Immunisation of maternally immune turkey poults against Newcastle disease

Turkey poults possessing maternally-derived antibody to Newcastle disease respond poorly, in terms of haemagglutination inhibiting (HAI) antibody response, to vaccination within the first 4 weeks of life. This unsatisfactory effect occurs both with live La Sota vaccine administered by intraocular/intranasal instillation or with killed oil emulsion adjuvant vaccine given by intramuscular injection. Re-vaccination of these birds with killed emulsion vaccine at 4 or 6-weeks-old indicates that they have become sensitised by either method of primary vaccination and results in the establishment within 4 weeks of high (8-9 log(2)) and prolonged HAI antibody levels. Further vaccination at 29-weeks-old raises the levels from 5 log(2) to 10-11 log(2).