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

Abstract

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.

Occurrence of infectious Laryngotracheitis Virus (ILTV) in 2009-2013 in the State of São Paulo - Brazil

“…This is consistent with previously reported results, indicating that greater viral replication was detected in the respiratory organs (Oldoni et al, 2009;Rodríguez Avila et al, 2007). However, other organs, such as the lungs, cecal tonsils, digestive tract, and kidneys were also positive.…”

“…Recent experimental studies indicate that the virus can also be detected in other organs, such as the heart, liver, spleen, lung, kidney, tongue, thymus, proventriculus, pancreas, duodenum, small intestine, large intestine, cecum, cecal tonsils, bursa, and brain (Oldoni et al, 2009;Wang et al, 2013;Zhao et al, 2013).…”

“…Molecular techniques, such as polymerase chain reaction (PCR), have been successfully used for the detection of ILTV in respiratory and other organs (Chacón et al, 2007;Oldoni et al, 2009;Rodríguez Avila et al, 2007). Polymerase chain reaction presents high sensitivity and specificity for the detection of ILTV.…”

Pathological, immunohistochemical, and molecular findings in commercial laying hens and in backyard chickens naturally infected with the infectious laryngotracheitis virus

“…A recent study showed that DNA virus was detected in the larynx, trachea, lungs, cecum, kidney, pancreas, and esophagus of chickens experimentally infected with GaHV-1 (Wang et al, 2013). Another study (Oldoni et al 2009) showed that GaHV-1 has been more frequently detected in the conjunctiva, sinuses, and trachea, and the authors suggested that these tissues are the site of active replication. Nevertheless, detection of virus in the thymus and cecal tonsil was less frequent and not related to active replication.…”

Molecular epidemiology of infectious laryngotracheitis: a review

“…In severe forms of the disease, haemorrhagic tracheitis together with gasping, coughing, and expectoration of bloody mucus are common. ILT occurs worldwide, and morbidity and mortality rates vary depending on the virulence of the circulating strain (Kirkpatrick et al, 2006a;Oldoni et al, 2009), the levels of virus circulating in the field and infections with other respiratory diseases of poultry (Guy & Garcia, 2008). With an overall mortality due to ILT that can reach 70%, large economic losses usually occur in highdensity poultry-producing regions (Bagust et al, 2000).…”