American Journal of Industrial Medicine 16: 55-66 (1989) Prevalence of Hazardous Exposures in Veterinary Practice Patricia Wiggins, MD, MPH, Marc B. Schenker, MD, MPH, Rochelle Green, MSPH, and Steven Sarnuels, PhD All female graduates of a major U.S. veterinary school were surveyed by mailed questionnaire to obtain details of work practice and hazard exposure during the most recent year worked and during all pregnancies. Exposure questions were based on previously implicated occupational hazards which included anesthetic gases, radiation, zoonoses, prostaglandins, vaccines. physical trauma, and pesticides. The response rate was 86% (4621537). We found that practice type and pregnancy status were major determinants of hazard exposure within the veterinary profession. Small-animal practi- tioners reported the highest rates of exposure to anesthetic gas (94%), X-ray (90%), and pesticides (57%). Large-animal practitioners reported greater rates of trauma (64%) and potential exposure to prostaglandins (92%~), Brucella abortus vaccine (23%), and carbon monoxide ( 18%). Potentially hazardous workplace practices or equipment were com- mon. Forty-one percent of respondents who reported taking X-rays did not wear film badges, and 76% reported physically restraining animals for X-ray procedures. Twenty- seven percent of the respondents exposed to anesthetic gases worked at facilities which did not have waste anesthetic gas scavenging systems. Women who worked as veteri- narians during a pregnancy attempted to reduce exposures to X-rays, insecticides, and other potentially hazardous exposures. Some potentially hazardous workplace exposures are common in veterinary practice, and measures to educate workers and to reduce these exposures should not await demonstration of adverse health effects. Key words: veterinarian workplace exposures, anesthetic gases, radiation, zoonosis, trauma, pes- ticides INTRODUCTION The potential for adverse health effects from occupational exposures in veter- inary practice has been recognized for many years. Clinical and epidemiologic studies have suggested that veterinarians are at increased risk for many occupational illnesses including site-specific cancers [Blair and Hayes, 1980, 1982; Fasal et al., 1966; Botts et al., 19661, fetal loss [Vaughan et al.. 1984; Johnson et al., 1987; Gold and Beran, 19831, acute pesticide-associated toxicity [Schuchman et al., 1975; Beat and Morgan, Division of Occupational and Environmental Medicine. and Northern California Occupational Health Center. University of California, Davis. Address reprint requests to Marc B. Schenker, M.D., M.P.H.. Division of Occupational and Environ- mental Medicine, University of California. Davi\. CA 95616. Accepted for publication January 19. 1989. 0 1989 Alan R. Liss. Inc.
Transcript
American Journal of Industrial Medicine 16: 55-66 (1989)
Prevalence of Hazardous Exposures in Veterinary Practice
Patricia Wiggins, MD, MPH, Marc B. Schenker, MD, MPH, Rochelle Green, MSPH, and Steven Sarnuels, PhD
All female graduates of a major U.S. veterinary school were surveyed by mailed questionnaire to obtain details of work practice and hazard exposure during the most recent year worked and during all pregnancies. Exposure questions were based on previously implicated occupational hazards which included anesthetic gases, radiation, zoonoses, prostaglandins, vaccines. physical trauma, and pesticides. The response rate was 86% (4621537). We found that practice type and pregnancy status were major determinants of hazard exposure within the veterinary profession. Small-animal practi- tioners reported the highest rates of exposure to anesthetic gas (94%), X-ray (90%), and pesticides (57%). Large-animal practitioners reported greater rates of trauma (64%) and potential exposure to prostaglandins (92%~), Brucella abortus vaccine (23%), and carbon monoxide ( 18%). Potentially hazardous workplace practices or equipment were com- mon. Forty-one percent of respondents who reported taking X-rays did not wear film badges, and 76% reported physically restraining animals for X-ray procedures. Twenty- seven percent of the respondents exposed to anesthetic gases worked at facilities which did not have waste anesthetic gas scavenging systems. Women who worked as veteri- narians during a pregnancy attempted to reduce exposures to X-rays, insecticides, and other potentially hazardous exposures. Some potentially hazardous workplace exposures are common in veterinary practice, and measures to educate workers and to reduce these exposures should not await demonstration of adverse health effects.
