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I R Dohoo

Publications and source records attributed to I R Dohoo.

At least 37 records · Page 2Linked to original sources
PubMed2000

Estimates of within-herd incidence rates of Mycobacterium bovis in Canadian cattle and cervids between 1985 and 1994.

We analysed the individual-animal data from six of the nine outbreaks of tuberculosis in Canadian cattle and cervids from 1985 to 1994. A "positive/reactor" animal was one which had either a positive culture or a positive or suspicious reaction on a mid-cervical, comparative cervical, or gross or histopathological test for tuberculosis. Individual-animal data were collected only for herds which had one or more positive/reactor animals. Data were collected from the outbreak records in the Regional or District offices of Agriculture and Agri-food Canada's Animal and Plant Health Directorate. The within-herd spread of Mycobacterium bovis was studied by determining the most-likely date at which the herd was first exposed to M. bovis and the number of reactions which had developed by the time the herd was investigated. The animal-time units at risk in the herd were probably overestimated, resulting in conservative estimates of the within-herd incidence rates. Negative-binomial regression was used to investigate factors which might have influenced the within-herd spread of tuberculosis. Increasing age appeared to be a risk factor for being a positive/reactor animal. When compared to animals 0-12 months old, animals 13-24 months old had an incidence rate ratio (IRR) of 7.6, while animals >24 months old had an IRR of 10.4 (p=0.009). Actual and predicted incidence rates for tuberculosis in mature (>24 months old) animals were calculated. Actual and predicted incidence rates were similar for cervids, within an outbreak. There was more variability between actual and predicted rates in the dairy and beef animals. In the one outbreak (Ontario) where there were positive/reactor cervid, dairy and beef herds, the actual incidence rate for cervids (IR=9.3 cases per 100 animal-years) was almost twice that of dairy cattle (IR=5.0) and three times that of beef cattle (IR=3.1).

Animals↗
PubMed1999

Relationships between bulk-tank antibodies to Ostertagia ostertagi and herd-management practices and measures of milk production in Nova Scotia dairy herds.

Monthly bulk-tank milk samples were obtained from 415 Nova Scotia dairy herds in each of the months of July-September 1998 and tested using an indirect microtitre ELISA against a crude saline-extract, whole-worm Ostertagia ostertagi antigen. ELISA results (optical densities (ODs)) were consistent across months (r=0.85) but there was considerable variation among herds. A questionnaire was sent by mail to all producers; information on management factors that would potentially influence parasite burdens in the herds was obtained from 239 farms. Data on annual milk production, summer milk production (July-September) and seasonal decline in milk production were obtained from the Animal Productivity and Health Information Network (APHIN) database. Associations between management practices and ODs, and between ODs and milk-production parameters were studied. Some management practices known to be associated with parasite burdens had expected directions of association with the ODs, giving supporting evidence that the ELISA is a reasonable measure of parasite burden. Most notably, ODs were increased with greater exposure of heifers or milking cows to pasture. ODs were not associated with either annual milk production or seasonal decline in milk production. However, there was a substantial relationship between the herd OD value and the level of milk production during the summer. An increase in the OD from 0.58 to 0.83 (the interquartile range of ODs) was associated with a reduction in production of 1.25kg/cow/day.

Animal Husbandry↗
PubMed1999

Results of bone scintigraphy in racing standardbred horses: 64 cases (1992-1994).

OBJECTIVE: To document anatomic patterns of scintigraphic uptake and related orthopedic disease associated with racing activity in Standardbred horses. DESIGN: Retrospective study. ANIMALS: 64 Standardbred horses evaluated for lameness. PROCEDURE: Medical records at the time of discharge were reviewed, and information regarding signalment; history; results of lameness examination, scintigraphy, and radiography; diagnosis; and treatment were obtained. RESULTS: 274 areas of increased radiopharmaceutical uptake were identified. Scintigrams of 218 limbs (106 forelimbs, 112 hind limbs) were available for review. Seventy-three (33%) scintigrams had increased radiopharmaceutical uptake associated with the proximal sesamoids, 46 of 106 (43%) fore-limb scintigrams had increased uptake associated with the third carpal bone, and 33 of 112 (33%) hind limb scintigrams had radiopharmaceutical uptake associated with the small tarsal bones. Forty-three of 218 (20%) scintigrams had increased uptake associated with the distal aspect of the third metacarpal and metatarsal bones. Abnormal scintigraphic uptake was bilateral in 91 of 139 (65%) forelimb locations and 99 of 134 (74%) hind limb locations with increased radiopharmaceutical uptake. The primary scintigraphically identified classifications of disease were exercise-induced bone remodeling, synovitis or arthritis, and soft-tissue avulsion from bone (66, 17, and 6% of areas with increased radiopharmaceutical uptake, respectively). Of 274 areas with increased radiopharmaceutical uptake, 244 (89%) were believed to be clinically important. CONCLUSIONS AND CLINICAL RELEVANCE: Distinctive patterns of increased radiopharmaceutical uptake were identified that suggested Standardbred horses used for racing may have a predilection to develop orthopedic disease at specific sites that are distinct from those in Thoroughbreds used for racing and horses used for jumping activities.

