Oxyurid Nematodes Detected by Colonoscopy in Patients with Unexplained Abdominal Pain
Abeer E Mahmoud1, Rasha AH Attia1, Hanan EM Eldeek1, Laila Abdel Baki2 and Hussein A Oshaish3
Departments of Parasitology1 and Tropical Medicine and Gastroenterology2 Faculty of Medicine, Assiut University, Egypt and GIT Consultant, Faculty of Medicine, Taez University, Yemen3
Received: April, 2009 Accepted: May, 2009
Abstract
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.
Keywords: Syphacia muris, Syphacia spp., E. vermicularis, Colonoscopy, Unexplained Abdominal Pain, Light Microscopy, SEM.
Introduction
Members of the Order Oxyurida are called pinworms because they, specially the females, have sharp pointed tails(1). Pinworms are one of the common helminthic infections which generally live in the gastrointestinal tract, leading to unexplained abdominal pain and may cause appendicitis. Abdominal pain seen in some patients infected with E. vermicularis is due to blockage of the appendiceal lumen with parasites, ischemia and associated acute appendicitis(2).
E. vermicularis worms or eggs were detected in histopathological sections of granulomas of abdominal and pelvic peritoneum, granulomas on the surface of the ovary and necrotic granuloma removed from the lung of many patients(3). Murata et al.(4) described a fatal infection with human pinworm, E. vermicularis, in a chimpanzee in which many worms were observed in the mucosa of the intestinal tract, especially in the ileum and caecum with caecal nodule formation. Other tissues were also affected as the portal venule, parenchyma of the liver, spleen, kidneys, adrenals and lung alveoli.
Species of the genus Syphacia (rodent pinworm) are cosmopolitan. Beside small mammals, they may also infect humans(5). Route of infection may quite probably be contamination from fecal droppings and hand to mouth infection. Kumar et al. (6) described several cases of rectal prolapses associated with pinworms infection in a colony of mice. Moreover, they added that rectal prolapse, constipation, intersucception and fecal impaction due to heavy infection with Syphacia were recorded.
Scanning electron microscopy (SEM) has made it possible to study the ultrastructure of the head end, genitalia and the surface structure of the body. This method revealed characters which had not been reported earlier for Syphacia spp. as the presence of longitudinal septa on the surface of the body and the ultrastructure of the transverse striations of the body(7). Scanning electron microscopy studies(8) pointed out that there are apparently four groups within the genus Syphacia based on the form of the head.
The present work aimed to diagnose the cause of unexplained abdominal pain in patients with mild eosinophilia using colonoscopy, to detect the relevance of Oxyurid nematodes as a cause of this unexplained abdominal pain, and to identify and describe the detected pinworms using light and SEM.
Patients and Methods
The study was approved by the Ethical Committee of Faculty of Medicine, Assiut University.
Clinical data: After obtaining an informed consent, 200 inpatients of different age groups ranging from 3-60 years were enrolled for the study, over a period of one year, in the Tropical Medicine and Gastroenterology Department, Assiut University Hospital. They all suffered from chronic abdominal troubles (diffuse colicky abdominal pain and abdominal distension) of 3-5 months duration.
Ultrasonography was done to exclude gall bladder stones, cholecystitis, and abdominal masses and to identify level of distension.
Laboratory investigations included complete blood picture, liver function tests, stool examination for helminthes and protozoa by direct smear of the stool with saline and iodine and formal ether concentration technique(1). Perianal swab was done for patients suffering from perianal itch by Scotch adhesive tape swab early in the morning before bathing or defecation(1). Antispasmodic treatment was given for 3-5 months to this group of patients to relieve the pain. Failure of this treatment indicated colonoscopy.
