RESUMEN
Leptospirosis is a major pig-associated zoonosis worldwide. There are also human occupational disease exposure risks. For better public health and sanitation, the prevalence of this disease was investigated. Four hundred sera were obtained from sows in central Thailand during August 2004 to January 2005 and examined with 20 reference leptospira serovars by a microscopic agglutination test (MAT). The results showed that 10% of samples gave a positive reaction. The most prevalent serovar was grippotyphosa which accounted for 55% of all positive cases. Other minor serovars were canicola and a non-pathogenic strain (patoc). It follows that, the sow may be one of the disease transmitting sources for humans in this area. The disease correlation between pigs, humans and the environments should be evaluated.