A marked increase in leptospirosis in dogs was observed in 2000, part of an increasing trend observed in previous years in Ontario. The highest frequency of seropositive cases occurred from September to December 2000, with the peak in November. Large breed dogs were particularly affected. Clinical and clinicopathological data for 31 dogs admitted between 1998 and 2000 to the Ontario Veterinary College Veterinary Teaching Hospital were analyzed. Major clinical presenting features were acute onset of anorexia, depression, fever, and vomiting. Ninety percent of dogs, on admission, showed biochemical evidence of injury to several organs, notably combinations in the order of kidney, muscle, pancreas, and liver. Almost all dogs showed increased serum urea and creatinine levels, and the majority had increased total creatine kinase, bilirubin, alkaline phosphatase, and leukocytosis with neutrophilia. One-third were thrombocytopenic. Of dogs with liver-related abnormalities, most had evidence of cholestasis, with or without hepatocellular damage. Based on serologic studies, in the year 2000, the major serovar involved was autumnalis, but bratislava, grippotyphosa, and pomona were also implicated. The microscopic agglutination test often gave a confusing pattern of reactivities to the serovars that were tested. The high reactivity to serovar autumnalis may represent an erroneous or “paradoxical” reaction typical of early leptospiral serology. The year 2000 was the warmest in Ontario in each of the 4 fall months (September–December) of the previous decade...

Mortality was studied among a group of 328 employees of an Ontario asbestos-cement factory who had been hired before 1960 and who had been employed for a minimum of nine years. The group of 87 men who had worked in the rock wool/fibre glass operations, or who had been otherwise minimally exposed to asbestos, had mortality rates similar to those of the general Ontario population, while the group of asbestos-exposed employees had all-cause mortality rates double those of the Ontario population, mortality rates due to malignancies five times higher than expected, and deaths attributed to lung cancer eight times more frequent than expected. According to the best evidence available, 10 of 58 deaths among the production workers were due to malignant mesothelioma and 20 to lung cancer. The men dying of mesothelioma were younger than the men dying of lung cancer with mean ages at death of 51 and 64 years respectively. An exposure model was constructed on the basis of the available air sampling data, and individual exposure histories were calculated. These exposure histories were used to investigate the exposure-response relationships for asbestos-associated malignancies.

OBJECTIVES: To assess the factors affecting the severity of motor vehicles traffic crashes involving young drivers in Ontario. POPULATION: Ontario young drivers, aged 16 to 20, involved in traffic crashes resulting in injury, between 1 January 1988 and 31 December 1993, on public roads in Ontario. METHODS: Population based case-control study. Cases were fatal injury, major injury, and minor injury crashes involving young drivers. Controls were minimal injury crashes involving young drivers. Cases and controls were obtained retrospectively from the Canadian Traffic Accident Information Databank. Unconditional logistic regression was used for data analysis. RESULTS: Factors significantly increasing the risk of fatal injury crashes include: drinking and driving (odds ratio (OR) 2.3), impairment by alcohol (OR 4.8), exceeding speed limits (OR 2.8), not using seat belts (OR 4.7), full ejection from vehicle (OR 21.3), intersection without traffic control (OR 2.2), bridge or tunnel (OR 4.1), road with speed limit 70-90 km/hour (OR 5.6) or 100 km/hour (OR 5.4), bad weather (OR 1.6), head-on collision (OR 80.0), and overtaking (OR 1.9). Results of the same model applied to major and minor injury crashes demonstrated consistent but weaker associations with decreasing levels of crash severity. CONCLUSIONS: A casual relationship between crash severity and the risk factors listed above was proposed. Risk factors recommended for preventive intervention include: alcohol consumption...

OBJECTIVES: Radium induces bone sarcomas at high doses, but there is controversy about risk at low doses. A previous study in Ontario found an association between the presence of radium in birthplace water supplies and an increased risk of death from bone cancer in young people. An investigation was performed to test the findings of the previous study with an independent group of subjects for whom complete information on radium exposure would be obtained. METHODS: A population based case-control study (238 cases; 432 controls) was conducted with incident cases of bone sarcoma identified from the Ontario cancer registry. Residential histories were collected by questionnaire and water samples were obtained and analysed for radium content. RESULTS: There was an association between risk of osteosarcoma and birthplace exposures (odds ratios (ORs) and 90% confidence intervals (90% CIs) 1.77 (1.03-3.00) but not with lifetime measures of exposure. When lifetime exposure was dichotomised, the OR was 1.31 (0.76-2.24) for osteosarcoma. There was no trend with increasing exposure. Bootstrap resampling was used to simulate lifetime doses in a pooled analysis of 1293 subjects from the two Ontario studies. The ORs were 1.38 (1.08-1.73) for all sarcomas...

