Epidemic leg ulcers in Thailand.

In 1981, two outbreaks of chronic leg ulcers occurred in central Thailand and affected thousands of persons. The lesions were characterized by granulomatous bases with erythematous edges and purulent slough. They were about 1 cm in diameter with irregular shapes. The ulcers lasted two weeks to one month. Ninety percent of the lesions were found on the lower extremities. The outbreak in Nakorn Pathom province occurred in fruit yards. Most of patients were gardeners and students. The outbreak in Ratchaburi province occurred on a sugar cane plantation. The age group of 5-19 years had the highest attack rate in all areas, and there was no significant difference between the attack rates in males and females. The peak incidence occurred in the rainy season with an abrupt decrease at the onset of the dry season. It is hypothesized that trauma precedes the occurrence of the leg ulcer and that a small fly may be a mechanical vector of the causative organism. The organism may be corynebacterium pyogenes, which is a pathogen of certain livestocks and is found in soil. Further studies are planned.