Abstract
Simple SummaryInfectious laryngotracheitis virus is an economically important acute upper respiratory tract disease in chickens. To control the disease, there are two types of vaccines commercially available, the recombinant viral vector and the live attenuated vaccines. The live attenuated vaccines are effective in disease control, but because of their residual virulence, they can replicate, cause disease, and revert to their original virulent form. Strains of the virus can be categorized as vaccine-related or wild type related. Information is scarce on the type of strains that are circulating in Canada. This study aims to discriminate between wild type and vaccine strains associated with infectious laryngotracheitis cases in the provinces of Alberta and British Columbia between the years 2009–2018. To accomplish this objective, the sequencing of two specific partial genes was performed. As a result, 27 samples from Alberta, and 5 samples from British Columbia were successfully sequenced. From the total samples, ~85% were related to vaccine strains and the rest categorized as wild type. These results reinforce the concern on current practices surrounding vaccination and the need to implement better biosecurity measures.Infectious laryngotracheitis virus (ILTV) causes an acute upper respiratory disease in chickens called infectious laryngotracheitis (ILT). Live attenuated vaccines are effective in disease control; however, they have residual virulence, which makes them able to replicate, cause disease and revert to the original virulent form. Information is scarce on the molecular nature of ILTV that is linked to ILT in Canada. This study aims to determine whether isolates originating from ILT cases in Western Canada are a wild type or vaccine origin. Samples submitted for the diagnosis of ILT between 2009–2018 were obtained from Alberta (AB, n = 46) and British Columbia (BC, n = 9). For genotyping, a Sanger sequencing of open reading frame (ORF) a and b was used. A total of 27 from AB, and 5 from BC samples yielded a fragment of 1751 base pairs (bp). Three of the BC samples classified as group IV (CEO vaccine strains) and 2 as group V (CEO revertant). Of the AB samples, 22 samples clustered with group V, 3 with group VI (wild type), and 2 with group VII, VIII, and IX (wild type). Overall, 17 non-synonymous single nucleotide polymorphisms (SNPs) were detected. Further studies are underway to ascertain the virulence and transmission potential of these isolates.
Highlights
The etiological agent responsible for infectious laryngotracheitis (ILT), an acute upper respiratory tract disease in chickens, is the Gallid alphaherpesvirus 1 (infectious laryngotracheitis virus (ILTV))
The background backgroundinformation informationrelevant relevanttotothe the analyzed samples is depicted in Table samples is depicted in Table samples originated from commercial broiler and layer flocks, the only sample
CEO vaccines have not been used for decades in AB, it is possible that underground transmission of CEO revertants in unvaccinated chickens had been taking place for decades resulting in these recent ILT outbreaks
Summary
The etiological agent responsible for infectious laryngotracheitis (ILT), an acute upper respiratory tract disease in chickens, is the Gallid alphaherpesvirus 1 (infectious laryngotracheitis virus (ILTV)). ILT is most commonly seen in large, high-density production areas where it is horizontally transmitted [1]. Enzootic forms of ILT show high morbidity (90–100%), and depending on the infecting strain, more variable mortality (5–70%) can be observed [2]. Even though viremia has not yet been described, in vitro experiments indicated that ILTV can infect macrophages, potentially leading to infection of non-respiratory sites [3]. Lifelong latent infections will be established following the acute phase. This was first described in the trachea [7] and further demonstrated in the recent year [8]. The predominant site of latency is the trigeminal ganglia (TG) [9,10,11,12]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