The potential for adverse health effects from occupational exposures in veter- inary practice has been recognized for many years. Clinical and epidemiologic studies have suggested that veterinarians are at increased risk for many occupational illnesses including site-specific cancers [Blair and Hayes, 1980, 1982; Fasal et a l . , 1966; Botts e t a l . , 19661, fetal loss [Vaughan et a l . . 1984; Johnson et al., 1987; Gold and Beran, 19831, acute pesticide-associated toxicity [Schuchman e t al., 1975; Beat and Morgan,
Division of Occupational and Environmental Medicine. and Northern California Occupational Health Center. University of California, Davis. Address reprint requests to Marc B . Schenker, M.D., M.P.H.. Division of Occupational and Environ- mental Medicine, University of California. Davi\. CA 95616. Accepted for publication January 19. 1989.
0 1989 Alan R. Liss. Inc.
56 Wiggins et al.
19771, zoonotic infections [Schnurrenberger et al., 1964, 1978a1, occupational dermatoses [Falk et al., 19851, and respiratory tract illnesses [Donham et al., 1977; Falk et al., 19851. Interest has focused on several potentially hazardous exposures including radiation [Jacobsen and Van Farowe, 19641, anesthetic gases [Short and Harvey, 1983; Manley and McDonell, 1980a; Wingfield et al., 1981; Manley et al., 19821, zoonoses [Constable and Harrington, 1982; Robinson and Metcalfe, 19761, pesticides, and trauma. Despite this interest and evidence for illnesses due to occupational exposures in veterinary practice, there have been few studies to assess the prevalence of these exposures.
As part of a study of reproductive outcomes among female graduates of a major U.S. veterinary school [Schenker et al., 19881, we collected data on current work practices and exposures to specific hazards. To identify high-risk groups within this profession, we explored practice type, temporal trends in work practice, and changes in work practice with pregnancy as predictive variables for hazard exposure.
MATERIALS AND METHODS
The study population consisted of all women who had graduated as of 1985 from the University of California, Davis, School of Veterinary Medicine. The list of female graduates was obtained through the Student Affairs Office at the university. Current addresses were obtained from the American Veterinary Medicine Association (AVMA) and the California State License Board. Address corrections were requested through the postal service for all mailings which were forwarded or returned. A self-administered questionnaire was mailed to each potential study subject and three follow-up mailings were sent to nonrespondents.
The questionnaire was used to obtain demographic information and details of work practice and hazard exposure for the most recent year worked in veterinary medicine. In the reproductive history section of the questionnaire, work practice and hazard exposure questions were repeated for correlation with each pregnancy out- come. Exposure questions were based on a list of previously implicated occupational hazards including anesthetic gases, radiation, zoonoses, prostaglandins, vaccines, carbon monoxide, physical trauma, and pesticides.
Anesthetic gas exposure was ascertained by asking if exposure had occurred on the job any time during the last year worked. If respondents answered “yes,” further exposure questions included the average number of hours per week, whether the workplace used scavenging equipment, and what type of breathing system was most commonly used when animals were anesthetized [Manley et al., 1982; Short and Harvey, 1983; Manley and McDonell, 1980a,b; Wingfield et al., 1981; Ward and Byland, 1982; Ruby et al., 19801. If the subjects indicated that they took X-rays of animals, further questions addressed the frequency of taking X-rays, use of X-ray badges, and frequency of restraining animals for X-ray.
Questionnaires were returned between October 1986 and September 1987. Responses were keypunched and entered into files on a VAX 1 1/750 for data analysis. Statistical Analysis System [SAS Institute, 19871 programs were used for frequency counts and univariate analysis. Chi-square tests were used when comparing propor- tions.
