Review of Viral Arthritis in Canada.

Viral arthritis/tenosynovitis, a disease caused by avian reovirus (ARV), leads to great economic losses for the chicken industry worldwide. Since autumn 2011, the poultry industries in the United States and Canada have sustained significant economic losses in the progeny of broiler breeders vaccinated with classic strains of ARV. Vaccination failure has been caused by field challenge with variant ARVs. The variant field ARVs are refractory to the immunity stimulated by classic vaccines and have become the prevalent challenge in the field. Because all genotypes described in the literature have been reported to be circulating in Canada, genotyping of circulating ARVs is paramount for the selection of appropriate isolates, representative of the field challenge, for use in autogenous vaccines. In this review, the history of ARVs and the current situation in Canada are discussed. On the basis of recent field data, inadequate measures commonly used in the field are discussed, and successful vaccination strategies are recommended.

Estudio recapitulativo- Revisión de la artritis viral en Canadá La artritis/tenosinovitis viral, una enfermedad causada por el reovirus aviares (ARV), genera grandes pérdidas económicas para la industria avícola en todo el mundo. Desde el otoño del 2011, las industrias avícolas de los Estados Unidos y Canadá han sufrido pérdidas económicas significativas en la progenie de reproductoras de pollos de engorde vacunadas con cepas clásicas de reovirus aviares. Las fallas de la vacunación han sido causadas por el desafío de campo con reovirus aviares variantes. Los reovirus aviares de campo variantes son refractarios a la inmunidad estimulada por las vacunas clásicas y se han convertido en el desafío predominante en el campo. Debido a que se ha reportado que todos los genotipos descritos en la literatura están circulando en Canadá, la determinación del genotipo de los reovirus aviares circulantes es fundamental para la selección de aislamientos apropiados, representativos del desafío de campo, para su uso en vacunas autógenas. En esta revisión, se discute la historia de los reovirus aviares y la situación actual en Canadá. Sobre la base de datos de campo recientes, se analizan las medidas inadecuadas comúnmente utilizadas en el campo y se recomiendan estrategias de vacunación exitosas.

Chicken Astrovirus (CAstV) Molecular Studies Reveal Evidence of Multiple Past Recombination Events in Sequences Originated from Clinical Samples of White Chick Syndrome (WCS) in Western Canada.

In this study, we aimed to molecularly characterize 14 whole genome sequences of chicken astrovirus (CAstV) isolated from samples obtained from white chick syndrome (WCS) outbreaks in Western Canada during the period of 2014-2019. Genome sequence comparisons showed all these sequences correspond to the novel Biv group from which no confirmed representatives were published in GenBank. Molecular recombination analyses using recombination detection software (i.e., RDP5 and SimPlot) and phylogenetic analyses suggest multiple past recombination events in open reading frame (ORF)1a, ORF1b, and ORF2. Our findings suggest that recombination events and the accumulation of point mutations may have contributed to the substantial genetic variation observed in CAstV and evidenced by the current seven antigenic sub-clusters hitherto described. This is the first paper that describes recombination events in CAstV following analysis of complete CAstV sequences originated in Canada.

Genotyping of Infectious Laryngotracheitis Virus (ILTV) Isolates from Western Canadian Provinces of Alberta and British Columbia Based on Partial Open Reading Frame (ORF) a and b.

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.

Molecular Characterization of Hemorrhagic Enteritis Virus (HEV) Obtained from Clinical Samples in Western Canada 2017-2018.

Hemorrhagic enteritis virus (HEV) is an immunosuppressive adenovirus that causes an acute clinical disease characterized by hemorrhagic gastroenteritis in 4-week-old turkeys and older. Recurrent incidence of secondary infections (e.g., systemic bacterial infections, cellulitis, and elevated mortality), may be associated with the presence of field-type HEV in Canadian turkey farms. We speculate that field-type HEV and vaccine/vaccine-like strains can be differentiated through analysis of the viral genomes, hexon genes, and the specific virulence factors (e.g., ORF1, E3, and fib knob domain). Nine out of sixteen spleens obtained from cases suspected of immunosuppression by HEV were analyzed. The limited data obtained showed that: (1) field-type HEV circulates in many non-vaccinated western Canadian flocks; (2) field-type HEV circulates in vaccinated flocks with increased recurrent bacterial infections; and (3) the existence of novel point mutations in hexon, ORF1, E3, and specially fib knob domains. This is the first publication showing the circulation of wild-type HEV in HEV-vaccinated flocks in Western Canada, and the usefulness of a novel procedure that allows whole genome sequencing of HEV directly from spleens, without passaging in cell culture or passaging in vivo. Further studies focusing more samples are required to confirm our observations and investigate possible vaccination failure.

