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Biomedical subjects

S W Martin

Publications and source records attributed to S W Martin.

At least 109 records · Page 6Linked to original sources
PubMed1991

An epidemiological study of paratuberculosis in dairy cattle in Ontario: study design and prevalence estimates.

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.

Abattoirs↗
PubMed1991

An evaluation of selected screening tests for bovine paratuberculosis.

The objective of this study was to evaluate the performance of the lipoarabinomannan antigen enzyme-linked immunosorbent assay (LAM-ELISA), carbohydrate antigen complement fixation (CH-CFT), and protein D antigen agar gel immunodiffusion (D-AGID) tests for bovine paratuberculosis, relative to histopathology, and to culture and isolation of Mycobacterium paratuberculosis from tissues and feces. Samples for test evaluation were collected from four sources including blood and tissues from 400 cull cows at three abattoirs in Ontario, blood and feces from a paratuberculosis survey of cattle from 120 dairy farms in Ontario, a serum bank containing samples from cattle from Ontario and Québec, and a bank of sera from cattle from Pennsylvania and the northeastern United States. The data were analyzed using receiver operator characteristic curves, estimates of relative sensitivity and specificity, and kappa statistics of agreement between tests. The LAM-ELISA performed significantly better than both the CH-CFT and the D-AGID tests. The LAM-ELISA was better at predicting fecal shedding status than tissue infection. However, the LAM-ELISA also had limitations. When interpreted as positive or negative (+/-), at a critical optical density of 0.675, its sensitivity and specificity relative to bacteriology were 49% and 87% respectively. Although the serological tests examined in this study provided some information, they did not predict well the infection status of individual animals.

Animals↗
PubMed1990

The effect of prostaglandin administration to Holstein-Friesian cows at Day 26 postpartum on clinical findings, and histological and bacteriological results of endometrial biopsies at Day 40.

Ninety-two cows that calved between April and August 1984 in a commercial dairy herd were studied. The cows were randomly assigned to receive either cloprostenol (500 mug) or saline placebo on Day 26 postpartum. In addition, each cow was examined per rectum, had three endometrial biopsies taken and milk progesterone level determined. Double-blind techniques were used in administering treatments and in assessing response to treatment. The results of histological and bacteriological assessment of endometrial biopsies and clinical findings at Day 40 were compared between the cows that received prostaglandin at Day 26 and those that did not. Each Day 40 variable which was significantly associated with prostaglandin treatment at Day 26 was regressed against the treatment variable and progesterone level at Day 26 as well as a prostaglandin progesterone interaction term. Prostaglandin-treated cows had less vaginal discharge, smaller diameter uterine horns, less inflammation and fibrosis in the endometrium, and were less likely to have Actinomyces pyogenes isolated from a biopsy at Day 40 than untreated cows. These effects were independent of progesterone level at the time of treatment.

Journal Article↗
PubMed1990

A group level analysis of the associations between antibodies to seven putative pathogens and respiratory disease and weight gain in Ontario feedlot calves.

The associations, at the group level, between serological titer to Pasteurella haemolytica surface antigens (Ph), Pasteurella haemolytica cytotoxin (Ph-cytox), infectious bovine rhinotracheitis virus (IBRV), bovine virus diarrhea virus (BVDV), parainfluenza-3 virus (PIV3), respiratory syncytial virus (RSV), Mycoplasma dispar (Md), M. bovis (Mb), and respiratory disease treatment rates, relapse rates, and 28 day weight gains were investigated in 14 groups of calves entering two feedlots during years 1983-1985, in Ontario. Based on least squares regression analyses, seroconversion rates to Mb and BVDV were predictive of increased respiratory disease rates, and seroconversion rates to Ph, Ph-cytox, Md and PIV3 were predictive of decreased weight gains. The R2 for predicting weight gains was much higher than for morbidity rates (0.75 vs 0.47 respectively). Titer data were not predictive of relapse rates. Group level analyses were performed because calves are managed as groups (e.g. pens) in commercial feedlots. Only BVDV seroconversion rates were related to increased risk of respiratory disease at both the individual and group levels of organization. Mycoplasma may be important factors in causing respiratory disease, and their relationship to potentiating the effects of other respiratory pathogens needs further investigation.

Animals↗
PubMed1989

A field evaluation of an indirect fluorescent antibody-based broodstock screening test used to control the vertical transmission of Renibacterium salmoninarium in Chinook salmon (Oncorhynchus tshawytscha).

