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Biomedical subjects

I R Dohoo

Publications and source records attributed to I R Dohoo.

At least 55 records · Page 3Linked to original sources
PubMed1993

Evaluation of rapid gross visual appraisal of swine lungs at slaughter as a diagnostic screen for enzootic pneumonia.

A rapid gross visual appraisal of enzootic pneumonia lesions was made of 87 lungs at a local abattoir and the lungs were then set aside and examined in more detail. A sample of pulmonary tissue was taken from each lung and submitted for bacterial and histological examination. The principal investigator who had performed the gross and detailed lung scores was then used to assess the agreement of two inspectors who were scoring lung lesions in the abattoir. The Pearson's correlation coefficient between grossly scored lungs and scores derived from a detailed examination was 0.94. Using histological examination as the gold standard, rapid gross examination had a sensitivity of 76% and a specificity of 71%. Using bacterial recovery as a gold standard yielded a sensitivity of 77% and a specificity of 51%. The sensitivity and specificity of inspectors 1 and 2 compared to the principal investigator were: sensitivity = 97.5% and specificity = 97.4% for inspector 1, and 97% and 98% for inspector 2. The kappa values for both of the inspectors compared to the principal investigator were 0.95 suggesting that designated lay inspectors consistently agreed with the principal investigator.

Abattoirs↗
PubMed1992

A cohort study of coagulase negative staphylococcal mastitis in selected dairy herds in Prince Edward Island.

The epidemiology and importance of coagulase negative staphylococcal (CNS) mastitis in Prince Edward Island had not been documented. To investigate this, a cohort of 84 cows at seven farms were quarter sampled eight times over a lactation, commencing with samples taken prior to drying off in the previous lactation. Thirteen species of CNS were isolated. The quarter prevalence of CNS mastitis varied from 4.8% to 6.4% in the first five months of lactation and increased to 14.2 to 16.6% in the last four months of lactation. The geometric mean somatic cell counts (SCC) for quarters infected with CNS and uninfected quarters were 90 x 10(3) and 64 x 10(3) respectively (difference significant at p > 0.005). The two month new infection risk of CNS was 9.0% while the two month elimination risk was 74.4%. Infection with CNS did not alter the risk of subsequent infection with Staphylococcus aureus. The results from this project support the classification of CNS as a minor pathogen in mastitis control programs.

Animals↗
PubMed1991

Epidemiological associations between Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae antibody titers and lung lesions in Prince Edward Island swine herds.

A survey of anteroventral (AV) lung lesions, pleuritis and serology for Mycoplasma hyopneumoniae (MH) and Actinobacillus pleuropneumoniae (AP) was conducted on a minimum of 25 slaughter hogs from each of 18 randomly sampled Prince Edward Island farms (producing over 1,000 market hogs per year). The data were analyzed to evaluate the potential role of these two agents as risk factors for the two conditions, using crude and multivariable techniques, as well as individual and herd data. Anteroventral lung lesions were present in 50.5% of hogs at slaughter, and pleuritis was present in 15.4% of the hogs. Least squares multivariable regression was used to analyze the simultaneous ability of MH, AP and MH/AP interaction to predict the herd prevalence of AV lung lesions. Only MH was associated with AV lung lesions (p = 0.035). In spite of this statistical significance, MH accounted for only 53% of the herd variation in prevalence of lung lesions (R2 = 0.529). As well, some herds maintained very low levels of lung lesions despite moderate (up to 30%) prevalence of MH. Discrepancies between the analytic techniques suggested herd-level factors play an important role in the development of lung lesions. Pleuritis did not appear to be associated with either of the agents studied (p = 0.478).

Actinobacillus Infections↗
PubMed1991

A serological survey of leptospirosis in Prince Edward Island swine herds and its association with infertility.

A serological survey was undertaken to determine the prevalence of leptospirosis, and to investigate associations between leptospiral antibody titers, and herd measures of reproduction. Production records and leptospirosis serology were analyzed for 25 slaughter hogs from each of eleven randomly sampled farrow-finish operations on Prince Edward Island. The effect of selected leptospiral serovars on nonproductive sow days per parity (NPSD/P) and the proportion of pigs born dead was evaluated. The four most common serovars to which antibodies were detected were Leptospira icterohaemorrhagiae, L. bratislava, L. autumnalis and L. pomona, with respective prevalences of 57.1%, 35.1%, 3.4% and 1.5% of PEI slaughter hogs. None of these serovars was associated with increased frequency of stillbirths (p greater than 0.05). However, farms with a higher prevalence of L. bratislava antibody titers tended to have more infertility, as measured by NPSD/P (r = 0.738, p = 0.036 with Bonferroni adjustment). Also, farms with L. pomona antibody titers had higher NPSD/P than farms without L. pomona antibody titers (p = 0.0008 with Bonferroni adjustment). There was no association between NPSD/P and antibodies to either L. autumnalis or L. icterohaemorrhagiae (p greater than 0.05).