Long-term protection against a virulent field isolate of infectious laryngotracheitis virus induced by inactivated, recombinant, and modified live virus vaccines in commercial layers.

Infectious laryngotracheitis (ILT) is an acute respiratory disease of chickens controlled through vaccination with live-modified attenuated vaccines, the chicken embryo origin (CEO) vaccines and the tissue-culture origin (TCO) vaccines. Recently, novel recombinant vaccines have been developed using herpesvirus of turkey (HVT) and fowl pox virus (FPV) as vectors to express ILTV immunogens for protection against ILT. The objective of this study was to assess the protection efficacy against ILT induced by recombinants, live-modified attenuated, and inactivated virus vaccines when administered alone or in combination. Commercial layer pullets were vaccinated with one or more vaccines and challenged at 35 (35 WCH) or 74 weeks of age (74 WCH). Protection was assessed by scoring clinical signs; and by determining the challenge viral load in the trachea at five days post-challenge. The FPV-LT vaccinated birds were not protected when challenged at 35 weeks; the HVT-LT and TCO vaccines in combination provided protection similar to that observed in chickens vaccinated with either HVT-LT or TCO vaccines when challenged at 35 weeks, whereas protection induced by vaccination with HVT-LT followed by TCO was superior in the 74 WCH group compared with the 35 WCH group. Birds given the inactivated ILT vaccine had fewer clinical signs and/or lower viral replication at 74 WCH when combined with TCO or HVT-LT, but not when given alone. Finally, the CEO-vaccinated birds had top protection as indicated by reduction of clinical signs and viral replication when challenged at 35 weeks (74 weeks not done). These results suggest that certain vaccine combinations may be successful to produce long-term protection up to 74 weeks of age against ILT.

Molecular characterization of emerging avian reovirus variants isolated from viral arthritis cases in Western Canada 2012-2017 based on partial sigma (σ)C gene.

Viral Arthritis (VA), a disease caused by Avian Reovirus (ARV), has emerged as a significant cause of economic losses in broiler chicken flocks in Western Canada. These outbreaks were characterized by 4-13% morbidity, followed by a spike in mortality/culling that in extreme cases required total flock depopulation. From 2012-2017, 38 ARV isolates were recovered. Molecular characterization of a partial segment of the sigma (σ)C gene shows all six previously known ARV clusters in Western Canadian broiler chickens. The most numerous clusters were Cluster#4 and Cluster #5 while the most variable clusters were Cluster#1 (76.7-100% identity), Cluster#2 (66-99.3%), and Cluster#4 (62-100%). This variation suggests that an autogenous vaccine may not protect against a same-cluster challenge virus. This is the first publication showing the wide genetic diversity of ARV Cluster#4, the circulation of all six worldwide reported ARV clusters in Canada, and important differences in ARV Cluster classification among researchers.

In ovo CpG DNA delivery increases innate and adaptive immune cells in respiratory, gastrointestinal and immune systems post-hatch correlating with lower infectious laryngotracheitis virus infection.

Cytosine-guanosine deoxynucleotides (CpG) DNA can be delivered in ovo at embryo day (ED)18 for the stimulation of toll-like receptor (TLR)21 signaling pathway that ultimately protects chickens against a number of bacterial and viral infections. There is a dearth of information understanding the mechanisms of protection induced by in ovo delivered CpG DNA. The objective of this study was to determine the immune cell changes post-hatch following in ovo delivery of the TLR21 ligand, CpG DNA. In order to quantify changes of percentage of KUL01+, IgM+ B, cluster of differentiation (CD)4+ and CD8α+ cells, trachea, lung, duodenum, large intestine, spleen and bursa of Fabricius were collected on day 1 post-hatch. We found increased recruitments of KUL01+ cells, in organs of these body systems post-hatch following in ovo delivery of CpG DNA. Although IgM+ B cells, CD4+ and CD8α+ cells were increased in lungs and immune system organs, these cells were not quantifiable from the trachea, duodenum and large intestine immediately following the hatch. Furthermore, when CpG DNA is delivered in ovo and subsequently infected with infectious laryngotracheitis virus (ILTV) post-hatch on day 1, CpG DNA reduces morbidity and mortality resulting from ILTV infection. This study provides insights into the mechanisms of host responses elicited following in ovo delivery of CpG DNA in avian species.