Ovarian fluid samples from erythromycin treated and untreated spawning three year old Chinook salmon were screened independently by two laboratories for the presence of Renibacterium salmoninarum using the indirect fluorescent antibody technique (IFAT). Agreement between the results of the two laboratories could be explained by chance when R. salmoninarum cell numbers as low as one per sample were considered sufficient to represent a positive result. If a positive result was considered to be the detection of larger numbers of R. salmoninarum cells (greater than 51 cells per sample), agreement increased and there was a statistically significant association between the results of the two laboratories. However, the level of agreement did not reach satisfactory levels for a population screening test. Furthermore, approximately 60% of the samples yielded false negative results when IFAT results were compared with positive culture results. These results led to the conclusion that the IFAT screening procedure, as carried out, was unsuitable for the purposes intended. Erythromycin injection of the spawning fish had no statistically significant effect on the results of the IFAT screening test.

Animals↗
PubMed1989

The associations between milk production, milk composition and Salmonella in the bulk milk supplies of dairy farms in Ontario.

The purpose of this study was to assess changes in dairy herd milk production and milk composition associated with changes in Salmonella contamination of bulk milk on dairy farms in southwestern Ontario. Twenty-three dairy farms that had submitted milk filters for culture from which Salmonella were isolated (cases) and 23 farms that submitted Salmonella-negative milk filters (controls) were included in the study. The rolling herd averages for milk and fat of case and control farms for the months of December 1985, December 1986 and April 1987 were compared and no significant differences were detected. Case and control farms were divided into three groups (A,B,C) on the basis of Salmonella culture results of milk filters submitted at various time periods throughout the study. Daily and monthly changes in milk production and composition parameters that reflected the time periods of milk filter culture were compared. The following unconditional associations between a changing Salmonella infection status on dairy farms and changes in milk production or composition variables were significant (p less than or equal to 0.05): group A: case farms had higher plate loop counts than control farms; group B: case farms had younger cows than control farms; group C: case farms had cows with longer average days in lactation than control farms. After analytical control of confounding variables, the disappearance of Salmonella from bulk milk supplies of dairy farms was associated with a decrease in percent fat and in somatic cell count.

Animals↗
PubMed1989

The frequency, distribution and effects of antibodies, to seven putative respiratory pathogens, on respiratory disease and weight gain in feedlot calves in Ontario.

During 1983-85, 279 calves requiring treatment for bovine respiratory disease and 290 comparison (control) animals from 15 different groups of feedlot calves were bled on arrival and again at 28 days postarrival. Their sera were then analyzed for antibodies to seven putative respiratory pathogens. On arrival, the prevalences of indirect agglutination titers to Pasteurella haemolytica, P. haemolytica cytotoxin, Mycoplasma bovis and M. dispar were greater than 50%, the prevalence of titers to bovine virus diarrhea virus (BVDV) was approximately 40%, and the prevalences of titers to infectious bovine rhinotracheitis virus (IBRV), bovine respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) were all below 25%. Seroconversion during the first month after arrival occurred in more than half the calves to P. haemolytica cytotoxin, PIV3 and RSV. Seroconversion of agglutination titers to P. haemolytica, Mycoplasma and BVDV occurred in about 40% of calves, and seroconversion to IBRV was infrequent (less than 5%). Initial titers were negatively correlated to subsequent titer changes within organism. Initial titers, and titer changes between organisms were essentially independent. Light calves had an increased risk of being selected for treatment for respiratory disease. Seroconversion to P. haemolytica cytotoxin, RSV and BVDV were predictive of respiratory disease cases, explaining approximately 69% of all respiratory disease cases in the feedlots. It was not possible to accurately predict weight gain or relapse from the serological data.

Animals↗
PubMed1988

Reproductive performance of dairy cows following treatment with cloprostenol 26 and/or 40 days postpartum: a field trial.

One hundred and seventy Holstein Friesian cows were randomly assigned to receive either 500 ug cloprostenol or saline placebo on Day 26 postpartum followed by 500 ug cloprostenol or saline on Day 40 postpartum. Four treatment groups were formed: Group 1-saline (Day 26)/saline (Day 40); Group 2-cloprostenol/(Day 26) saline (Day 40); Group 3-saline (Day 26)/cloprostenol (Day 40); Group 4-cloprostenol (Day 26)/cloprostenol (Day 40). Double blind techniques were used in administering treatments and in assessing the response to treatment. Palpation of the reproductive tract per tectum and uterine biopsies were performed on 92 cows prior to each treatment at Day 26 and Day 40 postpartum. Progesterone concentrations were determined on milk samples collected prior to treatment. There were no significant differences among treatment groups with respect to services per conception, number of heats detected before first service and culling for infertility. Cloprostenol treatment at Day 26 appeared to delay the first estrus, but it reduced the number of days to conception after the first service. Cows receiving cloprostenol at Days 26 and/or 40 had a decreased calving-to-conception interval compared to controls (P=0.01). Sequential therapy with two doses of cloprostenol resulted in slightly better reproductive performance than either treatment on Day 26 or 40 alone. Treatment with cloprostenol resulted in a decrease in the subsequent incidence of pyometra (P<0.05). It is concluded that in the herd studied, cloprostenol therapy at Day 26 and/or 40 postpartum was beneficial to reproductive performance. Although it was anticipated that cloprostenol would be more effective in cows with elevated progesterone levels, the opposite was observed at the Day 26 cloprostenol treatment. Uterine biopsy at Days 26 and/or 40 had a detrimental effect on subsequent reproductive performance.