Of the 537 female veterinary school graduates surveyed, 462 (86%) returned a completed questionnaire. Of these women, 457 had worked as veterinarians and
Veterinary Practices-Hazardous Exposures 57
TABLE I. Comparison of Practice Type for Survey Respondents Vs. All U.S. Veterinarians Listed in AVMA Economic Statistics for 1986
All AVMA Female AVMA listed veterinarians" listed veterinarians" Survey respondents
(n = 43,184) (n = 6,909) (n = 457) lo % %
Large-animal practice Mixed large-animal predominate Mixed-animal 50-50 large and small Mixed small-animal predominate Small-animal practice College or university Government Industry and "Other"
9 I I 8
I 1 40 9 8 5
6 4 7
I I 52 12 3 5
6 2 3 7
62 14 2 3
'Active AVMA members and directory-verified nonmembers.
completed a work exposure history for the most recent year worked. For 98% of the women the exposure history described work practices in 1986 or 1987 while the remaining 2% reported exposures which occurred between 1982 and 1985.
Several attempts were made to contact a random sample of 20 nonrespondents. Of these 20 women, valid phone numbers could not be obtained for five (25%), a limited phone interview was conducted with 11 (55%), and four (20%) were contacted but refused to participate. For the sample of 20 nonrespondents, mean age and year of graduation did not differ from the averages found in the respondent group.
RESULTS
Of the 457 respondents who were practicing veterinarians, 76% were currently living in California. The geographic distribution using U.S. Census Geographic Regions was: West, 86%; North Central, 3%; Northeast, 4%; South, 5%; and foreign or unlisted location, 2%. The year of graduation from veterinary school ranged from 1953 to 1986, with a mean of 1979 (S.D. = 6.1 years). Current ages ranged from 25 to 65 with a mean of 35 (S.D. = 5.7 years).
Reported practice types for the 457 veterinarians were grouped into four major categories for purposes of analysis and discussion. Small-animal practice accounted for 74% of practitioners, large-animal practice 9%, teaching and research 13%, and other practice types 4%. Respondents who reported 50-50 mixed practice (50% large animal-50% small animal) were included in the small-animal category after prelim- inary analysis revealed that the prevalence of exposures in this group closely resembled that reported by small-animal practitioners.
The distribution of practice type for our female respondents was compared with the distribution in the 1986 statistics of the AVMA for all male and female members and directory-verified nonmembers [AVMA, 19871. For this comparison we used private practice and public job subgroups, the format used by the AVMA for reporting of economic statistics (Table I). With the AVMA groupings, the distribution of practice type among respondents to our survey differed from all U.S. veterinarians, with fewer of the survey participants in large- or predominantly large-animal practice (8% vs. 20%), and a greater percentage of survey respondents in small-animal
58 Wiggins et al.
TABLE 11. Self-Reported Anesthetic Gas Exposure in Past Year by Practice Type for Female Veterinarians (n = 457)
Practice type (n)
Exposure to Small-animal Large-animal Teaching anesthetic practice practice research Other Totals
practice (62% vs. 40%) and in university-based practice (14% vs. 9%). Practice type among survey respondents was similar to that for all female AVMA members and directory-verified female non-members.
The mean number of reported hours worked per week for the 457 practitioners was 46 (S.D. = 15.1). The year of graduation from veterinary school correlated with the number of hours worked (p < .05), with more of the recent graduates (1981- 1986) working over 50 hours per week (33%) compared to those who graduated before 1969 (13%). Practice type was also associated with hours worked (p < .001), with more of the veterinarians in large-animal practice working over 50 hours per week (62%), as compared to veterinarians in small-animal practice (26%) and in teaching and research (42%).
During pregnancy the number of hours worked per week, averaged over three trimesters, was 34 hours. The trend during pregnancy was a gradual reduction in hours worked from 36 hours per week in the first trimester to 30 hours per week in the third trimester. The distribution of practice type reported during pregnancy did not differ from the distribution reported by all women for the last year worked.
Workplace Exposures
Exposure to anesthetic gas (Table 11) was reported by 83% of the 457 veteri- narians surveyed. Of those reporting exposure, 43% spent less than five hours per week, 25% spent five-nine hours per week, and 32% spent 10 or more hours per week in the operating suite and recovery-room area. For hospitals and clinics that employed veterinarians who were exposed to anesthetic gas, 27% did not use waste anesthetic gas (WAG) scavenging to decrease ambient exposure. The type of anes- thetic breathing systems used most frequently by the veterinarians surveyed were “circle systems” (56%), “partial rebreather” ( 19%), and “nonrebreathing” systems (16%). Eight percent of practitioners reported that they routinely used more than one type of breathing system.
