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D Waltner-Toews

Publications and source records attributed to D Waltner-Toews.

36 records · Page 2Linked to original sources
PubMed1994

The seroprevalence of maedi-visna in Ontario sheep flocks and its relationship to flock demographics and management practices.

The objectives of this study were to describe the serological prevalence of maedi-visna in a sample of Ontario sheep flocks, and to identify management and demographic variables that were associated with seroprevalence for maedi-visna. A sample of 103 sheep flocks in Ontario was randomly selected from those flocks participating in the Red Meat Plan. The owners of these flocks were surveyed regarding management procedures on their farms, and blood samples were taken from a random sample of ewes in each flock. At least one ewe tested serologically positive, based on the agar gel immuno-diffusion test, in 69.9% of the farms. Positive serological reactions occurred in 20.9% of the 3880 sheep tested. Flock demographics and farm management variables were considered in a multiple regression model, and several factors were positively associated with higher maedi-visna seroprevalence rates. These included the average age of the flock, the number of years the owner had been sheep farming, the practice of using foster ewes, the practice of allowing lambs to have contact with other ewes that are lambing, and the average pasture acreage per ewe.

Animal Husbandry↗
PubMed1992

Distribution and characteristics of verocytotoxigenic Escherichia coli isolated from Ontario dairy cattle.

Faecal swabs obtained from a random sample of 1131 cows and 659 calves on 100 southern Ontario dairy farms were examined for verocytotoxigenic Escherichia coli (VTEC) using a Vero cell assay. Five isolates from each positive culture were tested similarly. Positive colonies were examined with DNA probes for Shiga-like toxin I (SLT-I) and SLT-II sequences. Probe-negative colonies were tested for neutralization of verocytotoxicity using anti-SLT-I and anti-SLT-IIv antisera. Colonies showing no neutralization response were examined in a polymerase chain reaction procedure. Colonies positive by any test were confirmed to be E. coli biochemically, serotyped, biotyped and tested for antimicrobial resistance. Faecal culture supernatants which were positive in the Vero cell assay, but culture negative, were examined using the neutralization assay. Animals were classified positive by faecal culture supernatant or by positive VTEC isolate. The prevalence rates of VTEC infection in cows and calves were estimated to be 9.5 and 24.7%, respectively. The proportion of animals infected on each farm ranged from 0 to 60% for cows and 0 to 100% for calves. Of 206 VTEC isolates identified, few were of serotypes which have been isolated from humans and none were E. coli O 157.H7.

Animals↗
PubMed1992

A case-control study of selected pathogens including verocytotoxigenic Escherichia coli in calf diarrhea on an Ontario veal farm.

A case-control study of diarrheal disease in veal calves was conducted over a three month period on a single large veal farm in southern Ontario. One hundred diarrheic calves (cases) were identified by visual examination of their feces. Each case was matched to two nondiarrhetic controls from the same room on the same day, and a fecal sample was obtained from each animal. Fecal consistency of cases and controls was observed daily for one week following sample collection. Control calves which developed diarrhea during that period were excluded from the study. Breed, sex and the date and nature of antimicrobial drugs administered to each calf were recorded. Moisture content of fecal samples was measured by weighing samples before and after oven drying. Samples were screened for verocytotoxigenic Escherichia coli (VTEC) using a Vero cell assay, for enterotoxigenic E. coli (ETEC) using an immunoblot procedure with anti-K99 monoclonal antibodies, and for Salmonella species using modified semi-solid Rappaport-Vassiliadis medium. A latex agglutination test was used to detect rotaviruses, and samples were examined for cryptosporidia using sucrose wet mounts. No VTEC were identified in cases or controls. One calf was positive for Salmonella and three were positive for ETEC. Rotaviruses were detected in four cases and four controls. A significant positive association was found between diarrhea and infection with Cryptosporidium. This study thus provided no evidence of an association between diarrhea and infection with either VTEC, ETEC, Salmonella spp. or rotaviruses in the population examined. On the other hand our results do suggest that Cryptosporidium infection may promote transient diarrheal disease in veal calves in Ontario.

Animals↗
PubMed1991

The seroprevalence of coxiellosis (Q fever) in Ontario sheep flocks.

A serological survey for Coxiella burnetii was undertaken on a randomly selected population of 103 Ontario sheep flocks. Twenty-two flocks had at least one positive ewe; seven flocks had two or more reactors. The positive flocks were geographically clustered northwest of Guelph. Crutch-clipping of the ewe's wool prior to lambing, and total confinement housing at lambing in winter and spring seemed to lower the probability of seroreactivity of the flock (p less than 0.05). The study suggests that sheep are not a major reservoir for Coxiella burnetii in Ontario.

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 effect of early calfhood health status on survivorship and age at first calving.

Survival to maturity and age at first calving were studied in heifer calves from 34 randomly selected Holstein dairy farms in southwestern Ontario. Calves were divided into cohorts on the basis of treatment for pneumonia, scours, other diseases, or no treatments, during the first 90 days of life. An effect of pneumonia and scours together, over and above the effects of each disease alone, was assessed by means on an interaction term in the statistical analyses. Heifers which had been treated for pneumonia during the first three months of life were 2.5 times more likely to die after 90 days of age than heifers which had not been treated for pneumonia, after controlling for the farm effect. Heifers with a calfhood history of being treated for scours were 2.5 times more likely to be sold for dairy purposes than other calves. Heifers which had been treated for scours were 2.9 times more likely to calve after 900 days of age than other heifers, after controlling for the farm effect.

Age Factors↗
PubMed1986

Selenium content in the hair of newborn dairy heifer calves and its association with preweaning morbidity and mortality.

