Human sparganosis in Thailand: an overview

Abstract

Human sparganosis is caused by cestode larvae (spargana) of the genus Spirometra, which exploit copepods as the first intermediate host. A wide range of amphibians, reptiles, birds, and mammals serve as second intermediate/paratenic hosts. Human infections occur mainly by ingesting raw intermediate/paratenic hosts. Cases are found mainly in China, Japan and Korea, and sporadically also in Thailand and other Asian countries. In the period 1943-2010, there were 52 reported cases of sparganosis in Thailand. The average patient age was 32 years (range 11-82 years). From the available patient information, the prevalence of sparganosis infection was higher among females than males, at a ratio of F:M=2:1 (27:15). Patients have mainly been found in the northeast, north, and central regions of Thailand, with only a few in the south. Although a single subcutaneous nodular lesion was the most common feature, about one third of patients had ocular lesions. In particular, patients having ocular lesions were about half of total cases reported pre-1990, with several confirmed cases' applying fresh frog muscle as a poultice to relieve sore eyes, according to traditional medicine. In Thailand, sparganosis is not merely a food-borne disease but is also caused by the traditional belief of applying frog muscles (contaminated with sparganum) to sore eyes.