Ontario Veterinary College

Mouse: Nomenclature Anatomic Features Genetically Engineered Laboratory Mice Viral Infections Bacterial Infections, Mycotic Infections Parasitic Diseases Nutritional and Metabolic Disorders Behavioural Disorders Environment-Related Disease Aging, Degenerative and Miscellaneous Disorders Genitourinary Disorders Neoplasms. Rat: Anatomic Features Viral Infections Bacterial Infections Pulmonary Lesions of Unknown Etiology Mycotic Infections Parasitic Diseases Aging and Degenerative Disorders Neoplasms. Hamster: Anatomic Features Viral Infections Bacterial and Mycotic Infections Parasitic Diseases Nutritional and Metabolic Disorders Environmental, Genetic and Other Disorders Diseases Associated with Aging Neoplasms. Gerbil: Anatomic Features Viral Infections Bacterial Infections Parasitic Diseases Genetic Disorders Toxic and Metabolic Disorders Diseases Associated with Aging Neoplasms. Guinea Pig: Anatomic Features Viral Infections RNA Viral Infections Bacterial Infections Mycotic Infections Parasitic Diseases Nutritional, Metabolic and Other Disorders Diseases Associated with Aging Neoplasms. Rabbit: Anatomic Features Viral Infections Bacterial Infections Mycotic Infections Parasitic Diseases Miscellaneous Disorders Nutritional, Toxic and Metabolic Diseases Hereditary Disorders Neoplasms.

The Canadian Integrated Program for Antimicrobial Resistance Surveillance describes a strong correlation (r = 0.9, p<0.0001) between ceftiofur-resistant Salmonella enterica serovar Heidelberg isolated from retail chicken and incidence of ceftiofur-resistant Salmonella serovar Heidelberg infections in humans across Canada. In Quebec, changes of ceftiofur resistance in chicken Salmonella Heidelberg and Escherichia coli isolates appear related to changing levels of ceftiofur use in hatcheries during the study period, from highest to lowest levels before and after a voluntary withdrawal, to increasing levels after reintroduction of use (62% to 7% to 20%, and 34% to 6% to 19%, respectively). These events provide evidence that ceftiofur use in chickens results in extended-spectrum cephalosporin resistance in bacteria from chicken and humans. To ensure the continued effectiveness of extended-spectrum cephalosporins for treating serious infections in humans, multidisciplinary efforts are needed to scrutinize and, where appropriate, limit use of ceftiofur in chicken production in Canada.

BACKGROUND: Pimobendan is effective in treatment of dogs with congestive heart failure (CHF) secondary to myxomatous mitral valve disease (MMVD). Its effect on dogs before the onset of CHF is unknown. HYPOTHESIS/OBJECTIVES: Administration of pimobendan (0.4-0.6 mg/kg/d in divided doses) to dogs with increased heart size secondary to preclinical MMVD, not receiving other cardiovascular medications, will delay the onset of signs of CHF, cardiac-related death, or euthanasia. ANIMALS: 360 client-owned dogs with MMVD with left atrial-to-aortic ratio ≥1.6, normalized left ventricular internal diameter in diastole ≥1.7, and vertebral heart sum >10.5. METHODS: Prospective, randomized, placebo-controlled, blinded, multicenter clinical trial. Primary outcome variable was time to a composite of the onset of CHF, cardiac-related death, or euthanasia. RESULTS: Median time to primary endpoint was 1228 days (95% CI: 856-NA) in the pimobendan group and 766 days (95% CI: 667-875) in the placebo group (P = .0038). Hazard ratio for the pimobendan group was 0.64 (95% CI: 0.47-0.87) compared with the placebo group. The benefit persisted after adjustment for other variables. Adverse events were not different between treatment groups. Dogs in the pimobendan group lived longer (median survival time was 1059 days (95% CI: 952-NA) in the pimobendan group and 902 days (95% CI: 747-1061) in the placebo group) (P = .012). CONCLUSIONS AND CLINICAL IMPORTANCE: Administration of pimobendan to dogs with MMVD and echocardiographic and radiographic evidence of cardiomegaly results in prolongation of preclinical period and is safe and well tolerated. Prolongation of preclinical period by approximately 15 months represents substantial clinical benefit.

