Clinical Guidelines of the British Infection SocietyEosinophilia in returning travellers and migrants from the tropics: UK recommendations for investigation and initial management
Introduction
Eosinophilia occurs commonly in individuals returning from the tropics. In a UK series of 852 asymptomatic returning travellers, 8% had eosinophilia,1 and in a Canadian series of 1605 individuals returning from the tropics 10% of asymptomatic individuals had eosinophilia.2 For the purpose of these recommendations, eosinophilia is defined as a peripheral blood eosinophil count of >0.45 × 109/L.
Helminth infection is the commonest identifiable cause of eosinophilia in the returning traveller or migrant, rates varying from 14%2 to 64%.3 However there are multiple causes, both infectious and non-infectious, of a peripheral blood eosinophilia and patients may present to a range of specialities other than infectious diseases. These recommendations are intended to guide infection specialists investigating and managing individuals returning from the tropics with eosinophilia, and do not attempt to cover non-infectious causes comprehensively.
Many of the infections discussed are seen rarely in the UK, and are rarely diagnosed outside tropical medicine units. Box 1 summarises contact details of tropical units in the UK offering 24 h clinical advice. All NHS microbiology laboratories offer concentrated stool microscopy for ova, cysts and parasites, and can access most other tests through a UK network of specialised laboratories (Box 1).
Helminth infections causing eosinophilia are usually self-limiting and benign, but some can cause long-term health problems. For example, Strongyloides stercoralis infection in the immunocompromised can result in a hyperinfestation syndrome with a high mortality, and may present over 50 years after exposure.4, 5, 6 Schistosomiasis is occasionally associated with spinal cord compression7 or bladder carcinoma.8, 9 Potentially serious helminth infections are diagnosed in 10–73% of returning travellers and migrants with eosinophilia.2, 3, 10 Human immunodeficiency virus (HIV) infection may also present with eosinophilia, although helminth co-infection is still a more likely cause in this setting.11
Eosinophilia has numerous non-infectious causes. Common non-infectious causes include drugs (non-steroidal anti-inflammatory drugs, beta-lactam antibiotics, nitrofurantoin and others), atopy (asthma, eczema and hay fever) and allergy. These and uncommon but serious non-infectious causes such as haemopoietic malignancies and connective tissue disorders are not covered in these recommendations, but have been comprehensively reviewed elsewhere.12, 13, 14 Long-standing moderate/high-grade eosinophilia (>1.5 × 109/L) can itself result in significant end organ damage.15
Section snippets
Patient group
Clinical presentation may vary depending on the patient group. Migrants tend to have a higher burden of infection1, 2, 16, 17 while travellers are often newly infected and have a greater immune response with more pronounced eosinophilia.18 Infection with multiple helminth species may occur in migrants, however, which is also associated with more pronounced eosinophilia.2, 3 Rare complications of chronic schistosomiasis such as bladder carcinoma or portal hypertension are more often seen in
Investigating asymptomatic eosinophilia
Eosinophilia is asymptomatic in 21–33% of returning travellers and migrants3, 10; common causes of asymptomatic eosinophilia are intestinal helminths, schistosomiasis, strongyloidiasis and filiariasis.2, 3, 10, 20 We propose a scheme for investigating asymptomatic eosinophilia in returning travellers and migrants based on geographical area visited.3 Initial investigations with a high yield are suggested, to be followed if necessary by further investigations. Screening for helminths in the
Eosinophilia associated with specific symptoms
The remainder of the recommendations is divided into the clinical syndromes associated with eosinophilia that may be encountered in returning travellers and migrants. Each section is organised with the more frequently seen syndromes or conditions in this population listed first.
Conclusion
Eosinophilia is common in returning travellers and migrants, and often indicates an underlying helminth infection. Concentrated stool microscopy and strongyloides serology should be performed on all patients regardless of geographic exposure. Recommended additional investigations depend on the region visited and the presence of suggestive signs and symptoms. In the absence of a specific diagnosis empiric treatment with an antihelminthic agent such as albendazole may be considered. Non-infective
Acknowledgements
For generous provision of photographs, many thanks to Dr. Ron Behrens, Hospital for Tropical Diseases, London (Fig. 2) and Dr. Alison Grant, Hospital for Tropical Diseases, London (Fig. 3). For helpful comments and advice, many thanks to Dr. Andy Ustianowski, North Manchester General Hospital, Dr. Nick Beeching, Liverpool School of Tropical Medicine and Mr. David Manser, Hospital for Tropical diseases, London. We would like to thank the referee for helpful comments which improved the manuscript.
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