An epidemiological survey of Cryptosporidium parvum infection in randomly selected inhabitants of Seoul and Chollanam-do.

An epidemiological survey was performed to know the status of Cryptosporidium sp. infection among the people in Seoul and Chollanam-do in 1992. One village of Chollanam-do (Hwasun-gun) which showed the highest oocyst positive rate was re-surveyed in 1995 for human infection and for cattle also. The subjected areas consisted of 8 urban villages ( = dongs) of Seoul and 4 urban ( = dongs) and 7 rural ( = myons) villages of Chollanam-do. A total of 3,146 fecal samples was collected randomly, and smears were made from formalin-ether sediments. They were examined for Cryptosporidium oocysts by modified acid fast staining. The overall oocyst positive rate was 7.9% (248/3,146), but the rate was remarkably different between Seoul and Chollanam-do, 0.5% (4/853) and 10.6% (244/2,293), respectively. The average size of oocysts was 4.8 +/- 0.5 by 4.2 +/- 0.5 microns, compatible with C. parvum. In Chollanam-do, rural villages showed significantly higher rate (14.0%) than urban villages (3.7%). Especially the people in Iyang-myon. Hwasun-gun, a typical rural village, revealed a very high rate of 40.0% (74/185). Adults aged 51-70 years revealed the highest positive rate among all age groups. At the re-survey of the same village of Hwasun-gun in 1995, 44 (35.2%) of 125 villagers and 14 (93.3%) of 15 cattle examined were positive for C. parvum oocysts. The results suggest that C. parvum is highly prevalent in rural areas of Chollanam-do, and an important source or mode of infection seems to be contaminated water or contact with the feces of infected cattle.