Dynamic distribution and tissue tropism of infectious laryngotracheitis virus in experimentally infected chickens

Abstract

Infectious laryngotracheitis (ILT), caused by infectious laryngotracheitis virus (ILTV), is an Office International des Epizooties (OIE) notifiable disease. However, we have not clearly understood the dynamic distribution, tissue tropism, pathogenesis, and replication of ILTV in chickens. In this report, we investigated the dynamic distribution and tissue tropism of the virus in internal organs of experimentally infected chickens using quantitative real-time polymerase chain reaction (qPCR) and a histopathological test. The study showed that ILTV could be clearly detected in eight internal organs (throat, trachea, lung, cecum, kidney, pancreas, thymus and esophagus) of infected chickens, whereas the virus was difficult to detect in heart, spleen, proventriculus, liver, brain and bursa. Meanwhile, the thymidine kinase (TK) gene levels in eight internal organs increased from 3 days to 5 days postinfection, and then decreased from 6 days to 8 days postinfection. The log copy number of ILTV progressively increased over 3 days, which corresponds to the clinical score and the result of the histopathological test. The results provide a foundation for further clarification of the pathogenic mechanism of ILTV in internal organs and indicate that throat, lung, trachea, cecum, kidney, pancreas and esophagus may be preferred sites of acute infection, suggesting that the tissue tropism and distribution of ILTV is very broad.

Real-time PCR quantification of infectious laryngotracheitis virus in chicken tissues, faeces, isolator-dust and bedding material over 28 days following infection reveals high levels in faeces and dust

“…Clarke et al (1980) reported infection of both the conjunctiva and the naso-lachrymal duct epithelium of spray vaccinated chickens with ILTV vaccine strain SA2. Detection in kidneys supports the finding of Wang et al (2013) and, as in that study, the genome was detected at a comparatively low level. This may simply reflect presence of viraemic virus in a highly vascular tissue.…”

“…The ILTV viral genome was also readily detected in dust and litter samples with sustained high levels found in dust. There is considerable age-related resistance to infection with ILTV (Clarke et al, 1980;Fahey et al, 1983) and high-dose ILTV vaccination at 1-day-old in the present experiment undoubtedly resulted in the induction of more severe ILT than would have been the case had the birds been challenged at 3-5 weeks of age, which is more typical of ILTV challenge studies (Coppo et al, 2012b;Oldoni et al, 2009;Wang et al, 2013). This probably resulted in higher levels of viral genome detection, but, as discussed below, where similar measurements permit comparison, the results are broadly consistent with other studies.…”

“…However, recent studies have indicated a wide range of tissues may be infected with the virus (Oldoni et al, 2009;Wang et al, 2013) and transmission of ILT has been demonstrated by intra-tracheal inoculation of suspensions of liver and spleen tissue from affected birds (Beach, 1931), raising the possibility of alternative modes of shedding and transmission. Another avian herpesvirus, gallid herpesvirus 2 (GaHV-2) or Marek's disease virus (MDV), is the causative agent of Marek's disease and is also transmitted by inhalation of infective material.…”

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.…”

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

“…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).…”