Colonoscopy was performed for all cases. Preparation was done by purgative and enema. The instrument used was videoscope long colonoscopy (Pentax EPM-3500), and the colonscope No. was F110118. The procedure performed was complete colonic examination till the caecum in all patients. Detected worms were removed by biopsy forceps and sent to the Parasitology Department, Faculty of Medicine, Assuit University in saline containing containers within 15-30 minutes. Stool specimen was collected on the next day and perianal swab was done before treatment of cases. Anti-helminthic treatment was given to the positive cases (Albendazole) 200 mg twice/day for 3 successive days and repeated after one week. Follow up of these patients was done for one month. Detected nodules were removed by biopsy forceps and sent to the Pathology Department, Faculty of Medicine, Assuit University in formalin containing containers for histopathological examination.
Parasitological studies: Adult worms recovered from the lumen of the colon of examined patients were washed with saline and preserved in a solution of 5 parts glycerin plus 95 parts 70% alcohol(5). For detailed examination, the specimens were placed in a drop of lactophenol and examined under a light microscope, equipped with a calibrated eye piece micrometer. Light photomicrographs were taken with the aid of digital microscopic camera. Identification of worms was done according to keys of Yamaguti(9) and Younis(10). For SEM, some worms were relaxed in warm water then fixed in 5% glutaraldehyde for 24 hours and sent to SEM unit to be processed for examination. Finally, the specimens were segmented to anterior, posterior and middle parts, put on holder, and examined with JEOL JSM-5400 LV scanning electron microscope, operated at 15 kV(11).
Statistical methods: SPSS ver. 11 was used for data entry and analysis and unpaired t-test was used to compare between the mean of Syphacia muris and Syphacia spp.
Ethical consideration: The study was approved by Ethical Committee of Faculty of Medicine, Assiut University.
Results
Over a period of one year, 200 patients of different age groups ranging from 3-60 years, suffering from abdominal pain and chronic abdominal troubles of unidentified etiology, were examined by colonoscopy. Twenty-five patients (12.5%) were diagnosed as pinworm infection of the genus Syphacia except for 5 children who had mixed infection with E. vermicularis. In these 25 patients, stool examination was negative for other helminthes and protozoa, and perianal swab proved positive only for E. vermicularis eggs in the five children who were presenting with perianal itch.
All laboratory investigations in these 25 patients were normal apart from mild eosinophilia (6-8%). Neutrophilia with moderate shift to the left was observed in one patient with a recto-sigmoid nodule. Abdominal sonar revealed distention at the colonic level.
Colonoscopy examination revealed non specific diffuse colitis and hyperemia. Small worms were seen wandering inside the lumen of the colon and picked up by biopsy forceps (Figure 1). A small mucosal nodule was detected in one case at the recto-sigmoid junction. Histopathology of this nodule revealed chronic non specific inflammation with marked eosinophilic infiltration. Improvement of appetite, abdominal pain and distension was noticed in patients after anti-helminthic treatment.
Light microscopic examination: All extracted worms from the 25 patients were gravid females and only one male. All shared the general characters of the family Oxyuridae. Pinworms differentiation into three species of the family Oxyuridae was done by light microscope depending mainly on the marked difference in the shape of cephalic end, cervical alae and eggs. They proved to be Syphacia spp., Syphacia muris females and E. vermicularis male and females in five children.
1. Genus Syphacia: Two female species were identified; their differences are described in table (1):
Syphacia muris (Figures 2-4): The worms are opalescent white in color. Body is relatively wide, tapering at both ends. The anterior end has a small mouth with three distinct membranous lips and small cervical alae ending sloppy while lateral alae are absent (Figure 2). The vulva opening is at the end of anterior fourth of the body. The esophageal bulb is rounded in shape, separated from the rest of the esophagus by a constriction (Figure 3). The adult female ends posteriorly with a long pointed tail which is one fourth of the body length. The eggs are characteristically planoconvex in shape, transparent, thin shelled and containing morula stage cells. A large pitted area at one pole was seen which may represent an operculum or hatching area (Figure 4).
