Parasitologia

Review

Trends in parasitic diseases in the Republic of Korea
Eun-Hee Shin, Sang-Mee Guk, Hyo-Jin Kim, Soon-Hyung Lee and Jong-Yil Chai
Department of Parasitology and Tropical Medicine, Seoul National University College of Medicine, and Institute of Endemic Diseases, Seoul National University Medical Research Center, Seoul 110-799, South Korea

In the Republic of Korea, cases of zoonotic,opportunistic and imported parasitoses are being detected increasingly. Vivax malaria disappeared in the late 1970s but reemerged in 1993 and, currently, 1000–2000 cases occur annually. Brugian filariasis was endemic on offshore islands until 1990 but has now been eradicated. Soiltransmitted helminthiases (ascariasis, trichuriasis and hookworm infections) were highly prevalent until the 1970s butare now well controlled. However, food-borne trematode infections, such as clonorchiasis and intestinal trematodiases (including heterophyidiasis, echinostomiasis and gymnophalloidiasis), each show steady prevalence. This review focuses on trends in parasitic diseases in the Republic of Korea. Parasites and public health Parasitic diseases of medical importance have changed remarkably in theRepublic of Korea (hereafter referred to as South Korea), not only in terms of their prevalence and intensity but also in terms of their relative public-health importance (recent trends are summarized in Box 1). In this review, trends in parasitic diseases in South Korea are reviewed briefly. Malaria Plasmodium vivax malaria, the only naturally occurring human malaria species in South Korea, was endemicin South Korea until the late 1970s, when the country became malaria free owing to national control efforts together with improved socioeconomic status of the Korean people [1]. However, vivax malaria re-emerged in 1993 when a soldier working at the western edge of the demilitarized zone (DMZ) (the border between South and North Korea) in Gyeonggi-do (the suffix -do indicates a province) wasconfirmed to have contracted vivax malaria [2]. Subsequently, the annual incidence of malaria cases increased exponentially year after year, to a peak in 2000 (4142 cases), decreasing during 2001 (2488 cases) and 2004 (826 cases) and then increasing again in 2005 (1324 cases) and 2006 (2021 cases) [3,4] (Box 2, Figure I). The high-, medium- and low-risk areas in South Korea, as of 2006, are shown in Box 2,Figure II. Clinically, the re-emerging vivax malaria is associated characteristically with a combination of short (1–2 months) and long (5–13 months) incubation periods with a predominance of the long incubation period type (two-thirds of
Corresponding author: Chai, J.-Y. (cjy@snu.ac.kr).

patients) [1]. Fever intervals are usually 48 h, although 20% of patients have atypical intervals [1].Anemia is not encountered commonly, whereas thrombocytopenia is common (61.5%–100%, depending on different reports) [1] and a few subclinical cases show apparent parasitemia. There is no doubt that vivax malaria re-emergence in South Korea originated from mosquitoes infected in North Korea that flew to South Korea through the DMZ [1,5,6]. Even at present, it is likely that this type of border malaria(due to migration of infected mosquitoes but not of infected humans) continues to occur every year in South Korea. In addition, it is suggested strongly that indigenous malaria transmission occurs by locally infected mosquitoes in South Korea. In this respect, it is of note that, in 2006, many high-, medium- and low-risk areas were located at least 10 km from the DMZ, which exceeds the normalflight distance of Anopheles sinensis (the major vector mosquito species), which is known to be less than 5 km [1]. Control efforts, including early case detection and treatment, mosquito control by insecticide spraying and mass chemoprophylaxis using chloroquine and primaquine on military soldiers working in the risk areas, brought about temporary reduction in annual malaria incidences during 2001...