title: Persistence and spreading of field and vaccine strains of infectious laryngotracheitis virus (ILTV) in vaccinated and unvaccinated geographic regions, in Brazil.
abstract: Infectious laryngotracheitis (ILT) is a highly infectious respiratory disease that causes morbidity and mortality in commercial chickens. Despite the use of attenuated vaccines, ILT outbreaks have been described in broiler and long-lived birds. Molecular approaches, including polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing, are used to characterize ILT viruses (ILTVs) detected in vaccinated and unvaccinated geographical regions. As part of an ILT control program implemented in a region of commercial layer production, samples of conjunctiva, trachea, and trigeminal ganglia were collected from chickens in a vaccinated and quarantined region over a period of 8 years after initiation of vaccination. To determine the origin of new ILT outbreaks in unvaccinated regions, samples collected from ill chickens were also analyzed. Chicken embryo origin (CEO) vaccine viruses and the Bastos field strain were detected circulating in healthy chickens in the vaccinated region. CEO strains and field viruses molecularly related to the Bastos strain were also detected outside of the quarantined region in chickens showing clinical signs of ILT. This study reveals the persistence and circulation of a wild field strain, despite the intensive use of tissue culture origin (TCO) and CEO vaccines in a quarantined region. Spreading of CEO viruses to unvaccinated regions and the capacity of this virus to establish latent infections and cause severe outbreaks were also observed.
authors.affiliation: Department of Pathology, School of Veterinary Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Jorge Luis
authors.initials: JL
authors.lastname: Chacón
authors.forename: Luis Fabian Naranjo
authors.initials: LF
authors.lastname: Núñez
authors.forename: Maria Pilar
authors.initials: MP
authors.lastname: Vejarano
authors.forename: Silvana Hipatia Santander
authors.initials: SH
authors.lastname: Parra
authors.forename: Claudete Serrano
authors.initials: CS
authors.lastname: Astolfi-Ferreira
authors.forename: Antonio José Piantino
authors.initials: AJ
authors.lastname: Ferreira
mesh_terms: D000818:Animals; D001938:Brazil / Q000453:epidemiology; D002645:Chickens; D004196:Disease Outbreaks / Q000517:prevention & control / Q000662:veterinary*; D006566:Herpesviridae Infections / Q000453:epidemiology / Q000662:veterinary*; D001352:Herpesvirus 1, Gallid / Q000235:genetics / Q000276:immunology*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012150:Polymorphism, Restriction Fragment Length; D011201:Poultry Diseases / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D014611:Vaccination / Q000662:veterinary; D014613:Vaccines, Attenuated / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage*
chemical_list: D014613:Vaccines, Attenuated; D014765:Viral Vaccines