Evaluation of risk and protective factors for work-related bite injuries to veterinary technicians certified in Minnesota

Leslie D. Nordgren Midwest Center for Occupational Health and Safety Education and Research Center and Regional Injury Prevention Research Center, Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, MN 55455.
Minnesota Department of Health, 625 Robert St N, Saint Paul, MN 55164.

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Susan G. Gerberich Midwest Center for Occupational Health and Safety Education and Research Center and Regional Injury Prevention Research Center, Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, MN 55455.

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Bruce H. Alexander Midwest Center for Occupational Health and Safety Education and Research Center and Regional Injury Prevention Research Center, Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, MN 55455.

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Timothy R. Church Midwest Center for Occupational Health and Safety Education and Research Center and Regional Injury Prevention Research Center, Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, MN 55455.

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Jeff B. Bender Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

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Andrew D. Ryan Midwest Center for Occupational Health and Safety Education and Research Center and Regional Injury Prevention Research Center, Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, MN 55455.

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Abstract

Objective—To identify risk and protective factors for work-related bite injuries among veterinary technicians certified in Minnesota.

Design—Nested case-control study.

Sample—868 certified veterinary technicians (CVTs).

Procedures—A questionnaire was mailed to CVTs who previously participated in a survey regarding work-related injuries and did (cases; 301 surveys sent) or did not (controls; 567) report qualifying work-related animal bite injuries in the preceding 12 months. Descriptive statistics were summarized. Demographic and work-related variables for the month preceding the bite injury (for cases) or a randomly selected month (controls) were assessed with univariate analysis (489 CVTs) and multivariate analysis of a subset of 337 CVTs who worked in small or mixed mostly small animal facilities.

Results—Responses were received from 176 case and 313 control CVTs. For the subset of 337 CVTs, risk of bite injury was higher for those < 25 years of age (OR, 3.82; 95% confidence interval [CI], 1.84 to 7.94) than for those ≥ 35 years of age, for those who had worked < 5 years (OR, 3.24; 95% CI, 1.63 to 6.45) versus ≥ 10 years in any veterinary facility, and for those who handled ≥ 5 species/d (OR, 1.99; 95% CI, 1.06 to 3.74) versus < 3 species/d. Risk was lower for CVTs who handled < 10 versus ≥ 20 animals/d (OR, 0.23; 95% CI, 0.08 to 0.71).

Conclusions and Clinical Relevance—Several work-related factors were associated with the risk of work-related bite injury to CVTs. These findings may serve as a basis for development of intervention efforts and future research regarding work-related injuries among veterinary staff.

Abstract

Objective—To identify risk and protective factors for work-related bite injuries among veterinary technicians certified in Minnesota.

Design—Nested case-control study.

Sample—868 certified veterinary technicians (CVTs).

Procedures—A questionnaire was mailed to CVTs who previously participated in a survey regarding work-related injuries and did (cases; 301 surveys sent) or did not (controls; 567) report qualifying work-related animal bite injuries in the preceding 12 months. Descriptive statistics were summarized. Demographic and work-related variables for the month preceding the bite injury (for cases) or a randomly selected month (controls) were assessed with univariate analysis (489 CVTs) and multivariate analysis of a subset of 337 CVTs who worked in small or mixed mostly small animal facilities.

Results—Responses were received from 176 case and 313 control CVTs. For the subset of 337 CVTs, risk of bite injury was higher for those < 25 years of age (OR, 3.82; 95% confidence interval [CI], 1.84 to 7.94) than for those ≥ 35 years of age, for those who had worked < 5 years (OR, 3.24; 95% CI, 1.63 to 6.45) versus ≥ 10 years in any veterinary facility, and for those who handled ≥ 5 species/d (OR, 1.99; 95% CI, 1.06 to 3.74) versus < 3 species/d. Risk was lower for CVTs who handled < 10 versus ≥ 20 animals/d (OR, 0.23; 95% CI, 0.08 to 0.71).

Conclusions and Clinical Relevance—Several work-related factors were associated with the risk of work-related bite injury to CVTs. These findings may serve as a basis for development of intervention efforts and future research regarding work-related injuries among veterinary staff.