BACKGROUND: Myxomatous mitral valve disease (MMVD) continues to be an important cause of morbidity and mortality in geriatric dogs despite conventional therapy. HYPOTHESIS: Pimobendan in addition to conventional therapy will extend time to sudden cardiac death, euthanasia for cardiac reasons, or treatment failure when compared with conventional therapy plus benazepril in dogs with congestive heart failure (CHF) attributable to MMVD. ANIMALS: Two hundred and sixty client-owned dogs in CHF caused by MMVD were recruited from 28 centers in Europe, Canada, and Australia. METHODS: A prospective single-blinded study with dogs randomized to PO receive pimobendan (0.4-0.6 mg/kg/d) or benazepril hydrochloride (0.25-1.0 mg/kg/d). The primary endpoint was a composite of cardiac death, euthanized for heart failure, or treatment failure. RESULTS: Eight dogs were excluded from analysis. One hundred and twenty-four dogs were randomized to pimobendan and 128 to benazepril. One hundred and ninety dogs reached the primary endpoint; the median time was 188 days (267 days for pimobendan, 140 days for benazepril hazard ratio = 0.688, 95% confidence limits [CL]=0.516-0.916, P= .0099). The benefit of pimobendan persisted after adjusting for all baseline variables. A longer time to reach the endpoint was also associated with being a Cavalier King Charles Spaniel, requiring a lower furosemide dose, and having a higher creatinine concentration. Increases in several indicators of cardiac enlargement (left atrial to aortic root ratio, vertebral heart scale, and percentage increase in left ventricular internal diameter in systole) were associated with a shorter time to endpoint, as was a worse tolerance for exercise. CONCLUSIONS AND CLINICAL IMPORTANCE: Pimobendan plus conventional therapy prolongs time to sudden death, euthanasia for cardiac reasons, or treatment failure in dogs with CHF caused by MMVD compared with benazepril plus conventional therapy.

A total of 1010 dry cows and pregnant heifers was randomly selected from 25 dairy farms near Guelph, Ontario, Canada to receive either a controlled-release capsule of monensin or a placebo at 3 wk prior to expected calving. Serum samples were obtained at the time of treatment administration, and both serum and milk samples were collected at wk 1, 2, 3, 6, and 9 postcalving. The threshold used to define subclinical ketosis was selected a priori at a concentration of > or = 1200 mumol/L of beta-hydroxybutyrate. Using this threshold, the prevalence and incidence of subclinical ketosis were significantly reduced (50%) by monensin treatment. The duration of subclinical ketosis for cows that had been treated with monensin was also shorter than that for cows treated with the placebo. Monensin treatment significantly reduced the incidence of subclinical ketosis when the threshold was defined using higher concentrations of serum beta-hydroxybutyrate (1400 and 2000 mumol/L). In addition, monensin significantly reduced the prevalence of positive milk ketone tests.

Exposure measurements from several countries indicate that humans are routinely exposed to low levels of bisphenol A (BPA), a synthetic xenoestrogen widely used in the production of polycarbonate plastics. There is considerable debate about whether this exposure represents an environmental risk, based on reports that BPA interferes with the development of many organs and that it may alter cognitive functions and mood. Consistent with these reports, we have previously demonstrated that BPA antagonizes spine synapse formation induced by estrogens and testosterone in limbic brain areas of gonadectomized female and male rats. An important limitation of these studies, however, is that they were based on rodent animal models, which may not be representative of the effects of human BPA exposure. To address this issue, we examined the influence of continuous BPA administration, at a daily dose equal to the current U.S. Environmental Protection Agency's reference safe daily limit, on estradiol-induced spine synapse formation in the hippocampus and prefrontal cortex of a nonhuman primate model. Our data indicate that even at this relatively low exposure level, BPA completely abolishes the synaptogenic response to estradiol. Because remodeling of spine synapses may play a critical role in cognition and mood, the ability of BPA to interfere with spine synapse formation has profound implications. This study is the first to demonstrate an adverse effect of BPA on the brain in a nonhuman primate model and further amplifies concerns about the widespread use of BPA in medical equipment, and in food preparation and storage.