Animals↗
PubMed1991

A survey of biological productivity of Prince Edward Island swine herds.

Sow and feeder pig productivity were measured on a random sample of 32 Prince Edward Island swine farms (each producing over 1000 market hogs per year). Productivity parameters could be arranged in a hierarchy, with the highest level on farrow-finish operations represented by pigs weaned per sow per year. The 17 farrow-finish farms in this study averaged 19.6 (+/- 2.2 SD) pigs weaned per sow per year. Large variation between farms was observed with a range from 16.2 to 24.9 pigs weaned per sow per year. The major opportunities for improving productivity, as compared to reviewed targets, lie in reducing the average weaning age, reducing preweaning mortality, and reducing non-productive sow days per parity. The 14 feeder operations were characterized by 0.58 +/- 0.07 kg average daily gain. Average daily gain was negatively correlated with mortality (r = -0.662, p = 0.010), suggesting that herds that achieved a high rate of gain also had lower mortality.

Agriculture↗
PubMed1991

Epidemiological approach to the association between economic efficiency and productivity on swine farms in Prince Edward Island.

Regression analysis was used to determine the ability of a number of biological parameters to predict economic efficiency. Detailed feed, financial, and production records were maintained by a random sample of eighteen Prince Edward Island (PEI) swine producers (each producing over 1000 market hogs per year). Relative economic efficiency of the operations was measured using return to management and labor (RML). Of the routinely monitored biological parameters, RML on PEI farrow-finish operations was best predicted (R2 = 64.8%) by: marketed per square meter per year (p = 0.008) and marketed per sow per year (p = 0.096). Regression of fixed costs revealed that biological parameters had limited ability to predict fixed costs per hog on farrow-finish operations (R2 = 30.7%). The only parameter contributing to the prediction of the fixed cost component of RML was feeder hog density (p = 0.077). The variable cost component of RML on farrow-finish operations was predicted (R2 = 94.3%) by feed cost per kg gain (p = 0.000), and marketed per sow per year (p = 0.044). The routinely recorded biological parameters on feeder farms had only limited ability to predict RML in this study (R2 = 43.7%). The only parameter of any importance was marketed per square meter per year (p = 0.106). Prediction of the fixed cost component of RML on feeder farms (R2 = 67.4%) was best realized by measuring feeder hog density (p = 0.045). The variable cost component of RML on feeder farms was reasonably well predicted (R2 = 74.7%) by feed cost per kg gain (p = 0.012). Although this parameter is difficult to monitor from records currently maintained on most farms, it points out the need to monitor feed consumption on swine farms.

Agriculture↗
PubMed1990

Ascariasis, respiratory diseases and production indices in selected Prince Edward Island swine herds.

The levels of production, ascarid burden and respiratory disease were measured on 15 purposively selected swine herds, and the relationships between the various measures of ascarid burden were examined. On each farm 30 randomly selected pigs were weighed and rectal fecal samples were collected at approximately 11, 15, 19 and 22 weeks of age, and at slaughter. Fecal ascarid-egg counts and duration of infection were combined to calculate a composite measure of ascarid burden called "lifetime burden". At the abattoir the carcass weight and levels of anteroventral pneumonia, atrophic rhinitis, and liver lesions were recorded for each hog. The number of ascarids in the small intestines were counted. Study hogs were marketed at an average of 189 +/- 22 days. The average dressed carcass weight was 77.0 +/- 5.9 kg and the mean average daily gain was 0.519 +/- 0.071 kg/day. The percent of hogs with ascariasis varied widely among farms, no matter what measure of ascariasis was used; the percent with intestinal ascarids at slaughter ranged from 0% to 96%, the percent that shed ascarid eggs during their lifetime ranged from 0% to 100%, and the range for hogs with liver lesions ranged from 27% to 100%. Of the hogs slaughtered, 82% had milk spot lesions, 32% shed ascarid eggs during their lifetime and 35% had intestinal ascarids. The latter had an average of 12 intestinal ascarids. Anteroventral pneumonia occurred in 55% of the slaughtered hogs and 9% had atrophic rhinitis scores of five. The percent of hogs per farm with pneumonia ranged from 17% to 96%. The percent of hogs per farm with atrophic rhinitis scores of five ranged from 0% to 57%.

Analysis of Variance↗
PubMed1990

A critical assessment of abattoir surveillance as a screening test for swine ascariasis.