Animals↗
PubMed1999

Risk factors for the between-herd spread of Mycobacterium bovis in Canadian cattle and cervids between 1985 and 1994.

Microorganisms of the genus Mycobacterium cause tuberculosis in many animal species including humans. Generally, Mycobacterium bovis (M. bovis) infects cattle and cervids, but it has the potential to infect virtually all species of mammals. This study examined and analysed the data from the nine outbreaks of tuberculosis in Canadian cattle and cervids from 1985 to 1994. For the purposes of this study, a positive herd was one with at least one culture-positive animal. A reactor herd had at least one animal which was positive or suspicious on a mid-cervical, comparative cervical, or gross or histopathologic test for tuberculosis. Herd classification was either reactor/positive or negative. Data for the study were collected from the outbreak records in the Regional or District offices of Agriculture and Agri-Food Canada. Logistic regression was used to study spread of tuberculosis between herds. Two risk factors were identified: increasing herd size; and, the reason why a herd was investigated as part of the outbreak. This latter factor was interpreted as a surrogate measure for the nature of contact between the study herd and other potentially infected herds in the outbreak. Increasing herd size was associated with an increased risk of being positive for tuberculosis with herds of 16-35, 36-80, and >80 animals having odds ratios of 2.9, 5.8, and 9.3, respectively, when compared to a herd size of <16 animals (p < 0.001). When compared to perimeter testing (i.e. testing herds within a specified radius of an infected herd), all other reasons for investigation had higher odds ratios (p < 0.001). These odds ratios were 57.8 for traceout herds (i.e. herds which had purchased animal(s) from a reactor/positive herd), 31.8 for herds with pasture or fence-line contact with a reactor/positive herd, and 14.9 for traceback herds (i.e. herds which had been a source of animals for reactor/positive herd(s)).

Animals↗
PubMed1998

Results of bone scintigraphy in horses used for show jumping, hunting, or eventing: 141 cases (1988-1994).

OBJECTIVE: To determine anatomic patterns and clinical importance of increased radiopharmaceutical uptake in bones of horses used for show jumping, hunting, and eventing. DESIGN: Retrospective study. ANIMALS: 141 horses evaluated because of lameness. PROCEDURE: Medical records were reviewed, and information on results of physical examination, radiography, and scintigraphy were obtained. Scintigrams were evaluated to identify areas of increased radio-pharmaceutical uptake. RESULTS: 834 areas of increased radiopharmaceutical uptake were identified. Scintigraphy of the vertebral column was performed in 78 horses, and 50 had areas of increased radiopharmaceutical uptake involving the spinous processes. Scintigraphy of the proximal phalanx of the forelimb was performed in 88 horses. Similarly, scintigraphy of the proximal phalanx of the hind limb was performed in 99 horses, and scintigrams of 374 proximal phalanges were available for review. One hundred fifty-five scintigrams had areas of increased radiopharmaceutical uptake. Scintigraphy of the tarsal joint was performed in 99 horses, and scintigrams of 198 joints were available for review. Eighty-five had areas of increased radiopharmaceutical uptake. Overall, 214 of 834 areas of increased radiopharmaceutical uptake were definitively associated with lameness. CLINICAL IMPLICATIONS: Results of this study suggest that jumping creates unique stresses on the bones of horses. The distinctive patterns of increased radiopharmaceutical uptake identified in this study suggest that horses used for jumping may have a predilection to develop orthopedic disease at specific sites distinct from those in racehorses.

Animals↗
PubMed1998

Associations between passive immunity and morbidity and mortality in dairy heifers in Florida, USA.

