Molecular epidemiology of Infectious laryngotracheitis vírus isolated from an outbreak in commercial layer flocks in São Paulo State
The objective of this study was the molecular detection and characterization of field isolates of infectious laryngotracheitis virus (ILTV) detected from commercial chickens with and without clinical signs of the disease from regions of the São Paulo state. The study included samples collected during and after of the first epidemic infectious laryngotracheitis (ILT) outbreak in Brazil, Bastos region, and from other regions during 2002-2008. The molecular characterization was developed by restriction fragment length polymorphic analysis (RFLP) of polymerase chain reaction (PCR) products of glycoprotein E, G, thymidine kinase (TK) and regulatory protein of transcription (ICP4) gene, and by sequence analysis of TK and ICP4 gene. For ICP4 gene sequencing, two PCR assays have been developed for amplification of two different fragments of ICP4 gene. The PCR-RFLP and DNA sequencing techniques showed identical results, they could differentiate the field isolates from vaccine strains, tissue culture origin (TCO) and chicken embryo origin (CEO). The results showed that the severe outbreak in Bastos region was caused by a non-vaccine and virulent strain (Bastos strain); however it was possible to detect two isolates closely related to the CEO vaccine strain circulating during the outbreak. This study showed that the strain, which it caused the severe outbreak in Bastos region continue circulating in these region despite of the use of attenuate vaccines. In addition, the present research showed that isolates related to CEO and Bastos strains are circulating in commercial layer flocks located outside the Bastos region, and were involving in clinical cases of the disease. This study shows (1) the persistence of the wild field strain in Bastos region (Bastos strain) despite of the control measures and the use of attenuate vaccines, (2) the dissemination of the Bastos and CEO strains to other regions, and (3) the efficacy of the strategy standardized in this study to characterization and differentiation of field isolates and vaccine strain.
Advisor:Antônio José Piantino Ferreira; Claudio Wageck Canal; Ivomar Oldoni; Tânia de Freitas Raso; Rodrigo Martins Soares; Antônio José Piantino Ferreira
School:Universidade de São Paulo
Source Type:Master's Thesis
Keywords:Infectious laryngotracheitis Molecular characterization PCR-RFLP Sequences analysis Vaccine and Field strain
Date of Publication:01/09/2009