The following data on ascarid burden were collected on an individual basis for 380 hogs marketed in the fall of 1987: a series of fecal ascarid-egg counts during the growing period; the level of milk spot lesions on the liver at slaughter; and the number of ascarids in the small intestines at slaughter. The presence of milk spots had a high sensitivity, very low specificity, and a high negative predictive value as a screening test for ascariasis in individual hogs. Results were consistent whether ascariasis was measured as the presence of intestinal ascarids at slaughter (sensitivity 91%, specificity 22%, negative predictive value 82%), or by a positive fecal egg count during the hog's lifetime (sensitivity 96%, specificity 24%, negative predictive value 93%). The presence of milk spots does not necessarily indicate that an ascarid infection has been established in the small intestine. The absence of milk spots, however, is a reliable indicator of the absence of an established ascarid infection, provided that the prevalence of ascariasis is equal to or less than that observed in this study. The severity of the ascarid infection in an individual hog could not be ascertained by the number of milk spot lesions on the liver.

Abattoirs↗
PubMed1990

Effect of ascariasis and respiratory diseases on growth rates in swine.

Growth rates, measures of ascarid burden, and the levels of anteroventral pneumonia and atrophic rhinitis at slaughter were determined for 352 hogs born between March 8 and March 28, 1987 on 15 farms located in Prince Edward Island. Regression analyses were used to determine associations between average daily gain (ADG) and independent variables controlling for sex, farm, and litters nested within farm. The regression model accounted for 75.4% of the variation in ADG. The number of intestinal ascarids at slaughter did not affect ADG. However, the "life-time burden" (a composite measure based on fecal egg counts and duration of infection) was associated with ADG (p less than 0.05) in a quadratic manner. Although heavy ascarid burdens decreased the growth rate of swine, the magnitude of the effect was minimal. The maximum improvement one could expect from reducing the ascarid burden on heavily infected farms would be less than 1%. Severe atrophic rhinitis and the presence of anteroventral pneumonia each had a detrimental effect on ADG (p less than 0.001). The corresponding reductions in mean ADG were 7.7% and 2.8% respectively. There was significant interaction between the effects of atrophic rhinitis and anteroventral pneumonia on ADG (p less than 0.05). Hogs with both anteroventral pneumonia and severe atrophic rhinitis had a 17.6% lower ADG than hogs with neither disease. There is much greater potential for improvement in ADG through control of respiratory diseases than through control of ascariasis.

Animals↗
PubMed1988

Disease outbreak investigation. Three case studies.

Three case studies of the investigation of outbreaks of disease or deviations from target performance are presented. The first is a study of a mastitis problem in a dairy herd, made evident by increased somatic cell counts. The pattern of the production problem is carefully analyzed and conclusions are reached that indicate an infection with environmental contaminant organisms, thus permitting control measures to be introduced. The second case study is an investigation of an outbreak of neonatal mortality in sheep. Analysis suggests a multiple etiology, with infection by border disease virus predominating. The third case study describes the investigation of foothill abortion in a beef herd in California and demonstrates the use of epidemiologic techniques to try to identify the source of infection in a subgroup of the study population, thus allowing specific control measures to be introduced.

Abortion, Veterinary↗
PubMed1987

Factors associated with productivity in Canadian sheep flocks.

A mail survey of Canadian sheep flocks registered on the Record of Performance program was conducted, and the association of management practices and diseases with productivity was studied using multiple regression techniques. The relationships between management practices and diseases of lambs which were associated with production were also investigated using discriminant analysis. Flocks in the maritimes had a lower average flock productivity than those in Ontario-Quebec and the western provinces. In purebred flocks, the average adjusted weight at 100 days of age was higher than in other types of flocks, and the prevalence of scours was lower. At the herd level, the rates of pregnancy toxemia and vaginal prolapse were associated with heavier lambs, while the average daily weight gain between 50 and 100 days of age was lower in herds affected by scours and starvation. Using pasture and bush as winter housing was also detrimental to lamb productivity. No management practices discriminated between case and control flocks for scours and starvation in lambs. It was concluded that the reasons for the geographic differences should be investigated as should the management differences between purebred and other producers. Prevention of scours and starvation in lambs should be given priority in order to increase productivity.

Animal Husbandry↗
PubMed1986

A comparison of five serological tests for bovine brucellosis.

Five serological assays: the buffered plate antigen test, the standard tube agglutination test, the complement fixation test, the hemolysis-in-gel test and the indirect enzyme immunoassay were diagnostically evaluated. Test data consisted of results from 1208 cattle in brucellosis-free herds, 1578 cattle in reactor herds of unknown infection status and 174 cattle from which Brucella abortus had been cultured. The complement fixation test had the highest specificity in both nonvaccinated and vaccinated cattle. The indirect enzyme immunoassay, if interpreted at a high threshold, also exhibited a high specificity in both groups of cattle. The hemolysis-in-gel test had a very high specificity when used in nonvaccinated cattle but quite a low specificity among vaccinates. With the exception of the complement fixation test, all tests had high sensitivities if interpreted at the minimum threshold. However, the sensitivities of the standard tube agglutination test and indirect enzyme immunoassay, when interpreted at high thresholds were comparable to that of the complement fixation test. A kappa statistic was used to measure the agreement between the various tests. In general the kappa statistics were quite low, suggesting that the various tests may detect different antibody isotypes. There was however, good agreement between the buffered plate antigen test and standard tube agglutination test (the two agglutination tests evaluated) and between the complement fixation test and the indirect enzyme immunoassay when interpreted at a high threshold. With the exception of the buffered plate antigen test, all tests were evaluated as confirmatory tests by estimating their specificity and sensitivity on screening-test positive samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination Tests↗
PubMed1985

A survey of sheep diseases in Canada.