A prospective cohort study was undertaken to determine calf-level factors that affected calf health status between birth and 6 months of age. A convenience sample of approximately 3300 female Holstein calves born in 1991 on two large Florida dairy farms was used for the study. Data collected on each calf at birth included farm of origin, weight, height at the pelvis, birth date, and serum total protein (a measure of colostral immunoglobulin absorption). Birth season was dichotomized into summer and winter using meteorological data collected by University of Florida Agricultural Research Stations. Health data including date of initial treatment and number of treatments were collected for the diseases diarrhea, omphalitis, septicemia and pneumonia. All calves were followed for 6 months. Cumulative incidences of mortality and occurrence of diarrhea, omphalitis, septicemia and pneumonia were 0.12, 0.35, 0.11, 0.24 and 0.21, respectively. Serum total protein (TP) was a significant risk factor for mortality. The association of TP and mortality was quadratic and showed a dramatic decrease in mortality as TP increased from 4.0 to 5.0 g/dl, a small improvement from 5.0 to 6.0 g/dl and virtually no improvement in mortality rates as TP increased over 6.0 g/dl. The hazard mortality ratio was constant from birth to six months, indicating that the increased risk of mortality associated with low levels of TP was evident through six months of age. No interactions between TP, farm, season, or birth weight were found in these analyses. Serum total protein concentration was a significant risk factor for the occurrences, age of onset and severity of septicemia and pneumonia. The association between TP and septicemia was linear and an interaction with birth season was found. The association between TP and pneumonia was quadratic, and in contrast to the TP-and-septicemia relationship, the morbidity hazard ratio for pneumonia was not constant over the time measured; that is, colostral immunity protected the calf from developing pneumonia early in life, but this effect disappeared as the calf got older. Total protein was not a significant risk factor for diarrhea or omphalitis.

Animals↗
PubMed1998

Calf and disease factors affecting growth in female Holstein calves in Florida, USA.

A prospective cohort study was undertaken to determine calf-level factors that affect performance (growth) between birth and 14 months of age in a convenience sample of approximately 3300 female Holstein calves born in 1991 on two large Florida dairy farms. Data collected on each calf at birth included farm of origin, birth date, weight, height at the pelvis, and serum total protein (a measure of colostral immunoglobulin absorption). Birth season was dichotomized into summer and winter using meteorological data collected by University of Florida Agricultural Research Stations. Data collected at approximately 6 and 14 months of age included age, weight, height at the pelvis, and height at the withers. Growth in weight and stature (height) was calculated for each growth period; growth period 1 (GP1) = birth to 6 months, and growth period 2 (GP2) = 6 to 14 months. Health data collected included data of initial treatment and number of treatments for the diseases diarrhea, omphalitis, septicemia, pneumonia and keratoconjunctivitis. After adjusting for disease occurrence, passive transfer of colostral immunoglobulins had no significant effect on body weight gain or pelvic height growth. Season of birth and occurrence of diarrhea, septicemia and respiratory disease were significant variables decreasing heifer growth (height and weight) in GP1. These variables plus farm, birth weight and exact age when '6 month' data were collected explained 20% and 31% of the variation in body weight gain and pelvic height growth, respectively, in GP1. The number of days treated for pneumonia before 6 months of age significantly decreased average daily weight gain in GP2 (P < 0.025), but did not affect stature growth. Treatment for pneumonia after 6 months of age did not significantly affect weight or height gain after age 6 months. Neither omphalitis nor keratoconjunctivitis explained variability in growth in either of the growth periods.

Animals↗
PubMed1998

Attitudes and concerns of Canadian animal health technologists toward postoperative pain management in dogs and cats.

Three hundred and twenty-two Canadian animal health technologists (AHTs) were surveyed to determine their attitudes toward postoperative pain management in dogs and cats following 6 surgical procedures, their concerns regarding the use of opioid analgesics, and their role within veterinary practices with respect to postoperative pain control. Two hundred and sixty-four (82%) returned the questionnaire. Pain perception was defined as the average of pain rankings for dogs and cats (on a scale of 1 to 10) following abdominal surgery, or the value for dogs or cats if the AHT worked with only 1 of the 2 species. Maximum concern about the risks associated with the postoperative use of morphine or oxymorphone was defined as the highest rating assigned to any of the 6 risks evaluated in either dogs or cats. Animal health technologists reported significantly higher pain perception scores than did veterinarians who completed a similar survey 2 years previously. Higher pain perception scores were associated with decreased satisfaction with the adequacy of analgesic therapy in their practice, higher pain control goals, and attendance at continuing education within the previous 12 months. The majority of AHTs (55%) agreed that one or more risks associated with the use of morphine or oxymorphone outweighed the benefits. The 3 issues that were perceived to pose the greatest risk were respiratory depression, bradycardia, and sedation and excitement, for dogs and cats, respectively. Most AHTs (68%) considered their knowledge related to the recognition and control of pain to be adequate, compared with 24% of veterinarians who responded to a similar previous survey. As for veterinarians, experience gained while in practice was ranked as the most important source of knowledge, while the technical program attended was ranked as least important. Over 88% of the AHTs provided nursing care during the postoperative period, monitored animals for side effects of postoperative analgesic therapy, informed veterinarians when animals were in pain, recommended analgesic therapy when they believed it was warranted, reported that animals received analgesics when they believed it was warranted, administered analgesics under the instruction of a veterinarian, and believed they were part of a team working to provide adequate postoperative pain control.

