Enterobius vermicularis infection is well controlled among preschool children in nurseries of Taipei City , Taiwan

[1]. Departamento de Administração dos Cuidados com a Saúde, Disciplina de Saúde Pública e Nutrição, Universidade Médica de Taipei, Taipei, Taiwan. [2]. Departamento de Parasitologia, Universidade Médica de Taipei, Taipei, Taiwan. [3]. Departamento de Parasitologia Molecular e Celular, Universidade Juntendo de Medicina, Tóquio, Japão. [4]. Instituto de Graduação em Ciências Médicas, Faculdade Medicina, Universidade Médica de Taipei, Taipei, Taiwan. [5]. Centro de Medicina Tropical Internacional, Faculdade Medicina, Universidade Médica de Taipei, Taipei, Taiwan.

Enterobius vermicularis (pinworm or threadworm) is the most common intestinal parasitic infection worldwide and has been present for thousands of years.Approximately 3.5 billion people are infected by intestinal parasites, and more than 400 million children are ill because of this parasitic infection.The high prevalence in children is attributed to many factors, particularly environmental and personal hygiene 1 .Embryonated eggs measure 30-60μm and are found in clothing, house dust, and other surface areas.Infection takes place through ingestion or inhalation of infective eggs or retrograde migration of hatched juveniles from the anus to the intestines, where larvae mature into adults.Gravid adult female worms migrate by night to the perianal region and deposit up to 11,000~15,000 eggs.Eggs are infective within 6h of ovideposition.Enterobiasis is usually asymptomatic or accompanied by perianal pruritus.However, there can be symptoms of restlessness, loss of appetite, insomnia, and irritability, particularly in children with high parasitic burdens.In rare instances, pinworms can cause serious gastrointestinal problems and ectopic infections in some areas, such as lung, beast, liver, and spleen.It is difficult to detect E. vermicularis eggs in stool because only approximately 5% eggs are to be revealed.Therefore, diagnosis of E. vermicularis infection is usually done using the cellophane tape method for screening instead of stool examination [2][3] .The Taipei City government, which has undertaken an annual mass pinworm screening and treatment program since 1990 4 , gained excellent achievement of enterobiasis control as seen from a decreasing prevalence rate among preschool children of 4.3% in 1990 to 0.6% (27/4,349) in 2008 3 .We intended to continue monitoring the prevalence trend of pinworm infection among preschool children in kindergarten, with the aim of presenting the result to the Taipei City Government as reference to undertake further E. vermicularis screening program.
Taipei City may be largely divided into 4 major geographical districts (MGDs), namely, North district (including Beitou, Shillin, and Zhongshan district), South district (including Wenshan district), East district (including Xinyi, Neihu, Nangang, Songshan, and Daan districts), and West district (including Wanhua, Datong, and Zhongzheng districts).The highest average yearly family income in 2009 was 52,000 United States Dollar (USD) in the East district, followed by 50,000 USD in the North district, then 48,000 USD in the South district, and 47,000 USD in the West district according to a report by the Department of Budget, Accounting, and Statistics, Taipei City Government.
From each of the 4 MGDs, 7~8 nurseries were randomly selected for investigation on E. vermicularis infection by an adhesive thin cellophane tape swab method to screen the perianal region for pinworm eggs from March to June 2009.A total of 6,661 children were examined, of which 3,524 were boys and 3,137 were girls.Parents were notified of the procedure beforehand and were asked not to shower their children or have them defecate in the morning of the examination, with letters of consent sent to be signed and returned before the examinations were undertaken.Collected specimens were screened microscopically for pinworm eggs by at least 3 medical technologists.Statistical analysis was performed using SPSS (SPSS Inc., Chicago, IL, USA).Crude odds ratios (ORs) with their 95% confidence intervals (CIs) were estimated by means of logistic regression analysis, and correlation analysis was performed using the Pearson productmoment correlation coefficient; p values of less than 0.05 were considered to be statistically significant.

ACKNOWLEDGMENTS
The authors declare that there is no conflict of interest.1).Interestingly, the correlation analysis showed that the prevalence significantly increased with the average yearly family income by district (r=0.64,p<0.001).

CONFLICT OF INTEREST
Compared with those in other countries, the present prevalence was much lower than that reported in the State of Minas Gerais (8.8%, 14/160) in Brazil 5 , Ankara province (10.6%, 22/207) in Turkey 6 , Tartu City (31.5%, 190/604) in Korea 7 , and also in southeastern Estonia (24.4%, 233/954) 8 .The present result indicates that boys had higher pinworm infection prevalence than girls, and this finding was previously reported worldwide [6][7][8] .Preschool children have contact with each other more frequently in nurseries and also expose themselves to unsatisfactory sanitary environments.Inadequate personal hygiene can also increase the risk of E. vermicularis infection among preschool children, particularly boys.Other factors, including playing on the floor, nail biting, failure to wash hands before meals, and living in nonapartment dwellings, were also reported to be associated with the prevalence of enterobiasis 1 .
Although Jang et al. indicated that families with a low economic status have a higher association with E. vermicularis infection among preschool children in Taipei City 9 , our present study indicates the opposite results.It may be alternatively explained by the fact that parents with high economic status might still overlook the importance of personal hygiene of children, thus resulting in a higher prevalence of E. vermicularis infection in the North and East districts.Although the symptoms of infection often are mild, the itchiness and restlessness that children experience from the infections can be discomforting and affect their learning, and the shame of having worms can have a negative impact on their mental health.In rare cases, enterobiasis has led to serious consequences such as acute or chronic appendicitis, eosinophilic colitis, intestinal obstruction, intestinal perforation, leukocytosis, bandemia, carcinoma, Crohn's disease, salpingitis, weight loss, urinary tract infection, and ectopic infections 2 .In addition, E. vermicularis might act as the vector of Dientamoeba fragilis, a frequently seen but rarely diagnosed protozoon as a neglected cause of diarrhea 10 .Nevertheless, enterobiasis control in Taipei City has gained excellent achievement that may be attributed not only to the infected children and family members who take medication simultaneously but also to some preventive measures like exposing clothes to sunlight, as this could help block pinworm transmission.
In conclusion, although Taipei City Government has performed a long-term pinworm screening and treatment program and gained excellent control outcome as seen from 1990 to 2009, we still urge the city government to continue its annual screening program until complete eradication of the parasite is achieved.This is important not only because of the short life cycle of E. vermicularis that is easy to control but also because of the need to become aware of its threat to the health of preschool children in some parts of Taipei City.
We thank the Department of Health, Taipei City Government, for supporting this investigation and all the participating nurseries as well.
et al -Low pinworm infection among preschool children in Taipei City