Very High Prevalence of Enterobiasis Among the Hilltribal Children in Rural District "Mae Suk," Thailand

Tisak Chaisalee, MSc; Attapol Tukaew, MSc; Viroj Wiwanitkit, MD; Akkaradej Suyaphan, MD; Surasith Thiamtip, MMPH; Jamsai Suwansaksri, MSc


Medscape General Medicine. 2004;6(2):5 

Enterobius vermicularis is an important helminthic infection among children in rural areas of developing countries. Enterobiasis is frequently asymptomatic. The most typical symptom is perianal pruritus, especially at night, which may lead to excoriations and bacterial superinfection.[1,2] Occasionally, invasion of the female genital tract with vulvovaginitis and pelvic or peritoneal granulomas can occur.

A high prevalence of enterobiasis can be detected in children with low socioeconomic status, and this infection affects the general health as well as the intelligence of the infected children.[3,4] High prevalence of enterobiasis is mentioned in many developing countries; therefore, control of this infection in developing countries is still needed.

In Thailand, there has been rapid development of sanitation systems in the past decade, resulting in the decline of many infectious diseases. The prevalence of enterobiasis among Thai children has decreased from up to 60% in the past 4 decades[5] to less than 30% in the past decade.[6] However, high prevalence among the children in far rural areas can be expected. Separate from the general rural population, the hilltribers, who settle in the northern regions of Thailand, Myanmar, and southern China, can be considered an underprivileged population that receives little primary healthcare. Here, we report the very high prevalence of enterobiasis in a community of hilltribers in a far rural area of Thailand.

We visited the hilltribe villages of the Mae Suk District, Chiangmai Province, Thailand, during the rainy season (May to August) in 2001. The setting is the rural district of Thailand, surrounded by hills, and a number of hilltribers have settled here. Its location is about 800 km from Bangkok, the capital of Thailand. All 291 children (aged 1-10 years old) from 10 villages in this district were recruited into the study. In cooperation with local health workers, we dealt directly with the community leaders, who assisted us in maximizing community participation and compliance. The Thai-tribal language translator was used in all of the communication. The local people in this area were willing to participate in the study. Informed consent was obtained from each individual's parents before the study.

After asking for informed consent from the children's parents, the specimen collection for each subject was performed. In this study, the examination for the presence of E vermicularis egg was performed by perianal tape examination. All specimen collections were performed at the subjects' homes between 6:00 and 8:00 AM. All collected samples were sent for identification of the parasite under light microscope at the nearest laboratory, Mae Jam Hospital, Chiangmai, by the medical technologist teams.

Of the total 291 children examined (123 males and 168 females, average age = 4.58 ± 2.62 years), 122 (60 males and 62 females) were found to be positive for E vermicularis egg, yielding an overall infection rate of E vermicularis of 41.6%. The infection rate in boys (48.8%) was higher than in girls (36.9%) (proportional Z test, P = .03).

Through this survey, we were able to determine that E vermicularis infection is prevalent among children in these hilltribe villages ( Table 1 ). A very high rate of infection, 41.6%, was detected in our studies. Of interest, all positive cases presented with > 5 eggs/field. This intensity is considerably high. One of the possible explanations for our findings is that the hilltribers can be considered as minorities, lacking in primary healthcare. Their daily lifestyle is the same as their ancestors -- all of them still live on the dirt, without running water or electricity. We found that all children in our study had never been examined for the parasite before, nor had they ever received antihelminthic drugs.

Although our technique is perianal tape examination, which has lower sensitivity than the perianal swab technique, our study presented a higher infection rate than that found in the general population of Thai children (17%).[7] This prevalence was also the highest vs other recent reports from many developing countries (14% to 19%).[8,9,10]

Therefore, enterobiasis is a very important infectious disease in our setting. According to our findings, an active control program for enterobiasis in our community is necessary. We plan to distribute antihelminthic drugs and perform a longitudinal follow-up to assess the effectiveness of our control program.