Brucellosis Seroprevalence Among Workers in High-Risk Professions Northwestern Wyoming, 2005 2006

1. Brucellosis Seroprevalence Among Workers in High-Risk Professions � Northwestern Wyoming, 2005�2006 Richard Luce, DVM, MA, MPhil Epidemic Intelligence Service Officer Wyoming Department of Health Centers for Disease Control and Prevention Good Morning. I will be discussing a brucellosis seroprevalence study conducted among workers in high-risk professions in northwestern Wyoming from 2005-2006.Good Morning. I will be discussing a brucellosis seroprevalence study conducted among workers in high-risk professions in northwestern Wyoming from 2005-2006.

2. Background February 2004, WY cattle lost certification as �Brucellosis-free� Adverse economic impact on state Establishment of Brucellosis Task Force Potential for adverse impact on public health Highest incidence of human Brucellosis in US occurs in WY (1.5 cases/100,000) In February 2004 Wyoming lost its certification as a Brucellosis-free state after Brucella was detected in a second cattle herd within the state. This development had a substantial adverse economic impact upon an important industry in the Wyoming due to restrictions imposed on inter-state shipment of cattle. The State Governor established a Brucellosis Task Force to address not only economic issues but also the potential for an adverse impact on public health. Additionally, the highest incidence of human brucellosis occurs in Wyoming with 1.5 cases reported per 100,000 population.In February 2004 Wyoming lost its certification as a Brucellosis-free state after Brucella was detected in a second cattle herd within the state. This development had a substantial adverse economic impact upon an important industry in the Wyoming due to restrictions imposed on inter-state shipment of cattle. The State Governor established a Brucellosis Task Force to address not only economic issues but also the potential for an adverse impact on public health. Additionally, the highest incidence of human brucellosis occurs in Wyoming with 1.5 cases reported per 100,000 population.

3. Brucella sp. Small Gram-negative coccobacilli Category B agent of bioterrorism Low infectious dose Animal reservoir Humans infected by contact with infected animals or contaminated animal products Brucella are small gram-negative coccobacilli and are considered a category B agent of bioterrorism. The infectious dose can be as low as 10 organisms. Brucella are passed among various animals which serve as a disease reservoir. Humans are usually infected by contact with infected animals or animal products contaminated with the bacteria.Brucella are small gram-negative coccobacilli and are considered a category B agent of bioterrorism. The infectious dose can be as low as 10 organisms. Brucella are passed among various animals which serve as a disease reservoir. Humans are usually infected by contact with infected animals or animal products contaminated with the bacteria.

4. Brucellosis in Humans Symptoms � fever, night sweats, malaise, chills, headache Complications Pneumonia Hepatitis Endocarditis Death <5% of untreated patients Approximately 100 cases per year in US Symptoms of brucellosis in humans are usually nonspecific and include: fever, night sweats, malaise, chills, and headache. Complications such as pneumonia, hepatitis or endocarditis can occur. Death is rare and occurs in <5% of untreated patients. Brucellosis is rare in the United States, with approximately 100 reported human cases per year.Symptoms of brucellosis in humans are usually nonspecific and include: fever, night sweats, malaise, chills, and headache. Complications such as pneumonia, hepatitis or endocarditis can occur. Death is rare and occurs in <5% of untreated patients. Brucellosis is rare in the United States, with approximately 100 reported human cases per year.

5. Objectives Determine Brucellosis seroprevalence in high-risk professions Identify sources and risk factors for infection Implement control measures Our objectives in this investigation were to determine the Brucellosis seroprevalence among a defined group of individuals working in professions thought to be at a higher-risk for exposure in those areas of the state where brucellosis had been identified in animals. Additionally, we wanted to identify potential sources of infection and to implement appropriate control measures if necessary.Our objectives in this investigation were to determine the Brucellosis seroprevalence among a defined group of individuals working in professions thought to be at a higher-risk for exposure in those areas of the state where brucellosis had been identified in animals. Additionally, we wanted to identify potential sources of infection and to implement appropriate control measures if necessary.

6. Recruitment of Study Subjects To announce study letters sent to members of professional organizations Radio and newspaper ads Participants interviewed at County Public Health Nursing Offices Participation in the study was solicited through letters sent to members of targeted professional organizations. Radio and newspaper ads in local markets were also used to announce the study. Participants were then enrolled at county public health nursing offices in the northwestern portion of Wyoming.Participation in the study was solicited through letters sent to members of targeted professional organizations. Radio and newspaper ads in local markets were also used to announce the study. Participants were then enrolled at county public health nursing offices in the northwestern portion of Wyoming.