Hair samples from newborn heifer calves on Holstein dairy farms in southwestern Ontario were analyzed for selenium content by means of instrumental neutron activation analysis. The mean selenium level in the hair of calves which subsequently died at less than six weeks of age did not differ from selenium levels in the hair of calves matched by farm and birthday (overall mean 0.28 ppm). The mean selenium level in the hair of calves which were not treated for disease during the first four weeks of life was 0.42 ppm, while that from appropriately matched treated calves was 0.36 ppm; the difference between the means was significant at p = 0.054. Based on the above associations, it is suggested that higher selenium levels in newborn calves may have some protective effect against morbidity.

Animals↗
PubMed1985

A field trial to evaluate the efficacy of a combined rotavirus-coronavirus/Escherichia coli vaccine in dairy cattle.

A field trial was designed to determine the efficacy of a combination rotavirus-coronavirus/Escherichia coli vaccine on dairy farms in southwestern Ontario. In Part A of the trial, 321 cows on 15 farms were randomly assigned to either vaccination or placebo groups. On eight farms, 50% of the dams were vaccinated, while on the other seven farms, 80% of the dams were vaccinated. In Part B of the trial, 26 farms were randomly assigned to either a total vaccination program or to no vaccination program. Mortality, disease occurrence and weight gains were recorded on all calves for the first two weeks of life. In Part A, 23.5% of all calves were treated in the first two weeks of life, 20.9% were treated specifically for scours and 3.6% of live-born calves died. Enteropathogenic E. coli was identified on 13 of the 15 farms, rotavirus on 11 and coronavirus on ten. At least one of the three potential pathogens was found on every farm. There were no significant differences between calves from placebo-treated and vaccine-treated dams with regard to the proportion treated for all diseases, or for scours, or the proportion which died. Neither were there differences in days to first treatment for all diseases (seven days on average), days to first scour (6.7 days), duration of treatments (3.9 days for all diseases, 3.7 days for scours), or estimated weight gains (0.5 kg/day to 14 days). These results were not altered when the presence or absence of enteropathogenic E. coli, rotavirus or coronavirus on the premises was accounted for.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Urolithiasis in a herd of beef cattle associated with oxalate ingestion.

An unusually high incidence of urinary calculi in a group of feeder cattle is described. Necropsy findings in one affected animal suggested that oxalates in the feed, specifically in fescue (Festuca spp.) seed screenings, may have been the cause. Low dietary calcium and decreased water intake by the cattle appear to have been predisposing factors. Control measures are discussed.

Animal Feed↗
PubMedDate not supplied

The effects of prehospital advanced life support drug treatment on patient improvement and in-hospital utilization.

OBJECTIVE: There is little published evidence to support the benefits of prehospital drug administration by ambulance personnel in reducing subsequent hospital utilization by the medical patients receiving such drugs. The authors studied the outcome of patients treated by Ontario's Emergency Health Services "Symptom Relief Drug Program," which was developed to relieve patient symptoms in the field for specific medical emergencies. METHODS: A retrospective study spanning a three-year period from January 1996 to December 1998 was undertaken in a mid-sized southern Ontario community. From a review of ambulance call reports (ACRs), eligible patients were recruited by mail and divided into two groups: those treated before the introduction of the program (pre) and those treated after (post). Out-of-hospital data were retrieved from ACRs and in-hospital data were gathered from medical chart reviews. Outcomes included emergency department (ED) length of stay (LOS), frequency of admissions, and departmental use. Secondary endpoints included differences in prehospital improvement, ED interventions, and ambulance scene times. RESULTS: For the unpaired analysis, 406 patients provided consent (pre: 215 vs post: 191). Ambulance time on scene was longer in the post group, 14.2 minutes (95%CI 13.7-14.8), versus the pre group, 12.3 minutes (95% CI 11.7-12.9), p < 0.001. A larger proportion of patients receiving prehospital drug treatment were judged to have improved on ED arrival (pre: 19.5% vs post: 48.2%, chi2 p < 0.0001). The ED LOSs did not differ between groups (pre: 206.9 min, 95% CI 185.9-230.4, vs post: 220.9 min, 95% CI 196.9-247.7, p = 0.42) but were shorter within the post group for hypoglycemic patients receiving glucagon. The overall proportion of admissions was significantly lower in the post group (pre: 145 [67.4%] vs post: 102 [54.3%], chi2 p < 0.01), and this was driven by chest pain patients. CONCLUSIONS: The lower rate of admissions for chest pain patients is the first published evidence of prehospital drug treatment's reducing hospital utilization in a sub-group of such medical patients. The "Symptom Relief Drug Program" is effective in improving patients' field conditions and can decrease ED LOS in hypoglycemic persons receiving glucagon injections. More outcome research pertaining to ambulance-administered prehospital drug treatment is warranted.

Aged↗
PubMedDate not supplied

How reliable are selected scales from population-based health surveys? An analysis among seniors.

The objective of the study was to assess the internal consistency and test-retest reliability of selected scales from four national and provincial surveys used to study the health status of community-dwelling seniors. Items on physical impairment, psychological well-being, activities of daily living, chronic health problems, social support, and stressful life events were selected from these surveys and administered in a group of 1,054 seniors, aged 65 and over, living in Wellington County, Ontario. Each scale exhibited high internal consistency (Cronbach's alpha > or = 0.70) except for the stressful life events and social support scales. The intra-class coefficients (rho) for all scales were > 0.80. In addition, almost all single items measures used in this study also exhibited high test-retest reliability (kappa > 0.80) except for measures of perceived health status (kappa = 0.69) and availability of help in crisis situation (kappa = 0.48).

Activities of Daily Living↗