Mansoura Veterinary Medical Journal

Assessments of required levels of immunity to protect against genotype VII Newcastle disease virus in broiler chickens

Mohammed K. Fahad, Department of Poultry and Rabbit Diseases, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, EgyptFollow
Salah M. Hassan, Department of Pathology and Poultry diseases, College of Veterinary Medicine, Al Qassim Green University, Iraq
Sanaa S. Awad, Department of Poultry and Rabbit Diseases, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt
Kamel I. Abou El-Azm, Department of Poultry and Rabbit Diseases, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, EgyptFollow

Corresponding Author

Mohammed K. Fahad

Document Type

Original Article

Keywords

Newcastle disease virus genotype VII, poultry, virus shedding, maternal immunity, Egypt

Abstract

Objective: To assess therequired levels of immunity required to protect against genotype VII Newcastle disease virus.

Design: A Rrandomized experimental design

Animals: One hundred and fifty chicks

Procedures: One hundred fifty chicks at one-day-old were randomly divided into six groups and subgroups (25 chicks each). G1 was considered thea control group that was unchallenged with the virus. G2-G4, birds challenged with the virus at 1, 7, and 14 days old via the oculo-nasal route at a dose of 107.5 EID50. However, G5 was subdivided into two sub-groups inoculated at 21-day-old via the oculo-nasal (G5-I/N) and intramuscular routes (G5-I/M). All experimental birds were monitored and recorded for clinical signs, mortality rates, and gross pathological lesions within 5 weeks period. Blood samples and body weights were measured weekly. Cloacal swabs for viral shedding were detected 3 and 7 days post-challenge (PC).

Results: All birds in G5-I/N and G5-I/M groupswere dieddead within 7 days of PC. Infectivity and mortality rates wereshowed to be reversibly correlated with the MDA titers of, 20%, 28%, 48%, and 0.0%, 8%, and 28% for– the G2-G4, respectively. Clinical signs starting within 2-3 days PC for the all challenged birds werebeing more severe at 7 and 14 days of age. The signs observed were compatible with thoseat of ND, namely; marked depression, severe respiratory signs, torticollis, and a marked decrease in feed intake. Gross pathological changes revealed an ideal lesion for ND, most commonly the hemorrhage aton the tips of the proventricular gland, congested tracheitis, andwith congested liver and spleen. Birds challenged at 14 days of ageold (G4) showedrevealed prominent kidney lesions.

The HI titer assays revealed that the virus broke downbreakthrough the MDA level byof 3.8 log2 at 28 days of ageold, as it recorded a significant elevation of HI titers. However, in birds challenged at 7 and 14 days old, significant elevation in HI titer was shown at two weeks, i.e. 6.10 log2 and 6.0 log2, respectively. Cloacal shedding was detected in cloacal swabs at 3 and 7 days PC atin similar rates inat birds in G2 and G3, ( i.e. 33.5% and 66.7%, respectively). However, virus shedding in birds challenged at 14 days of ageold at 3 and 7 days PC was 66.7% and 110%, respectively.

Conclusion and clinical relevance: The causative agent of recent ND outbreaks in most vaccinated flocks inat El-Dakahlia governorate, Egypt, was characterized as velogenic genotype VII NDV, which is highly pathogenic tofor commercial broilers.

How to Cite This Article

Fahad, Mohammed K.; Hassan, Salah M.; Awad, Sanaa S.; and El-Azm, Kamel I. Abou (2023) "Assessments of required levels of immunity to protect against genotype VII Newcastle disease virus in broiler chickens," Mansoura Veterinary Medical Journal: Vol. 24: Iss. 4, Article 16.
DOI: https://doi.org/10.35943/2682-2512.1218