Animal bites, including dog bites, to humans have been recognized as an important public health problem.1,2 More than 300,000 patients are treated for dog bites in hospital emergency departments annually, with associated medical costs > $1 million/y.2,3 In addition, there are also costs associated with medical insurance, workers’ compensation, lost wages, sick leave–associated business costs, and physical and emotional damage to injured persons. Among bite-related injuries treated in hospital emergency departments, aerobic and anaerobic infections were reported in 24 of 50 (48%) cases associated with dog bites and 36 of 57 (63%) cases associated with cat bites.4 In a study by the CDC,2 work-related dog bite injuries accounted for an estimated 8% of dog bite injuries treated in emergency departments.

Previous studies5–13 have found that cat and dog bites were among the most common injuries to veterinarians and their staff and that most injuries primarily involved the arms or hands. Yet very little is known about the risk factors associated with work-related bite injuries to veterinary clinic staff, including CVTs. Veterinary technicians have direct contact with animals when collecting specimens, providing specialized nursing care, preparing animals for surgery, assisting in diagnostic surgical and medical procedures, performing or preparing for radiographic imaging, and providing dental prophylaxis. More than 80,000 CVTs across the United States are at potential risk of traumatic occupational injuries,14 which can be costly in terms of medical expenses, lost work time, or career loss because of a disability. The prevalence and severity of work-related injuries to veterinary technicians certified in Minnesota were described in a previous study,15 in addition to potential risk factors. Developing appropriate bite injury prevention and control measures requires a better understanding of the risks specific to CVTs. Consequently, the purpose of the study reported here was to identify factors associated with work-related bite injuries to CVTs that can serve as a basis for development of intervention efforts.

Materials and Methods

Data were collected to identify specific risk factors for work-related bite injuries among veterinary technicians certified in Minnesota. The study was approved by the University of Minnesota Institutional Review Board Human Subjects Committee.

Population and study design—Veterinary technicians who were certified in Minnesota through the end of October 2004 and who worked as CVTs within the 12 months prior to initial survey administration were eligible for inclusion in the study. A total of 1,465 CVTs were identified from a database maintained by the Minnesota Veterinary Medical Association, and surveys were sent to 1,427 who had valid mailing addresses; those who had not worked as CVTs during the 12 months prior to the survey were excluded from the study (although certified in Minnesota, participants could have worked in any state during the specified period). The initial surveya sent through postal mail between April 30 and June 30, 2005, was used to identify individuals with and without work-related injury events during the previous 12 months, to collect information on the consequences of those injuries, and to identify potential risk factors associated with those injuries. Of 1,052 individuals who responded to the initial survey, 873 were eligible for inclusion in the analysis. Data obtained from that survey were described elsewhere.15

For the present study, a nested case-control design was used to identify specific risk factors and potential protective factors associated with animal-bite injury–related outcomes identified in the previous study.15 Questionnairesa that consisted of 41 multiple-choice or open-ended questions were sent between August 31 and November 30, 2005, to all participating CVTs who had answered questions regarding bite-related injuries in the initial survey. Similar to the initial survey method, case-control questionnaires were mailed up to 3 additional times if individuals did not respond. All mailings included cover letters that provided information about the study and informed consent. To encourage participation, each participating CVT could choose to be included in a random drawing with a 1 in 30 chance to win a retail gift card. Follow-up was performed by mail and telephone to clarify missing or unclear written responses.

Bite injuries—To be defined as a work-related bite injury, an injury must have been associated with occupational activities, involved bruising or breaking of the skin, or resulted in ≥ 1 of the following: restriction of normal activities (for any length of time), loss of consciousness, or use of medical assistance, including self-treatment. In the initial survey,15 descriptive information was requested for up to 4 of the most severe injuries incurred by a respondent; for purposes of the present study, only those respondents with bite injuries that had this descriptive information provided were included in the case group.

Group assignment and data collection—Case CVTs (301 surveys sent) were defined as those who reported ≥ 1 qualifying work-related bite injury within the 12 months prior to the initial survey.15 If > 1 eligible bite injury event was reported by a CVT, a single event was selected randomly as the event of interest. This method was chosen over selecting the most remote event, the most recent event, or the most severe event because each of the alternate methods of case event selection could have contributed to potentially greater study bias owing to misclassification and recall bias. Exposure information was collected for the month prior to the month in which the selected bite injury occurred.