Anesthetic gas exposure was most prevalent in small-animal practice (94%) as compared to large-animal practice (54%), teaching and research (50%), and other categories (65%). Use of WAG scavenging showed no trend with year of graduation from veterinary school and did not correlate with the type of veterinary practice.
Eighty-two percent (n = 375) of the 457 veterinarians surveyed reported poten-
Veterinary Practices-Hazardous Exposures 59
TABLE I l l . Self-Reported X-Ray Exposure in Past Year by Practice Type for Female Veterinarians (n = 457)
Exposure to X-ray
Exposed Do not use
Restrain
X-rays
film badge
> llmonth
per week < 5 5 -9 > 10
Small-animal Large-animal practice practice (339) (39)
304(90%) 30(77%)
I12(37%) 19(63%)
253(83%) I5(50%)
172(57%) 14(47%2) 65(21%) 9(30%) 67(22%) 7(23%)
Teaching research
(62)
30(48%)
16(53%)
I1(37%)
21(70%) 2(7%)
7(23%)
6(56%)
8(73%) 1(9%)
2( 18%)
Total (457)
375( 82%)
153(41%)
286(76%)
215(57%) 77(21%) 83(22%)
tial exposure to ionizing radiation (Table HI) . Of these practitioners, 57% took X-rays of animals fewer than five times per week, 21% took five to nine X-rays per week, and 22% took ten or more X-rays per week. X-ray exposure was most prevalent in small-animal practice (90%) as compared to large-animal practice (77%), teaching and research (48%), and other categories (65%).
Of the 375 veterinarians who reported taking X-rays, 41% did not wear film badges. Approximately 70% of the 222 practitioners who wore film badges knew the results of their film badge readings. No one reported exposures in excess of 120 mrems (0.12 rem) per month. Year of graduation did not correlate with film badge use. Practice type, however, was predictive with large-animal practitioners being the least likely to wear film badges (pC.05).
In our survey, 76% of practitioners reported that they restrained animals during X-ray procedures at least one to four times per month. Of these practitioners who frequently restrained animals during X-ray procedures, 67% reported that they did not wear film badges. Year of graduation was not predictive for restraining of animals for X-ray. Practice type was predictive (p< .OOl), with small-animal practitioners report- ing this activity most frequently.
Pesticide use (Table IV) on at least a weekly basis was reported by 52% of veterinarians. Of the respondents who reported weekly pesticide use, the most commonly used pesticides were the pyrethrins (49%) and the carbamates (36%). The prevalence of pesticide use on at least a weekly basis was highest for small-animal (60%) and large-animal (46%) practice and less frequent for teaching and research (24%) and other categories (18%).
Questions regarding zoonotic infections acquired by the practitioner during the last year worked were misinterpreted by a large number of respondents. Some respondents listed diseases treated during the last year while others listed zoonotic diseases which they personally contracted. Because of this misinterpretation the actual frequencies for zoonotic exposures or disease are not reported. Zoonoses that the veterinarians reported they were exposed to during the last year worked included toxocariasis, psittacosis, toxoplasmosis, rabies, brucellosis, leptospirosis, listeriosis, avian tuberculosis, echinococcosis, and equine encephalitis. No respondents reported
60 Wiggins et al.
TABLE IV. Miscellaneous Exposures During the Past Year by Practice Type for Female Veterinarians (n = 457)
Practice type (n)
Small-animal Large-animal Teaching Occupational practice practice research Other
glandins 60( 18%) 36(92%) I I ( 18%) 1(6%) N e c r o p s y 304(90%) 35(90%) 38(61%) 10(59%) All trauma 108(32%) 25(64%) 16( 26%) 6(35%) Carbon
monoxide 4( 1 %) 7( 18%) 6(10%) 0
Total (457) 239
222(49%) 164(36%)
9(2%)
29(6%)
13(3%)
108(24%) 387(85%) I55(34%)
17(4%)
aReported weekly use of pesticide.
treating Q fever, tularemia, or plague. The most commonly reported zoonotic diseases in the veterinarians were cat scratch fever, ringworm, and salmonella.
