There are a number of intestinal worms and parasites responsible for human infection, including tapeworms, hookworms, pinworms, Ascaris, flukes, Giardia lamblia and Entamoeba histolytica. Infections may present with abdominal pain, nausea, diarrhoea, unexplained weight loss, fatigue and bloating. However asymptomatic infection is also recognised. Pruritus ani may also be present in association with intestinal helminthiasis.
A number of these pathogens are geographically restricted, therefore an accurate travel history is of paramount importance when assessing patients with suspected infection.
Fixed, false health beliefs regarding parasite infection are not uncommon. Empirical therapy in the absence of objective evidence of parasite infection is not recommended; patients should be reassured that they are being investigated appropriately.
Delusional infestation has been reported in association with other medical and psychiatric conditions and a thorough history and physical exam is required if this is being considered. Substance use disorders and some prescription drugs may cause parasitic delusions, and drug history should be carefully assessed.
Non-infectious GI pathologies with similar symptoms may also need to be considered, including cancer and inflammatory bowel disease.
C.M & N.B 12-12-23
The Infectious Diseases team is happy to provide advice for/review of patients with confirmed infection, unexplained eosinophilia, or any patient with compatible symptoms and a relevant travel history/exposure to a known case.
Please refer using SCI Gateway.
A thorough travel history is needed, to assess for potential exposures, such as contact with confirmed cases, ingestion of undercooked meat, contact with potentially contaminated soil and water. Patients should be counselled regarding hygiene measures.
Investigations
In addition to parasite specific investigations outlined below, please consider checking renal, liver & thyroid function, vitamin B12 and folate levels, HbA1c, syphilis and HIV serology.
- FBC for anaemia/eosinophilia
- At least 3 stool samples, collected on alternate days, sent for microscopy for ova, cysts and parasites (OCP). Directions for collection/requesting are available in the Edinburgh and Lothians Laboratory Medicine Test Directory. Molecular investigations for Entamoeba histolytica, Giardia lamblia and Cryptosporidium will be performed automatically on stool samples sent for OCP
- Parasite specimens provided by patients should also be sent for microscopy: please contact the laboratory in advance to ensure that they are processed appropriately
- If amoebiasis is suspected, please also send a sample for Amoebic serology (5-10mLs clotted blood/serum)
- In patients with pruritus ani, a transparent sticky tape slide from the anus/surrounding skin should be sent for Enterobius vermicularis (pinworm) ova detection. Please see the Laboratory Medicine Test Directory for further information.
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