Aproximately one third of threadworm infections are completely asymptomatic (1)
Threadworms may cause symptoms by mechanical stimulation and irritation, allergic action, and migration to parts of the body where they create a pathogenic response (2)
- the main clinical feature is that of pruritis ani
- in bed at night
- scratching the perianal area and transferring infective eggs to the mouth with contaminated hands is a way in which children may often reinfect themselves
- in young girls, the irritation may spread from the anus to the vulva
- an infected individual may occasionally see adult worms in the toilet pan after defaecating
Threadworms in the appendix may result in symptoms mimicking appendicitis or appendiceal ‘colic’ - intermittent chronic right lower quadrant and pelvic pain (in the absence of histological evidence of acute inflammation).
- consider E. vermicularis when a child presents with signs of acute appendicitis (1).
Eosinophilia is not generally a feature - it may be seen in the rare circumstance when invasion into the peritoneal cavity has occurred
In the vast majority of threadworm infections there is no significant damage to the intestine or host.
Occasionally, threadworm infections have been associated with extrintestinal infections which results in atypical presentations:
- female genital tract
- most common extraintestinal site
- genital tract symptoms reflect the site of involvement e.g. - vaginitis, endometritis, tubo-ovarian abscess, pelvic inflammatory disease
- infertility or peritonitis may be a secondary complication.
- ovaries are affected rarely
- other sites include: lungs, liver, spleen, kidney, prostate and bladder (4)
- threadworm migrations may result in the formation of nodules or granulomas that have been mistaken for tuberculosis, schistosomiasis, and carcinomatosis
- increased frequency of urinary tract infections and in boys, urethral and prostate irritation
- perianal skin eruptions due to hypersensitivity reactions and secondary bacterial infection have been described
Reference:
- Dunphy L, Clark Z, Raja MH. Enterobius vermicularis (pinworm) infestation in a child presenting with symptoms of acute appendicitis: a wriggly tale! BMJ Case Rep. 2017;2017. pii: bcr-2017-220473.
- Tietze E, Jones JE. Parasites during pregnancy. Prim Care 1991;18: 75–99.
- Shoup B.Diagnosis and management of pinworm infection. Primary Care Update for Ob/Gyns 2001;8 (6): 240-243.
- Powell G, Sarmah P, Sethi B, Ganesan R. Enterobius vermicularis infection of the ovary. BMJ Case Reports. 2013;2013:bcr2013201146