Table of Contents and Abstracts

A 4-year-old castrated male golden retriever dog was brought to a veterinary teaching hospital for evaluation of acute progressive paraparesis. Neurological examination indicated a spinal cord lesion between the third thoracic vertebra and third lumbar vertebrae. Magnetic resonance imaging (MRI) revealed an intradural, extra medullary, and/or intramedullary mass centered over the eleventh and twelfth thoracic disc space. The dog underwent cytoreductive surgery and histopathologic analysis diagnosed a nephroblastoma. Following this, the dog underwent multimodal therapy, including multiple surgeries, 2 courses of radiation, and combination chemotherapy. The dog had serial restaging using MRI, computed tomography (CT), and fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography throughout the course of therapy. The dog survived 350 d from date of first presentation until humane euthanasia was elected due to worsening of neurologic status. During postmortem examination, extensive infiltration of the spinal cord by nephroblastoma cells was discovered as well as pulmonary metastatic disease.

Key clinical message:
Based on the literature search, this is the first case in which surgery, radiation therapy, and chemotherapy were all used for the treatment of canine spinal nephroblastoma. This case report details the aggressive nature of a case of canine spinal nephroblastoma despite multi-modal therapy.

A 14-month-old feedlot steer was depressed and died while being examined. The gross post-mortem examination of the steer conducted at the feedlot identified numerous masses within the abdomen and thorax, including a large mass in the liver that eroded into the vena cava. Many masses in the lungs appeared to be the result of hematogenous distribution. Histologic examination of the masses confirmed the presence of neoplasia. Although the histologic appearance of the neoplasms was not typical of well-differentiated leiomyosarcoma, immunohistochemical staining supported that diagnosis. Leiomyosarcomas are rare among North American cattle. In this case, the primary neoplasm appears to have originated in the wall of the vena cava within the liver.

Key clinical message:
This report adds to the limited information on leiomyosarcomas in cattle, while highlighting both the challenges faced by veterinarians conducting post-mortem examinations on large animals in below freezing temperatures, as well as the current methods available to arrive at a diagnosis of a rare disease.

A 9-year-old spayed female 18.8 kg mixed breed boxer dog was referred for evaluation of a 7-month history of difficulty swallowing and prehending food, regurgitation, hypersalivation, and an abnormal dorsiflexion of the tongue. Prior to referral, a barium study was performed, which revealed a mildly dilated esophagus. Treatment with sucralfate, cisapride, and prednisone was initiated.

Physical examination revealed bilateral, symmetric atrophy of the temporalis muscles, dorsiflexion of the distal aspect of the tongue with concurrent muscle atrophy, and a reduced gag reflex. Electrodiagnostic examinations revealed spontaneous electrical activity in the muscles of mastication and tongue. Biopsies from the right temporalis, tongue, and biceps femoris muscles were collected. An immune-mediated myositis with fibrosis, scattered CD3, CD4, and CD8+ T-lymphocytes, and upregulation of markers for major histocompatibility antigens were observed in the tongue and temporalis muscles.

The dog was treated with a tapering course of prednisone over 2 months and cyclosporine long-term. The dog was maintained on cyclosporine alone for > 2 years and clinical signs remained static, although multiple episodes of aspiration pneumonia occurred. Ultimately, euthanasia was performed due to chronic kidney disease with associated anemia, lethargy, and anorexia.

A dog was examined because of acute onset of respiratory distress following a cervical dog bite. Physical examination revealed a deep ventral cervical bite wound associated with localized mild subcutaneous emphysema. Thoracic radiographs showed moderate pneumomediastinum. Medical management consisting of oxygen therapy, antibiotics, and anti-inflammatories was initiated. After 2 days, respiratory distress suddenly worsened. Tracheoscopy showed a discontinuity between the tracheal rings of the cervical trachea; however, the inner tracheal wall appeared intact. Computed tomography scan revealed a ~3-cm complete rupture of all layers of the trachea. Surgical resection and anastomosis of the trachea were performed successfully. Follow-up 15 days after surgery showed complete resolution of respiratory signs, as well as subcutaneous emphysema. A mild ventral angulation of the trachea at the surgical site was noticed on thoracic radiographs.

This is the first case report of a pseudotrachea in a dog. Persistence of a pseudotrachea may initially result in only minor clinical signs responsive to medical therapy despite tracheal rupture. In the presence of a pseudotrachea, tracheal rupture may be difficult to identify with tracheoscopy alone. Therefore, CT scan should be proposed in every patient with suspected tracheal trauma.

Key clinical message:
This case report highlights the importance of including a tracheal rupture in the differential diagnosis of cervical subcutaneous emphysema, even if the amount is small and not associated with significant respiratory signs. The presence of a pseudotrachea may result in less severe clinical signs than expected based on the actual degree of tracheal injury; however, the clinical status may rapidly deteriorate and become life-threatening.

This case report also underlines the importance of a CT scan as a complement to tracheoscopy, which may not be sufficient to identify a tracheal rupture in the presence of a pseudotrachea.

This case study describes a severe tail-biting event on a multi-site swine operation in Ontario and outlines the management strategies implemented in an attempt to control the problem. An established social order was clearly present before the tail-biting event occurred. Over 40% of tail-docked pigs in 3 of 8 grower-finisher barns were severely affected, leading to higher mortality and increased numbers of pigs re-housed in hospital pens. Environmental factors, management practices, and animal health in the barns experiencing the tail-biting event are described, including detection of the mycotoxin deoxynivalenol in corn at > 2 ppm. Changes implemented in response to tail-biting included altering the phase-feeding schedule, adding enrichment devices, and increasing surveillance. The subsequent cohort of pigs was followed through the finisher barns and did not engage in the same severity or prevalence of tail-biting as the previous cohort of pigs which experienced the tail-biting event.

