nail biting habits of their child. Children with a positive tape-test were offered medical treatment, which in- cluded family members (according to the present rec-.
ORIGINAL PAPER
Enterobius vermicularis and finger sucking in young Swedish children Per Herrstrom1, Anette Fristrom2, Anita Karlsson3 and Benkt Hogstedt3 'Primary Care Centre Hertig Knut, 2Primary Care Centre Backagard, Department of Occupational Medicine, Central Hospital, Halmstad, Sweden. Received March 1996. Accepted October 1996.
Scand J Prim Health Care 1997;15:146-48. ISSN 0281-3432 Objective - To study the prevalence of Enterobius vermicularis and its association with finger sucking in young Swedish children. Design - Cross-sectional survey with a questionnaire for symptoms of infestation with Enterobius vermicularis, and the children's habit of finger sucking (including fingernail biting). Perianal tape-test for identification of eggs of Enterobius vermicularis. Setting - Primary care, day-care centres, and schools in a Swedish middle-sized town (approx. 80 000 inhabitants). Participants - 172 children of both sexes, 4-10 years old. Main outcome measures - The prevalence of Enterobius vermi-
Enterobius vermicularis (oxyuris, pinworm, or threadworm) has recently been shown to be more prevalent than was previously known in preschool children in Uppsala, Sweden (1). In that study, 27% of 152 preschool children were found infested with E. vermicularis and most of the cases were free from symptoms. There is no other publication on the prevalence of threadworm in Swedish children.The prevalence of E. vermicularis in preschool and school children varied between 3% and 23% in the USA during the early 1960s, with a peak prevalence at 5-9 years of age (2,3). A significant difference between ethnic groups was also observed, with a higher prevalence in white children than in black and Puerto Rican children (2,3). Another American study reported a decline in the prevalence of pinworm from 35% to 12% in 2nd grade schoolchildren from 1960 to 1982 (4). Repeated surveys in Canada in the 1960s showed a prevalence of 40-60% in schoolchildren and 30% in preschool children (5). A more recent study from Tunis demonstrated a prevalence of 20%, 50%, and 30% in children aged 2-4 years, 6 years, and 10 years, respectively (6). The life cycle of E. vermicularis implies that eggs laid by female worms on the perianal skin surface will mature within a few hours and then be capable of infestation and reinfestation by different routes (5,7). The pruritus and scratching that go with the condition frequently transfer eggs to the fingers; eggs are found under the fingernails in 60% of the cases (5). Short and Scand J Prim Health Care 1997; 15
cularis and its association with finger sucking. Results - 21% of the children were symptom-free carriers of Enterobius vermicularis, and finger sucking was strongly associated with a positive tape-test (p=0.01). Conclusion - More children than previously known seemed to be symptom-free carriers of Enterobius vermicularis. Finger sucking should be considered when treating infested children and especially those with relapsing symptoms. Key words: children, cross-sectional study, Enterobius vermicularis, finger sucking, primary health care. Per Herrstrom, MD, Primary Care Centre Hertig Knut, Bryggaregatan 1, S-302 43 Halmstad, Sweden.
long fingernails, however, are equally frequent in children with a positive tape-test (6). Mature eggs could thus be transported to the mouth by fingers, through inhalation of dust, or via utensils and food contaminated by unclean hands (5,7). To our knowledge there is, however, no publication on the association between finger sucking and the prevalence of E. vermicularis. The present study was undertaken for two reasons. First, to assess the prevalence of threadworm infestation in young children in our community. Second, to explore the association between E. vermicularis and the habit of finger sucking among the children. SUBJECTS AND METHODS Subjects and questionnaire Three low-grade schools (six classes) and 11 day-care centres in a Swedish middle-sized town were randomly selected to participate in the study during spring 1994. All children, 4-10 years of age, belonging to these units (n=286 children) were invited by a letter to the parents to take part. Much effort was given to informing the staff and teachers about the study either by telephone or at a personal visit by one of us. Teachers and staff were asked to inform the parents both verbally and by handing over a letter of information prepared by us. The parents of 177 children (99 boys and 78 girls) gave written consent for participation in the study. This included a perianal tape-test of the child to detect E.
Enterobius vermicularis and finger sucking in young Swedish children
vermicularis eggs (5,7) and also a questionnaire to be answered by the parents about previously treated infestation with oxyuris and present perianal itching symptoms in the child. All the parents were informed of the result of the tape-test by telephone. Simultaneously they were interviewed about the finger sucking and fingernail biting habits of their child. Children with a positive tape-test were offered medical treatment, which included family members (according to the present recommendations). The protocol was approved by the Ethics Research Committee, Faculty of Medicine, University of Lund. Non-participation and drop-outs Refusal to participate varied extensively and seemed partly to depend on the attitude of the teachers and staff. In some day-care units drop-outs were numerous possibly because the staff considered a tape-test an improper examination in symptom-free children. Such units (n=45 children) were excluded. Eventually, written consent to participate was received from 177 individuals of the study population (n=241 children). Total drop-outs represented approximately 25% of the study population and included those who did not answer the questionnaire and those absent from school and day-care due to sickness and other reasons. Three boys and two girls who intended to participate but hesitated to take part in the tape-test examination were also excluded from the study. Thus, tape-tests were performed in 172 children, of whom 51 were 4-6 year-olds and 121 were 7-10 year-olds. No analysis of drop-outs was performed to describe differences between participants and non-participants with regard to variables of possible importance for the outcome such as age, sex, and finger sucking. Tape-test All tape-tests were carried out during morning hours between 8 and 11 at the schools and in the day-care centres. Parents and children were informed about the time for testing in advance. Two persons examined one child at a time in a private room. One of us separated the buttocks of the child and the other placed the tape (ordinary office tape) repeatedly around the anus and thereafter transferred it to a glass for microscopic examination. Only one sample was taken from each child. Microscopic examination was performed by one experienced person and only one reading per test was done. The presence of one or more typical E. vermicularis eggs was considered to be a positive test. No attempt was made to quantify the parasite burden. Statistical analyses The results were analysed with chi2-test, t-test or ANOVA test (to analyse the coincident effect of sex, age and finger sucking on the prevalence of £. vermicularis). P values
