Molecular Characterization for Strains of Newcastle Disease Virus Circulating in Chickens in Selected Migratory Birds Abundant Areas in the Mid Rift Valley and Central Part of Ethiopia

Abstract

Newcastle disease (ND) is a highly infectious chicken disease that causes major economic losses worldwide. The disease caused by Avian paramyxovirus type 1 (APMV-1). A cross sectional study was conducted from February 2020 to October 2020 to investigate Newcastle virus strains circulating in chickens from selected migratory birds abundant areas in the mid Rift Valley and the central part of Ethiopia. A total of 98 samples: 78 tracheal and cloacal swabs from chickens pools of five, and 20 tissue samples were collected. The main functional region of the F gene has been amplified (270 nucleotides) by qRT-PCR and sequenced by Sanger. Accordingly, 13.26% samples were positive for NDV base on the qRT-PCR test. Phylogenic analysis of the partial cleavage site of F-gene indicated that one field isolate of the Ethiopian NDV isolates had a velogenic motif 112R-R-Q-K-R-F117 at the fusion protein cleavage site and clustered within the lineage 5 (genotype VIIg) whereas three of the isolates had a lentogenic motif 112G-R-Q-G-R-L117and belonged to the sub-genotype of lineages 1, 2, and 3 (genotype I, II, and III). The genotype VIIg isolate was genetically similar to Egypt and Iran NDV isolates, indicating the possible epidemiological relation of NDV outbreaks in the study area were are due to seasonal migratory wild birds. The current vaccine strain (HB1 vaccine) used in the study area grouped into lineage 2 (genotype II) showing 73% to 89% similarity to some of the field isolated Newcastle disease viruses and shared similarities with many countries in Africa, Asia, Europe, North, Central, and South America. The current analysis showed that different NDV genotypes circulated in the middle Rift Valley and central part of Ethiopia. The virulent NDV continues has been an issue in the poultry sector in Ethiopia, and its continuous circulation in the village and commercial poultry needs better surveillance and effective vaccine.