Helminth infections: migrant health guide
Source: gov.uk (2025-03-31)

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 (#background) at the time of their arrival in the UK.

Consider the possibility of helminths in patients who have:
- unexplained symptoms, especially gastrointestinal
- eosinophilia (#testing), as there is around a 60% chance that it will be due to helminth infection in those coming or returning from the tropics
Background

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 (#Strongyloides-stercoralis), schistosomiasis (#schistosomiasis), soil-transmitted helminths (#soil-transmitted-helminths) (Ascaris, Trichuris and hookworm), and filariasis (#filariasis).

Most of these infections are self-limiting, but:
- some can persist for decades after leaving an epidemic country
- strongyloides (https://www.bmj.com/content/347/bmj.f4610) can remain for life if not treated
A raised eosinophil count (https://www.ncbi.nlm.nih.gov/pubmed/19931558) (>0.4 x 109 per litre) may be the only clinical manifestation of a parasitic infection.

Soil-transmitted helminth infections are associated with hygiene. Children are particularly vulnerable to infection (https://www.who.int/teams/control-of-neglected-tropical-diseases/soil-transmitted-helminthiases/strongyloidiasis).

The risk of helminth infections is often measured by the proportion of the population requiring preventative chemotherapy treatment (PCT) (https://www.who.int/publications/i/item/9789240696471).

Transmission, symptoms and treatment

Strongyloides stercoralis

Strongyloides (https://www.bmj.com/content/347/bmj.f4610) is common, especially in:
- South and Southeast Asia
- the Caribbean
Around 30 to 100 million people are infected worldwide (https://www.who.int/teams/control-of-neglected-tropical-diseases/soil-transmitted-helminthiases/strongyloidiasis).

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, for example by corticosteroids or chemotherapy, overwhelming infection can occur with a high mortality.

Diagnosis is via 1 of 2 methods:
- serology (high sensitivity in migrants)
- stool microscopy (low sensitivity in migrants)
Treatment with ivermectin (unlicensed) is safe and effective.

Schistosomiasis

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 (https://www.nhs.uk/conditions/schistosomiasis/) in many tropical regions, particularly sub-Saharan Africa (https://apps.who.int/neglected_diseases/ntddata/sch/sch.html), where it can affect up to 20% of travellers and residents.

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

There are two major forms of schistosomiasis (https://www.who.int/news-room/fact-sheets/detail/schistosomiasis), intestinal and urogenital, caused by different species. Symptoms depend on the form of disease but include:
- abdominal pain
- diarrhoea
- blood in stool and/or urine
Depending on the infecting species, untreated infection can result in:
- chronic renal failure
- liver enlargement
- bladder cancer
- portal hypertension
In women, schistosomiasis can present with:
- genital lesions
- vaginal bleeding
- pain during sexual intercourse
- nodules in the vulva
Diagnosis is made by:
- stool microscopy
- urine microscopy
- schistosoma serology
Treatment with praziquantel is recommended (https://www.nhs.uk/conditions/schistosomiasis/).

To find out about screening, see the Schistosomiasis screening algorithm (https://assets.publishing.service.gov.uk/media/5a7dea20ed915d74e6222e30/Schistosomiasis_Algorithm.pdf) (PDF, 25.9 KB, 1 page).

The above Schistosomiasis screening algorithm shows various referral pathways dependent on the symptoms of the patient after freshwater contact in schistosomiasis endemic areas.

The NaTHNaC travel health information sheet on schistosomiasis (https://travelhealthpro.org.uk/disease/159/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 (roundworm)
- Necator americanus (hookworm)
- Trichuris trichiura (whipworm)
There is a high risk of contracting soil-transmitted helminths in the Indian subcontinent, Indonesia and parts of sub-Saharan Africa (https://apps.who.int/neglected_diseases/ntddata/sth/sth.html).

Heavy infections can cause a range of symptoms and complications (https://www.who.int/news-room/fact-sheets/detail/soil-transmitted-helminth-infections). 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 (https://www.who.int/news-room/fact-sheets/detail/lymphatic-filariasis) (which causes lymphoedema and elephantiasis)
- loiasis (https://www.cdc.gov/parasites/loiasis/index.html) caused by Loa loa (eye worm)
- onchocerciasis (https://www.who.int/news-room/fact-sheets/detail/onchocerciasis), also known as river blindness, caused by onchocerca volvulus (which can result in loa loa severe pruritus and blindness)
Testing

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 the Eosinophilia screening algorithm (https://assets.publishing.service.gov.uk/media/5a7df9c8e5274a2e8ab45081/Eosinophilia_Algorithm.pdf) (PDF, 51.5 KB, 1 page)

The above Eosinophilia screening algorithm shows pathways for referral and follow-up dependent on the patient’s initial screening results.

Tests are available through your local hospital.

Refer to an infectious diseases unit (https://www.nhs.uk/Service-Search) if these tests are negative and eosinophilia persists.

Resources

Migrant Health Training Seminars (7); Parasitic infections: diagnosis in primary care (https://www.youtube.com/watch?v=7cr-QYbjZN8)

The WHO databank (https://www.who.int/teams/control-of-neglected-tropical-diseases/preventive-chemotherapy/pct-databank) for neglected tropical diseases contains global data about PCT for helminth infections.

The Hospital for Tropical Diseases (http://www.thehtd.org/) is an NHS Hospital dedicated to the prevention, diagnosis and treatment of tropical diseases and travel-related infections.

Liverpool School of Tropical Medicine (https://www.lstmed.ac.uk/), and the associated Tropical and Infectious Disease Unit at The Royal Liverpool University Hospital (https://www.rlbuht.nhs.uk/search?query=Tropical%20and%20infectious%20diseases), provide advice on the prevention, diagnosis and management of tropical infections.

London School of Hygiene and Tropical Medicine (https://www.lshtm.ac.uk/) conducts research on various tropical diseases.

National Travel Health Network and Centre (NaTHNaC) (https://travelhealthpro.org.uk/countries) provides country-specific travel advice.