This study determined the prevalence of diseases and pathogens associated with mortality or severe morbidity in 72 Ontario beef feedlots in calves that died or were euthanized within 60 days after arrival. Routine pathologic and microbiologic investigations, as well as immunohistochemical staining for detection of bovine viral diarrhea virus (BVDV) antigen, were performed on 99 calves that died or were euthanized within 60 days after arrival. Major disease conditions identified included fibrinosuppurative bronchopneumonia (49%), caseonecrotic bronchopneumonia or arthritis (or both) caused by Mycoplasma bovis (36%), viral respiratory disease (19%), BVDV-related diseases (21%), Histophilus somni myocarditis (8%), ruminal bloat (2%), and miscellaneous diseases (8%). Viral infections identified were BVDV (35%), bovine respiratory syncytial virus (9%), bovine herpesvirus-1 (6%), parainfluenza-3 virus (3%), and bovine coronavirus (2%). Bacteria isolated from the lungs included M. bovis (82%), Mycoplasma arginini (72%), Ureaplasma diversum (25%), Mannheimia haemolytica (27%), Pasteurella multocida (19%), H. somni (14%), and Arcanobacterium pyogenes (19%). Pneumonia was the most frequent cause of mortality of beef calves during the first 2 months after arrival in feedlots, representing 69% of total deaths. The prevalence of caseonecrotic bronchopneumonia caused by M. bovis was similar to that of fibrinosuppurative bronchopneumonia, and together, these diseases were the most common causes of pneumonia and death. M. bovis pneumonia and polyarthritis has emerged as an important cause of mortality in Ontario beef feedlots.

BACKGROUND: Understanding of chronic sequelae development after Campylobacter infection is limited. The objective of the study was to determine via systematic review and meta-analysis the proportion of Campylobacter cases that develop chronic sequelae. METHODS: A systematic review of English language articles published prior to July 2011 located using Pubmed, Agricola, CabDirect, and Food Safety and Technology Abstracts. Observational studies reporting the number of Campylobacter cases that developed reactive arthritis (ReA), Reiter's syndrome (RS), haemolytic uraemic syndrome (HUS), irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) ,Guillain Barré syndrome (GBS) or Miller Fisher syndrome (MFS) were included. Data extraction through independent extraction of articles by four reviewers (two per article). Random effects meta-analysis was performed and heterogeneity was assessed using the I(2) value. Meta-regression was used to explore the influence of study level variables on heterogeneity. RESULTS: A total of 31 studies were identified; 20 reported on ReA, 2 reported on RS, 9 reported on IBS, 3 studies reported on IBD, 8 reported on GBS, 1 reported on MFS and 3 reported on HUS. The proportion of Campylobacter cases that developed ReA was 2.86% (95% CI 1.40% - 5.61%, I(2) = 97.7%), irritable bowel syndrome was 4.01% (95% CI 1.41% - 10.88%, I(2) = 99.2%). Guillain Barré syndrome was 0.07% (95% CI 0.03% - 0.15%, I(2) = 72.7%). CONCLUSIONS: A significant number of Campylobacter cases develop a chronic sequela. However, results should be interpreted with caution due to the high heterogeneity.

Cognitive responses to stress follow the temporally dependent pattern originally established by Selye (1) wherein short-term stressors elicit adaptive responses whereas continued stress (chronic) results in maladaptive changes--deleterious effects on physiological systems and impaired cognition. However, this pattern for cognitive effects appears to apply to only half the population (males) and, more specifically, to young, adult males. Females show different cognitive responses to stress. In contrast to impaired cognition in males after chronic stress, female rodents show enhanced performance on the same memory tasks after the same stress. Not only cognition, but anxiety, shows sex-dependent changes following chronic stress--stress is anxiolytic in males and anxiogenic in females. Moreover, behavioral responses to chronic stress are different in developing as well as aging subjects (both sexes) as compared to adults. In aged rats, chronic stress enhances recognition memory in both sexes, does not alter spatial memory, and anxiety effects are opposite to young adults. When pregnant dams are exposed to chronic stress, at adulthood the offspring display yet different consequences of stress on anxiety and cognition, and, in contrast to adulthood when the behavioral effects of stress are reversible, prenatal stress effects appear enduring. Changing levels of estradiol in the sexes over the lifespan appear to contribute to the differences in response to stress. Thus, theories of stress dependent modulations in CNS function--developed solely in male models, focused on peripheral physiological processes and tested in adults--may require revision when applied to a more diverse population (age- and sex-wise) at least in relation to the neural functions of cognition and anxiety. Moreover, these results suggest that other stressors and neural functions should be investigated to determine whether age, sex and gonadal hormones also have an impact.