Hatchery Vaccination Against Poultry Viral Diseases: Potential Mechanisms and Limitations.

Commercial broiler and layer chickens are heavily vaccinated against economically important viral diseases with a view of preventing morbidity, mortality, and production impacts encountered during short production cycles. Hatchery vaccination is performed through in ovo embryo vaccination prehatch or spray and subcutaneous vaccinations performed at the day of hatch before the day-old chickens are being placed in barns with potentially contaminated environments. Commercially, multiple vaccines (e.g., live, live attenuated, and viral vectored vaccines) are available to administer through these routes within a short period (embryo day 18 prehatch to day 1 posthatch). Although the ability to mount immune response, especially the adaptive immune response, is not optimal around the hatch, it is possible that the efficacy of these vaccines depends partly on innate host responses elicited in response to replicating vaccine viruses. This review focuses on the current knowledge of hatchery vaccination in poultry and potential mechanisms of hatchery vaccine-mediated protective responses and limitations.

Interferencia de la vacunación simultánea contra Metapneumovirus aviar, bronquitis infecciosa y enfermedad de Newcastle en pollos de carne / Interference of simultaneous vaccination against avian metapneumovirus, infectious bronchitis, and Newcastle disease in broilers

El estudio evaluó la interferencia en la protección contra la enfermedad de Newcastle (ENC) ocasionada por la vacunación contra Metapneumovirus (aMPV) en un programa de vacunación simultánea al primer día de edad contra ENC y Bonquitis Infecciosa (BI) en pollos de carne. Se usaron 400 pollos de carne Cobb-Vantress 500 divididos en cuatro grupos. El grupo I vacunado al primer día contra BI (H120), ENC (VG/GA) y aMPV (11/94) y revacunado al día 9 contra ENC (VG/GA). El Grupo II vacunado al primer día contra BI (Ma5), ENC (C2) y aMPV (11/94) y, revacunado al día 9 contra ENC (Clone 30). El grupo III vacunado al primer día contra BI (H120) y ENC (VG/GA) y revacunado al día 9 contra ENC (VG/GA). El Grupo IV no fue vacunado. Todos los grupos fueron desafiados el día 30 con una cepa velogénica viscerotrópica del virus de ENC. Se valuó mortalidad, signos clínicos, respuesta serológica, reacción post vacunal y parámetros productivos. La mortalidad fue de 12 y 16% para los grupos vacunados contra aMPV versus 23% para el grupo no vacunado contra aMPV, y 88% para el control sin vacunas; sin embargo, las diferencias entre los tres grupos vacunados no fueron significativas. Los resultados indican que la vacunación contra aMPV en pollos de carne no ocasionó interferencia en la protección contra la ENC en ninguno de los grupos vacunados simultáneamente contra la ENC, BI y aMPV al primer día de edad, y se vio menor reacción post vacunal usando la cepa entérica que con la cepa de tropismo respiratorio del virus de la ENC.

The study evaluated the interference in the immune protection system against Newcastle disease (ENC) caused by the vaccination against Avian Metapneumovirus (aMPV) in a simultaneous vaccination against ENC and Infectious Bronchitis (BI) in one-day-old broilers. Four hundred Cobb-Vantress 500 broilers were distributed into four groups. Group I vaccinated at 1-day-old against BI (H120), ENC (VG/GA) and aMPV (11/94) with revaccination at day 9 against ENC (VG/GA). Group II vaccinated at 1-day-old against BI (Ma5), ENC (C2) and aMPV (11/94)and revaccinated atday 9 against ENC (Clone 30). Group III vaccinated at 1-day-old against BI and ENC (VG/GA) and revaccinated at day 9 against ENC (VG/GA). Group IV received no vaccine. All groups were challenged at day 30 with a velogenic viscerotropic strain of ENC virus. Mortality, clinical signs, serologic response, post-vaccination reaction, and productive performance were evaluated. Mortality was 12 and 16% for groups vaccinated against aMPV versus 23% for the non-vaccinated group against aMPV, and 88% for the control group;however, no significant difference was found between the three vaccinated groups. Findings indicate that vaccination against aMPV in broilers did not cause interference in the protection against ENC in any of the vaccinated groups; besides, there was less post-vaccination reaction with the enteric strain vaccine instead of a respiratory strain of ENC.