Avian influenza has been a prevalent disease in Vietnam and around the world for many decades. It has caused significant damage to the country’s livestock industry since its initial outbreak in 2003 and its rapid spread in 2005.

Efforts to prevent and control avian influenza in Vietnam have become increasingly challenging as the disease continuously evolves with new strains, which diminish the effectiveness of vaccines over time and render them less effective than desired.

According to Professor Dr. Nguyễn Văn Giáp from the Vietnam National University of Agriculture (Ministry of Agriculture and Rural Development), avian influenza currently circulates in Vietnam with two types: high pathogenic avian influenza viruses (HPAIV) and low pathogenic avian influenza viruses (LPAIV).

Since the avian influenza virus entered Vietnam in 2003, high pathogenic strains have continually mutated. New strains have emerged over the years, starting with H5N1, followed by H5N6 in 2014, and the most recent, H5N8, since early 2021. To this day, all three strains are still present in Vietnam.

Additionally, the high pathogenic avian influenza viruses have continually produced new genetic branches. Currently, Vietnam is dealing with branches 2.3.2.1 and 2.3.4.4, while other branches, such as branch 1 or branch 7, have appeared and then disappeared.

Professor Giáp emphasizes that the genetic mutations of avian influenza A viruses have led to changes in antigenic properties to some extent. In veterinary medicine, the effectiveness of certain vaccines depends on matching the vaccine strains with the pathogens. This principle is particularly crucial for vaccines against diseases such as avian influenza, foot-and-mouth disease, and leptospirosis.

“Regarding avian influenza, there are continuous appearances, disappearances, and mutations of various strains and genetic lineages of high pathogenic avian influenza viruses, accompanied by changes in antigenic properties. Therefore, from a professional standpoint, the use of avian influenza vaccines needs to be strain-specific,” said Associate Professor Dr. Nguyễn Văn Giáp.

This specificity needs to be addressed from two perspectives. Firstly, vaccine manufacturers must produce vaccines with antigens that match the circulating virus strains. Secondly, poultry farmers need to select vaccines that are appropriate for the specific strains of avian influenza in their region.

“This is particularly important in the context of having many vaccines made from different genetic lineages available on the market,” the expert emphasized.

Additionally, Associate Professor Dr. Nguyễn Văn Giáp noted that authorities consistently have programs to monitor the circulation and identify strains, and genetic lineages of high pathogenic avian influenza across different regions. Therefore, farmers can refer to annually updated documents to determine the appropriate strains. Furthermore, farmers can contact vaccine suppliers for testing and identifying suitable virus strains.

According to Associate Professor Dr. Nguyễn Văn Giáp, China is the second-largest poultry producer in the world (after the United States). Therefore, the situation of high pathogenic avian influenza in China is much more complex than in Vietnam.

For instance, in addition to the H5 strain, China also has the H7 strain. Even within the H5 lineage, the number of genetic groups in China is far more diverse.

However, from the perspective of commonly circulating genetic lineages, such as 2.3.2.1 and especially 2.3.4.4, Vietnam shows significant similarities with the strains circulating in China.

“This can be explained by the trade between the two countries, particularly the movement of animals and animal products, as well as the free movement between nations. From another angle, I believe the role of migratory birds in spreading avian influenza virus strains across continents is also significant,” the expert from the Vietnam Academy of Agriculture analyzed.