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Objective

To examine the study design of, and the practice of causal inference in, investigations of bacterial foodborne disease outbreaks occurring in the United States and to summarize agents and vehicles identified.

Design

Retrospective study.

Procedure

An online medical reference database was searched for reports of bacterial foodborne disease outbreak investigations published between 1986 and 1995. Reports were retrieved and reviewed for use of 9 causal criteria in investigations Information on etiologic agents, vehicles, seasonality, and primary study design from each outbreak was also retrieved.

Results

82 reports were retrieved and reviewed Coherence, consistency, temporality, and strength of association were the causal criteria most commonly used in foodborne disease outbreak investigations. Coherence was used in all investigations. The number of criteria used ranged from 3 to 7. Meat (n = 20) and eggs (12) were the most commonly implicated vehicles. Salmonella sp and Escherichia coli 0157:H7 accounted for 55% of agents reportedly isolated. Cohort and case-control methods were the most common study designs.

Clinical Relevance

Patterns were found in the use of causal criteria in foodborne disease outbreak investigations. These criteria can provide veterinarians and other public health practitioners with a means to effectively conceptualize, communicate, and summarize causal conclusions. The 4 most commonly used criteria may represent core criteria that investigators consider most useful in explaining foodborne disease outbreaks. (J Am Vet Med Assoc 1998:212:1874–1881)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To characterize a 2007 bluetongue disease (BT) epizootic caused by bluetongue virus (BTV) serotype 17 in sheep in the Big Horn Basin of Wyoming.

Design—Cross-sectional study.

Animals—1,359 sheep from ranches in Wyoming and Montana.

Procedures—Information on clinical signs and history of BT in sheep was obtained from ranchers and attending veterinarians. At 3 to 6 months after the 2007 BT epizootic, blood samples were collected from rams, ewes, and lambs within and outside the Big Horn Basin; blood samples were also collected from lambs born in the spring of 2008. Sera were tested for anti-BTV antibodies by use of a competitive ELISA to determine the seroprevalence of BTV in sheep and to measure antibody titers. Virus isolation and reverse transcriptase PCR assays were used to determine long-term presence of the infectious virus or viral genetic material in RBCs of sheep.

Results—The percentage of sheep seropositive for BTV closely matched morbidity of sheep within flocks, indicating few subclinical infections. Flocks separated by as little as 1 mile had substantial variation in infection rate. Rams were infected at a higher rate than ewes. There was no evidence of BTV successfully overwintering in the area.

Conclusions and Clinical Relevance—This epizootic appears to be a new intrusion of BTV into a naïve population of sheep previously protected geographically by the mountains surrounding the Big Horn Basin. Rams may have a higher infection rate as a result of increased vector biting opportunity because of the large surface area of the scrotum.

Full access
in Journal of the American Veterinary Medical Association

Summary

In March 1989, the USDA Food Safety and Inspection Service sampled raw chicken carcasses and giblets at a federally inspected slaughter establishment in Puerto Rico to determine the effects of adding chlorine to carcass and giblet chill water on bacterial contents of raw poultry products. Over four 8-hour workdays, 200 carcass rinse samples were collected at 3 sites in the establishment; 39 giblet rinse samples were collected at 1 site. Analyses of the carcass rinse samples indicated that carcasses had average aerobe plate counts of log10 3.20 before chilling and 2.51 after chilling; Enterobacteriaceae counts of log10 2.57 before chilling and 1.75 after chilling; and Escherichia coli counts of log10 2.04 before chilling and 1.20 after chilling. Salmonellae were found on 43% of the carcasses before chilling and on 46% after chilling. Analyses of the giblet and neck rinse samples indicated that raw giblets and necks after chilling had average aerobe plate count of log10 3.49, Enterobacteriaceae count of log10 2.57, and E coli count of log10 1.06. Salmonellae were found on 12% of the giblets and necks sampled.

Results compared favorably with giblet and neck rinse sample results obtained during a baseline sampling study in November and December 1987. The baseline results indicated aerobe plate count of log10 3.72; Enterobacteriaceae count of log10 2.90; E coli count of log10 1.14; and salmonellae on 69% of the giblets and necks sampled.

Placing raw chicken carcasses in chlorinated chill water reduced aerobe, Enterobacteriaceae, and E coli plate counts. Prevalence of carcasses with salmonellae remained nearly the same. Results indicate that chlorination of chill water aids in control of bacterial crosscontamination of carcasses and giblets and necks.

Free access
in Journal of the American Veterinary Medical Association

Summary

The USDA Food Safety and Inspection Service determined populations of bacteria on poultry during processing at a slaughter plant in Puerto Rico in November and December 1987. The plant was selected because of its management's willingness to support important changes in equipment and processing procedures. The plant was representative of modern slaughter facilities. Eight-hundred samples were collected over 20 consecutive 8-hour days of operation from 5 sites in the processing plant. Results indicated that slaughter, dressing, and chilling practices significantly decreased the bacterial contamination on poultry carcasses, as determined by counts of aerobic bacteria, Enterobacteriaceae, and Escherichia coli. Salmonella was not enumerated; rather, it was determined to be present or absent by culturing almost the entire rinse. The prevalence of Salmonella in the study decreased during evisceration, then increased during immersion chilling.

