Post-Vaccinal Observation of Lymphoid Organs in Broiler Chicks Inoculated with Hot and Mild Vaccinal Strains of Infectious Bursal Disease Virus

S. Azhar*, S. Akhtarand M. A. Munir

*Department of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan

ABSTRACT

This project was carried out to study the effect of two intermediate plus (hot) vaccines (228-E and BUR-706) and one mild (Gumboral CT) vaccinal strain of Infectious Bursal Disease virus (IBDV) on antibody response and their effect on different lymphoid organs including bursa, spleen and thymus in chickens. Chicks (n=250) were divided into 4 groups and vaccinated with these strains of IBDV on day 15th of their age and antibody levels were monitored using indirect haemagglutination (IHA) test every week up to 5th weeks of their age. On days 25th post vaccination, IHA results revealed that the birds vaccinated with 228-E and Bur-706 had significantly higher antibody titers, respectively as compared to those vaccinated with Gumboral CT. Reduction in total body weights and lymphoid organs-body weight ratios were recorded, showing that intermediate strains were more damaging than milder one. Histopathological studies also showed severe damage in bursae of broilers inoculated with intermediate plus vaccines than milder. On 25th day of age, five birds from each treatment group were challenged with a virulent IBDV field isolate. After seven day post-challenge, high morbidity and mortality was observed in control group than vaccinated groups. This study suggested the use of intermediate strains as vaccine since they induced high antibody titers as compared to that of the milder strain. However, more invasive and pathogenic intermediate strains showed adverse effects on the development of lymphoid organs harboring B cells. In conclusion, there is a need to develop an effective infectious bursal disease vaccine, low in virulence, which could be used for mass vaccination in chickens, conferring excellent protection against the disease with minimum immunosuppressive effects.

Key Words: Infectious bursal disease; Intermediate plus vaccines; histopathological examination; protective efficacy; immunosuppression

Corresponding author
shajeelazhar@hotmail.com