All initial survey respondents who did not report a qualifying work-related bite injury in the 12 months prior to the survey were eligible as controls. Of 572 possible control CVTs identified, questionnaires were sent to 567 (5 CVTs had withdrawn from the study). To obtain exposure information, each control was randomly assigned a month on the basis of the months he or she indicated working during the study period; data were then collected for the month prior to the selected month.

The CVTs included in the case and control groups were asked to provide personal information (including demographic data; time, place, and type of animal restraint training received; duration of experience working in a veterinary facility of any kind; and whether they had incurred work-related animal bite injuries that resulted in bruises or broken skin prior to the month covered by the questionnaire). Additionally, information regarding employer practices (eg, animal restraint and bite prevention practices, support and encouragement for use of proper animal restraint, training requirements and practices, and whether any staff member could stop a procedure if they felt staff safety may be compromised), facility environment (eg, type of clinic or practice; number of veterinarians, CVTs, assistants, and other staff that handled animals in the facility or department; relevant coworker training and experience; coworker support of safety practices; workload and scheduling; quality of staff communication; species and number of animals handled daily; and availability of adequate restraint equipment), and animal owners (eg, whether owners were allowed to restrain their own animals during examination or treatment, the CVT's perception of owners’ capability to restrain their animals, and whether presence of the owner affected restraint procedures) were collected. These data were then used to compare exposures between the case and control groups.

Data analysis—Risk factors for animal bite injuries were assessed through multivariate modeling with a causal model and specific directed acyclic graphs16–18,a pertinent to exposures of interest. This method was used in a prior study19 of injuries acquired by veterinarians. To determine associations between exposures of interest and bite-related injuries, the directed acyclic graphs facilitated identification of potential confounders to be controlled for in each multivariate model. These methods identify parsimonious models and exclude covariates that should not be entered into the regression because of the potential to introduce bias. Multiple logistic regression was used to calculate ORs and 95% confidence intervals. Findings were considered significant if the 95% confidence interval did not include 1.0. Differences in the levels of exposure variables were considered significant if the confidence intervals did not overlap. In addition, the potential impact of an unmeasured confounder related to the magnitude and direction of potential bias was examined by means of sensitivity analyses.20

Results

Of 868 CVTs that were sent questionnaires for the nested case-control study (301 and 567 recruited as potential cases and controls, respectively), 489 responded. These included 176 case CVTs who had incurred a work-related bite injury in the 12 months prior to the initial survey and 313 control CVTs who had not; not every respondent answered all questions. Characteristics for each group were summarized (Table 1). Both groups predominantly comprised females. Fifty-four of 176 (31%) respondents in the case group were ≥ 35 years of age, compared with 139 of 313 (44%) controls (data were not reported for 9 CVTs). One hundred twelve (64%) CVTs of the case group worked in small animal clinics, and 10 (6%) worked in a college or university setting, compared with 166 (53%) and 44 (14%), respectively, for the control group. Other apparent differences among groups included the proportions that reported working ≥ 8 h/d on average (case group, 153/176 [87%]; control group, 251/313 [80%]), having had a work-related bite injury prior to the period included in the questionnaire (case group, 155 [88%]; control group, 245 [78%]), and having worked < 5 years in any veterinary facility (case group, 80 [45%]; control group, 87 [28%]). Case CVTs more commonly handled ≥ 10 animals during a typical day (163 [93%]) and handled ≥ 3 species during a typical day (82 [47%]), compared with control CVTs (244 [78%] and 114 [36%], respectively).

Table 1—

Characteristics of 489 veterinary technicians certified in Minnesota who responded to a postal mail survey between August 31 and November 30, 2005, and did (cases; n = 176) or did not (controls; 313) have a work-related animal-bite injury.

