Investigating the infectious process in chickens infected with Newcastle disease virus genotype VII via different routes

Introduction. Newcastle disease is a notifiable disease and is a major threat for commercial poultry. There are many known genotypes of the Newcastle disease virus (NDV), which differ in virulence. In recent years, there is an increasing interest in NDV genotype VII that stems from its prevalence and high pathogenicity in chickens and other species of commercial poultry, causing severe disease with up to 100% mortality. Objective. Investigation of the infectious process and other clinical and post-mortem signs in chickens infected with Newcastle disease virus via different routes. Materials and methods. Thirty-day-old chicks were experimentally infected with NDV genotype VII via three different routes: intranasal, oral and intramuscular. Forty eight hours post infection, six intact chickens were introduced in each group. Over the next 10 days, the clinical condition of the infected and contact poultry was assessed. Oropharyngeal and cloacal swabs were collected and tested by polymerase chain reaction. Dead chicks were subjected to post-mortem examination. Results. The experiment demonstrated that NDV/chicken/rus/Saratov/2403-3/22 isolate causes poultry mortality within 5–7 days. Intramuscular infection led to faster disease progression and death in poultry compared to oral or intranasal routes. The NDV genome was identified in samples of oropharyngeal and cloacal swabs tested by polymerase chain reaction. While nonspecific signs of the disease were recorded in all individuals, the predominant clinical presentation varied with the infection route. Pronounced neurological symptoms were observed in birds infected via the intramuscular and oral routes. In contrast, respiratory signs were characteristic of infections via the oral and intranasal routes. The autopsy results indicate that specific pathological signs characteristic of Newcastle disease developed within 24 hours of the disease onset. A number of post-mortem lesions were found in the internal organs of individuals that died early. However, these lesions were not informative for a diagnosis of Newcastle disease. Conclusion. The Newcastle disease virus NDV/chicken/rus/Saratov/2403-3/22 strain (genotype VII) was pathogenic to chickens during experimental infection. The disease was easily reproduced by intramuscular, intranasal, and oral routes of infection and was characterized by a peracute course with respiratory and neurological symptoms.