[Epidemiology of leptospirosis in a livestock production area of the Andes].

A cross-sectional study was conducted to estimate the prevalence of Leptospira infection in populations of workers, cattle, and pigs in livestock operations and to explore some environmental and production system variables associated with seropositivity. The research was done between November 1997 and February 1998 in the municipality of Don Matías, in the northern part of the department of Antioquia, Colombia. The area has a cold climate, and there is a "pigs-grasses-milk" production system that utilizes pig dung to fertilize grazing pastures. A total of 23 farms were studied, and blood samples were obtained from 67 dairy and pig-raising workers, 174 dairy cows, 68 pigs for fattening, and 214 pigs for breeding. The microagglutination test (MAT) was used for six Leptospira serotypes. The seropositivity prevalence was 22.4% among the workers (95% confidence interval: 13.1% to 34.2%), 60.9% among the dairy cows (95% CI: 53.2% to 68.2%), 10.3% in the fattening pigs, and 25.7% in the breeding pigs. Four logistic regression models were constructed to identify the variables that predicted infection in the workers and in the dairy cows. A high prevalence of infection with Leptospira (serotypes pomona, bratislava, and hardjo) was found in this production system, where conditions are favorable for transmitting this microorganism to the different animal species and to humans.