Persistence and spreading of field and vaccine strains of infectious laryngotracheitis virus (ILTV) in vaccinated and unvaccinated geographic regions, in Brazil

• Published in: Tropical animal health and production 2015-08, Vol.47 (6), p.1101-1108
• Main Authors: Chacón, Jorge Luis, Núñez, Luis Fabian Naranjo, Vejarano, Maria Pilar, Parra, Silvana Hipatia Santander, Astolfi-Ferreira, Claudete Serrano, Ferreira, Antonio José Piantino
• Format: Article
• Language: English
• Subjects: Animals; Biomedical and Life Sciences; Brazil - epidemiology; Chickens; Disease Outbreaks - prevention & control; Disease Outbreaks - veterinary; Herpesviridae Infections - epidemiology; Herpesviridae Infections - veterinary; Herpesvirus 1, Gallid - genetics; Herpesvirus 1, Gallid - immunology; Infectious laryngotracheitis virus; Life Sciences; Outbreaks; Polymerase Chain Reaction - veterinary; Polymorphism, Restriction Fragment Length; Poultry; Poultry Diseases - epidemiology; Poultry Diseases - prevention & control; Poultry Diseases - transmission; Regular Articles; Respiratory diseases; Vaccination - veterinary; Vaccines; Vaccines, Attenuated - immunology; Veterinary Medicine/Veterinary Science; Viral Vaccines - administration & dosage; Zoology
• ISSN: 0049-4747; 1573-7438
• DOI: 10.1007/s11250-015-0834-3

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.