Vaccination

Vaccinated birds are less likely to become infected and are less likely to excrete the virus; therefore, vaccination can be used either as a tool to support eradication or as a tool to control the disease and reduce the viral load in the environment. FAO has described three broad categories of vaccination strategies:

Vaccination in response to an outbreak using a "ring vaccination" approach or vaccination of only designated high-risk poultry; this approach should be used in conjunction with culling of infected poultry.

Vaccination in response to a "trigger," such as evidence from surveillance information that a HPAI virus has entered the area: this approach may be used in situations where the potential to improve biosecurity is limited.
Preemptive baseline vaccination, such as vaccinating poultry during restocking of farms in previously infected areas.

Free Ask Question:

1. Definition of Avian Influenza?

2. Agent?

3. Hosts?

4. Transmission?

5. Key Outbreaks of HPAI in Domestic Avian Populations?

6. Current Status of H5N1 in Asia?

7. HPAI As a Biological Weapon?

8. Clinical Features?

9. Differential Diagnosis?

10. Laboratory Diagnosis?

11. Treatment?

12. Prevention?

13. Outbreak Control in Poultr?

Two different types of vaccines are currently available:

Inactivated whole avian influenza virus antigen in oil-based emulsion adjuvant
- These vaccines use a homologous H determinant (such as H5 for the strain currently circulating in Asia).
- They possess either a homologous (such as N1 for the strain currently circulating in Asia) or heterologous N determinant.
- The use of a heterologous N determinant allows use of serologic surveillance to detect the circulation of field virus through the detection of antibodies to the N subtype of the field virus; this is known as the DIVA approach.
- The DIVA approach was used successfully during an LPAI outbreak in Italy.
Recombinant fowlpox virus-vector vaccine
- This contains the gene encoding production of the H5 antigen.
- It may be less effective in older poultry because of earlier exposure to fowlpox virus.
Both types of vaccines are administered by injection.
A number of additional novel vaccines either have been developed or are under development. Examples include:
- Subunit vaccines
- DNA vaccines
- Vaccines based on reverse genetics
- Adenovirus-vectored vaccine delivered via drinking water
- Newcastle disease-vectored vaccine delivered via aerosol

Accepted methods for prevention of avian flu are outlined below. In response to the situation in Asia at present, several short-term strategies were put forth by the international health agencies at a meeting in Malaysia in July 2005. The World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO) issued a statement outlining a multipronged approach that includes:

Educational efforts focusing on small-scale and backyard farms, where most cases of human cases of H5N1 have occurred
Segregation of different animal species (eg, chickens, ducks, pigs) and elimination of these animals' intermingling with humans
Incentives for farmers to report suspected cases of avian flu and to apply control measures
Vaccination of poultry flocks

In August 2005, OIE reiterated this approach, calling for intensification of the mesaures in view of the spread of H5N1 in late summer 2005 into Russia and Kazakhstan and urging financial support from wealthy nations.