Free access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE

To determine the effect of a mobile UV-C disinfection device on the environmental bacterial bioburden in veterinary facilities.

SAMPLES

40 swab samples of surfaces from the operating theaters of 3 veterinary hospitals and 1 necropsy laboratory.

PROCEDURES

Various surfaces were swabbed, and collected material was eluted from the swabs in PBSS. Then, an aliquot of the sample fluid was processed with a bacteria-specific rapid metabolic assay to quantify bacterial bioburden. Each site was then treated with UV-C light with an automated disinfection device for approximately 45 minutes. The same surfaces were swabbed following UV-C treatment, and bioburden was quantified. The bioburden at additional time points, including after a second UV-C treatment, was determined for the small animal operating theater.

RESULTS

All surfaces at all sites had a persistent viable bacterial population following manual cleaning. Disinfection with UV-C achieved a mean bioburden reduction of 94% (SD, 5.2%; range, 91% to 95%) for all surfaces, compared with manual disinfection alone. Repeated UV-C treatment of the small animal operating theater reduced mean bioburden by 99% (SD, 0.8%), including no detectable bacteria on 4 of 10 surfaces.

CONCLUSIONS AND CLINICAL RELEVANCE

Disinfection with UV-C light may be a beneficial adjunct method for terminal disinfection of veterinary operating theaters to reduce environmental bioburden.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate tendon injuries in horses over a 16-week period by use of ultrasonography and low-field magnetic resonance imaging (MRI).

Sample—Tendons of 8 young adult horses.

Procedures—The percentage of experimentally induced tendon injury was evaluated in cross section at the maximal area of injury by use of ultrasonography and MRI at 3, 4, 6, 8, and 16 weeks after collagenase injection. The MRI signal intensities and histologic characteristics of each tendon were determined at the same time points.

Results—At 4 weeks after collagenase injection, the area of maximal injury assessed on cross section was similar between ultrasonography and MRI. In lesions of > 4 weeks' duration, ultrasonography underestimated the area of maximal cross-sectional injury by approximately 18%, compared with results for MRI. Signal intensity of lesions on T1-weighted images was the most hyperintense of all the sequences, lesions on short tau inversion recovery images were slightly less hyperintense, and T2-weighted images were the most hypointense. Signal intensity of tendon lesions was significantly higher than the signal intensity for the unaltered deep digital flexor tendon. Histologically, there was a decrease in proteoglycan content, an increase in collagen content, and minimal change in fiber alignment during the 16 weeks of the study.

Conclusions and Clinical Relevance—Ultrasonography may underestimate the extent of tendon damage in tendons with long-term injury. Low-field MRI provided a more sensitive technique for evaluation of tendon injury and should be considered in horses with tendinitis of > 4 weeks' duration.

Full access
in American Journal of Veterinary Research

Summary

In June and September 1988, the USDA Food Safety and Inspection Service sampled raw chicken carcasses at a federally inspected slaughter establishment in Puerto Rico to determine the effects of changing the scalding equipment on bacterial contents of raw poultry products. The scalding equipment was changed to a countercurrent configuration, with a postscald hot-water rinse cabinet that sprayed carcasses as they exited the scalder. Analysis of 250 carcass-rinse samples collected at preevisceration, prechill, and postchill sites over 7 days indicated that carcasses had mean aerobe plate counts of log103.73 before evisceration, 3.18 before chilling, and 2.87 after chilling; Enterobacteriaceae counts of log102.70 before evisceration, 2.25 before chilling, and 1.56 after chilling; and Escherichia coli counts of log102.09 before evisceration, 1.61 before chilling, and 0.89 after chilling. Salmonellae were found on 24% of the carcasses before evisceration, on 28% before chilling, and on 49% after chilling. Although bacterial count reductions were significant at all 3 sites, the proportion of carcasses contaminated with salmonellae in this study was higher at the postchill than prechill site (49 vs 28%). This no doubt was caused by cross-contamination in the chiller. These percentages indicated that although simple scalder changes contributed substantially to the improvement of the bacterial quality of chicken carcasses, additional interventions in the chilling process (such as chlorination of chill water) are important to control cross-contamination and to preserve the positive effects obtained by the scalder changes.

Free access
in Journal of the American Veterinary Medical Association

Summary

Long-term follow-up information pertaining to 162 dogs with appendicular osteosarcoma treated by amputation alone was collected from 17 veterinary institutions. The majority (72.5%) of dogs died or were euthanatized because of problems documented to be related to metastases. The first clinically apparent sites of metastasis were the lungs (60.8% of total), the skeleton (5.2%), or both (4.6%). A Kaplan-Meier survivorship distribution was plotted on the basis of available survival time data in all 162 dogs. The mean and median survival times were estimated to be 19.8 and 19.2 weeks, respectively, and the 1- and 2-year survival rates were estimated to be 11.5 and 2.0% respectively.

Statistically significant relationships were not found between survival time and reporting institution, gender, site of primary tumor, whether the primary tumor was proximally or distally located, whether the primary tumor was located in the forelimb or hind limb, whether presurgical biopsy was performed, and whether death was tumor related. A significant (P < 0.01) quadratic relationship was found between age and survival time. Survival time was longest in dogs 7 to 10 years old and was shorter in older and younger dogs.

Free access
in Journal of the American Veterinary Medical Association