Continuous circulation and mutation at the hypervariable region of the VP2 gene of very virulent infectious bursal disease virus in Nigeria

Infectious bursal disease (IBD) is a highly contagious viral disease of poultry with huge economic consequences. First reported in Nigeria in 1973, the disease has since become endemic across the country. Inspite of routine vaccine administration, outbreaks are frequently reported in vaccinated flocks which questions the effectiveness of the vaccine to confer adequate protection against the circulating strains of the virus. In this study, suspected IBD outbreaks from 9 poultry farms spanning 2015 – 2016 were investigated. The hypervariable region (HVR) of the VP2 gene of infectious bursal disease virus (IBDV) from these outbreaks was sequenced. Based on the phylogenetic tree and deduced amino acid sequences, the viruses clustered with African very virulent (vv) types (VV2-1) with markers typical for vvIBDV at positions 222A, 242I, 256I, 294I and 299S. Also, unique substitutions were identified at the hydrophilic peak A (215Q→P) and minor peak 2 (280N→Y) in addition to that previously unreported at position 308I→L. These results demonstrate continuous circulation and mutations at the HVR of the VP2 which underscores the need for constant monitoring of IBDV in Nigerian poultry. Further study is required to establish the biological function(s) of these mutations on the pathogenicity and antigenicity of the virus.Keywords: very virulent infectious bursal disease virus, VP2 gene, mutation, poultry, Nigeri

Sero-prevalence and serotypes of infectious bronchitis virus in free-range chicken in Plateau state, Nigeria

Globally, infectious bronchitis (IB) is an important respiratory viral disease responsible for enormous economic losses to poultry farmers.  In Nigeria, limited reports on the prevalence and serotypes of the IB virus are available. Here, we investigated the prevalence and serotypes of infectious bronchitis virus (IBV) in chicken in Plateau State. A descriptive cross-sectional study was carried out involving 440 apparently healthy free-range local chickens sampled from eleven villages in four Local Government Areas (LGA) of Plateau State. Sera collected from the birds were screened for the presence of four IBV serotypes namely; Massachusetts (Mass), Arkansas (Ark), Connecticut (Con) and Delaware (De-072) using haemagglutinationinhibition (HI) test. In all, a prevalence of 82.95% (n = 365) was recorded. At LGAlevel, prevalence of 79.50%, 47.37%, 95.45% and 100% were recorded in Kanam, Mangu, Qua’an pan and Bassa LGAs, respectively. Based on serotype prevalence, Mass had 89.30% (n = 326); Ark 79.70% (n = 291); Con 88.20% (n = 322) while De-072 was 42.70% (n = 156). There were statistically significant associations between dominant serotype and the LGAs (p≤0.001). This study shows high prevalence of IBwith at least four strains of IBV present in free-range chicken flocks in Plateau State requiring attention for control measures. Keywords: Free-range chicken; Infectious bronchitis virus; Plateau state, Serosurvey, Serotyp