Pathogenicity and growth characteristics of selected infectious laryngotracheitis virus strains from the United States

• Published in: Avian pathology Vol. 38; no. 1; pp. 47 - 53
• Main Authors: Oldoni, Ivomar, Rodriguez-Avila, Andres, Riblet, Sylva M, Zavala, Guillermo, Garcia, Maricarmen
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis Group 01-02-2009; Taylor & Francis Ltd
• Subjects: Animals; Avian flu; bacterial colonization; Cell Line; Chickens; disease course; disease severity; Gallid herpesvirus 1; Genetics; genotype; Genotype & phenotype; Herpesviridae Infections - epidemiology; Herpesviridae Infections - immunology; Herpesviridae Infections - pathology; Herpesviridae Infections - veterinary; Herpesviridae Infections - virology; Herpesvirus 1, Gallid - classification; Herpesvirus 1, Gallid - growth & development; Herpesvirus 1, Gallid - immunology; Herpesvirus 1, Gallid - pathogenicity; Infectious laryngotracheitis virus; inoculum; microbial growth; Ornithology; pathogenesis; pathotypes; Polymerase Chain Reaction - veterinary; Polymorphism; Poultry; poultry diseases; Poultry Diseases - epidemiology; Poultry Diseases - immunology; Poultry Diseases - pathology; Poultry Diseases - virology; respiratory system; respiratory tract diseases; signs and symptoms (animals and humans); Specific Pathogen-Free Organisms; strain differences; strains; tissue distribution; United States - epidemiology; vaccines; viral diseases of animals and humans; Viral Plaque Assay; Viral Vaccines - immunology; virulence; Virus Replication; United States; United States > US
• DOI: 10.1080/03079450802632031
• EISSN: 1465-3338
• ISSN: 0307-9457

In a recent study, several US infectious laryngotracheitis virus (ILTV) strains and field isolates were genotyped by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) into nine different genotypes. All of the commercial poultry isolates were identified within genotypes IV, V, and VI. Based on the PCR-RFLP, Group IV isolates were characterized as genetically identical to the chicken embryo origin (CEO) vaccines, Group V as genetically closely related to the CEO vaccines, and Group VI as genetically different to the vaccine strains. The objective of this study was to determine the pathogenicity and growth characteristics of six ILTV commercial poultry isolates as compared with the CEO vaccine. Two isolates representative of PCR-RFLP Groups IV, V, and VI were selected. Differences in disease severity, viral tissue distribution in chickens, and plaque formation ability in cell culture were observed among viral genotypes IV, V, and VI, and between V-A and V-B isolates. Mild respiratory clinical signs were produced by IV-A, IV-B and the CEO vaccine, while VI-A and VI-B isolates produced severe respiratory signs and severe depression, and during the peak of clinical signs both isolates were re-isolated from the conjunctiva, sinus, trachea and thymus. Similarly to Group VI isolates, V-A and V-B produced severe respiratory signs, depression, and were re-isolated from conjunctiva, sinus, and trachea; on cell culture, both isolates produced significant larger plaques than any of the other isolates analysed. Overall, differences in pathogenicity and growth characteristics were observed among genetically closely related US ILTV isolates; however, complete genomes will be necessary to identify molecular determinants linked to the pathogenic viral phenotypes.