New concepts have emerged in the past few years that help us to better understand the emergence and spread of antimicrobial resistance (AMR). These include, among others, the discovery of the mutator state and the concept of mutant selection window for resistances emerging primarily through mutations in existing genes. Our understanding of horizontal gene transfer has also evolved significantly in the past few years, and important new mechanisms of AMR transfer have been discovered, including, among others, integrative conjugative elements and ISCR (insertion sequences with common regions) elements. Simultaneously, large-scale studies have helped us to start comprehending the immense and yet untapped reservoir of both AMR genes and mobile genetic elements present in the environment. Finally, new PCR- and DNA sequencing-based techniques are being developed that will allow us to better understand the epidemiology of classical vectors of AMR genes, such as plasmids, and to monitor them in a more global and systematic way.

OBJECTIVE: To identify predictors of grief and client desires and needs as they relate to pet death. DESIGN: Cross-sectional mail survey. SAMPLE POPULATION: 177 clients, from 14 randomly selected veterinary practices, whose cat or dog died between 6 and 43 days prior to returning the completed questionnaire. PROCEDURE: Veterinary practices were contacted weekly to obtain the names of clients whose pets had died until approximately 200 clients were identified. Clients were contacted by telephone, and a questionnaire designed to measure grief associated with pet death was mailed to those willing to participate within 1 to 14 days of their pet's death. The questionnaire measured potential correlates and modifiers of grief and included three outcome measures: social/emotional and physical consequences, thought processes, and despair. Demographic data were also collected. RESULTS: Approximately 30% of participants experienced severe grief. The most prominent risk factors for grief included level of attachment, euthanasia, societal attitudes toward pet death, and professional support from the veterinary team. CONCLUSIONS AND CLINICAL RELEVANCE: Bivariate and multivariate analyses highlighted the impact owners' attitudes about euthanasia and professional intervention by the veterinary team had on reactions to pet death. Owners' perceptions of societal attitudes, also a predictor of grief, indicate that grief for pets is different than grief associated with other losses.

PURPOSE: To compare 2 techniques for optimizing joint congruency for miniature osteochondral autografting in the knee: intrinsic postoperative forces acting on overdrilled autografts protruding from the femur versus alignment by a surgeon at the time of grafting. TYPE OF STUDY: Controlled animal model experiment. METHODS: A full-thickness cartilage defect was created on the weight-bearing surface of the medial femoral condyle of 13 mature sheep. Three 4.5 x 10 mm cylindrical autografts were inserted into 14-mm deep recipient holes such that the grafts were held in place by side-wall friction alone. One treatment group received grafts that were delivered flush with the surrounding cartilage and the second group received grafts that were left 2-mm proud of the joint surface. RESULTS: Three months postoperatively, the proud grafts had been repositioned by weight bearing but perigraft fissuring and fibroplasia, and subchondral cavitations were serious complications. It is suspected that these complications were caused by excessive motion between the graft and recipient site in the proud grafts. CONCLUSIONS: Grafts should be delivered flush with the joint surface when performing osteochondral transfers to avoid graft micromotion and the consequent interference with graft integration and function.

The guidelines, authored by a Task Force of experts in feline clinical medicine, are an update and extension of the AAFP–AAHA Feline Life Stage Guidelines published in 2010. The guidelines are published simultaneously in the Journal of Feline Medicine and Surgery (volume 23, issue 3, pages 211–233, DOI: 10.1177/1098612X21993657) and the Journal of the American Animal Hospital Association (volume 57, issue 2, pages 51–72, DOI: 10.5326/JAAHA-MS-7189). A noteworthy change from the earlier guidelines is the division of the cat’s lifespan into a five-stage grouping with four distinct age-related stages (kitten, young adult, mature adult, and senior) as well as an end-of-life stage, instead of the previous six. This simplified grouping is consistent with how pet owners generally perceive their cat’s maturation and aging process, and provides a readily understood basis for an evolving, individualized, lifelong feline healthcare strategy. The guidelines include a comprehensive table on the components of a feline wellness visit that provides a framework for systematically implementing an individualized life stage approach to feline healthcare. Included are recommendations for managing the most critical health-related factors in relation to a cat’s life stage. These recommendations are further explained in the following categories: behavior and environmental needs; elimination; life stage nutrition and weight management; oral health; parasite control; vaccination; zoonoses and human safety; and recommended diagnostics based on life stage. A discussion on overcoming barriers to veterinary visits by cat owners offers practical advice on one of the most challenging aspects of delivering regular feline healthcare.