VariableCasesControls
Gender
 Female170 (96.6)304 (97.1)
 Male6 (3.4)8 (2.6)
 Not reported0 (0.0)1 (0.3)
Age (y)
 < 2530 (17.0)20 (6.4)
 25 to < 3589 (50.6)148 (47.3)
 ≥ 3554 (30.7)139 (44.4)
 Not reported3 (1.7)6 (1.9)
Facility type
 Small animal112 (63.6)166 (53.0)
 Mixed mostly small animal20 (11.4)39 (12.5)
 Mixed large and small animal (described as a 50:50 ratio)11 (6.3)14 (4.5)
 Equine, large animal, or mixed mostly large animal1 (0.6)7 (2.2)
 Emergency9 (5.1)5 (1.6)
 College or university10 (5.7)44 (14.1)
 Research8 (4.5)13 (4.2)
 Commercial or industrial0 (0.0)8 (2.6)
 Government or regulatory0 (0.0)5 (1.6)
 Humane society or shelter3 (1.7)3 (1.0)
 Other (equine, zoological, wildlife rehabilitation, or not specified)2 (1.1)9 (2.9)
No. of years worked in any veterinary facility
 < 580 (45.5)87 (27.8)
 5 to < 1054 (30.7)99 (31.6)
 ≥ 1042 (23.9)125 (39.9)
 Not reported0 (0.0)2 (0.6)
No. of hours worked per day (on average)
 < 823 (13.1)61 (19.5)
 872 (40.9)114 (36.4)
 > 881 (46.0)137 (43.8)
 Not reported0 (0.0)1 (0.3)
Previous bite injury
 Yes155 (88.1)245 (78.3)
 No20 (11.4)68 (21.7)
 Not reported1 (0.6)0 (0.0)
No. of animals handled on a typical day
 < 1010 (5.7)62 (19.8)
 10 to < 1537 (21.0)50 (16.0)
 15 to < 2039 (22.2)59 (18.8)
 ≥ 2087 (49.4)135 (43.1)
 Not reported3 (1.7)7 (2.2)
No. of species handled on a typical day
 11 (0.6)22 (7.0)
 290 (51.1)172 (55.0)
 332 (18.2)52 (16.6)
 418 (10.2)28 (8.9)
 513 (7.4)17 (5.4)
 618 (10.2)17 (5.4)
 71 (0.6)0 (0.0)
 Not reported3 (1.7)5 (1.6)
No. of years since most recent animal restraint training
 < 585 (48.3)147 (47.0)
 5 to < 1059 (33.5)76 (24.3)
 ≥ 1022 (12.5)68 (21.7)
 Not reported10 (5.7)22 (7.0)
Animal owners present during examinations and procedures
 Always17 (9.7)29 (9.3)
 Frequently84 (47.7)120 (38.3)
 Sometimes43 (24.4)81 (25.9)
 Infrequently or never17 (9.7)32 (10.2)
 Not applicable15 (8.5)48 (15.3)
 Not reported0 (0.0)3 (1.0)
Animal owners allowed to restrain pets during examination or treatment
 Yes106 (60.2)151 (48.2)
 No52 (29.5)114 (36.4)
 Not applicable18 (10.2)47 (15.0)
 Not reported0 (0.0)1 (0.3)
Adequate equipment available for restraint
 Yes165 (93.8)294 (93.9)
 No10 (5.7)13 (4.2)
 Not applicable0 (0.0)4 (1.3)
 Not reported1 (0.6)2 (0.6)
Adequate support from employer to use proper animal restraint
 Always85 (48.3)170 (54.3)
 Frequently67 (38.1)103 (32.9)
 Sometimes15 (8.5)26 (8.3)
 Infrequently or never8 (4.5)6 (1.9)
 Not applicable1 (0.6)6 (1.9)
 Not reported0 (0.0)2 (0.6)
Adequate staff available to help with restraint
 Always54 (30.7)141 (45.0)
 Frequently90 (51.1)112 (35.8)
 Sometimes23 (13.1)42 (13.4)
 Infrequently or never8 (4.5)6 (1.9)
 Does not apply1 (0.6)10 (3.2)
 Not reported0 (0.0)2 (0.6)
Felt confident in handling animals when applying restraint techniques
 Strongly agree84 (47.7)180 (57.5)
 Agree89 (50.6)126 (40.3)
 Disagree3 (1.7)1 (0.3)
 Not applicable0 (0.0)5 (1.6)
 Not reported0 (0.0)1 (0.3)
Sufficient time allowed in schedule to perform adequate animal restraint
 Always41 (23.3)109 (34.8)
 Frequently77 (43.8)107 (34.2)
 Sometimes45 (25.6)58 (18.5)
 Infrequently8 (4.5)23 (7.3)
 Never4 (2.3)7 (2.2)
 Not applicable0 (0.0)8 (2.6)
 Not reported1 (0.6)1 (0.3)
As likely to use muzzles and other proper restraint in presence of the owner as when owners were not present
 Yes124 (70.5)209 (66.8)
 No34 (19.3)45 (14.4)
 Not applicable18 (10.2)57 (18.2)
 Not reported0 (0.0)2 (0.6)

Data are reported as number (%).