The polymerase chain reaction (PCR) was used to amplify DNA of infectious laryngotracheitis virus (ILTV) isolates obtained from field specimens. The examined 47 samples included 37 isolates representing 35 cases of infectious laryngotracheitis from Ontario and 10 isolates originating from 10 field cases in New Brunswick. The viruses were grown in either embryonated chicken eggs or cell culture, the DNA extracted and amplified using primers designed from the sequence information of a 1.1 kb BamHI fragment of the Ontario 1598 ILTV strain. Thirty-four of the Ontario isolates and all of the New Brunswick isolates were amplified successfully. This suggests that the selected primers would be useful for the majority of the isolates encountered in outbreaks of ILTV.

BACKGROUND: There is continuing uncertainty over the relative contribution of outcomes monitoring to changes in surgical outcomes over time. The authors studied temporal trends in the clinical characteristics and short-term outcomes of patients who underwent coronary artery bypass grafting (CABG) in Ontario before and after the implementation, in 1993, of a province-wide program to provide feedback on cardiac surgery outcomes. METHODS: The authors analysed data from hospital discharge abstracts on the clinical characteristics and in-hospital death rates of all 67,784 patients who underwent isolated CABG in Ontario between Apr. 1, 1981, and Mar. 31, 1996. RESULTS: Death rates were relatively stable during the first half of the 1980s, then declined gradually in the second half of the decade; this decline continued into the first half of the 1990s. In the 1990s patients were older than those in the 1980s, and a higher proportion had coexisting diseases. Between 1986/87 and 1995/96 the unadjusted death rate decreased by 52% (5.0% v. 2.4%) (p < 0.001). The annual relative rate of decline was approximately 6% (95% confidence interval 5% to 7%) in the period before the outcomes feedback program was implemented and about 9% (95% confidence interval 7% to 11%) in the period after implementation. INTERPRETATION: Rates of death after CABG have been declining steadily in Ontario since the mid-1980s. Outcomes-based quality improvement interventions may facilitate; but are not a prerequisite for...

BACKGROUND: Every 2 years, the Addiction Research Foundation of Ontario, a division of the Centre for Addiction and Mental Health, sponsors the Ontario Student Drug Use Survey. The results of the surveys conducted in 1995 and 1997 are presented here and compared with results from the early 1990s. METHODS: Questionnaires were completed by 3870 and 3990 Ontario public school students enrolled in grades 7, 9, 11 and 13 in 1995 and 1997 respectively. The outcome measures were prevalence of use of 20 types of drugs and other substances, including alcohol, tobacco and prescription drugs, over the previous 12 months. RESULTS: For several drugs the prevalence of use in the previous 12 months had increased from 1993 to 1995, but from 1995 to 1997 there was a significant increase for only one type (hallucinogens such as mescaline and psilocybin). The inhalation of glue declined, and the use of the other 18 types of drugs remained stable. INTERPRETATION: Recent data suggest that increases in adolescent student drug use reported earlier this decade have not continued. However, the stability in rates of drug use is not a justification for complacency in this important area of public health.

BACKGROUND: Excess use of parenteral vitamin B12 has been reported from audits of clinical practices. The authors assessed the use of vitamin B12 injections in patients aged 65 years and over in Ontario. METHODS: A cross-sectional analysis was conducted that included all elderly people covered by the Ontario Health Insurance Plan who received insured services from general practitioners or family physicians (GP/FPs). For each practice the proportion of elderly patients who received regular vitamin B12 injections between July 1996 and June 1997 was calculated. The frequency of injections was determined for each patient receiving regular B12 replacement. RESULTS: Of the 1,196,748 elderly patients (mean age 74.8 [standard deviation 6.8], 58.0% female) treated by 14,177 GP/FPs, 23,651 (2.0%) received regular B12 injections. The rate of B12 injections per patient, standardized for age and sex, varied between practices (range 0%-48.6%). Although no authoritative sources support the practice, 3303 (19.8%) of the 16,707 patients receiving long-term parenteral therapy had, on average, overly frequent injections (more than 1 injection every 4 weeks). For 76 (12.3%) of the 617 practices with 10 or more patients receiving regular vitamin B12 injections...