Journal Article↗
PubMed1988

The interpretation of laboratory results.

This article outlines the concepts of epidemiologic sensitivity, specificity, predictive value, and agreement of tests. These features are important when selecting a test and when interpreting test results. The application of tests to aggregates (herds) of animals and methods to assess the etiologic importance of factors (for example, agents) are introduced.

Animals↗
PubMed1988

The prevalence, incidence, geographical distribution, antimicrobial sensitivity patterns and plasmid profiles of milk filter Salmonella isolates from Ontario dairy farms.

The prevalence, incidence and geographical distribution of Salmonella on dairy farms in southwestern Ontario were determined by culturing bulk milk filters from 511 randomly selected dairy farms. Milk filters from 22 farms (2.9%) were Salmonella-positive, with a cumulative incidence rate of 9.0% per year. Positive farms were distributed throughout southwestern Ontario, but were regionally clustered. The serotype, biotype, antimicrobial sensitivity pattern and plasmid profile of the Salmonella isolates from six farms where Salmonella were recovered on two occasions were identical. All of the Salmonella strains isolated were sensitive to commonly used antimicrobials.

Animals↗
PubMed1988

Seroprevalence and association with abortion of leptospirosis in cattle in Ontario.

Sera were collected using a systematic random sampling from 348 cattle herds in Ontario, in proportion to the cattle population in different areas. One cow in five from 296 dairy herds and one in three from 52 beef herds were sampled. The sera were analyzed for prevalence of antibodies to Leptospira interrogans serovar grippotyphosa, hardjo, icterohaemorhagiae and pomona using the microscopic agglutination test. Herd seroprevalence (one or more animals with titer greater than or equal to 80) in beef and dairy herds combined was grippotyphosa 2%, hardjo 13.8%, icterohaemorrhagiae 10.1% and pomona 25.8%; 39% of all herds showed evidence of leptospiral infection with one or more serovars; 44.2% of 52 beef herds had serological evidence of infection with serovar hardjo compared to 8.4% of 296 dairy herds (P less than 0.0001). Seroprevalence of other serovars was not significantly different between beef and dairy herds. The proportion of beef animals seropositive for hardjo and for pomona increased with age, particularly for hardjo; 26.5% of beef animals aged nine years or over were seropositive for hardjo. Dairy animals showed a significant rise of hardjo but not pomona titers with age. The seroprevalence of pomona infection was significantly higher in dairy cattle in eastern Ontario than in other regions. Thirty-four (6.1%) of 553 aborted bovine fetuses had leptospires detected by immunofluorescence techniques. Sixty-five percent of these fetuses were from submissions made between November and January. Leptospires were identified as serovar hardjo by specific immunofluorescence. There appeared, however, to be a paradoxical serological response in that eight aborting cows had antibody titers to pomona rather than hardjo.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Veterinary↗
PubMed1988

Bronchoalveolar lavage of cranial and caudal lung regions in selected normal calves: cellular, microbiological, immunoglobulin, serological and histological variables.

Of a group of 30 clinically normal male Holstein calves two to eight weeks of age, six two week old and six four week old calves met various radiographical and clinicopathological criteria for normality. Bronchoalveolar lavage was performed by fiberoptic bronchoscopy on cranial and caudal lung regions in all 30 calves and samples analyzed for free cells, microorganisms, and immunoglobulins. Lateral chest radiographs and lung biopsies were also conducted on each calf. Calves were euthanized and necropsied ten days after bronchoalveolar lavage was conducted. Reported in this paper are results from the 12 normal calves. Microorganisms were present in small numbers in the lower respiratory tract of some normal calves. There were no differences in the above parameters between cranial and caudal lobes. There were statistically significant changes in bronchoalveolar lavage cell proportions with age although there were no detectable differences in clinical signs. Four week old calves had a lower percentage of macrophages and a higher percentage of epithelial cells than two week old animals (p less than 0.05). There was also a trend toward an increased percentage of neutrophils in older calves but this was not significant (p greater than 0.05). Total bronchoalveolar lavage protein also appeared to increase with age (p less than 0.05). In both groups a higher proportion of IgG2 in bronchoalveolar lavage compared to serum was found, suggesting the presence of a local selective transfer mechanism into respiratory secretions.

