Successful long-term outcome with radiation and prednisolone following a postoperative feline vertebral angiomatosis relapse.

Case summary: A 1-year-old male castrated domestic shorthair cat was presented to the Ontario Veterinary College for a week-long history of lethargy and reluctance to walk. CT and MRI revealed a monostotic T5 compressive vertebral lesion that was excised in surgery via pediculectomy. Histology and advanced imaging were consistent with feline vertebral angiomatosis. The cat relapsed both clinically and on CT 2 months postoperatively and was therefore treated with an intensity-modulated radiation therapy protocol (45 Gy over 18 fractions) and tapering doses of prednisolone. On follow-up CT and MRI at 3 and 6 months post-radiation, the lesion was static and then improved at 19 months post-radiation, with no signs of pain reported. Relevance and novel information: To our knowledge, this is the first described case of a postoperative relapse of feline vertebral angiomatosis treated with radiation therapy and prednisolone with a successful long-term follow-up.

Experimental infection of aquatic bird bornavirus 1 in domestic chickens.

Aquatic bird bornavirus 1 (ABBV-1), classified in the Orthobornavirus genus, is a neurotropic virus that infects wild waterfowl causing persistent infection of the nervous system. Given the conspicuous presence of wild waterfowl in urban areas and farmlands, spillover of this virus into domesticated poultry species is a concern. The goal of this study was to test the ability of ABBV-1 to infect and cause disease in chickens. Two day-old, White Leghorn chickens (n, 176) were inoculated with ABBV-1 through the oral, intramuscular, or intracranial routes, and sampled at 1, 4, 8, and 12-weeks post infection (wpi) to assess virus replication and lesion development. Chickens became infected only through the intracranial and intramuscular routes, developing earliest infection in the brain by 1 wpi (intracranial group), and spinal cord by 8 wpi (intramuscular group). Except for the kidney of one bird in the intracranial group, no other tissues (including choanal and cloacal swabs) tested positive for the virus. Therefore, while the virus could reach the central nervous tissue (CNS) from the muscle in approximately 20% of birds (centripetal spread), it inefficiently reached peripheral sites after replication in the CNS (centrifugal spread). Inflammation in the CNS was observed in the intracranial and intramuscular groups starting at 8 and 12 wpi, respectively, and consisted of mononuclear perivascular cuffing. This is the first study to document the susceptibility of chickens to ABBV-1 infection, and indicates that this species can become infected with ABBV-1, although less extensively than what is observed in waterfowl. This suggests that ABBV-1 replication is partially restricted in gallinaceous birds.

Transcriptome Analysis of Duck and Chicken Brains Infected with Aquatic Bird Bornavirus-1 (ABBV-1).

Aquatic bird bornavirus 1 (ABBV-1) is a neurotropic virus that infects waterfowls, resulting in persistent infection. Experimental infection showed that both Muscovy ducks and chickens support persistent ABBV-1 infection in the central nervous system (CNS), up to 12 weeks post-infection (wpi), without the development of clinical disease. The aim of the present study was to describe the transcriptomic profiles in the brains of experimentally infected Muscovy ducks and chickens infected with ABBV-1 at 4 and 12 wpi. Transcribed RNA was sequenced by next-generation sequencing and analyzed by principal component analysis (PCA) and differential gene expression. The functional annotation of differentially expressed genes was evaluated by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The PCA showed that the infected ducks sampled at both 4 and 12 wpi clustered separately from the controls, while only the samples from the chickens at 12 wpi, but not at 4 wpi, formed a separate cluster. In the ducks, more genes were differentially expressed at 4 wpi than 12 wpi, and the majority of the highly differentially expressed genes (DEG) were upregulated. On the other hand, the infected chickens had fewer DEGs at 4 wpi than at 12 wpi, and the majority of those with high numbers of DEGs were downregulated at 4 wpi and upregulated at 12 wpi. The functional annotation showed that the most enriched GO terms were immune-associated in both species; however, the terms associated with the innate immune response were predominantly enriched in the ducks, whereas the chickens had enrichment of both the innate and adaptive immune response. Immune-associated pathways were also enriched according to the KEGG pathway analysis in both species. Overall, the transcriptomic analysis of the duck and chicken brains showed that the main biological responses to ABBV-1 infection were immune-associated and corresponded with the levels of inflammation in the CNS.

Experimental infection of aquatic bird bornavirus in Muscovy ducks.

Aquatic bird bornavirus (ABBV-1), an avian bornavirus, has been reported in wild waterfowl from North America and Europe that presented with neurological signs and inflammation of the central and peripheral nervous systems. The potential of ABBV-1to infect and cause lesions in commercial waterfowl species is unknown. The aim of this study was to determine the ability of ABBV-1 to infect and cause disease in day-old Muscovy ducks (n = 174), selected as a representative domestic waterfowl. Ducklings became infected with ABBV-1 through both intracranial and intramuscular, but not oral, infection routes. Upon intramuscular infection, the virus spread centripetally to the central nervous system (brain and spinal cord), while intracranial infection led to virus spread to the spinal cord, kidneys, proventriculus, and gonads (centrifugal spread). Infected birds developed both encephalitis and myelitis by 4 weeks post infection (wpi), which progressively subsided by 8 and 12 wpi. Despite development of microscopic lesions, clinical signs were not observed. Only five birds had choanal and/or cloacal swabs positive for ABBV-1, suggesting a low potential of Muscovy ducks to shed the virus. This is the first study to document the pathogenesis of ABBV-1 in poultry species, and confirms the ability of ABBV-1 to infect commercial waterfowl.

Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.

Characteristics of broiler chicken breast myopathies (spaghetti meat, woody breast, white striping) in Ontario, Canada.

Spaghetti meat (SM), woody breast (WB), and white striping (WS) are myopathies affecting breast muscle of broiler chickens, and are characterized by a loss of myofibers and an increase in fibrous tissue. The conditions develop in intensive broiler chicken production systems, and cause poor meat process-ability and negative customer perception leading to monetary losses. The objectives of the present study were to describe the physical and histological characteristics of breast myopathies from commercial broiler chicken flocks in Ontario, Canada, and to assess the associations between the severity of myopathies with the physical and histological characteristics of the affected breast muscle fillets. Chicken breast fillets (n = 179) were collected over 3 visits from a processing plant and scored macroscopically to assess the severity of myopathies, following an established scoring scheme. For each fillet, the surface area, length, width, thickness, weight, and hardness (compression force) were measured. A subset of 60 fillets was evaluated microscopically. Multinomial logistic regression models were built to evaluate associations between physical parameters and macroscopic scores. The odds of SM co-occurring with severe WB (SM1WB2) were significantly associated with increased fillet thickness (OR = 1.59, 95% CI 1.31-1.94) and weight (OR = 1.06, 95% CI 1.03-1.09). Histologically, myopathies had overlapping lesions consisting of polyphasic myodegeneration, perivascular inflammatory cuffing and accumulation of fibrous tissue and fat. The pairwise correlation between macroscopic and microscopic scores was moderate (rho 0.45, P < 0.001). This is the first study to characterize breast myopathies in Canadian broiler flocks. Results show that the morphologic and microscopic changes of fillets from this cohort are similar to data from other countries, and provide database to benchmark these parameters in future studies. Our standardized categorization can be applied to broiler breast fillets in other regions of the world.