Genotypic and pathogenic characterization of genotype VII Newcastle disease viruses isolated from commercial farms in Egypt and evaluation of heterologous antibody responses.
Newcastle disease viruses (NDV) represent a major threat to poultry production worldwide. Recently in Egypt NDV circulated extensively, even in vaccinated farms. In the present study samples were collected from sixteen vaccinated broiler farms in animals exhibiting the typical gross lesions of NDV. Virus isolation and pathogenicity studies for positive samples were carried out in accordance to reference procedures and phylogenetic analysis was carried out based on partial sequences of the Fusion gene. Furthermore, in vivo investigation of the ability of heterologous antibody, induced by commercially available lentogenic strain-based vaccines, to efficiently reduce viral shedding was examined. Results revealed that all the sixteen farms were positive for the presence of NDV. Out of these fifteen were confirmed to due to velogenic viruses, based on a main death time (MDT) ≤ 48 hours and partial sequencing of the F gene that showed the presence of a polybasic amino acid motif. However, three patterns in the cleavage site of these velogenic viruses were identified in the present study. Phylogenetic analysis revealed that all fifteen isolates were clustered with class II genotype VIIb while the remaining isolate (B81) was class II genotype II. Results of the in vivo study revealed that adequate heterologous antibody levels, induced by the proposed vaccination program, sufficiently protected birds from morbidity and mortality. However, virus shedding was quantitatively affected in relation to the time of challenge after vaccination. Altogether, with an absence of vaccines able to induce homologous antibody to the presently circulating viruses, higher antibody levels, which depend on efficient and timely implementation of the vaccination program, are considered as highly important in relation to the reduction of virus shedding.
Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza, 12618, Egypt.
A M
AM
Saad
Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza, 12618, Egypt. dr.ahmed189@gmail.com.|Avian and Rabbit Virology Immunology and Parasitology Unit (VIPAC), French Agency for Food, Environmental and Occupational Heath Safety (Anses), 22440, Ploufragan, France. dr.ahmed189@gmail.com.
Ahmed
http://orcid.org/0000-0002-0038-3342
A
Samy
Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza, 12618, Egypt.
M A
MA
Soliman
Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza, 12618, Egypt.
A
A
Arafa
Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza, 12618, Egypt.
A
A
Zanaty
Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza, 12618, Egypt.
M K
MK
Hassan
Poultry Diseases Department, Faculty of Veterinary Medicine, Sadat University, Sadat, Egypt.
A H
AH
Sultan
Virology Department, Faculty of Veterinary Medicine, Sadat University, Sadat, Egypt.
A I
AI
Bazid
Virology Department, Faculty of Veterinary Medicine, Cairo University, Giza, 12211, Egypt. husvirol@link.net.
A H
AH
Hussein
D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D000918:Antibody Specificity; D002645:Chickens; D004534:Egypt / Q000453:epidemiology; D009521:Newcastle Disease / Q000453:epidemiology / Q000821:virology*; D009522:Newcastle disease virus / Q000235:genetics*; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000914:Antibodies, Viral