Key clinical message:
No single factor was identified as the initiating cause for the severe tail-biting event. The subsequent cohort of pigs in 4 barns of the same operation were monitored for tail-biting from entry until market, and the incidence of tail-biting was very low.

The surgical treatment of a gastroesophageal intussusception (GEI) in a 4-week-old male intact German shepherd puppy is described in this report. Bilateral gastropexies were performed; an incisional gastropexy on the right and a gastrostomy tube gastropexy on the left.

The dog recovered well and is thriving long-term with no clinical signs of persistent megaesophagus.

With the combination of early detection and surgical correction of GEI, mortality rates may be lower than the 95% mortality rate that has been reported in previous literature and supports new studies that have reported a 65% survival rate long-term.

Key clinical message:
Young animals presenting with vague clinical signs require thorough evaluation to identify uncommon, yet life-threatening diseases such as GEI. Early detection and interventions can subsequently lead to successful outcomes.

Objective
Bacterial bronchopneumonia occurs in mature dairy cows but much of the information is extrapolated from knowledge of the disease in calves. The study was prompted by perceptions of an increasing occurrence and a paucity of information on fatal Mannheimia haemolytica pneumonia in dairy cows in Ontario. The study objectives were to describe the seasonality, main pathogens involved, and suggested predisposing factors for cases of fatal bacterial bronchopneumonia in mature dairy cows submitted for postmortem examination to a diagnostic laboratory, and to evaluate if the frequency of such submissions has increased over time.

Animals
Mature dairy cows.

Procedure
Retrospective study of cases submitted for postmortem examination to a diagnostic laboratory from 2007–2020 that were diagnosed as bacterial bronchopneumonia.

Results
Most of the postmortem cases of bacterial bronchopneumonia in dairy cows were submitted from November to February (54% of cases). Mannheimia haemolytica was isolated from lung of 61/101 cases. Viruses were only identified in 8/55 cases tested. A minority (29/92) of bacterial isolates had in vitro resistance to antimicrobials used to treat pneumonia. Frequently suggested predisposing factors included recent introductions or movement of animals, recent or imminent calving, inclement weather, concurrent diseases, and poor ventilation in barns.

Conclusion and clinical relevance
This study describes seasonal and annual trends, major pathogens, antimicrobial resistance profiles, and suggested predisposing factors in Ontario dairy cows submitted to a diagnostic laboratory for postmortem investigation of pneumonia and provides insights for understanding why outbreaks occur.

Objective
To calculate prescribed daily doses (PDDs) for selected antimicrobials and evaluate application of defined daily doses (DDDs) using an antimicrobial purchasing dataset.

Animals
Data from dogs and cats treated for bacterial cystitis at a veterinary practice network were evaluated.

Procedure
A dataset containing antimicrobial prescriptions for dogs and cats diagnosed with bacterial cystitis was evaluated. Median dose and frequency and median weight of treated animals were used to calculate PDDs. To account for differences in use between dogs and cats, an adjusted DDD was calculated based on adjustment for proportional use in dogs versus cats.

Results
PDDs for dogs and cats were determined and adjusted DDDs were calculated and applied to an antimicrobial purchasing dataset from 886 veterinary clinics, demonstrating the difference between mass-based and DDD data.

Conclusions
DDDs can be estimated using prescription datasets, accounting for differences in weights (between and within species) and relative use between dogs and cats. These can be applied to broader (sales, purchase) datasets to provide a more detailed understanding of how antimicrobials are used.

Clinical relevance
DDDs could be a useful measure for assessing mass-based antimicrobial use datasets as part of antimicrobial stewardship surveillance efforts.

A 1-year-old male golden retriever-poodle crossbred dog was brought to a veterinary clinic with a 1-month travel history to Muskoka, Ontario and a 1-week history of left eye irritation and ocular discharge. Ophthalmic examination and blood analysis revealed bilateral uveitis with a normal complete blood (cell) count and biochemistry panel. Symptomatic treatment was administered with no improvement observed and the dog returned 2 weeks later for assessment of a draining swelling of the left hind 4th digit. Clinical examination of thoracic radiographs and abdominal ultrasound showed evidence of disseminated blastomycosis characterized by pulmonary lesions, and multifocal lymphadenopathy. Biopsy of the draining lesion and cytological examination of an enlarged lymph node established diagnosis. The dog was started on a standard antifungal treatment protocol (itraconazole) but returned after 11 d of treatment with neurological signs including ataxia, paraparesis, left head tilt, and compulsive turning. Humane euthanasia was chosen and the diagnosis was confirmed at postmortem examination.

This case study-based paper outlines the thought processes linked to the ethical decision in Canadian animal protection work, about when a case warrants investigation as an offence under provincial animal protection legislation and when it is a criminal code offence. Conflict of laws and jurisdiction as well as prosecutorial discretion give us cause to consider whether methods of mass depopulation of animals in emergency situations can breach prohibitions against animal cruelty. The current practice of overheating enclosed holding facilities to intentionally kill pigs by induced heat stroke is, in the authors’ opinions, an action consistent with a general understanding of animal cruelty.