Abstract

Background:
Several Newcastle disease virus (NDV) genotypes are circulating worldwide, and the virus continually evolves, leading to more diversity and severity. Of several viral genotypes, VII is particularly important because it has been linked to recent ND outbreaks worldwide.

Aim:
This investigation aimed to diagnose the NDV from the broilers Ross 308 and to investigate the evolutionary relationship and molecular characteristics of the isolates that caused the outbreak during 2023–2024.

Methods:
Approximately 250 tissue samples were collected from broilers with different clinical signs and postmortem lesions related to NDV. The samples were diagnosed and analyzed using conventional polymerase chain reaction and sequencing analyses with bioinformatics.

Results:
Using polymerase chain reaction targeting the F gene, NDV was successfully detected in the examined samples. The NDV was isolated from geographical areas in four governorates. The global genetic diversity and epidemiological distribution of genotype VII of NDV in Iraq. Based on the 767-bp fusion gene sequences of the nine isolates of the present study and other reference viruses, further detailed characterization of the current Iraqi genotype VII and lentogenic or vaccine strains was performed. In addition, the phylogenetic study showed that the NDV strains of the current work (4FF, 7FF, 8FF, 10FF, 12FF, and 15FF) have an F protein cleavage site 112RRQKR↓ F117 and fit the new identified include sub-genotype VII 1.1.

Conclusion:
Our study explained that the virulent NDV strains are enzootic and are particularly widespread in Iraq. The ND isolates in this study also showed high similarity to Afghan and Iranian strains of genotype VII (97.95%–98.01% similarity).

Key words: Newcastle disease virus, Broilers, F gene, Pathogenicity, Phylogenetic tree