Infectious bursal disease (IBD) is a contagious immunosuppressive viral infection of young
chickens. Intra-cloacal approach is effective for vaccinating chicks with high maternally
derived IBD antibodies; however, the vaccinal traditional dose may be unsuitable for this route.
A total of 60 one-day-old specific-pathogen-free (SPF) chicks were randomly distributed into
four groups. Group-1: was control and chicks in group-2: were vaccinated with 103.5 TCID50
of D78 strain/ bird via intra-cloacal route, chicks in group-3: were vaccinated with a ten-fold
higher dose (104.5 TCID50/bird) and chicks in group-4: were vaccinated with a dose of 102.5
TCID50 of D78 strain/bird using same approach. IBD antibody titers were measured at the 14th
and 21st days of age. The immunosuppressive effects of different doses were determined
through humoral immune response to avian influenza and Newcastle disease vaccines, the
relative weight of primary lymphoid organs, and histopathologically evaluated bursal lesions.
The results indicated that a dose even ten-fold higher than the usual dose to SPF chicks via
intra-cloacal route caused neither morbidity nor mortality. All vaccine doses induced potent
immune responses against IBD, but the highest IBD antibodies titers were observed in group-
4 while IBD antibodies titers were decreased with increasing vaccine doses in other
experimental groups. Even the vaccinated birds showed moderate histopathological lesions and
the diminutive relative weight of bursae; there was no immunosuppressive effect in the immune
response to other vaccines in group-4 and transient immunosuppressive effect in groups-2 and-
3. All that proves the safety and effectiveness of various intra-cloacal vaccination approach
doses.