7. Inclusion Criteria Veterinarians Hunting guides/ Outfitters Ranchers Game processors State Game and Fish Dept. National Park Service State Veterinary Lab History of hunting elk In order to be eligible to participate in the study, individuals were required to be a member of a defined group of professions. These included: veterinarians, hunting guides or outfitters, ranchers, game processors, State Game and Fish Department workers, National Park Service employees and State veterinary lab employees. Also, individuals who had a history of hunting elk were also deemed eligible. Individuals could list more than one profession. Participants were asked to complete a questionnaire and provide a blood sample for serological testing.In order to be eligible to participate in the study, individuals were required to be a member of a defined group of professions. These included: veterinarians, hunting guides or outfitters, ranchers, game processors, State Game and Fish Department workers, National Park Service employees and State veterinary lab employees. Also, individuals who had a history of hunting elk were also deemed eligible. Individuals could list more than one profession. Participants were asked to complete a questionnaire and provide a blood sample for serological testing.

8. A total of 223 participants completed the study questionnaire and provided a blood sample. 12 of these were excluded since they did not meet the professional inclusion criteria, leaving 221 which comprised the study population. Participants ranged in age from 18 to 86 years with a median age of 53 years. 74% were male. A total of 223 participants completed the study questionnaire and provided a blood sample. 12 of these were excluded since they did not meet the professional inclusion criteria, leaving 221 which comprised the study population. Participants ranged in age from 18 to 86 years with a median age of 53 years. 74% were male.

9. Study Participants Professional groups with the greatest numbers of individuals who had anti-brucella antibodies included veterinarians [click] where 13 of 50 or 26% of participants had detectable anti-brucella antibodies. National Park Service workers [click] and those included solely due to a history of elk hunting [click] had seroprevalence rates of 50% and 25% respectively, however there were only 8 study participants in each of these groups.Professional groups with the greatest numbers of individuals who had anti-brucella antibodies included veterinarians [click] where 13 of 50 or 26% of participants had detectable anti-brucella antibodies. National Park Service workers [click] and those included solely due to a history of elk hunting [click] had seroprevalence rates of 50% and 25% respectively, however there were only 8 study participants in each of these groups.

10. Antibody Titer Results This table shows the titer at which measurable antibody was detected for all positive samples. Positive titers at dilutions greater than 1:160 were considered consistent with active infection. Those between 1:20 and 1:80 were considered consistent with previous infection. Those less than 1:20 were considered negative. Among all samples 16 (52%) were at the lowest dilution indicating a lower level of circulating antibody. Only 1 individual [click] had a titer consistent with active infection, however the subject reported no clinical symptoms consistent with active infection.This table shows the titer at which measurable antibody was detected for all positive samples. Positive titers at dilutions greater than 1:160 were considered consistent with active infection. Those between 1:20 and 1:80 were considered consistent with previous infection. Those less than 1:20 were considered negative. Among all samples 16 (52%) were at the lowest dilution indicating a lower level of circulating antibody. Only 1 individual [click] had a titer consistent with active infection, however the subject reported no clinical symptoms consistent with active infection.

11. The study identified National Park Service workers and veterinarians as having a statistically significant risk for the presence of a measurable anti-brucella titer. National Park Service workers had a prevalence odds ratio of 6.1 and veterinarians 2.5. However, only 8 National Park Service workers participated in the study so this association may not be representative of all National Park Service workers. Other professional categories did not have a significant association with measurable anti-brucella titers.The study identified National Park Service workers and veterinarians as having a statistically significant risk for the presence of a measurable anti-brucella titer. National Park Service workers had a prevalence odds ratio of 6.1 and veterinarians 2.5. However, only 8 National Park Service workers participated in the study so this association may not be representative of all National Park Service workers. Other professional categories did not have a significant association with measurable anti-brucella titers.