A mail survey of disease occurrence in Canadian sheep flocks was conducted. The survey, which covered the period from September 1982 to August 1983, utilized flocks on the Record of Performance (ROP) sheep program and relatively complete data were available from 116 flocks. Data about lambing rates, incidence of a variety of lamb and ewe diseases and reasons for culling were obtained. At the same time a retrospective evaluation of records of diagnoses of sheep diseases recorded at diagnostic laboratories across the country was performed. Data from the years 1978 to 1982 were obtained and summarized. A lambing percentage of 153% (1.53 lambs live born per ewe lambing) was observed and an additional 0.05 lambs were stillborn. The major identified causes of mortality amongst lambs were starvation, pneumonia, scours and accidents. Pasteurella spp. were the etiological agents most commonly associated with pneumonia in lambs and Escherichia coli had the same predominant position with regards to nonparasitic scours. A large discrepancy existed between the proportional mortality rates for internal parasites and coccidiosis as determined from the farm survey data compared to diagnostic laboratory data. This suggests that clinical parasitism may not be adequately recognized at the farm level. Abortions in ewes occurred in approximately half the flocks, but generally at a low level and no severe abortion storms occurred. Pneumonia was the most commonly identified cause of mortality in ewes and although Pasteurella spp. appear to be the most important etiological agents, regional differences were apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Veterinary↗
PubMed1985

Interrelationships between postpartum events, hormonal therapy, reproductive abnormalities and reproductive performance in dairy cows: a path analysis.

Path analysis was used to determine the interrelationships between postpartum administration of gonadotrophin releasing hormone and cloprostenol and the occurrence of reproductive disease and reproductive performance in dairy cows. The data analysed were those collected on 226 Holstein-Friesian cows calving in a commercial dairy herd during a 17 month period (May 1, 1981 to October 1, 1982). Cows administered gonadotrophin releasing hormone at day 15 postpartum experienced an improved rate of uterine involution as determined by rectal palpation nine days later. Although this improved rate of uterine involution reduced the risk of pyometritis, it actually directly delayed conception. Also, gonadotrophin releasing hormone therapy directly resulted in an increased incidence of pyometritis which in turn resulted in an increase incidence of cystic ovarian disease and anestrus. The occurrence of these abnormalities resulted in increased intervals from calving to first observed estrus, first service and conception. In addition to this effect, the administration of gonadotrophin releasing hormone was also associated with increased plasma progesterone concentrations at days 24 and 28 postpartum which delayed conception. Cloprostenol therapy at day 24 postpartum resulted in a decreased plasma progesterone concentration at day 28 postpartum which was directly and indirectly associated with a decrease in the calving to conception interval. The indirect effects were mediated by a reduction in days to first estrus. Cloprostenol therapy also directly resulted in a decreased calving to first observed estrus interval for reasons not attributable to the level of progesterone at day 28.

Anestrus↗
PubMed1985

Interrelationships between ambient temperature, age at calving, postpartum reproductive events and reproductive performance in dairy cows: a path analysis.

Path analysis was used to determine the interrelationships between ambient temperature, age at calving, postpartum reproductive events and reproductive performance in dairy cows. The data used in the analysis were collected on 226 Holstein-Friesian cows calving in a commercial dairy herd during a 17 month period (May 1, 1981 to October 1, 1982). The data were obtained from a double blind study evaluating the effects of gonadotrophin releasing hormone and cloprostenol in postpartum cows. Rectal palpation to assess uterine involution and ovarian activity was performed on each cow on days 15, 24 and 28 postpartum. At the same time, blood samples were collected for subsequent progesterone assay. Data were recorded on the occurrence of reproductive diseases and events from the time of parturition until the diagnosis of pregnancy or until the cow left the herd in the case of culled cows. There was an increase in the incidence of retained placenta, in the percentage of cows with abnormal vaginal discharge in the early postpartum period as well as a delay in uterine involution during the winter months. In addition, cows calving during the winter had prolonged intervals to first estrus, first service and conception compared to cows calving during the summer. (Cows calving during the warmest months, on average, were seen in estrus 24 days sooner, received first service 42 days sooner and conceived 27 days sooner than cows calving during the coldest months of the year).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