The injuries reported most frequently by our respondents were “animal bites” (17%), “struck by animal” (6%), and “scratches and minor lacerations” (3%). The year of graduation was not associated with reporting of trauma. Practice type was predictive (p< .OO 1) with large-animal practitioners reporting the most injuries.
Other exposures for which data were collected included necropsy, carbon monoxide, rabies vaccine, Brucella abortus vaccine, and prostaglandins (Table IV). Of the 457 practicing veterinarians, 85% indicated that they had performed necropsies during the past year while 36% indicated that they did two or more per month. Carbon monoxide exposure was reported by only 4% of the veterinarians surveyed.
Responses to questions on vaccine or biological exposures revealed that 6% of practitioners had accidental exposure to rabies vaccine and 3% had accidental exposure to Brucella abortus vaccine. Use of prostaglandins was reported by 24% of the veterinarians surveyed. For carbon monoxide exposure, accidental exposure to rabies or Brucella aborrus vaccine, and prostaglandin use, the prevalence of exposure was highest for large-animal practitioners (Table IV).
Exposures During Pregnancy
Exposure during pregnancy was analyzed separately for women who had worked as veterinarians during a pregnancy (n = 226). Temporal trends reflecting changes in work practices between 1962 and 1987 as well as modification of work practices during pregnancy were noted (Table V). The prevalence of anesthetic gas exposure during pregnancy increased from 66% in the 1960s to 79% in the 1980s. However, for the animal clinics or hospitals that employed these women, the number
Veterinary Practices-Hazardous Exposures 61
TABLE V. Temporal Trends in Hazard Exposure for Female Veterinarians During Pregnancy and for the Last Year Worked
Exposures reported by veterinarians All vets with pregnancies last year worked
Anesthetic gas 2 l(66%) 40( 74%) I l0(79%) 381(83%) No WAG scavenging 18(86%) 20(50%) 29(26%) 104(27%)
X-ray 26(8 I %) 34(63%) 65(46%) 375(82%) No film badge 14(54%) 22(65%) 38(58%) 153(41%) Restrainedh 19(73%) 17(50%) I9( 29%) 286(76%)
Insecticide use on weekly basis 8(25%) 15(28%) 45(32%) 239(52%)
Prostaglandins 3(9%) 4(7%) 7(5%) 108(24%)
”Last year worked was 1986 or 1987 for 98% of survey respondents. bRestrained animals for X-ray llmonth or more.
that did not use waste anesthetic gas scavenging declined from 86% in the 1960s to 26% in the 1980s.
The potential for exposure to X-ray during pregnancy was reported by 81% of the women who were pregnant in the 1960s. This decreased to 63% in the 1970s and 46% in the 1980s. More than half of the women who took X-rays of animals during pregnancy did not wear film badges, a trend which did not change over the time interval studied. For pregnant women the practice of restraining animals for X-ray declined over time from 73% in the 1960s to 29% in the 1980s.
For pesticide and prostaglandin use during pregnancy, the prevalence of expo- sure did not appear to change over time. However, exposures reported during pregnancy were significantly lower than exposures reported for the last year worked, suggesting that many women avoided these exposures during pregnancy (Table V) .
DISCUSSION
We have completed a survey of current work practices and potential for hazard exposure in veterinary medicine. For individual clinicians, practice type was a major determinant of the prevalence of hazard exposure. Small-animal practitioners re- ported the highest rates of exposure to anesthetic gas (94%), X-ray (90%), and pesticides (57%). Large-animal practitioners reported greater rates of trauma (64%) and potential for exposure to prostaglandins (92%), Brucella abortus vaccine (23%), and carbon monoxide (18%).
