Abstract
Vaccination failure is one of the major constraints to disease control in poultry. To investigate Infectious bursa disease (IBD)-vaccination failures (frequently/globally reported), batches of the Nigerian live-vaccine were tested for viral units before vaccinating following chick-groups: 16 doses (65,536 units), 8 doses (32,768 units), 4 doses (6,384 units), 2 doses (8,192 units), 1 dose (4,096 units), 1:2 dose (2,048 units), 1:4 dose (1,024 units), 1:8 dose (512 units), 1:16 dose (256 units) and control. Each batch gave 4,096 viral units. Mean bursa weight/body weight ratios (immune stimulation) and mean antibody titres of the chick-groups were 47.40 ±5.45 and 51.20 ±7.83; 44.25 ±7.28 & 48.00 ±9.24; 45.25 ± 4.28 and 64.00 ± 0.00; 43.00 ±7.58 and 101.60 ± 35.05; 44.60 ± 5.51 and 128.00 ± 0.00; 42.60 ± 6.23 and 268.80 ± 16.00; 40.50 ± 1.76 and 80.00 ±16.00; 31.40 ± 3.80 and 80.00 ± 27.71; 37.18 ± 4.07 and 89.60 ± 15.68 and 26.20 ± 3.31 and 19.20 ± 5.99, respectively. Half (2,048 units) of the recommended 1-dose gave optimal antibody-titre. The higher doses gave lower antibody-titres like the lower doses but immune stimulation continued to increase as doses/units increased. Both over-stimulating the immune system (too high vaccine-doses/viral-units/viral-virulence) and under-stimulation cause vaccination failure.
Publisher
Michael Okpara University of Agriculture, Umdike (MOUAU)
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