Abstract
BackgroundNewcastle disease viruses (NDVs) can spread across continents via migratory birds. Hence, we investigated the frequency of NDV in both non-migratory and birds migrating on the Black Sea-Mediterranean flyway, in Istanbul, Turkey. Birds were trapped using nets placed around the Kucukcekmece lake Avcilar, Istanbul, in spring seasons of 2016 and 2018. In total, 297 birds belonging to 42 different species were trapped, categorized according to species and sex, and flocked oropharyngeal swabs were collected. In addition, flocked swabs were also collected from 115 mallards caught by hunters around Edirne and from 207 birds which had been treated in the Veterinary Faculty of Istanbul university-Cerrahpasa. Tissue samples were taken from dead wild birds brought by public to Veterinary Faculty. A total of 619 flocked oropharyngeal swabs were pooled into 206 samples. RNA was extracted from swabs and tissue samples. Real-time RT-PCR prob. assay was used to detect NDV-RNA in samples.ResultsThere was no amplification in real time RT-PCR in samples taken from wild birds caught by traps. However, amplification of NDV-F gene was observed in oropharyngeal swabs taken from 2 waterfowls (Common Moorhen and Mallard), and in tissue samples taken from 2 little owls and 1 common kestrel. Sequencing and phylogenetic analyses of these 5 samples for NDV-F gene showed great similarity with NDV subgenotype VII.2 viruses. Analysis also showed that there is a high similarity with the F gene sequences previously reported from Turkey in 2012 and as well as the sequences from neighbouring countries Bulgaria and Georgia and geographically close country such as Pakistan. Although the strains found in this study are closely related, there is a relatively small degree of molecular divergence within 543 bp of F gene of the Turkish NDV isolate and strains detected in Israel, Pakistan, Iran, United Arab Emirates and Belgium.ConclusionsOur findings revealed the presence of subgenotype VII.2 of NDVs in wild birds in north west of Turkey and demonstrated some degree of molecular evolution when compared to the earlier NDV-VII.2 isolate in Turkey.
Highlights
Newcastle disease viruses (NDVs) can spread across continents via migratory birds
The strains found in this study are closely related, there is a relatively small degree of molecular divergence within 543 bp of F gene of the Turkish NDV isolate (KT585629.1; 96,65%) and strains detected in Israel (KF792020.1, KF792021.1; 96,96%), Pakistan (JX854452, KX791186; 91,79-96,65%), Iran (MG871466.1; 96,96%), United Arab Emirates (KT995481.1; 96,81%) and Belgium (MH432252.2, 96,81%) (Supplementary Figure 4)
We determine the dominance of NDV strains prevailing in both migratory and non-migratory birds and ducks in the Marmara region of Turkey that could potentially spillover NDV strains to local commercial poultry as well as transnational dissemination risks to other countries via wild bird migration [9, 10, 12, 15]
Summary
Newcastle disease viruses (NDVs) can spread across continents via migratory birds. we investigated the frequency of NDV in both non-migratory and birds migrating on the Black Sea-Mediterranean flyway, in Istanbul, Turkey. 297 birds belonging to 42 different species were trapped, categorized according to species and sex, and flocked oropharyngeal swabs were collected. Flocked swabs were collected from 115 mallards caught by hunters around Edirne and from 207 birds which had been treated in the Veterinary Faculty of Istanbul university-Cerrahpasa. Tissue samples were taken from dead wild birds brought by public to Veterinary Faculty. A total of 619 flocked oropharyngeal swabs were pooled into 206 samples. RNA was extracted from swabs and tissue samples. Newcastle disease virus (NDV) can potentially infect all species of birds and widely circulates in poultry and wild birds. Class II viruses are known to infect a wide range of domestic and wild birds and show higher genetic and virulence variability. Diversity of NDV is still unfolding, they are divided into 21 genotypes named I to XXI [2]
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