Exposure data reported for pregnancies that occurred while working as veteri- narians reflected temporal changes in work practices (Table V). From 1960 to 1987, there was a marked increase in the use of WAG scavenging units. Over this same time period the number of pregnant women who reported that they took X-rays of animals decreased, as did the practice of restraining animals for X-ray. Comparison of exposures reported for the most recent pregnancies ( 1980-1987) with those reported for the last year worked suggests that this reduction in radiation exposure is specific for pregnancy and does not reflect exposure prevalence for women who are not currently pregnant. This differs from the increased use of WAG scavenging units
62 Wiggins et al.
which appears to be independent of pregnancy status. Although there is a potential for bias in the reporting of exposures which occurred as long as 25 years ago, these observations of general trends are felt to be valid.
In assessing the generalizability of our results, the limitation of studying only female veterinarians was recognized. Comparison of practice type among respondents to our survey with all U.S. veterinarians [AVMA, 19871 showed that a slightly higher proportion of practitioners in our survey were in small-animal practice. This is consistent with the AVMA differences in practice type between men and women. Demographic and life-history variables have also been shown to affect practice type choice [Snizek and Bryant, 19761. Veterinarians participating in this study were predominantly from California and the western United States. Regional differences in livestock production as well as increased opportunity for small-animal practice in urban areas may affect the distribution of practice type in a given geographic location. While we cannot directly compare work practices of male vs. female veterinarians, it is unlikely that potential exposures within practice types would vary substantially by sex.
Animal-health technicians, pet-store owners, and animal handlers represent another large population with many of the same occupational exposures as veterinar- ians. Although we were not able to directly compare exposures among veterinarians studied in our survey to those of animal-health technicians or other animal handlers, based on our current study we would expect exposure prevalences in these groups to vary according to practice type and geographic location. Other factors such as the subspecialization of animal-health technicians into anesthesiology or X-ray technol- ogy would also affect personal exposure parameters and may result in substantially increased exposures.
Anesthetic agents used in veterinary practice include nitrous oxide, halothane, methoxyflurane, and enflurane. Individual practitioner preference and prior experi- ence with specific agents will largely determine which of these agents are used in a particular veterinary practice. Occupational exposure to low levels of anesthetic gas has been associated with a wide range of adverse health effects including decreased hepatic and renal function, central nervous system effects of headache, irritability, impaired cognitive function, and adverse reproductive outcomes [Short and Harvey, 1983; Manley and McDonell, 1980a; Vessey, 1978; Gold and Beran, 1983; Infante and Tsongas, 19851. In our survey, one-third of the practitioners reported that they spent 10 or more hours per week in areas where anesthetic gases were being used. In addition, specific questions regarding environmental controls for WAG revealed that one-third of practices did not use WAG scavenging. Surveys of anesthetic gas use in veterinary practice have shown that effective WAG scavenging, adequate room ventilation, and attention to proper use and maintenance of equipment can signifi- cantly reduce the risk of exposure to waste anesthetic gas in the operating suite [Manley and McDonell, 1980b; Short and Harvey, 1983; Wingfield et al., 1981; Ward and Byland, 1982; Ruby et al., 1980; Manley et al., 1982; Whitcher et al., 19711.
Ionizing radiation is a known carcinogen at high exposures and has been associated with cancer and possibly increased rates of spontaneous abortion and congenital anomaly at lower levels of occupational exposure [Brent, 1983; Gold and Beran, 1983; Mettler and Moseley, 1985; NCRP, 19871. The potential for exposure to ionizing radiation was reported by 82% of the veterinarians surveyed. Approxi-
Veterinary Practices-Hazardous Exposures 63
mately 20% of these practitioners took ten or more X-rays per week. A survey of work practices associated with X-ray revealed that a large proportion of practitioners did not wear film badges and that the practice of restraining animals for X-rays was relatively common. Although the use of lead aprons protects some radiation-sensitive organs, exposure to the lens of the eye, the thyroid, and skin is not prevented. While standards and regulation of radiographic equipment have improved greatly since the 1960s, work practices continue to be an important determinant of personal exposure to ionizing radiation. [Jacobson and Van Farowe, 1964; NCRP, 1970; Schuchman et al., 19751.
Pesticide exposure in veterinary practice occurs primarily through cutaneous exposure to pet grooming products such as flea dips and insect-repellant wipes. Secondary routes of exposure include inhalation of products such as insect fumigants sprayed in animal confinement areas. We found that half of the veterinarians surveyed were exposed to pesticides on at least a weekly basis. Pyrethrins and carbamates, both of which are readily absorbed through the skin, were the two most commonly used agents.
