Helminth infections: migrant health guide

Advice and guidance on the health needs of migrant patients for healthcare practitioners.

Main messages

Up to 20% of migrants from endemic countries may have helminth infections at the time of their arrival in the UK.

Consider the possibility of helminths in patients who have:

  • unexplained symptoms, especially gastrointestinal
  • eosinophilia, as there is around a 60% chance that it will be due to helminth infection in those coming or returning from the tropics


Helminth infections:

  • are distributed worldwide
  • may affect up to 20% of migrants from endemic countries at the time of their arrival in the UK
  • are often asymptomatic, but can cause significant morbidity and mortality if left untreated

There are a number of helminth infections, including strongyloides stercoralis, schistosomiasis, soil-transmitted helminths (Ascaris, Trichuris and hookworm), and filariasis.

Most of these infections are self-limiting, but:

  • some can persist for decades after leaving an epidemic country
  • strongyloides can remain for life if not treated

A raised eosinophil count (>0.4 x 109 per litre) may be the only clinical manifestation of a parasitic infection.

Transmission, symptoms, and treatment

Strongyloides stercoralis

Strongyloides is common, especially in:

  • South and Southeast Asia
  • the Caribbean

Infection can be lifelong and can become serious if:

  • steroids or other immunosuppressives are prescribed in later life
  • other immunosuppressive conditions co-exist

Infection is usually asymptomatic, but may cause:

  • characteristic skin rashes
  • nonspecific gastrointestinal symptoms

When infected patients are immunosuppressed, eg by corticosteroids or chemotherapy, overwhelming infection can occur with a high mortality.

Diagnosis is via 1 of 2 methods:

  • stool microscopy (low sensitivity in migrants)
  • serology (high sensitivity in migrants)

Treatment with ivermectin (unlicensed) is safe and effective.


Schistosomiasis is caused predominantly by:

  • schistosoma haematobium, a common cause of microscopic and macroscopic haematuria in patients from endemic areas
  • schistosoma mansoni

Schistosomiasis is acquired by exposure to snail-contaminated fresh water in many tropical regions, particularly sub-Saharan Africa, where it can affect up to 20% of travellers and residents.

Infection can persist for many years after exposure, and pathology is cumulative.

Depending on the infecting species, untreated infection can result in:

  • chronic renal failure
  • bladder cancer
  • portal hypertension

Diagnosis is made by:

  • stool microscopy
  • urine microscopy
  • schistosoma serology

Treatment with praziquantel is recommended.

To find out about screening, see the Schistosomiasis screening algorithm (PDF, 25.9KB, 1 page).

The NaTHNaC travel health information sheet on schistosomiasis provides further information, including epidemiology and risks to travellers.

Soil-transmitted helminths

Soil-transmitted helminths may be a cause of eosinophilia in migrants, but:

  • rarely cause significant disease except among heavily-infected people
  • are generally self-limiting

Soil-transmitted helminths include:

  • ascaris lumbricoides
  • hookworm
  • trichuris trichiura

Consider hookworm in those who are anaemic.

Diagnosis is by stool microscopy, which has good sensitivity.

Treatment with mebendazole or albendazole is safe and generally effective.

Filarial infections

Filarial infections may be a cause of eosinophilia but are rarely encountered in general practice. They include:

  • lymphatic filariasis (which causes lymphoedema and elephantiasis)
  • loa loa (eye worm)
  • onchocerciasis (which causes severe pruritus and blindness)


Screen patients with eosinophilia (>0.4 x 109 per litre) according to the place of exposure:

  • anywhere in the tropics
  • sub-Saharan Africa

Anywhere in the tropics

If the patient was exposed anywhere in the tropics, screen by:

  • stool microscopy
  • strongyloides serology

Sub-Saharan Africa

If the patient was exposed in sub-Saharan Africa, screen by:

  • stool microscopy
  • urine microscopy
  • strongyloides serology
  • schistosoma serology

To find out about screening, see theEosinophilia screening algorithm (PDF, 51.5KB, 1 page)

Tests are available through your local hospital.

Refer to an infectious diseases unit if these tests are negative and eosinophilia persists.


Parasitic infections, diagnosis in primary care: Migrant Health Training Seminar 7.

Migrant Health Training Seminars (7); Parasitic infections: diagnosis in primary care

The Hospital for Tropical Diseases is an NHS Hospital dedicated to the prevention, diagnosis and treatment of tropical diseases and travel-related infections.

Liverpool School of Tropical Medicine, and the associated Tropical and Infectious Disease Unit at The Royal Liverpool University Hospital, provide advice on the prevention, diagnosis and management of tropical infections.

National Travel Health Network and Centre (NaTHNaC) provides country-specific travel advice.

Published 31 July 2014
Last updated 25 October 2017 + show all updates
  1. Updated and made editorial changes to meet GOV.UK style.

  2. First published.