Bird Flu in Poultry: Causes, Signs, Prevention & Control

Avian influenza, commonly known as bird flu, is a contagious respiratory disease that primarily affects poultry, especially turkeys. It is characterized by symptoms such as respiratory distress, depression, and decreased feed and water consumption, and can lead to a decline in hatchability among breeders and a significant drop in egg production.

Causes of Avian Influenza:

Avian Influenza Type A Orthomyxovirus, the causative agent, is deactivated at temperatures of 56°C within 3 hours and 6°C within 30 minutes.

In nature, the virus is mainly found in wild waterfowl and shorebirds, which act as natural reservoirs by carrying and transmitting the virus without exhibiting clinical signs.

The virus is easily destroyed by most common disinfectants. Avian influenza has two forms: highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI).

The virus is classified based on the glycoproteins present on its surface envelope, including 16 types of hemagglutinin (H) and 9 types of neuraminidase (N).

The H5N2 strain has been traced back to bird markets, and the virus can undergo form changes.

Transmission of the Disease:

Avian influenza can spread through direct contact between infected and susceptible birds, as well as through indirect contact, including exposure to aerosol droplets, contaminated boots, clothing, equipment, and offal.

Live birds and even eggs can carry and transmit the virus, which can survive freezing temperatures. Poultry infected with low-pathogenic avian influenza may experience reduced egg production and respiratory signs, while highly pathogenic avian influenza can cause rapid death, severe coughing, nervous involvement, paralysis, and decreased egg production.

Affected birds may isolate themselves, display physical abnormalities, and die within a short period.

Gross Lesions:

Low pathogenic avian influenza may present no symptoms, while severe lesions can be observed in the highly pathogenic virulent form. These lesions include hemorrhages in the pericardial sac, mesentery, air sacs, fat tissues, and shanks. Fibrinous exudates can also be found in the trachea, air sacs, sinuses, and abdominal fat.

Diagnosis of Avian Influenza:

Diagnosing avian influenza involves considering clinical signs and a history of exposure to wild birds or selling meat from deceased birds. Organ samples such as the liver, spleen, lungs, and intestines can be sent to the laboratory for testing. Differential diagnosis includes Newcastle disease, colibacillosis, and infectious bronchitis.

Treatment and Prevention:

There is no specific treatment for avian influenza, but preventing bacterial infections is essential. Strict biosecurity measures and hygiene practices should be implemented, along with eradication programs. Culling affected birds and ensuring proper disposal are crucial steps. Vaccination is not commonly practiced, and prevention and control efforts are the responsibility of all personnel involved.

Bird Flu and Human Health

Some strains, especially H5N1 and H7N9, have caused illness and death in humans, though such cases are rare and usually involve direct contact with infected poultry or contaminated environments.

Human symptoms can include fever, cough, sore throat, difficulty breathing, and, in severe cases, pneumonia and multi-organ failure.

There is no evidence of sustained human-to-human transmission, but the possibility of viral mutation is a concern.

Clinical Signs in Humans:

In humans, the incubation period for bird flu is typically 7 days. Symptoms include shortness of breath during minimal exertion, sputum containing blood, drowsiness, extreme ear pain, and coughing.

Prevention in humans:

Efforts to control and prevent bird flu include several measures:

1. Restrict imports of poultry and products from Asian countries to prevent the entry of potentially infected birds or contaminated products.
2. Implement a 30-day quarantine period for birds and conduct testing to ensure they are free from the virus before allowing their movement.
3. Conduct avian influenza surveillance in live bird markets to monitor and detect any signs of the virus.
4. Perform avian influenza surveillance in wild migratory birds, as they can carry and spread the virus over long distances.
5. Educating the public on the safe handling and proper cooking of poultry products to minimize the risk of infection.
6. Promote and enforce biosecurity programs to prevent the introduction and spread of avian influenza on farms and poultry production facilities.
7. Implement a national poultry improvement plan to ensure the overall health and quality of poultry stocks.
8. Encouraging individuals to report any suspected cases of avian influenza to the relevant regulating or governing authorities for immediate action.

Challenges in Control:

Despite these preventive measures, several challenges persist:

1. The movement of infected wild birds from infected to non-infected areas poses a continuous risk of spreading the virus.
2. Individuals who handle chickens with feathers may be at risk of contracting the disease if proper precautions are not followed.
3. Raising awareness and sensitizing communities about avian influenza and its prevention remains an ongoing challenge.
4. Although there is currently no evidence of direct human-to-human transmission, the possibility of the virus mutating and gaining the ability to infect humans is a concern.
5. Vaccinated birds can become carriers of the virus, potentially complicating control and eradication efforts.
6. Emergency drugs used for the treatment of human cases, such as the antiviral drug Tamiflu (oseltamivir), may be limited in availability or effectiveness.
7. Basic hygiene practices, including regular handwashing and sanitation, are crucial in minimizing the risk of infection.

Conclusion

In conclusion, avian influenza is a highly contagious respiratory disease that affects poultry and poses a risk to human health. Implementing strict biosecurity measures, conducting surveillance, and promoting public education are vital in controlling and preventing the spread of the virus.

Continual monitoring and research are essential to stay ahead of any potential mutations or outbreaks, ensuring the health and safety of both animals and humans.