). There are 16 H subtypes and 9 N subtypes of influenza A viruses. Many different combinations of H and N antigens are possible. Wild birds carry the H5 and H7 subtypes that can be deadly to domestic poultry.

Since the H5N1 strain first appeared in Southeast Asia in the late 1990s, several outbreaks of avian influenza virus infection in poultry and humans have occurred. The virus has since spread across Asia, Europe, the Middle East, and Africa. Countries that have reported H5N1 outbreaks in poultry and humans include Azerbaijan, Bangladesh, Cambodia, China, Egypt, Indonesia, Vietnam, and others. The World Organisation for Animal Health reports that over 50 countries have confirmed cases of H5N1 infection in poultry. This widespread geographic distribution poses challenges for controlling outbreaks in poultry and preventing transmission to humans.

Impact on Poultry Industries and Livehoods

Avian influenza viruses can spread readily through domestic poultry populations and cause severe disease and high mortality rates in flocks. Transmission generally occurs through direct contact with infected birds or contaminated surfaces, equipment, and materials. Countries experiencing outbreaks in commercial and backyard poultry flocks have reported death losses of up to 100% in some flocks. To control outbreaks, millions of Bird Flu have been culled, leading to massive economic losses for poultry industries and farmers. For example, Bangladesh, China, Egypt, and Indonesia have each lost tens or hundreds of millions of birds to curb avian influenza outbreaks over the past decade.

In many low and middle-income countries, poultry farming provides crucial livelihoods for smallholder farmers and income generation. Widespread culling of poultry not only devastates farmers financially but also threatens food security. Outbreaks significantly impact poultry trade and exports. Countries that are free of avian influenza report billions in losses from trade restrictions and reduced consumer demand for poultry products during outbreak periods in other countries. The global socioeconomic impacts have been estimated at over $30 billion in the past 15 years. Recurring outbreaks continue to threaten poultry industries worldwide and undermine economic development.

Threat to Human Health

While avian influenza viruses usually do not infect humans, some strains such as H5N1, H7N9, and H10N3 have caused severe disease in people and spread from person to person in rare cases. Since 1997, there have been over 850 confirmed human cases of H5N1 infection according to the World Health Organization, of which over 450 resulted in death. Most cases have occurred after direct contact with infected live or dead poultry. However, some cases of limited human-to-human transmission of H5N1 have been reported among family clusters.

There is concern that avian influenza viruses could mutate or reassort to gain the ability for efficient and sustained transmission between humans, potentially triggering a global pandemic. If a new influenza virus emerged that passed easily from person to person but retained its high mortality rate, the consequences could be severe. Research suggests that a strain of avian influenza with this capability may emerge through either genetic changes or adaptation in an intermediate host prior to human infection. Close monitoring of these events is crucial for pandemic preparedness and timely response.

While human cases have thus far occurred mainly in those exposed directly to infected to bird flu , the geographic spread of avian influenza viruses in poultry increases the risk of animal-human transmission in new locations and raises the chances that a strain may emerge with pandemic potential. Furthermore, recurrent outbreaks prolong exposure opportunities and threaten public health through food systems and indirect contact as well as occupational hazards to those responding to outbreaks or working in live bird flu and in poultry barns. This highlights the critical need to effectively control avian influenza at the animal-human interface.

Challenges of Detection and Response

A major challenge in combating bird flu is efficient detection of viruses in poultry. As the viruses often cause no or mild illness in birds, outbreaks can go unnoticed initially. By the time clinical signs and mortality become apparent, the disease may have spread extensively within and between flocks. Rapid diagnosis and investigation of potential outbreaks is critical for timely response. However, developing countries face capacity challenges for surveillance, laboratory testing, and diagnosis. Delays in detection significantly undermine control efforts through culling and movement restrictions.

When outbreaks are confirmed, effective control requires rapid, coordinated action. However, resource limitations, logistical hurdles, and insufficient contingency planning have hampered response in many countries. Large-scale culling operations involve complex coordination and resources that may be lacking. Disposal of infected carcasses also poses environmental and public health risks if not conducted properly. Tracing contacts and restricting animal movement over large geographical areas is challenging. Effective control ultimately requires multisector collaboration between animal health, public health, agriculture, and other stakeholders at all levels. Building robust surveillance and response capacities remains an ongoing global priority to control bird flu .

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