Participants were recruited on the basis of their participation in a previous survey15 in which they were asked to identify any work-related injuries incurred in the 12 months prior to that survey. For the present study, only those work-related bite injuries that were included in respondents’ descriptions of their most severe work-related injuries were included. Facility type, gender, and age were determined from data collected in the previous study.15

One hundred one of 176 (57%) CVTs of the case group indicated that animal owners were always present or frequently present during examinations, compared with 149 of 313 (48%) in the control group. One hundred six (60%) and 151 (48%) case and control CVTs, respectively, indicated that animal owners were allowed to restrain their pets during examination or treatment.

On a scale ranging from 1 (always) to 5 (never), 85 of 176 (48%) and 170 of 313 (54%) CVTs of the case and control groups, respectively, indicated that they always had adequate support from their employer to use proper animal restraint. On the same scale, 54 (31%) case and 141 (45%) control CVTs indicated they always had adequate staff available for animal restraint, and 41 (23%) case and 109 (35%) control CVTs reported that sufficient time was always allowed in the schedule to perform adequate animal restraint. By use of a scale from 1 (strongly agree) to 4 (strongly disagree), 84 (48%) CVTs in the case group strongly agreed with the statement “I felt confident in handling animals when applying restraint techniques,” whereas 180 (58%) CVTs in the control group selected this response.

Given that most (337/489 [69%]) CVTs in the study worked in small or mostly small animal clinics (cases, 132/176 [75%]; controls, 205/313 [65%]), as identified in the previous study,15 multivariate analysis was focused on this more homogeneous population to investigate potential differences in types of exposures (Table 2).

Table 2—

Odds ratios and 95% confidence intervals for work-related bite injury among CVTs working in small animal or mixed mostly small animal facilities who did (cases; n = 132) or did not (controls; 205) incur such injuries.

VariableNo. of casesNo. of controlsOR95% CI
Gender
 Female1282011
 Male432.090.46–9.51
Age (y)
 ≥ 3534811
 25 to < 35691021.590.97–2.60
 < 2526163.821.84–7.94
Animal owners present during examinations and procedures
 Always to frequently871251
 Sometimes38640.870.53–1.41
 Infrequently to never7101.280.45–3.65
No. of years worked in any veterinary facility*
 ≥ 1025741
 5 to < 1041661.900.98–3.72
 < 566633.241.63–6.45
No. of hours worked per day (on average)*
 < 822471
 848590.620.32–1.20
 > 862980.790.48–1.31
Previous bite injury
 Yes1161681
 No15370.520.27–1.01
No. of animals handled on a typical day
 ≥ 2064911
 15 to < 2034470.930.52–1.64
 10 to < 1529321.280.69–2.38
 < 104290.230.08–0.71
No. of species handled on a typical day§
 < 3631191
 3 to 441551.340.80–2.26
 ≥ 527261.991.06–3.74
No. of years since most recent animal restraint training
 < 568981
 5 to < 1040471.200.71–2.04
 ≥ 1014450.660.31–1.39
Animal owners allowed to restrain pets during examination or treatment
 Yes901211
 No41800.760.46–1.26
 Not applicable132.100.12–35.45
Adequate equipment available for restraint
 Yes1271931
 No5100.600.19–1.88
Adequate support from employer to use proper animal restraint#
 Always641091
 Frequently52691.180.73–1.92
 Sometimes11200.870.38–1.95
 Infrequently to never541.680.42–6.64
Adequate staff available to help with restraint**
 Always39881
 Frequently71782.021.13–3.60
 Sometimes16311.110.48–2.61
 Infrequently to never634.700.94–23.50
Felt confident in handling animals when applying restraint techniques††
 Strongly agree611101
 Agree68941.200.71–2.01
 Disagree30
Sufficient time allowed in schedule to perform adequate animal restraint‡‡
 Always27601
 Frequently58771.170.62–2.20
 Sometimes37471.190.57–2.48
 Infrequently to never9200.450.14–1.47
As likely to use muzzles and other proper restraint in presence of the owner as when owners were not present§§
 Yes1001631
 No31351.350.69–2.61
 Not applicable150.330.02–5.11

Not all respondents answered every question.

