Background: Pinworms are one of the common helminthic infections that generally live in the gastrointestinal tract causing appendicitis and leading to unexplained abdominal pain. Species of the genus Syphacia (rodent pinworm) are cosmopolitan and they also infect humans.
Objectives: To diagnose the cause of unexplained abdominal pain in patients with mild eosinophilia by colonoscopy; to detect the relevance of Oxyurid nematodes as a cause of this unexplained abdominal pain; and to identify and describe the extracted pinworms using light and scanning electron microscopy (SEM).
Patients and Methods: The study was performed on 200 inpatients of different age groups ranging from 3-60 years over a period of one year in the Tropical Medicine and Gastroenterology Department, Assiut University Hospital. Laboratory investigations were done for each case, including complete blood picture, liver function tests, stool examination for helminthes and protozoa, and perianal swab for patients suffering from perianal itch. Colonoscopy was performed for all cases not responding to antispasmodics. Detected worms were picked up by biopsy forceps and sent to the Parasitology Department, Faculty of Medicine, Assuit University and examined using light and SEM.
Results: Out of 200 patients, 25 (12.5%) were diagnosed as pinworm infection of the genus Syphacia except in 5 children who had mixed infection with E. vermicularis. Laboratory findings were mild eosinophilia (6-8%) and neutrophilia with moderate shift to the left in one patient with recto-sigmoid nodule and negative stool examination. Perianal swab of patients presenting with perianal itch was positive for Enterobius. vermicularis eggs. Light microscopic examination illustrated the presence of three different species of Oxyurida: E. vermicularis, S. muris and Syphacia species. SEM studies showed that Syphacia spp. were classified into two groups according to morphological differences, and allowed for the reporting of additional morphological and taxonomical features.
Conclusion and recommendations: Syphacia is considered as a cause of unexplained chronic abdominal pain and E. vermicularis is not the only human pinworm in Egypt. Further studies using SEM are needed to detect new characters that may help in differentiating Syphacia spp. from different hosts.