Syphacia spp. (Figures 5-10): Body of the adult is stout, narrowing at its posterior end. The cephalic plate is spherical with three lips. Striated elongated cup-shaped cervical alae-like shields are projecting from and cover the entire anterior end (Figures 5 and 6). Esophageal bulb is spheroid (Figure 7). The vulva opening lies at the end of anterior fifth of the body. The whole cuticle is transversely striated, except at the pointed tail (Figures 8 and 9). The lateral alae illustrated characteristic zigzag shaped thickening of the cuticle running longitudinally and directly backwards along the body of worm and ending at the tail beginning. It begins 125-155 µm from the anterior end, its width is 10-12 µm (Figures 8 and 9). The adult female ends posteriorly with a long pointed tail which is one fourth of the body length. The eggs are planoconvex, transparent, thin shelled and either contain morula stage or larvae. A large pitted area seen at one pole may represent an operculum or hatching area (Figure 10).
Genus Enterobius (Figures 11-12): E. vermicularis was detected from children presenting with perianal itch.
SEM examination of Syphacia spp. adult females (Figures 13-24): This separated Syphacia spp. into two groups according to the difference in morphology, measurements and cuticular structures which were evident from the region below the lips up to the anus (Table 2). In the first group, which proved larger than the second, the cephalic plate is relatively large and rounded with three large elevated and symmetrical lips surrounding the mouth. The mouth and the lips are surrounded by a well defined cuticular collar which is not protruded apart from the body circumstance and without conspicuous surface structure; it appears depressed in the first group (Figure 13) but elevated in the second group (Figure 14). There are two cervical alae surrounding the anterior end. Their width is more or less similar to the lateral alae in the first group (Figure 15) but is thinner than the lateral alae in the second group (Figure 16). Their shape is markedly different from that of the lateral alae appearing as a shield, not penetrating deep into the cuticle. Transverse cuticular striations are more marked in the second group. The two long lateral alae are very characteristic, well developed, corrugated (zigzag shaped), penetrating deep into the cuticular surface, are free from transverse striations while their margin appears beaded and extending up to the beginning of the tail. Their width is 12 µm in the first group and 10 µm in the second group. There is a free distance between cervical and lateral alae of 5 µm (Figures 17-19).
The cuticle appears transversely striated immediately below the cuticular collar but longitudinal septa are lacking. In the first group the spaces between the transverse striations are narrow anteriorly (6 µm) but they widen gradually (Figure 19) until they disappear in the posterior third (Figure 20). In the second group, the cuticular transverse striations begin simple and then appear as branching and interconnecting at a distance of 180-190 µm from the anterior end up to the tail with the end of lateral alae (Figures 16 and 21). The long pointed tail is free from transverse striations in the first group but crossly striated in the second group; the distance between these striations being 13 µm (Figures 22 and 23). The vulva appears as a transverse slit with thick margin, having two upper lips one behind and inner than the other. The surrounding cuticle is transversely striated (Figures 15 and 24).
Table (1): The measurements and morphological differences between Syphacia muris and Syphacia spp., using light microscope
Syphacia muris / Syphacia spp. / P-valueMean ± SD / Range / Mean ± SD / Range
Total body length (mm) / 5.6 ± 0.4 / 5 – 6 / 5.2 ± 0.6 / 4 – 6 / 0.053
Cervical alae length (µm) / 60.3 ± 4.2 / 55 – 66 / 137.3 ± 11.0 / 120 – 150 / 0.000*
Cervical alae width (µm) / 37.5 ± 2.0 / 35 – 40 / 9.9 ± 1.6 / 8 – 12 / 0.000*
Lateral alae / Absent / Present / --
Vulva opening from anterior end / In the anterior fourth / In the anterior fifth / --
Length of cylindrical esophagus (µm) / 678.3 ± 2.2 / 674 – 680 / 688.9 ± 2.0 / 685 – 691 / 0.000*
Egg shape / Planoconvex / Planoconvex / --
Egg length (µm) / 59.8 ± 3.7 / 55 – 65 / 52.6 ± 2.0 / 50 – 55 / 0.000*
Egg width (µm) / 24.2 ± 4.4 / 20 – 30 / 27.3 ± 2.4 / 24 – 30 / 0.024*
Unpaired t- test was used, *Significant at the level < 0.05.