Relationships between measures for reproductive performance and net revenue were studied using data that had been generated by a stochastic model in a computer simulation program for Ontario dairy herds. These measures included projected calving interval, involuntary culling rate, and adjusted calving interval. Adjusted calving interval was calculated by dividing the projected calving interval for pregnant cows by the fraction of the cows that were not culled for reproductive failure. The regression of adjusted calving interval on net revenue had an R2 of 0.72, which was higher than the R2 of 0.59 obtained by the regression of projected calving interval on net revenue. Hence, the estimation of financial losses from suboptimal reproductive performance was more accurate when adjusted calving interval was used as a measure of this performance than when projected calving interval was used. This difference is because projected calving interval did not consider cows that were culled for reproductive reasons, but those cows contributed to a reduction in profit because of suboptimal reproductive performance. The highest R2 (0.78) was obtained with a model that included projected calving interval and involuntary culling rate. However, use of that model might not be practical because herd operators differ in their ability to distinguish between involuntary and voluntary culling. The mean reduction in net revenue from a 1-d increase in adjusted calving interval was estimated at $4.7 (Canadian) per cow. This economic value was not significantly affected by level of adjusted calving interval, carcass price, feed costs, cost of a replacement heifer, or milk price.

Described are data in a retrospective study of the epidemiology of dystocia, retained placenta, metritis, cystic follicle, and luteal cyst. The 2960 lactation records by 1401 registered Holstein cows in 20 commercial herds were from the Canadian Record of Performance, and the disease data were from the herd health program of the Ontario Veterinary College. Means and standard deviations of production variables were age 4.6 yr, days dry 77.0 +/- 46.9, calving interval 417.6 +/- 71.5 days, breed class average for milk 129.4 +/- 22.5, fat 132.5 +/- 25.5, and days in milk 342.1 +/- 60.6. Rates of disease per lactation were dystocia 5.0%, retained placenta 7.1%, metritis 13.8%, cystic follicle 12.9%, and luteal cyst 3.2%. The distribution of calving ages suggested that the annual herd turnover was 20 to 25%. The distribution of diseases per lactation suggested that diseases occurred together in lactations more often than expected.

In the present paper, we are reviewing experimental evidence demonstrating that phagocytic cells, such as macrophages, may be used as a biomarker of immunotoxicity in wildlife studies. We will first present data obtained after exposure in vitro with selected chemicals showing the comparative sensitivity of phagocytic cells from different species. These results demonstrate that, at least for metals, each species produce a similar shaped dose-response curve, although considerate interspecies sensitivity is evident. These results also demonstrate the sensitivity of the phagocytic activity, suggesting indeed that this function could be used to monitor exposure to chemicals. The similar shaped dose-response curves imply that mechanisms of action may also be similar. Furthermore, based on the relative speices sensitivity, sentinel species could be selected for field monitoring. Such an approach may also be useful to establish correction factors required to extrapolate results between species. This sensitivity of the phagocytic activity of macrophages will be further under controlled conditions in laboratory animal models. Finally, the reliability of this approach will be demonstrated using case studies with wildlife species.

