Analysis of Amino Acid Changes in the Fusion Protein of Virulent Newcastle Disease Virus from Vaccinated Poultry in Nigerian Isolates

Abstract

The roles of fusion gene in the virulence of Newcastle disease virus are well established, but the extent of its variation among the XIV, XVII, and XVIII genotypes reported in Central Africa and West Africa has until recently been understudied. In this study, virulent Newcastle disease virus (vNDV) was isolated from dead chickens among vaccinated flocks between March and April 2020. Fusion (F) gene was sequenced and analysed for characterization and information about genetic changes. Many substitutions were observed along the region and some of their functions are yet to be determined. Results showed that all study isolates have virulent cleavage site sequence 112-RRRKR-116/F117 and clustered within genotype XIVb. Sequence analysis showed K78R mutation in the A2 antigenic epitope in all isolates and more along the F-gene which varied in some instances within the isolates. Mutation in this A2 antigenic epitope has been reported to induce escape mutation to monoclonal antibodies generated using the NDV LaSota strain. The range of percentage nucleotide and amino acid homology between the study isolates and commercially available vaccine strains is 81.14%–84.39% and 0.175–0.211, respectively. This report provides evidence of vNDV among vaccinated chicken flock and molecular information about circulating vNDV strains in Kano State, Nigeria, which is useful for the development of virus matched vaccines. Newcastle disease (ND) surveillance and molecular analysis of circulating strains in this region should be encouraged and reported. Furthermore, ND outbreaks or cases among vaccinated poultry presented to veterinary clinics should be reported to the state epidemiologist. Nucleotide sequences were assigned accession numbers OK491971–OK491977.

Phylogenetic Analysis of Newcastle Disease Virus Isolated from Poultry in Live Bird Markets and Wild Waterfowl in Zambia

“…The present study demonstrated the isolation of NDV in broiler and village chickens sold at a LBM in Lusaka and wild birds in the LNP, with a positivity rate of 0.3% and 0.07%, respectively. The positivity rate of NDV recorded in chickens at LBMs in the current study was lower than 4.36-91.67% reported in Ghana and Tanzania [29], 65.9% in Egypt [30], 54% in Nigeria [31], and 45% in Libya [32]. Moreover, the positivity rate of NDV in wild birds was also lower compared to 2-10% reported in other African countries [28,[33][34][35].…”

“…The observed difference in the positivity rates could be attributed to the differences in the health status of the birds sampled, the type of samples collected, and the methods of detection used. For example, other studies collected organ samples and cloacal or oropharyngeal swabs from sick or both sick and apparently healthy birds and used RT-PCR for detection [ 31 , 32 ], which may increase the detection rate. The low isolation rate of NDV in poultry could indicate some success in containing the disease through ND vaccinations in the country.…”