AKT · Infections/Tropical, zoonotic & travellow yield

Helminth (worm) infections

Parasitic worms — nematodes (round), cestodes (tape) & trematodes (fluke); often travel/soil/food-related

Overview

Parasitic worm infections, grouped into nematodes (roundworms), cestodes (tapeworms) and trematodes (flukes). Most are travel- or soil/food-related and many are mild, but several are high-yield: threadworm (the common UK childhood worm), schistosomiasis (a key travel diagnosis linked to bladder cancer), strongyloides (life-threatening hyperinfection in the immunosuppressed), and tapeworm cysts (hydatid disease, neurocysticercosis). Eosinophilia in a traveller is a classic clue. Most respond to a '-bendazole' or praziquantel.

Recognise

Threadworm (Enterobius, pinworm): perianal itch (worse at night) in a child; diagnosed with the 'sellotape test'; treat the whole household
Schistosomiasis (Schistosoma, freshwater snail exposure): swimmer's itch → Katayama fever (acute) → chronic — S. haematobium causes haematuria and is a risk factor for BLADDER (squamous) cancer; S. mansoni/japonicum → bowel/liver fibrosis
Strongyloides: chronic skin/GI/pulmonary symptoms; HYPERINFECTION syndrome (overwhelming, often fatal) when immunosuppressed (steroids) — screen before immunosuppression; eosinophilia is a common clue across helminths; tapeworms → hydatid cysts (Echinococcus) and neurocysticercosis (Taenia solium — seizures, 'swiss-cheese' brain lesions); hookworm → iron-deficiency anaemia

Red flags

Strongyloides HYPERINFECTION in the immunosuppressed (e.g. before starting steroids) → screen and treat first — it can be fatal
Neurocysticercosis presenting with seizures; hydatid cyst rupture → anaphylaxis; S. haematobium → bladder cancer surveillance

Differentials & how to tell them apart

Other causes of eosinophiliaallergy/atopy, drug reaction, vasculitis (EGPA), malignancy — but eosinophilia + relevant travel/exposure points to helminths

Other causes of haematuriaS. haematobium is the schistosomal cause + a bladder-cancer risk; otherwise stones/UTI/malignancy (cross-ref renal)

Other causes of seizures/brain lesionsneurocysticercosis is a leading cause of epilepsy worldwide — consider with relevant travel

Investigations

Eosinophilia on FBC (a common pointer); stool microscopy for ova/cysts/parasites; threadworm — perianal 'sellotape' test; schistosomiasis — serology + urine/stool microscopy for ova (terminal-spine ova in S. haematobium), urinalysis (haematuria); imaging for hydatid/neurocysticercosis; strongyloides serology (screen before immunosuppression); travel/exposure history.

Management

Benzimidazole/ivermectin (nematodes) or praziquantel (flukes/tapeworms); treat threadworm households

1Use eosinophilia + travel/exposure as the clue and confirm by stool/urine microscopy or serology. Treat by worm class — a '-bendazole' or ivermectin for roundworms, praziquantel for flukes/tapeworms; threadworm → treat the whole household with hygiene measures.Gate: Screen for and treat strongyloides BEFORE immunosuppression (hyperinfection is fatal); S. haematobium → bladder-cancer risk; neurocysticercosis → seizures (albendazole + steroids).
2Manage chronic complications (schistosomal bladder/bowel/liver disease, hydatid cysts, neurocysticercosis) with specialist input; counsel travellers on prevention (avoid freshwater contact for schistosomiasis).

Nematodes (threadworm, ascaris, hookworm, strongyloides): a benzimidazole (mebendazole/albendazole) or ivermectin (strongyloides) — threadworm — treat the whole household + hygiene measures; mebendazole

Trematodes (schistosomiasis, liver/lung flukes): PRAZIQUANTEL — treats schistosomiasis; manage chronic complications (bladder/bowel/liver)

Cestodes: praziquantel (tapeworm) / albendazole (hydatid, neurocysticercosis) — neurocysticercosis — albendazole + steroids ± anticonvulsants; hydatid — albendazole ± careful surgery (avoid rupture)

Screen strongyloides before immunosuppression — prevents fatal hyperinfection when steroids/immunosuppressants are started

Key points

Eosinophilia + travel/exposure = think helminths. High-yield: THREADWORM (perianal itch, sellotape test, treat household, mebendazole); SCHISTOSOMIASIS (freshwater, haematuria — S. haematobium → BLADDER CANCER; praziquantel); STRONGYLOIDES (HYPERINFECTION if immunosuppressed — screen before steroids); neurocysticercosis (seizures); hookworm (iron-deficiency anaemia). '-bendazole' for roundworms, praziquantel for flukes.

Monitor & prognosis

Symptom/parasite clearance, eosinophilia, chronic-complication surveillance (bladder/liver/CNS).

Most are easily treated; strongyloides hyperinfection and complications of schistosomiasis/cysticercosis are the serious outcomes.

Source: UKHSA / tropical-medicine references; cross-ref renal (bladder cancer), neurology (seizures), child_health (threadworm)