Efficacy and pathogenicity of three live infectious bursal disease vaccines [intermediate plus strains] in commercial native chickens breed in Egypt

ABSTRACT

In this study, three of live intermediate plus IBDV vaccines [A, B, and C] which are commonly used in Egypt were selected and their pathogenicity and efficacy were investigated. Groups of native breed chicks were vaccinated at 14 days of age with each vaccine by eye drop route and in drinking water then challenged with virulent field IBDV 14 days post vaccination [PV]. The efficacy and pathogenicity of each vaccine were evaluated based on clinical signs, mortalities, gross lesion, Bursa/ body weight ratio [BF/BW], and histopathological lesions of the bursa. It was found that these vaccines are efficient as they conferred 100% protection in all vaccinated and challenged groups compared with 20% mortality in unvaccinated challenged group. However, they did not prevent bursal atrophy or histological lesions. The bursal atrophy was observed at 7days PV in groups vaccinated with vaccine [A] while it was observed at 10 days PV in groups vaccinated with vaccines [B] and [C]. Vaccine [A] was proved to be more invasive compared with vaccines [B] and [C] as evidenced by higher bursal lesion scores and lower relative BF/BW ratios at certain intervals PV. When vaccine B and C were given in drinking water, moderate to severe bursal changes were observed. Meanwhile, when these vaccines [B and C] were given by eye drop route, mild to moderate changes in the bursa were observed indicating that vaccination by eye drop route would be better than in drinking water. It would be concluded that, all studied vaccines are efficacious and they vary in invasiveness and pathogenicity. Vaccines [B] and [C] are less pathogenic than vaccines [A] and the vaccination by eye drop route will result in less severe bursal lesions and better immune response than in drinking water