Helminths

Key messages for primary care practitioners

At the time of their arrival in the UK, up to 20% of migrants from endemic countries may have helminth infections.
Consider helminths in patients with unexplained symptoms, especially gastrointestinal, and in those who have an eosinophilia. In those coming/returning from the tropics there is around a 60% chance that eosinophilia will be due to helminth infection.

Background information

Testing

Specific infection information and treatment

Patient information (English only)

Other useful resources

References

Background information

Helminth infections are distributed worldwide.
At the time of their arrival in the UK, up to 20% of migrants from endemic countries may have helminth infections.
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, and one (Strongyloides) can remain lifelong if not treated.
Infections are often asymptomatic, but can cause significant morbidity and mortality if left untreated.
A raised eosinophilcount(>0.4 x 10⁹/l) may be the only clinical manifestation of a parasitic infection.

Testing

Patients with eosinophilia(>0.4 x 10⁹/l) should be screened as follows (tests are available through your local hospital) -see eosinophilia algorithm.
- Exposure anywhere in the tropics: Stool microscopy and Strongyloides serology.
- Exposure in sub-Saharan Africa: Stool microscopy, urine microscopy, Strongyloides serology & Schistosoma serology.
Refer to an infectious diseases unit [external link] if these tests are negative and eosinophilia persists.

Specific infection information and treatment

Strongyloides stercoralis

Strongyloides is common, especially in South and Southeast Asia and the Caribbean. Infection can be lifelong, and it can become a serious infection if steroids or other immunosupressives are prescribed in later life, or if other immunosuppressive conditions co-exist.

Infection is usually asymptomatic, but it may cause characteristic skin rashes and nonspecific gastrointestinal symptoms.
When infected patients are immunosuppressed, for example by corticosteroids or chemotherapy, overwhelming infection can occur with a high mortality.
Diagnosis can be made by stool microscopy (which has low sensitivity) or serology (which has high sensitivity in migrants).
Treatment with ivermectin (unlicensed) is safe and effective.

Schistosomiasis

Caused predominantly by Schistosoma haematobium and Schistosoma mansoni.
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.
Untreated infection can result in chronic renal failure, bladder cancer or portal hypertension, depending on the infecting species.
Schistosoma haematobium is a common cause of microscopic and macroscopic haematuria in patients from endemic areas.
Diagnosis is made by stool microscopy, urine microscopy and Schistosoma serology (see schistosomiasis algorithm).
Treatment with praziquantel is recommended.

Soil-transmitted helminths

Includes Ascaris lumbricoides, hookworm and Trichuris trichiura.
May be a cause of eosinophilia in migrants, but rarely cause significant disease except among heavily-infected people, and are generally self-limiting.
Hookworm should be considered 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

Includes lymphatic filariasis (which causes lymphoedema and elephantiasis), Loa loa (eye worm), Onchocerciasis (which causes severe pruritus and blindness) and other infections.
May be a cause of eosinophilia but are rarely encountered in general practice.

Patient information (English only)

NaTHNaC travel health information sheet: schistosomiasis [external link]

Other useful resources [external links]

Parasitic infections – diagnosis in primary care [external link] training video from HPA migrant health event 12 November 2012

NaTHNaC factsheet for health professionals: schistosomiasis [external link]

The Hospital for Tropical Diseases [external link] an NHS Hospital dedicated to the prevention, diagnosis and treatment of tropical diseases and travel related infections.

Liverpool School of Tropical Medicine [external link] this institution and the associated Tropical and Infectious Disease Unit in the Royal Liverpool University Hospital provide advice on prevention, diagnosis and management of tropical infections.

National Travel Health Network and Centre [external link] (NaTHNaC) - for country specific travel advice.

References

Eosinophilia in returning travellers and migrants from the tropics: UK recommendations for investigation and initial management. J Infect. 2010 Jan; 60(1):1-20