BACKGROUND: Deaths among patients awaiting coronary artery bypass grafting (CABG) are a source of private grief and public concern in Canada. However, some deaths are expected over time among patients with coronary artery disease. Methods of benchmarking the burden of delayed care may be useful in understanding and managing waiting lists for CABG and other health services. The authors therefore determined the vital risk among people waiting for CABG in Ontario and compared it with the risk in the general population and among people living with coronary artery disease. METHODS: Patients registered to undergo CABG in Ontario between 1991 and 1995 were followed to ascertain numbers and dates of preoperative deaths or completed operations. Linking hospital discharge abstract data to vital statistics for 1991 to 1994, the authors defined a cohort of people who had survived 6 months after an acute myocardial infarction (AMI) and followed them for an additional 6 months to determine numbers and dates of deaths. They matched patients by age and sex and then calculated the standardized mortality ratio for each cohort (i.e., the ratio of observed deaths to those expected based on age- and sex-specific daily probabilities of death for the provincial population). RESULTS: Among 21...

This paper recounts a study of the prevalence of malignant hyperthermia in a population of boars entering the Record of Performance Test Station at New Hamburg, Ontario over a period of ten months. The literature is briefly reviewed and an account of the present status of malignant hyperthermia (porcine stress syndrome) in Ontario boars using the halothane or halothane/succinylcholine screening tests is presented. It was determined in this population of boars that there was a 1.5% prevalence rate of malignant hyperthermia susceptible boars. This was based on a five minute halothane challenge carried out on 786 boars from 107 herds. The halothane reactors came from a total of eight herds or 7.5% of the total number of herds. A majority of 58.3% of the animals reacted after the three minute mark of the halothane challenge. In contrast, an 18.0% prevalence rate was determined using halothane/succinylcholine challenge on 123 boars. This further identified an additional eight herds with the problem, bringing the total to 16 or 15% of the total number of herds. It is suggested that the prevalence of malignant hyperthermia in Ontario breeding herds is much higher than was originally thought and that the halothane challenge is an inadequate screening test for this trait if the intention is to remove the genetic trait from the breeding herd. At the same time halothane challenge testing will identify those animals which have a strong susceptibility to the trait and if used on key breeding stock will help to maintain some control on the condition until a more definitive test is readily available.(ABSTRACT TRUNCATED AT 250 WORDS)

Between 1977 and 1981, the Fish Pathology Laboratory of the Ontario Veterinary College received 239 cases from trout farms of southern Ontario, 51 (21.3%) of which had diseased gills. Branchial lesions in 86.3% of these 51 cases were characterized by marked lamellar epithelial hyperplasia with epithelial hypertrophy and lamellar fusion. Filamentous bacteria were seen on the surface of the branchial filaments and lamellae in 68.6% of the cases. Our observations highlight the importance of gill diseases as a production problem of farmed salmonids in southern Ontario.

A survey of the efficiency of production of Ontario beef cow-calf herds was conducted using a stratified systematic random sample of Ontario producers. In general, about 87% of females exposed to breeding produced a live calf and 6% of these died before reaching four weeks of age. The herd to herd variation in these rates was quite large, the coefficient of variation being about 17%. The stillbirth rate was 1.7% and the abortion rate 1.2%. In general, herds in northern Ontario and herds whose owners kept breeding and calving records, had reduced livebirth rates, the latter probably reflecting accuracy of data. Herds with a restricted (less than three months) breeding season had increased livebirth rates. Herds using injectable vitamins ADE, and prophylactic antibiotics, had increased neonatal losses. Herds with a restricted calving season (less than or equal to 3 months) and/or feeding free choice salt to cows had decreased neonatal losses. Herdsize and calf mortality rate were directly related, but this did not appear to be due to increased density of cows at calving time. In herds, where calving occurred during the spring, using scour vaccines in calves was associated with increased calf mortality.