Model included age.

Model included age and number of years worked in any veterinary facility.

Model included number of hours worked per day, number of years worked in any veterinary facility, and age.

Model included age and number of hours worked per day.

Model included animal owner presence during examinations and procedures, adequate staff availability for animal restraint, confidence in handling animals when applying restraint, and sufficient time in schedule for adequate restraint.

Model included number of animals handled on a typical day and adequate support from employer to use proper animal restraint.

Model included number of years worked in any veterinary facility and history of previous bite injury.

Model included number of animals handled on a typical day, age, number of hours worked per day, number of years worked in any veterinary facility, and adequate support from employer to use proper animal restraint.

Model included age, number of years worked in any veterinary facility, number of years since most recent animal restraint training, history of previous bite injury, adequate staff availability for animal restraint, adequate support from employer to use proper animal restraint, sufficient time in schedule for adequate restraint, and number of animal species handled on a typical day.

Model included number of animals handled on a typical day, adequate staff availability for animal restraint, adequate support from employer to use proper animal restraint, number of years worked in any veterinary facility, and age.

Model included age, number of animals handled on a typical day, number of years worked in any veterinary facility, number of years since most recent animal restraint training, adequate support from employer to use proper animal restraint, animal owner presence during examinations and procedures, number of hours worked per day, history of previous bite injury, adequate staff availability for animal restraint, number of animal species handled on a typical day, adequate equipment availability for restraint, confidence in handling animals when applying restraint, and sufficient time in schedule for adequate restraint.

CI = Confidence interval.

Significant associations between risk of bite injury and age or duration of employment were identified; CVTs < 25 years of age were > 3 times as likely to incur a bite injury, compared with those ≥ 35 years of age. Similarly, CVTs who worked < 5 years in any veterinary facility were > 3 times as likely to receive a bite injury, compared with those who worked in such facilities for ≥ 10 years. Working with ≥ 5 species of animals on a typical day was associated with a risk of bite injury 2 times that of working with < 3 species. The risk for CVTs who reported they frequently had adequate staff available for animal restraint was 2 times that of CVTs who indicated they always had adequate staff for this purpose; however, risk did not differ significantly from that of the referent category for those who reported adequate staff were sometimes or infrequently (to never) available for this task. The risk of bite injury was significantly lower for CVTs who reported handling < 10 versus ≥ 20 animals on a typical day.

Sensitivity analyses were conducted to examine the impact of an unmeasured confounder related to the magnitude and direction of potential bias. Given that one of the results of this study suggested that CVTs’ perceptions that they frequently, but not always, had adequate staff available for proper animal restraint was associated with increased risk of bite injury, sensitivity analyses were conducted to consider the potential effect of the population density of the clinic location in which the CVTs worked during the month for which they had answered questions about their exposures. This factor could be associated with the pool of available trained veterinary staff within the community and the risk of bite injury; variability in characteristics of animals, such as animal species and behaviors, between rural and urban areas could also result in dissimilarity in risk of bite injuries to CVTs. With prevalence of the unmeasured confounder being defined as the proportion of CVTs who worked in a more densely populated work area, the examination of estimated ranges of this prevalence between staffing exposure rates was used to determine the effect of the unmeasured confounder on the risk associated with the exposure. To reverse the effect of frequently versus always having adequate staff available for restraint (eg, to change the OR from 2.02 to 0.93), the unmeasured confounder would have to be a relatively strong risk factor (OR, ≥ 3.0) with differences in prevalence across the exposed and unexposed groups (frequently having enough staff vs always having enough staff) of 0.8 and 0.1, respectively. The point estimate was considered, however, and not the precision of the estimate for this sensitivity analysis.