Animals↗
PubMed1987

A comparison of discriminant analysis and logistic regression for the prediction of coliform mastitis in dairy cows.

Results from discriminant analysis and logistic regression were compared using two data sets from a study on predictors of coliform mastitis in dairy cows. Both techniques selected the same set of variables as important predictors and were of nearly equal value in classifying cows as having, or not having mastitis. The logistic regression model made fewer classification errors. The magnitudes of the effects were considerably different for some variables. Given the failure to meet the underlying assumptions of discriminant analysis, the coefficients from logistic regression are preferable.

Animals↗
PubMed1987

The relationship of hematology and serum chemistry parameters to treatment for respiratory disease and weight gain in Ontario feedlot calves.

In the fall of 1983, 322 western calves, in five different groups, were bled on arrival at two Ontario feedlots. Calves receiving treatment for respiratory disease, within 35 days of arrival, were denoted as cases. The hematology and serum chemistry parameters of cases were compared to those of controls. Cases had significantly (p less than 0.05) lower hematocrits, fewer platelets, and more band cells on arrival, than did controls. Cases also had lower serum phosphorous, magnesium, potassium, iron and alkaline phosphatase levels, and increased bilirubin and aspartate aminotransferase levels relative to controls. Based on the results of multivariable logistic regression, hematocrit, platelet numbers, serum phosphorous, iron and aspartate aminotransferase levels were the most significant parameters for the prediction of respiratory disease. Reference values for stressed feedlot calves were created. Most parameters were distributed in an approximately normal manner, however the group to group variation in most parameters was significant.

Analysis of Variance↗
PubMed1986

An epidemiological study of selected calf pathogens on Holstein dairy farms in southwestern Ontario.

Fecal samples from calves on 78 randomly selected Holstein dairy farms in southwestern Ontario were screened for Salmonella, Campylobacter jejuni/coli, enteropathogenic Escherichia coli, rotavirus and coronavirus. Based on the observed prevalence, 22% of farms had calves infected with Salmonella, 13% with Campylobacter jejuni/coli, 41% with enteropathogenic E. coli, 19% with rotavirus and 5% with coronavirus. These estimates can be modified, using a method developed by Mullen and Prost (1983) for the World Health Organization, to account for the nature of the laboratory test used. If the test is assumed to have no false positives (that is, if an organism is detected it must be there), then the observed prevalence estimates seen on this study may greatly underestimate the true prevalence of infected premises. The use of nipple feeders for calves was associated with an increased probability of farms having calves shedding detectable fecal levels of Salmonella, E. coli, or one of the two viruses. The use of group pens was associated with an increased odds of finding C. jejuni. Calves with diarrhea on these farms tended to have increased odds of shedding rotavirus, and E. coli with the K99 antigen. However, at the farm level, none of the organisms was associated with above median levels of morbidity. Farms positive for one or other of the viruses had increased odds of experiencing calf mortality relative to virus-negative farms, and farms positive for C. jejuni/coli had decreased odds of mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The association between serological titers in infectious bovine rhinotracheitis virus, bovine virus diarrhea virus, parainfluenza-3 virus, respiratory syncytial virus and treatment for respiratory disease in Ontario feedlot calves.

A seroepidemiological study of the association between antibody titers to infectious bovine rhinotracheitis, parainfluenza-3, bovine virus diarrhea and bovine respiratory syncytial viruses, and treatment for bovine respiratory disease was conducted. A total of 322 calves from five different groups were bled on arrival, then one month later all cases (cattle treated for bovine respiratory disease) were rebled together with an equal number of controls (cattle not treated for any disease). Titers to these viruses varied significantly from group to group. Based on seroconversion, infectious bovine rhinotracheitis virus was active in 4.4%, bovine virus diarrhea virus in 24%, parainfluenza-3 virus in 69.5% and bovine respiratory syncytial virus in 71.3% of the cattle. Cattle with low titers to infectious bovine rhinotracheitis and/or bovine respiratory syncytial viruses on arrival, were at increased risk of subsequent treatment for bovine respiratory disease. Treated cattle also had significantly greater increases to parainfluenza-3 and/or bovine virus diarrhea viruses than control calves. Treatment rates varied considerably from group to group and were not strongly correlated with weight gain in the postarrival period.

Animals↗