Animal Technicians↗
PubMed1997

An overview of techniques for dealing with large numbers of independent variables in epidemiologic studies.

Many studies of health and production problems in livestock involve the simultaneous evaluation of large numbers of risk factors. These analyses may be complicated by a number of problems including: multicollinearity (which arises because many of the risk factors may be related (correlated) to each other), confounding, interaction, problems related to sample size (and hence the power of the study), and the fact that many associations are evaluated from a single dataset. This paper focuses primarily on the problem of multicollinearity and discusses a number of techniques for dealing with this problem. However, some of the techniques discussed may also help to deal with the other problems identified above. The first general approach to dealing with multicollinearity involves reducing the number of independent variables prior to investigating associations with the disease. Techniques to accomplish this include: (1) excluding variables after screening for associations among independent variables; (2) creating indices or scores which combine data from multiple factors into a single variable; (3) creating a smaller set of independent variables through the use of multivariable techniques such as principal components analysis or factor analysis. The second general approach is to use appropriate steps and statistical techniques to investigate associations between the independent variables and the dependent variable. A preliminary screening of these associations may be performed using simple statistical tests. Subsequently, multivariable techniques such as linear or logistic regression or correspondence analysis can be used to identify important associations. The strengths and limitations of these techniques are discussed and the techniques are demonstrated using a dataset from a recent study of risk factors for pneumonia in swine. Emphasis is placed on comparing correspondence analysis with other techniques as it has been used less in the epidemiology literature.

Animal Diseases↗
PubMed1997

Herd prevalence and incidence of Streptococcus agalactiae in the dairy industry of Prince Edward Island.

Herd prevalence and incidence of mastitis caused by Streptococcus agalactiae was determined for dairy cattle on Prince Edward Island during December 1992 and June 1994. For each census, bulk tank milk samples from all dairy herds (n = 452) in the province were tested on two occasions, and the results were interpreted in parallel. The combined sensitivity of the testing protocol was estimated to be 91%. The confirmatory latex agglutination test had previously reported specificities approaching 100%. Therefore, the estimated specificity of the testing protocol was assumed to be 100%. The apparent prevalence of S. agalactiae in December 1992 and in June 1994 was 17.7 and 13.1%, respectively. Based on the characteristics of the test, the estimated true prevalence was 18.9% in December 1992 and 14.4% in June 1994. Infection with S. agalactiae was associated with elevated bulk tank somatic cell count (SCC) and elevated standard plate counts. Economic losses associated with S. agalactiae were attributed to production losses (associated with bulk tank SCC), milk quality penalties (associated with bulk tank SCC and standard plate count), and decreases in milk quality (associated with bulk tank SCC). For herds that had been negative for S. agalactiae in December 1992, evaluation in June 1994 yielded an incidence of new infections of 3.51 per 100 herds per year.

Animals↗
PubMed1997

A benefit to cost analysis of the effect of premilking teat hygiene on somatic cell count and intramammary infections in a commercial dairy herd.

A field trial was conducted to determine the effect of premilking teat disinfection (predipping) on several measures of mastitis in a commercial dairy farm where the predominant organisms isolated from intramammary infections were coagulase negative Staphylococcus spp. Cows were randomly assigned to a treated (predipped with 0.5% iodine germicide plus "good udder preparation") or a control group ("good udder preparation" alone). Sterile composite milk samples were collected at the initiation of the trial and on an approximately bimonthly basis throughout the duration of the trial. There was no difference in the prevalence of isolation of coagulase-negative Staphylococcus spp. from composite milk samples obtained during the 6 herd cultures. The incidence rate for clinical mastitis in the control group was 1.38 cases per 1000 cow days. The incidence rate for clinical mastitis in the treatment group was 1.06 cases per 1000 cow days. The ratio of these 2 was 1.3, suggesting a higher rate in the control group, but the ratio was not statistically significant (P = 0.34). Logistic regression analysis indicated that the effect of treatment group was not significant, although the coefficient suggested that predipping reduced the risk of clinical mastitis. The benefit to cost ratio of 0.37 indicated that the benefit of reduced incidence of clinical cases of mastitis would not have justified the added expense required to predip the herd.

