NDV subgenotype VII(L) is currently circulating in commercial broiler farms of Iran, 2017–2018
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Based on our previous work, it was discovered that some Newcastle disease virus (NDV) isolates from backyard poultry between 2011 and 2013 in Iran formed a new separate cluster when phylogenetic analysis based on the complete F gene sequence was carried out. The novel cluster was designated subgenotype VII(L) and published.
In the current study, for further validation, we initiated a comprehensive epidemiological study to identify the dominant NDV genotype(s) circulating within the country. Collection of samples was executed between October 2017 and February 2018 from 108 commercial broiler farms which reported clinical signs of respiratory disease in their broilers.
We report that 38 of the farms (> 35%) tested positive for NDV. The complete F gene sequences of seven of the isolates are shown as representative sequences in this study. According to the phylogenetic tree constructed, the recent broiler farm isolates clustered into the newly designated cluster VII(L) together with the older Iranian backyard poultry isolates in our previous work. All the sequences shared the same virulence-associated F cleavage site of 112RRQKR↓F117.
Our phylogenetic analysis suggested that the NDV subgenotype VII(L) may have been derived from subgenotype VIId, and contrary to popular belief, subgenotype VIId may not be the dominant subgenotype in Iran. Tracking of the subgenotype on BLAST suggested that the NDV subgenotype VII(L), although previously unidentified, may have been circulating in this region as an endemic virus for at least a decade. Other NDV genotypes, however, have also been reported in Iran in recent years. Hence, ongoing study is aimed at determining the exact dominant NDV genotypes and subgenotypes in the country. This will be crucial in effective mitigation of outbreaks in Iranian broiler farms.
KeywordsNDV Subgenotype VII(L) Outbreak Poultry diseases Phylogenetic study
Newcastle disease virus
Iranian Veterinary Organization
SAH and MHFM collected the samples from broiler farms. MMA, AM, MHFM, and MB inoculated the samples in SPF eggs and harvested. MMA, AM, and MHFM performed the rapid hemagglutination test. MMA performed HA, HI, and MDT. AM and MB extracted RNA, synthesized cDNA, and ran PCR. AM designed the primers. AM cloned the PCR fragments, transformed, extracted plasmids, and prepared for sequencing. AM assembled the sequencing results and submitted to GenBank. MB did the phylogenetic analysis. AM wrote the first draft of the manuscript. SHEL, MB, and MHFM edited the manuscript.
AM, MHFM, and MB were supported by Razi Vaccine and Serum Research Institute grant number 1218181296006960282.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Research involving animals
All procedures involving human participant was in accordance with ethical standards.
Informed consent was obtained from all individual participants included in the study.
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