INTRODUCTION
Enterobiasis is a nematode infection caused by the pinworm, Enterobius vermicularis. Its principal mode of transmission is direct contact between infected and uninfected persons. For this reason, this infection is prevalent among primary school children who are easily exposed to overcrowded conditions and inadequate sanitation, and who actively contact each other (Beaver et al. 1984; Cook, 1994).
In the Republic of Korea, E. vermicularis is a common human intestinal parasite among pre-school and primary school children (Chai et al., 1976; Lee et al., 2000; Kim et al., 2003). Even though the national prevalence of soil-transmitted helminth infections has decreased remarkably, for example, only 0.05% of the general population were positive for Ascaris lubmricoides in 2004 (Ministry of Health and Welfare and Korea Association of Health Promotion, 2004). However, the same cannot be said for E. vermicularis, for example, in two nation-wide surveys on the general population in 1997 and 2004, the egg positive rates of E. vermicularis were unchanged at 0.6% (Ministry of Health and Welfare and Korea Association of Health Promotion, 1997, 2004). Moreover, its prevalence among children is much higher than in the general population.
The patterns and prevalence of human helminth infections on coastal islands seem to be quite different from those of the inland (Chai et al., 2001, 2004). For instance, intestinal trematodes including heterophyids and a gymnophallid are prevalent among residents of western and southern coastal islands, i.e., Heterophyes nocens (11.0%), Gymnophalloides seoi (3.8%), and Pygidiopsis summa (1.2%) (Chai et al., 2004). Moreover, because of their geographical isolation, less medical attention has been paid to these areas, and with regard to E. vermicularis infection, no surveys have been conducted. Therefore, the present survey was performed to determine the status of E. vermicularis infection among children living on these off-shore islands of the Republic of Korea.
MATERIALS AND METHODS
A total of 19 western and southern coastal islands in Gyeonggi-do, Incheon city, Chungcheongnam-do, Jeollabuk-do, Jeollanam-do, Gyeongsangnam-do, Busan city, and Jeju-do were involved in this study during July and August 2000, and a total of 39 kindergartens and primary schools were selected (Table 1; Fig. 1). After obtaining informed consent, 1,661 children (3-10 years old) in these schools were examined using the cello-tape anal swab technique (one smear per child), for the presence of E. vermicularis eggs. Skilled laboratory technicians of the branch offices of the Korea Association of Health Promotion (KAHP) collected samples. Anal swabs were transported to the Department of Parasitology and Tropical Medicine, Seoul National University College of Medicine, and examined using a light microscope. Results were analyzed with respect to locality, age, and sex using Fisher's exact test and the chi-square test.
RESULTS
A total of 307 (18.5%) of the 1,661 samples were positive for E. vermicularis eggs. The egg positive rate ranged from 0% to 59.3% by location (Table 1; Fig. 1). The egg positive rate among boys (21.3%) was significantly higher than that among girls (15.4%) (P = 0.02) (Tables 1, 2). No significant differences in egg positive rates according to age were observed in boys and girls (Table 2).
DISCUSSION
The results of the present study demonstrate a high prevalence (av. 18.5%) of E. vermicularis infection among children attending kindergartens and primary schools on the western and southern islands of the Republic of Korea. This prevalence is higher than those reported by other workers (7.8-17.5%) since 1991 in the Republic of Korea (Kim et al., 1991; Yang et al., 1997; Lee et al., 2000; Yoon et al., 2000, Kim et al., 2003), and is remarkably higher than the national figures of 4.2% for children aged 1-4 years and 3.5% for those aged 5-9 years in 2004 (Ministry of Health and Welfare and Korea Association of Health promotion, 2004).
It is of note that the detection of E. vermicularis eggs from the peri-anal region means the termination of parasitism by the adult worms that produced these eggs (Akagi, 1973; Cho and Kang, 1975), and that such a finding does not necessarily mean that further worms are present in the intestine. Nevertheless, egg detection from the perianal region is significant, because egg positivity indicates a high probability of infection in the intestine (Cho and Kang, 1975).
In the present study, E. vermicularis infection was found to be prevalent in all ages from 3 to 10 years, and boys were more highly infected than girls. Children in this age group contact each other more frequently in kindergartens and primary schools than children of other ages, and are also exposed to unsatisfactory sanitary environments (Chai et al., 1976; Kim et al., 2003). Inadequate personal hygiene could also increase the risk of E. vermicularis infection among children, particularly among boys. Other factors including playing on the floor, nail biting, a failure to wash hands before meals, and living in non-apartment dwellings have also been reported to be associated with the prevalence of enterobiasis (Sung et al. 2001). In this respect, kindergarten- and school-based mass control activities are likely to be more effective than individual treatment.
Enterobiasis is a disease with usually mild symptoms such as, perianal itching and dermatitis; it is asymptomatic in most adults who have low worm burdens. However, in children, particularly who have heavy worm burdens, neurological symptoms including nervousness, restlessness, irritability, and distraction may occur, and these may influence child growth (Beaver et al. 1984; Cook, 1994; Song et al. 2003). Rarely, ectopic infections in the pelvic area or urinary tract of women can occur (Ok et al. 1999; Tandan et al. 2002).
Effective chemotherapeutic regimens have been developed and used for decades; however, the control of enterobiasis is difficult because of frequent reinfection and a short life cycle (Lohiya et al. 2000; Lee et al., 2001). Repeated health education concerning improved personal hygiene and regular inspections and mass chemotherapy with appropriate anthelmintics are essentially required to control enterobiasis among children living on off-shore islands in the Republic of Korea.