Discussion

This population-based case-control study enabled identification of potential risk factors for work-related bite injuries to veterinary technicians certified in Minnesota, with a focus on those working in small animal or mostly small animal clinics. A similarly designed study19 previously investigated work-related bite injuries in a population of veterinarians through multivariate logistic regression analyses.

In the present study, the number of hours worked (on average) per day as reported by CVTs was analyzed as a surrogate measure of fatigue, and multivariate analysis revealed no significant differences in the risk of bite injury among CVTs working ≥ 8 h/d, compared with those working < 8 h/d. A prospective study design may be more effective in identifying any associations between risk of bite injury and number of hours worked daily.

Significant associations were found between the risk of bite injury and younger age (when CVTs < 25 and ≥ 35 years of age were compared) as well as fewer years worked in any veterinary facility (when CVTs with < 5 years and ≥ 10 years of experience were compared). Similar findings were reported by Gabel and Gerberich.19 Further research may attempt to explain the effects of the type and quality of work experience on the risk of bite injury.

Results of the present study suggested that having no prior bite injuries (that resulted in bruises or broken skin) was associated with a decreased risk of bite injury during the study period, similar to findings reported for veterinarians.19 It is possible that CVTs reporting a bite injury during the study period may have had enhanced recall of more distant events that may, in part, have been related to severity of the events or that they worked in an environment where bite-related injury was more likely to occur.

Our results also suggested that the risk of bite injury was associated with the CVTs’ perceptions of availability of staff for animal restraint. The CVTs who reported frequently having adequate staff for animal restraint were more than twice as likely to experience a bite injury, compared to those who reported always having adequate staff available. However, interpretation of this result was difficult, as lower frequencies (sometimes, infrequently, or never) of having adequate staff for animal restraint were not statistically associated with increased risk of bite injury. The findings of reduced risks associated with handling lower numbers and fewer species of animals on a typical day are also important considerations. In particular, this suggests a need for veterinarians and practice managers to consider, carefully, the patient load and to provide adequate staffing. Further research may also elaborate on the effect of types and ratios of staff to patients and the availability of other resources on the outcome of bite injury.

Our questionnaire-based study relied on the CVTs’ perceptions and self-reported descriptions of relevant bite injury events and exposures. These methods may possibly have resulted in some biases, including those related to recall, information misclassification, selection, and confounding. In an attempt to reduce recall bias, the recall period for exposures was limited to 1 month before a bite injury that occurred in the previous 12 months. This method was used in a prior study19 of work-related injuries among veterinarians. To reduce information bias, follow-up was performed by mail and telephone to clarify missing or unclear written responses. All veterinary technicians with active certification in Minnesota were selected for inclusion in the initial study.15 No demographic information was available in the CVT certification database, so it was not possible to consider response bias or eligibility. Although there may have been bias attributable to the influence of an earlier event for some case CVTs who experienced multiple bite-injury events during the study period, random selection of 1 event for analysis was expected to result in less bias than was selection of an event on the basis of timing or severity of the injury. The selection of potential confounders for logistic regression analyses was guided by directed acyclic graphs16–18,a to minimize the effect of confounding. The risk of bite injury may vary among different regions of the country and may also differ between certified and uncertified veterinary technicians.

This population-based study provided preliminary findings and analysis of case-control data pertinent to risk factors for work-related bite injuries among CVTs. The risk factors identified included younger age (< 25 years vs ≥ 35 years), shorter experience (< 5 years vs ≥ 10 years), perception of frequently versus always having adequate staff available for proper restraint, and greater number of animal species handled on a typical day (≥ 5 vs < 3 species). A decreased risk was associated with handling fewer animals on a typical day (< 10 vs ≥ 20). The results from this study add to our understanding of the relationships between various occupational exposures and work-related bite injuries among CVTs. Future studies might explore whether changes in various exposures over time have an impact on the frequency or severity of work-related bite injuries.

ABBREVIATION

CVT

Certified veterinary technician

a.

Copies of the questionnaire and other written materials are available from Regional Injury Prevention Research Center, Division of Environmental Health Sciences, School of Public Health, University of Minnesota. Minnesota certified veterinary technicians’ study. Available at: enhs.umn.edu/riprc/riprc.html. Accessed Nov 12, 2013.

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