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Analysis of the 1998 outbreak of leptospirosis in Missouri in humans exposed to infected swine

Enzo R. Campagnolo DVM, MPH1, Marion C. Warwick MD, MPH2, Harvey L. Marx Jr3, Ross P. Cowart DVM, MS4, H. Denny Donnell Jr MD, MPH5, Mary D. Bajani PhD6, Sandra L. Bragg PhD7, J. Emilio Esteban DVM, MPVM, MBA, PhD8, David P. Alt DVM, PhD9, Jordan W. Tappero MD, MPH10, Carole A. Bolin DVM, PhD11, and David A. Ashford DVM, MPH, DSc12
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  • 1 Centers for Disease Control and Prevention, Epidemiology Program Office, Epidemic Intelligence Service, Atlanta, GA 30333.
  • | 2 Department of Health, Section of Communicable Disease Control and Veterinary Public Health.
  • | 3 Department of Health, Section of Communicable Disease Control and Veterinary Public Health.
  • | 4 Department of Food Animal Medicine, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211.
  • | 5 Office of Epidemiology, Jefferson City, MO 65102-0570.
  • | 6 National Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases, Meningitis and Special Pathogens Branch, Atlanta, GA 30333.
  • | 7 National Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases, Meningitis and Special Pathogens Branch, Atlanta, GA 30333.
  • | 8 The National Center for Environmental Health, Division of Environmental Hazards and Health Effects, Health Studies Branch, Atlanta, GA 30341-3274.
  • | 9 United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Zoonotic Diseases Research Unit, Ames, IA 50010.
  • | 10 National Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases, Meningitis and Special Pathogens Branch, Atlanta, GA 30333.
  • | 11 United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Zoonotic Diseases Research Unit, Ames, IA 50010.
  • | 12 National Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases, Meningitis and Special Pathogens Branch, Atlanta, GA 30333.

Abstract

Objective—To determine the extent of leptospirosis in persons exposed to infected swine, confirm the source of disease, define risk factors for infection, and identify means for preventing additional infections during an outbreak in Missouri in 1998.

Design—Cross-sectional study.

Sample Population—240 people and 1,700 pigs.

Procedure—An epidemiologic investigation was conducted of people exposed to infected pigs from the University of Missouri-Columbia swine herd. The investigation included review of health of the pigs, a crosssectional study of the people handling the pigs, serologic testing of human and porcine sera, and risk-factor analysis for leptospirosis within the human population.

Results—Serologic testing of samples collected at the time of the investigation indicated that 59% of the pigs had titers to leptospires, denoting exposure. Of the 240 people in the exposed study population, 163 (68%) were interviewed, and of these, 110 (67%) submitted a blood sample. Nine (8%) cases of leptospirosis were confirmed by serologic testing. Risk factors associated with leptospirosis included smoking (odds ratio [OR], 14.4; 95% confidence interval [CI],1.39 to 137.74) and drinking beverages (OR, 5.1; 95% CI, 1.04 to 24.30) while working with infected pigs. Washing hands after work was protective (OR, 0.2; 95% CI, 0.03 to 0.81).

Conclusions and Clinical Relevance—Leptospirosis is a risk for swine producers and slaughterhouse workers, and may be prevented through appropriate hygiene, sanitation, and animal husbandry. It is essential to educate people working with animals or animal tissues about measures for reducing the risk of exposure to zoonotic pathogens. (J Am Vet Med Assoc 2000;216:676–682)

Abstract

Objective—To determine the extent of leptospirosis in persons exposed to infected swine, confirm the source of disease, define risk factors for infection, and identify means for preventing additional infections during an outbreak in Missouri in 1998.

Design—Cross-sectional study.

Sample Population—240 people and 1,700 pigs.

Procedure—An epidemiologic investigation was conducted of people exposed to infected pigs from the University of Missouri-Columbia swine herd. The investigation included review of health of the pigs, a crosssectional study of the people handling the pigs, serologic testing of human and porcine sera, and risk-factor analysis for leptospirosis within the human population.

Results—Serologic testing of samples collected at the time of the investigation indicated that 59% of the pigs had titers to leptospires, denoting exposure. Of the 240 people in the exposed study population, 163 (68%) were interviewed, and of these, 110 (67%) submitted a blood sample. Nine (8%) cases of leptospirosis were confirmed by serologic testing. Risk factors associated with leptospirosis included smoking (odds ratio [OR], 14.4; 95% confidence interval [CI],1.39 to 137.74) and drinking beverages (OR, 5.1; 95% CI, 1.04 to 24.30) while working with infected pigs. Washing hands after work was protective (OR, 0.2; 95% CI, 0.03 to 0.81).

Conclusions and Clinical Relevance—Leptospirosis is a risk for swine producers and slaughterhouse workers, and may be prevented through appropriate hygiene, sanitation, and animal husbandry. It is essential to educate people working with animals or animal tissues about measures for reducing the risk of exposure to zoonotic pathogens. (J Am Vet Med Assoc 2000;216:676–682)