The Role of Newcastle Disease Virus in Broiler Chickens with High Mortality of Kerman Province

The Newcastle disease virus (NDV) is a member of the paramyxoviridea family and has great significance in the poultry production industry, which spends a huge amount of money every year on prevention and economic loss caused by this disease. A wide range of symptoms, including respiratory and nervous disorders, as well as hemorrhage lesions in the digestive system are observed in this disease. This research investigated the presence of NDV in 10 poultry farms with high mortality and respiratory symptoms in Kerman province, Iran (between January 2020 to October 2020). Tissue samples were collected from mortalities of 10 flocks in different parts of Kerman province and inoculated into embryonated eggs. The NDV was detected in the allantoic fluid by polymerization of partial F gene protein. The virus was positive in the samples of 5 flocks. The results of the phylogenetic analysis also showed that the sequence of isolates was related to genotype II (three isolates) and sub-genotype VIId (two isolates) of NDVs. It was also found that the amino acid sequences of sub-genotype VIId isolates in the 113 to 116 positions were RRQKR and in the 117 positions was the presence of F (phenylalanine). The other three isolates were grouped with B1, Clone, and LaSota vaccines, and the amino acid sequence in the cleavage site included GRQGRL. The similarity between the studied isolates was 99.6%-98.4%. In this study, virulent viruses were isolated and tracked in broiler farms that were vaccinated with live and killed vaccines. It is recommended to pay more attention to designing the vaccination program.