Sera from Thoroughbred and Standardbred horses in southwest Ontario were tested for antibody to seven Leptospira interrogans serovars (autumnalis, bratislava, canicola, grippotyphosa, hardjo, icterohaemorrhagiae, pomona), using the microscopic agglutination test. There was significantly higher seroprevalence of bratislava than of other serovars, in which prevalence was low. Seroprevalence of bratislava increased significantly with age; only 5% of two to three year old horses had titers greater than or equal to 1:80 compared to 52% of horses older than seven years. Eight of 16 foals from two farms seroconverted at low titers to bratislava between four and eight months of age. Leptospires were not detected by immunofluorescence and isolation techniques in 50 kidneys collected from horses at slaughter. Fetal tissues from 52 aborted horse fetuses were also examined by these methods and serovar kennewicki was identified by immunofluorescence and by isolation in one fetus. Serovar bratislava appears to be widespread in horses in Ontario but unimportant in abortion. The clinical significance of this infection in horses in Ontario is unclear.

An observational study involving 304 dairy herds and three abattoirs was conducted between 1986 and 1989 to investigate the epidemiology of paratuberculosis in dairy cattle in Ontario. The objectives of this paper were to describe the method of data collection for the study, to present descriptive production statistics and to present estimates of the prevalence of paratuberculosis among dairy cattle in Ontario. Mycobacterium paratuberculosis was isolated from the distal ileum and/or the ileocecal lymph node of 5.5% of 400 cull cows. Based on a lipoarabinomannan antigen enzyme-linked immunosorbent assay (LAM-ELISA) on sera, the predicted true prevalence of paratuberculosis among 14,923 dairy cattle from 304 herds, was 6.1%. Nineteen percent of 2,943 fecal cultures were uninterpretable because of overgrowth with contaminating bacteria or fungi. It was concluded that the true prevalence of paratuberculosis among dairy cattle in Ontario was no greater, and may be less than the true prevalence among dairy cattle from various regions of the United States. However, at a practical level, for the purposes of trade policy, the present study suggests that the functional prevalence is very similar in the two countries.

Preweaning mortality in piglets constitutes a major loss to the swine industry. Congenital defects account for a small but significant proportion of these losses. To implement appropriate strategies to reduce such losses, it is necessary to identify the specific causes and their relative importance. Consequently, a mail survey of swine production in Ontario was carried out to determine the prevalence and types of birth defects. Statistical comparisons of the prevalence of overall defects were made between accurate and estimate records, breeds (cross vs. purebred), size of operation (number of sows) and geographic location. The mean litter size of 11 pigs born per sow was not significantly different for those with accurate versus estimate records, but the difference in the prevalence of defective pigs (live and dead) was significant (accurate 3.1% vs. estimate 4.1%). Splayleg (spraddleleg) was the most common defect. The next four defects for both groups were belly rupture, other rupture, ridglings and other, but not in the same ranking. Purebred and small farm operations (< 25 sows) had a significantly higher prevalence of birth defects for estimated data only. Geographic location had no effect. Further work is required to determine whether recording prevalence of birth defects in Ontario swine will provide a useful monitor of environmental stress. The study provides a baseline for the prevalence and type of defects in Ontario swine.

Genetic-variant analysis of rabies viruses provides the most sensitive epidemiologic tool for following the spread and persistence of these viruses in their wildlife hosts. Since its introduction by a southern epizootic movement that began in the far north, the arctic fox (AFX) strain of Rabies virus has been enzootic in Ontario for almost 50 y. Prior genetic studies identified 4 principal genetic variants (ONT.T1 to ONT.T4) that were localized to different regions of the province; furthermore, these viruses could be distinguished from the variant circulating in northern regions of Quebec, Newfoundland, and arctic zones, ARC.T5. Despite an intensive provincial control program undertaken over the last decade that involved aerial distribution of baits laden with rabies vaccine to combat fox rabies throughout the enzootic zone of Ontario, pockets of rabies activity persist. Re-evaluation of the genetic characteristics of the viral variants circulating in these areas of persistence has been undertaken. These data demonstrate that the recent outbreaks are, with 1 exception, due to persistence of the regional variant first identified in the area in the early 1990s. In contrast, the disease in the Georgian Bay area is a consequence of the incursion of a variant previously found further south. An outbreak that occurred in northern Ontario north and west of North Bay and in the neighboring border areas of Quebec in 2000–2001 was due to renewed incursion of the ARC.T5 variant from more northerly areas.

