Cryptosporidium parvum in Korea: prevalence in individuals residing in three major river valleys and genetic characteristics of the isolates.

Cryptosporidiosis is a diarrheal illness caused by apicomplexa parasite Cryptosporidium spp. In this study, to examine the overall infection status of Cryptosporidium spp. in individuals residing in southern parts of Korea, eight counties around Yeongsan, Seomjin and Nakdong River valleys was surveyed. The investigation was carried out from April to October 2005. A total of 9,498 stool samples were collected from individuals. Stool samples were analyzed for modified acid-fast stains, and DNA fragment extracted from positive samples was identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for 18S rRNA polymorphic region. Oocysts of Cryptosporidium spp. were detected in 239 specimens (2.5%) by a modified acid-fast stain. Infection rate was not significantly different between male (2.2%) and female (2.8%) individuals examined (P>0.05). In the infection rate by age, totally 1-9 (4.8%) and 80< (3.7%) age group were shown to the highest, and there was shown to significant differences (P<0.05). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of 18S rRNA gene from 51 isolates showed that all the isolates were identified as C. parvum. Our data collectively suggested that C. parvum infection is prevalent in the studied areas of Korea and more comprehensive nation-wide epidemiological studies are needed to elucidate the infection status of Cryptosporidium infection in Korea.