The effects of monensin on the energy metabolism of dairy cows in early lactation were investigated in a large clinical trial that was randomized and double-blinded. A total of 1010 Holstein cows and first lactation heifers were allocated to receive a controlled-release capsule of monensin or a placebo at 3 wk prior to expected calving date. Treatments were randomized across 25 dairy farms located near Guelph, Ontario, Canada. Serum samples obtained at the time of treatment administration and at wk 1, 2, 3, 6, and 9 postcalving were analyzed for beta-hydroxybutyrate, glucose, aspartate aminotransferase, urea, total protein, calcium, and phosphorus. Cows were also assigned a body condition score at the time each sample was obtained. Monensin treatment significantly reduced serum beta-hydroxy-butyrate concentrations at wk 1, 2, and 3 postpartum and significantly raised serum glucose concentrations during wk 1 and 2 of lactation. In addition, monensin treatment significantly reduced the loss of body condition score and decreased serum activity of aspartate aminotransferase during the postpartum period. Concentrations of serum urea were significantly higher during wk 2 and 3 postpartum for the cows that were treated with monensin. Monensin treatment had no effect on the concentrations of calcium, phosphorus, or total protein.

BACKGROUND: Clostridium difficile is an important cause of intestinal infections in some animal species and animals might be a reservoir for community associated human infections. Here we describe a collection of animal associated C. difficile strains from 12 countries based on inclusion criteria of one strain (PCR ribotype) per animal species per laboratory. RESULTS: Altogether 112 isolates were collected and distributed into 38 PCR ribotypes with agarose based approach and 50 PCR ribotypes with sequencer based approach. Four PCR ribotypes were most prevalent in terms of number of isolates as well as in terms of number of different host species: 078 (14.3% of isolates; 4 hosts), 014/020 (11.6%; 8 hosts); 002 (5.4%; 4 hosts) and 012 (5.4%; 5 hosts). Two animal hosts were best represented; cattle with 31 isolates (20 PCR ribotypes; 7 countries) and pigs with 31 isolates (16 PCR ribotypes; 10 countries). CONCLUSIONS: This results show that although PCR ribotype 078 is often reported as the major animal C. difficile type, especially in pigs, the variability of strains in pigs and other animal hosts is substantial. Most common human PCR ribotypes (014/020 and 002) are also among most prevalent animal associated C. difficile strains worldwide. The widespread dissemination of toxigenic C. difficile and the considerable overlap in strain distribution between species furthers concerns about interspecies, including zoonotic, transmission of this critically important pathogen.

OBJECTIVE: To determine whether dogs that visited human health-care facilities were at greater risk of acquiring certain health-care-associated pathogens, compared with dogs performing animal-assisted interventions in other settings, and to identify specific behaviors of dogs associated with an increased risk of acquiring these pathogens. DESIGN: Prospective cohort and nested case-control studies. ANIMALS: 96 dogs that visited human health-care facilities and 98 dogs involved in other animal-assisted interventions. PROCEDURES: Fecal samples and nasal swab specimens were collected from dogs at the time of recruitment and every 2 months for 1 year and were tested for methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile, and other selected bacteria. Information was also obtained on facilities visited during animal-assisted interventions, dog diet, dog illnesses, and antimicrobial use within the home. At the end of the study, dog handlers were asked about the behavior of their dogs during visits to health-care facilities. RESULTS: Rates of acquisition of MRSA and C difficile were 4.7 and 2.4 times as high, respectively, among dogs that visited human health-care facilities, compared with rates among dogs involved in other animal-assisted interventions. Among dogs that visited human health-care facilities, those that licked patients or accepted treats during visits were more likely to be positive for MRSA and C difficile than were dogs that did not lick patients or accept treats. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that dogs that visited human health-care facilities were at risk of acquiring MRSA and C difficile, particularly when they licked patients or accepted treats during visits.

The potential use of distraction osteogenesis in mandibular reconstruction has been limited by its questionable efficacy in previously radiated bone. We studied five mongrel dogs that had a hemimandible rendered edentulous and underwent a full course of external beam radiation therapy (50 Gy/20 fractions). Six months after completion of radiotherapy, a 2-cm critical-size segmental mandibular defect was created and stabilized with a stainless steel plate. A proximal mandibular transport segment was then formed and an external lengthening apparatus (Orthofix) applied. By means of bifocal distraction osteogenesis, the defects were filled with new bone in a period of 30 days in four of five dogs. Histologic analysis and fluorochrome microscopy confirmed the formation of new cortical bone. Our results suggest that distraction osteogenesis is successful in previously radiated bone and that it may be a simple method of mandibular reconstruction following ablative head and neck surgery.