OBJECTIVE: To analyse the geographic variation in the rates of coronary artery bypass grafting (CABG) between 1981 and 1991. DESIGN: Retrospective study of discharge abstracts (from the provincial hospital discharge database) for odd fiscal years. SETTING: Ontario. PARTICIPANTS: All Ontario residents undergoing CABG between 1981 and 1991. OUTCOME MEASURES: Age- and sex-standardized median, maximum and minimum (plus 25th and 75th percentile) rates of CABG per 100,000 population aged 20 years and over, as well as interregional variation. RESULTS: The median rate of CABG rose from 46.2 to 72.7 per 100,000 adults between 1981 and 1991. The minimum rate varied from 1.9 to 12.4 per 100,000 and the maximum rate from 110.4 to 172.1 per 100,000 during the study period. Variations in the area-specific rates were significant in all years (p < 0.0001, based on the likelihood ratio chi 2 test after adjustment for age and sex). None of the four summary statistical measures showed any obvious diminution between 1981 and 1989, nor was there a change in the utilization pattern during the waiting-list crisis years of 1987 and 1989. However, the summary measures did reach their lowest level in 1991. The relative consistency of local practice patterns was tested by means of ranking area-specific rates and comparing the rankings for different years. Correlation coefficients varied from 0.50 to 0.82 (p < 0.0001); the correlation coefficient for 1991 on 1981 was 0.61 (p < 0.0001). CONCLUSIONS: Consistent and marked variations in the use of CABG existed across the counties of Ontario from 1981 to 1991. Despite a major expansion in provincial caseload capacity and planned regionalization of CABG as a surgical service...

There is conflicting evidence as to whether physicians who are certified in family medicine practise differently from their noncertified colleagues and what those differences are. We examined the extent to which certification in family medicine is associated with differences in the practice patterns of primary care physicians as reflected in their billing patterns. Billing data for 1986 were obtained from the Ontario Health Insurance Plan for 269 certified physicians and 375 noncertified physicians who had graduated from Ontario medical schools between 1972 and 1983 and who practised as general practitioners or family physicians in Ontario. As a group, certificants provided fewer services per patient and billed less per patient seen per month. They were more likely than noncertificants to include counselling, psychotherapy, prenatal and obstetric care, nonemergency hospital visits, surgical services and visits to chronic care facilities in their service mix and to bill in more service categories. Certificants billed more for prenatal and obstetric care, intermediate assessments, chronic care and nonemergency hospital visits and less for psychotherapy and after-hours services than noncertificants. Many of the differences detected suggest a practice style consistent with the objectives for training and certification in family medicine. However...

To further understand the source of the epidemic of salmonellosis in some species of birds using bird feeders in southern Ontario in the winter of 1997-1998, 124 bird feeder stations were examined for their state of hygiene and for Salmonella on 5 occasions during the winter of 1999 in a city of 100,000 people in southwestern Ontario. No Salmonella were isolated from feed contaminated with feces recovered from the feeders. Squirrel-proof feeders were significantly less contaminated with feces than were other feeder types (hopper, platform, silo), which did not differ significantly in their hygiene scores. Contamination of squirrel-proof feeders increased significantly through the course of the study, but other feeder types showed no significant change. Hygiene was poorer if feeders were maintained equally by both male and female household members, particularly as they grew older, but no age or gender effect was observed if only one person was largely responsible for maintaining the feeders. We concluded that winter bird feeder stations in a southern Ontario city were not contaminated with Salmonella but that bird feeder stations could be designed better to reduce fecal contamination of feed.

OBJECTIVE: To examine the effect of the introduction of laparoscopic cholecystectomy (LC) on patterns of practice (number of cholecystectomy procedures, case-mix and length of hospital stay) and patient outcomes in Ontario. DESIGN: Cross-sectional population-based time trends using hospital discharge data. SETTING: All acute care hospitals in Ontario where cholecystectomy was provided. PATIENTS: All 119,821 Ontario residents who underwent cholecystectomy between 1989-90 and 1993-94. After exclusions (initial bile duct exploration, cancer, incidental cholecystectomy, or missing codes for age, sex or residence) 108,442 patients remained. OUTCOME MEASURES: Number of cholecystectomy procedures, proportion of patients with acute or chronic gallstone disease, length of hospital stay, and rates of death, readmission, and bile duct injury and other in-hospital complications after cholecystectomy by year. RESULTS: The number of cholecystectomy procedures increased by 30.4% between 1989-90 and 1993-94. The number of patients with chronic gallstone disease increased by 33.6%, and the number who underwent elective surgery increased by 48.3%. The proportion of procedures performed as LC increased from 1.0% in 1990-91 to 85.6% in 1993-94. Patients who received LC tended to be younger female patients with chronic gallstone disease with no coexisting conditions undergoing elective operations. The mean length of stay...