Animals↗
PubMed1996

A field trial to evaluate a Mycoplasma hyopneumoniae vaccine: effects on lung lesions and growth rates in swine.

A killed Mycoplasma hyopneumoniae vaccine was evaluated in a single swine herd in which the farrowing barn and weaner rooms were on one Mycoplasma-free farm, while the growing and finishing barn was on a separate farm on which Mycoplasma was present. The study was carried out in a cohort of pigs born in a 12-week period. Pigs born in 6 of the 12 wk were vaccinated and the rest were left as controls. The vaccine was administered twice at approximately 3 and 6 wk of age. Carcass characteristics, lung lesions, and growth rates were recorded on 893, 390, and 220 pigs, respectively. The vaccine reduced the prevalence of pneumonic lesions in slaughter hogs from 69% to 36% (P < 0.001). It also appeared to reduce the prevalence of pleuritis from 20% to 13%, but the difference was only statistically significant at P = 0.07. The vaccine had no effects on carcass characteristics except that carcasses of vaccinated pigs were, on average, 1 kg heavier than those of nonvaccinated pigs, and a smaller percentage of vaccinated pigs were shipped "light" (carcass weight < 70 kg). Two methods were used to estimate the effect of the vaccine on growth rates (as measured by days to 80 kg carcass weight) resulting in estimates of 11 and 2 d reduction attributable to vaccination, respectively. The latter estimate was probably an underestimate for reasons discussed in the paper.

Animals↗
PubMed1996

Postoperative use of analgesics in dogs and cats by Canadian veterinarians.

Four hundred and seventeen Canadian veterinarians were surveyed to determine their postoperative use of analgesics in dogs and cats following 6 surgical procedures, and to determine their opinions toward pain perception and perceived complications associated with the postoperative use of potent opioid analgesics. Three hundred and seventeen (76%) returned the questionnaire. The percentage of animals receiving analgesics postoperatively ranged from 84% of dogs and 70% of cats following orthopedic surgery to 10% of dogs and 9% of cats following castration. In general, with the exception of orthopedic surgery, roughly equal percentages of dogs and cats received postoperative analgesics. Opioids were used almost exclusively to provide postoperative analgesia, with butorphanol the most commonly administered drug to both dogs and cats. Analgesics were usually administered either once or twice postoperatively. With regard to the administration of potent opioid agonists, the 3 major concerns included respiratory depression, bradycardia, and sedation in dogs, and excitement, respiratory depression, and bradycardia in cats. Seventy-seven percent of veterinarians considered their knowledge of issues related to the recognition and control of postoperative pain to be inadequate. Experience in practice is currently the major source of knowledge, with undergraduate veterinary school and research articles in journals ranked as the least important sources. Lectures or seminars delivered at the regional level were the preferred format for continuing education.

Analgesics↗
PubMed1996

Factors influencing the postoperative use of analgesics in dogs and cats by Canadian veterinarians.

Four hundred and seventeen Canadian veterinarians were surveyed to determine their postoperative use of analgesics in dogs and cats following 6 categories of surgeries, and their opinion toward pain perception and perceived complications associated with the postoperative use of potent opioid analgesics. Three hundred and seventeen (76%) returned the questionnaire. An analgesic user was defined as a veterinarian who administers analgesics to at least 50% of dogs or 50% of cats following abdominal surgery, excluding ovariohysterectomy. The veterinarians responding exhibited a bimodal distribution of analgesic use, with 49.5% being defined as analgesic users. These veterinarians tended to use analgesics in 100% of animals following abdominal surgery. Veterinarians defined as analgesic nonusers rarely used postoperative analgesics following any abdominal surgery. Pain perception was defined as the average of pain rankings (on a scale of 1 to 10) following abdominal surgery, or the value for dogs or cats if the veterinarian worked with only 1 of the 2 species. Maximum concern about the risks associated with the postoperative use of potent opioid agonists was defined as the highest ranking assigned to any of the 7 risks evaluated in either dogs or cats. Logistic regression analysis identified the pain perception score and the maximum concern regarding the use of potent opioid agonists in the postoperative period as the 2 factors that distinguished analgesic users from analgesic nonusers. This model correctly classified 68% of veterinarians as analgesic users or nonusers. Linear regression analysis identified gender and the presence of an animal health technologist in the practice as the 2 factors that influenced pain perception by veterinarians. Linear regression analysis identified working with an animal health technologist, graduation within the past 10 years, and attendance at continuing education as factors that influenced maximum concern about the postoperative use of opioid agonists.

Abdomen↗
PubMed1994

Epidemiology.

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Animals↗