While pyrethrins have been associated with cutaneous and respiratory allergic reaction, their systemic mammalian toxicity is relatively low. Carbamate and organo- phosphate pesticides are associated with acute central nervous system effects, and cases of organophosphate toxicity have been documented among veterinary hospital and animal health care workers [California Department of Food and Agriculture, 1986; Centers for Disease Control, 1985, 19881. Monitoring of serum cholinesterase levels should be considered for practitioners exposed to organophosphate and car- bamate pesticides. However, as pesticide toxicity from these pesticides may occur without depression of cholinesterase levels, institution of proper pesticide handling procedures should not be dependent on results of cholinesterase monitoring.
Because many practitioners interpreted questions on zoonotic disease to include diseases treated in animal patients as well as those acquired by the practitioner, we cannot comment on the overall prevalence of infectious disease in our study. However, the observation that dermatomycosis and salmonellosis were the most frequently reported zoonotic infections is consistent with prior studies of zoonotic disease among veterinarians. These disorders are clearly work related and should be considered in preventive hygiene programs and treatment of veterinarians [Constable and Harrington, 1982; Robinson and Metcalfe, 1976; Elliot et al., 19851.
Studies of veterinarians that have included serologic testing for zoonotic disease have shown a relatively low prevalence of positive titers for toxoplasma gondii, leptospirosis, psittacosis, and Q-fever [Schnurrenberger et al., 1964, 1975, 1978a,b; Robinson and Metcalfe, 19761. For preemployment and periodic health screening, the low prevalence of zoonotic infections would indicate that freezing of baseline sera for future reference is probably an adequate precaution for most practitioners. Other recommendations should include preexposure immunization for rabies and tetanus and prompt treatment of animal bite wounds [Anderson et al., 1984; Bernard et al., 1987; Centers for Disease Control, 1984; Martin et al., 19821. Veterinarians who work with exotic animals or primate colonies may require a more active infectious disease surveillance program, including screening for tuberculosis.
Approximately 6% of veterinarians surveyed reported accidental exposure to animal vaccines. Manufacture of the live strain 19 Brucella vaccine ceased in 1979, eliminating the risk of human infection from this exposure [Constable and Har-
64 Wiggins et al.
rington, 19821. Likewise, there have been no reported cases of rabies in humans exposed to any of the licensed modified live virus vaccines marketed in the United States [Centers for Disease Control, 19841.
Use of prostaglandins was reported most frequently in our survey by large- animal practitioners. These drugs are primarily used for reproductive manipulation in cattle and other large animals. Prostaglandins are readily absorbed through the skin and may present a significant risk for causing spontaneous abortion or fetal death in pregnant women [Gold and Beran, 19831.
The potential for carbon monoxide exposure was reported relatively infre- quently by the veterinarians in this study. Carbon monoxide, which is produced by incomplete combustion of heating fuels in inadequately ventilated buildings, is just one of the health hazards associated with working in animal confinement units [Donham et al., 19771. The low prevalence of exposure in our survey may in part reflect underreporting of carbon monoxide exposure but may also be due to geo- graphic differences in large-animal practice and to the use of animal confinement units.
Our study addressed the prevalence of hazardous exposures in veterinary medicine and showed that considerable variability of exposure exists within the profession. Exposure classification is an important issue in occupational studies where the relationship between hazardous workplace exposures and adverse health outcomes may be obscured by heterogeneity of exposure within a cohort. While we did not have the resources to measure actual exposure levels, our data suggest several situations within veterinary practice where hazardous exposure may occur. Many of these exposures occur to women of childbearing age, a population with unique additional occupational health considerations. Measures to reduce potentially hazard- ous workplace exposures should be a primary goal and should not await demonstra- tion of adverse health effects before they are instituted.
ACKNOWLEDGMENTS
The authors wish to thank Drs. Calvin Schwabe and Susan Manley Hildebrand for their assistance, R e d Marker for secretarial help, and Rebecca Momson for editorial comments. This work was supported by grant #I591 from the March of Dimes.
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