Chicken infectious bursal disease is an acute, highly contagious infectious disease caused by a double stranded RNA infectious bursal virus, characterized by damage to the bursal and immune suppression.

Pathogen and clinical characteristics:

There are two serotypes of bursal virus with low cross protection rates, and only type 1 is pathogenic. The VP2 protein of the virus is associated with pathogenicity, inducing the production of serotype and strain specific neutralizing antibodies. There are two genotypes of chicken bursal disease virus, namely the classical type (weak strain, strong strain, and super strong strain) and the mutant strain. The classic strain causes "spike death" in chicks, including muscle bleeding, bleeding at the junction of glandular muscle and stomach, and diffuse bleeding from bursa of Fabricius. And mutant strains can cause slow growth in chicken flocks, with a low mortality rate of less than 3% and antibodies that can break through the classical strain vaccine, leading to atrophy of the bursa of Fabricius and immune suppression. In recent years, with the widespread use of COVID-19 vaccines in China, classic cases of COVID-19 have been well controlled, and currently over 90% of outbreaks are caused by mutant strains.

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Vaccine types:

At present, there are many types of bursa of Fabricius vaccines on the market, which are mainly classified into the following categories. The advantages and disadvantages of each vaccine are shown in the figure:

Prevention and control strategies:

Chicken farms need to strictly implement biosecurity measures and disinfect the breeding environment. Do a good job in daily chicken breeding management and feeding nutritionally balanced full price feed. For areas with high incidence of diseases, it is recommended to use inactivated vaccines that have good protective effects against local epidemic and variant strains within 7-10 days. In addition, epidemic areas need to develop a reasonable live vaccine immunization program based on the growth and decline of maternal antibodies in the chicken flock. Generally, oral or drinking water immunization is selected around 14 days.