Field evaluation of avian encephalomyelitis maternal antibody transfer in chicken flocks in Southwest Nigeria

Abstract

Avian encephalomyelitis (AE) is controlled by ensuring adequate level of maternal antibodies in chicks. Incessant outbreaks in chicken flocks in Southwest Nigeria in spite of vaccination of breeders prompted the assessment of AE virus antibody levels in breeder flocks and their progeny. Five prevaccinated chicken breeder flocks (A, B, C, D and E) were selected in Ibadan, Oyo State, and Mowe, Ogun State. Blood samples were collected from fifteen breeders from each flock, as well as their chicks at 1, 7 and 14 days of age and sera subjected to the passive hemagglutination test. Ranges of titers, modal titers, mean geometric titers (MGTs) and maternal antibody transfer rates were determined for each flock. MGTs ranged between 3.3 ± 0.09 and  4.8 ± 0.14 in breeder flocks, 0.8 ± 0.09 and 2.4 ± 0.21 in day-old chicks, and 2.8 ± 0.15 and 3.9 ± 0.06 in 7-day-old chicks. The highest values in all categories were observed in broiler flock D. MGTs ranged between 1.4 ± 0.18 and 2.3 ± 0.17 in 14-day-old chicks, and the highest value was found in broiler flock C. In general, significant (p < 0.05) declines in MGTs were recorded from breeder flocks to day-old chicks. Maternal antibody transfer rates were higher in broiler flocks C and D with 50 and 40.9%, respectively, whereas those of pullet flocks A, B and E were 24.2, 19.5 and 19.5%, respectively. Results showed that by six months post-vaccination, maternal antibody transfer was low especially in pullet flocks, resulting in low to undetectable antibody titers in day-old chicks. A modification of the vaccination schedule is therefore advised.