Abstract
In Alberta, infectious laryngotracheitis virus (ILTV) infection is endemic in backyard poultry flocks; however, outbreaks are only sporadically observed in commercial flocks. In addition to ILTV vaccine revertant strains, wild-type strains are among the most common causes of infectious laryngotracheitis (ILT). Given the surge in live attenuated vaccine-related outbreaks, the goal of this study was to assess the efficacy of a recombinant herpesvirus of turkey (rHVT-LT) vaccine against a genotype VI Canadian wild-type ILTV infection. One-day-old specific pathogen-free (SPF) White Leghorn chickens were vaccinated with the rHVT-LT vaccine or mock vaccinated. At three weeks of age, half of the vaccinated and the mock-vaccinated animals were challenged. Throughout the experiment, weights were recorded, and feather tips, cloacal and oropharyngeal swabs were collected for ILTV genome quantification. Blood was collected to isolate peripheral blood mononuclear cells (PBMC) and quantify CD4+ and CD8+ T cells. At 14 dpi, the chickens were euthanized, and respiratory tissues were collected to quantify genome loads and histological examination. Results showed that the vaccine failed to decrease the clinical signs at 6 days post-infection. However, it was able to significantly reduce ILTV shedding through the oropharyngeal route. Overall, rHVT-LT produced a partial protection against genotype VI ILTV infection.
Highlights
Gallid herpesvirus-1 (GaHV-1) or infectious laryngotracheitis virus (ILTV, by its historic nomenclature) is an alphaherpesvirus belonging to the genus Iltovirus and family Herpesviridae, which causes infectious laryngotracheitis (ILT) in chickens [1]
We evaluated if 1-day-old chickens vaccinated with a rHVT-LT vaccine were sufficiently protected against a challenge with a wild-type Canadian ILTV isolate at 3 weeks post-vaccination
The ILTV-infected chickens were maintained in high containment poultry isolators (Plas LabsTM, Fisher scientific, Ottawa, ON, Canada) at the Prion/Virology Facility at the Foothills Campus of the University of Calgary
Summary
Gallid herpesvirus-1 (GaHV-1) or infectious laryngotracheitis virus (ILTV, by its historic nomenclature) is an alphaherpesvirus belonging to the genus Iltovirus and family Herpesviridae, which causes infectious laryngotracheitis (ILT) in chickens [1]. There is published evidence that shows that ILTV is capable of infecting pheasants, peafowls and turkeys [2,3,4,5]. ILT is an acute upper respiratory disease that impacts mainly chickens reared in high-density populations [6]. Chickens of all ages are susceptible to ILTV infection, with reports as early as 3 weeks of age [8]. ILTV can establish latency mainly in the trigeminal ganglion [9] and to a lesser degree in trachea [10]
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