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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

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, 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
• can remain for life if not treated

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

Soil-transmitted helminth infections are associated with hygiene. .

The risk of helminth infections is often measured by the proportion of the population requiring .

Transmission, symptoms and treatment

Strongyloides stercoralis

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, 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 in many tropical regions, particularly , 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 , 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

.

To find out about screening, see the (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 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 .

Heavy infections can cause a . 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:

• (which causes lymphoedema and elephantiasis)
• caused by Loa loa (eye worm)
• , 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 (PDF, 51.5 KB, 1 page)

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

Tests are available through your local hospital.

if these tests are negative and eosinophilia persists.

Resources

The for neglected tropical diseases contains global data about PCT for helminth infections.

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

, and the associated , provide advice on the prevention, diagnosis and management of tropical infections.

conducts research on various tropical diseases.

provides country-specific travel advice.