IBD Vaccination in Broilers

IBD Vaccination in Broilers

Three categories of vaccines, based on their pathogenicity, have been described: 1) mild, 2) intermediate, and 3) virulent. The intermediate type IBD vaccines are most commonly used. These vaccines can stimulate the broiler to produce antibodies earlier than the mild-type vaccines, without significant damage to the BF as may occur with the virulent type vaccines.

The timing of broiler vaccination depends on the level of maternal antibody present in the chicks. High levels of maternal antibody at the time of vaccination will neutralize the vaccine virus. Thus, only a limited active immune response results, and chickens will be susceptible to disease as maternal titers decrease. If low levels of maternal IBD titers are present in the chicks, vaccination may not be effective on farms contaminated with virulent field virus.

Approximately 10 to 12 days are required after vaccination for chickens to develop minimal protective titers. During this "lag time," chickens are susceptible to IBD. In addition, virulent IBD viruses are able to break through higher maternal titers than milder vaccine viruses. Thus, if IBD field virus contamination on a broiler farm is high, nor broiler vaccination can stimulate protection in the flock before damage occurs.

If the maternal antibody titer is not uniform in the broiler flock, multiple costly vaccinations will be required. For example, some producers may vaccinate broilers at one day of age and again at fourteen days of age. This multiple IBD vaccination would be recommended when maternal titers are poorly uniform, which results from poor vaccine administration in breeders or when mixing broilers from different breeder flocks. In a recent study, even a group of breeders that had fairly uniform IBD titers had chicks with titers that were variable, with many chicks have little or no maternal antibody protection.

Although the 1 day of age vaccination would be of little direct benefit to broilers with high maternal titer levels, multiple vaccinations would provide some protection to chicks with lower levels of maternal antibody and would help reduce replication of IBD field virus and subsequent shed in the poultry house environment.

Ref: University of Florida IFAS Extension