12. Because the previously licensed S19 animal brucella vaccine is a potential source of human infection and results in antibody production subsequently detected by the assay used in this study, we examined S19 vaccine use as a risk factor for seropositivity. Among all participants, the use of the S19 animal vaccine was significantly associated with an increased prevalence odds ratio of 1.7. It is important to note that this vaccine was phased out beginning in 1996. This may account for the low titers observed among the seropositive subjects in our study. Other potential risk factors for seropositivity including consumption of unpasteurized milk or milk products, handling infected animal tissues, and international travel were not associated with detection of a measurable titer.Because the previously licensed S19 animal brucella vaccine is a potential source of human infection and results in antibody production subsequently detected by the assay used in this study, we examined S19 vaccine use as a risk factor for seropositivity. Among all participants, the use of the S19 animal vaccine was significantly associated with an increased prevalence odds ratio of 1.7. It is important to note that this vaccine was phased out beginning in 1996. This may account for the low titers observed among the seropositive subjects in our study. Other potential risk factors for seropositivity including consumption of unpasteurized milk or milk products, handling infected animal tissues, and international travel were not associated with detection of a measurable titer.

13. We further examined the use of the S19 animal vaccine solely among veterinarians. The use of the this vaccine was associated with an increased prevalence odds ratio of 4.1, however the association was not significant. The use of personal protective equipment when handling vaccine including gloves, eye protection, masks or coveralls was not associated with the absence of anti-brucella antibodies.We further examined the use of the S19 animal vaccine solely among veterinarians. The use of the this vaccine was associated with an increased prevalence odds ratio of 4.1, however the association was not significant. The use of personal protective equipment when handling vaccine including gloves, eye protection, masks or coveralls was not associated with the absence of anti-brucella antibodies.

14. Limitations Assay cross-reactivity with antibody to other pathogens Yersinia Francisella Escherichia coli O157:H7 This study was subject to limitations associated with the microagglutination assay used to detect anti-brucella antibody. Specifically, cross-reactivity with antibody to Yersinia, Francisella, and E coli O157:H7 could result in a false positive test. However, these diseases are not common in Wyoming making cross reactivity an unlikely explanation for positive anti-brucella results.This study was subject to limitations associated with the microagglutination assay used to detect anti-brucella antibody. Specifically, cross-reactivity with antibody to Yersinia, Francisella, and E coli O157:H7 could result in a false positive test. However, these diseases are not common in Wyoming making cross reactivity an unlikely explanation for positive anti-brucella results.

15. Conclusions Active infection among high-risk professions is uncommon Veterinarians had significantly increased risk of a measurable anti-brucella titer Exposure likely due to previous handling of S19 animal vaccine Public health risk of brucellosis due to re-emergence of Brucella in Wyoming is low In conclusion, active infection with brucella among workers in high-risk professions in Northwestern Wyoming does not appear to be common. Veterinarians in this study had a significantly increased risk for the presence of measurable anti-brucella antibody. Their exposure was likely due to previous handling of S19 animal vaccine, although the specific mechanism of infection could not be identified. Based on the study results, the risk of infection to the general public due to the re-emergence of brucellosis in cattle and it�s continued circulation in wildlife at current prevalence levels appears to be low.In conclusion, active infection with brucella among workers in high-risk professions in Northwestern Wyoming does not appear to be common. Veterinarians in this study had a significantly increased risk for the presence of measurable anti-brucella antibody. Their exposure was likely due to previous handling of S19 animal vaccine, although the specific mechanism of infection could not be identified. Based on the study results, the risk of infection to the general public due to the re-emergence of brucellosis in cattle and it�s continued circulation in wildlife at current prevalence levels appears to be low.

16. Recommendations Examine high risk professions outside of Northwestern Wyoming for comparison Increase numbers necessary to more precisely estimate risk To strengthen and complement the findings in this study it would be beneficial to expand the study population within the state to include veterinarians and high-risk professions outside of Northwestern Wyoming for comparison. Increasing study numbers of those in high-risk professions would be necessary to more precisely estimate risk of infection. To strengthen and complement the findings in this study it would be beneficial to expand the study population within the state to include veterinarians and high-risk professions outside of Northwestern Wyoming for comparison. Increasing study numbers of those in high-risk professions would be necessary to more precisely estimate risk of infection.

17. Disclaimer The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention. [2-3 seconds][2-3 seconds]

18. Acknowledgments Wyoming Department of Health Tracy Murphy Clayton Van Houten Jamie Snow Joe Grandpre Lincoln, Teton, Park, Sublette County Public Health Nursing Offices Wyoming Veterinary Medical Association CDC Randolph Daley Diane Gross Thomas Clark Mary Ari Lazenia Harris I would like to recognize the individuals and organizations that assisted with this study. Thank you.I would like to recognize the individuals and organizations that assisted with this study. Thank you.