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

Objective-To determine the extent of leptospirosis in persons exposed to in fected swine, confirm the source of disease, define risk factors for infect ion, and identify means for preventing additional infections during an outb reak 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 inv estigation included review of health of the pigs, a cross-sectional study o f 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 investiga tion indicated that 59% of the pigs had titers to leptospires, denoting exp osure. Of the 240 people in the exposed study population, 163 (68%) were in terviewed, and of these, 110 (67%) submitted a blood sample. Nine (8%) case s of leptospirosis were confirmed by serologic testing. Risk factors associ ated with leptospirosis included smoking (odds ratio [OR], 14.4; 95% confid ence interval [Cl],1.39 to 137.74) and drinking beverages (OR, 5.1; 95% Cl, 1.04 to 24.30) while working with infected pigs. Washing hands after work was protective (OR, 0.2; 95% Cl, 0.03 to 0.81). Conclusions and Clinical Relevance-Leptospirosis is a risk for swine produc ers and slaughterhouse workers, and may be prevented through appropriate hy giene, 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.