Infectious Bursal Disease Virus: Some Biological Properties of Three Vaccine Strains

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Mohamed Abdalla Mohamed Yousif, Yousif
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Since some cases or vaccination failure were reported after the usage of live infectious bursal disease (IBD) vaccine, this study was carried out to compare biological properties of three vaccines of different virulence (228E, Lukert and S706). Two groups of maternally immune chicks (two and three weeks old) were used in experiments. Each group was divided into four subgroups. IBD vaccines were administered via drinking water to three subgroups while the fourth was left as control. One week later, some birds from each subgroup were vaccinated with Newcastle disease (ND) vaccine (komarov strain). Challenge test was carried out after 3 weeks of IBD vaccination with standard strain of IBD virus (F52/70). Different S706 revealed the highest immune response to IBD vaccination in two week old chicks (59.65%) and relatively decreased in three weeks old chicks while 228 E strain revealed the lowest immune response in two weeks old chicks (28.70%) and markedly higher response in three weeks old chicks (72.72%). On respect to immunosuppressive effect, strain 228E exerted marked bursal regression at both ages and a relative decrease in humoral response to ND vaccination (4.01 log2 in two weeks old and log2 in three weeks old chicks). Bursal regression in two weeks old chicks was only revealed by Lukert strain, and the humoral responses were 4.8 log2 and 5.48 log2 in two and three weeks old, respectively. No bursal regression was observed in chicks vaccinated with strain S706, and the response titres to ND vaccination were 5.08 log2 in two weeks and 6.02 log2 in three weeks old chicks. Similarity was observed between vaccine strains in protection against IBD challenge and to some extent this was linked to the effect of vaccine strain on the bursa. The three strains were readily grown in chick embryo fibroblast cell culture (although Lukert strain revealed weak growth). In titration 5.35 log10 TCID50/ 0.1 ml and 4.66 log10 TCID50/0.1 ml obtained by strains 228E and S706, respectively. Growth in egg embryos was only recorded by 228E strain but the titration of the harvest was not carried out due some practical difficulties
Infectious Bursal Disease Virus: Some Biological Properties of Three Vaccine Strains