Strongyloidiasis is one of the most common geohelminth infections in tropical and subtropical areas. Accurate diagnosis remains challenging, leading to an overall underestimation of strongyloidiasis prevalence. The possibility of ongoing autochthonous transmission in some temperate areas and especially in southern Europe is still debated, and data supporting this hypothesis are scarce. The case of a young French woman, who had travelled frequently to Spain and had acquired Strongyloides stercoralis infection as revealed by gastrointestinal symptoms and hypereosinophilia, is reported here. Physicians should keep in mind the risk of being infected in some areas of southern Europe, even if low, in order to avoid the life-threatening manifestations of strongyloidiasis favoured by pathological or therapeutic immunosuppression.

The parasitological diagnosis of strongyloidiasis remains challenging due to the intermittent excretion of larvae in the faeces. Routine coprology lacks sensitivity, and the reference techniques, namely the Baermann method (using the hygro-thermotropic characteristics of S. stercoralis larvae) and agar plate culture, are time-consuming and cumbersome. ELISA serology is more sensitive and could be helpful for screening purposes among at-risk subjects.

The incubation period is about 1 month and acute strongyloidiasis is generally unnoticed. Chronic infection is often asymptomatic, or can be accompanied by mild gastrointestinal (dyspepsia, nausea, vomiting, diarrhoea), respiratory (cough, wheezing), or cutaneous manifestations (pruritus, urticaria, larva currens syndrome).If documented, hypereosinophilia is frequently found in this situation. In immunocompromised people, especially those receiving corticosteroids or immunosuppressants, severe and often fatal forms of the disease, either hyperinfection syndrome or disseminated strongyloidiasis, can occur. Infection by human T lymphotropic virus type 1 (HTLV-1), by disrupting the anti-parasitic Th2-weighted immune response and enhancing the Th1-oriented immune response, can also promote these clinical forms.

S. stercoralis is unique among geohelminths in its ability to develop two distinct reproductive cycles: one asexual cycle inside the human host allowing autoinfection and the other involving sexual reproduction into the soil. Due to autoinfection, one can remain infected for decades without further environmental exposure;this raises the issue of dating the exposure in areas where there is a low risk of transmission, such as the southern European countries. For this reason, data supporting recent infections in Italy,Spain,and France,although scarce, are of particular interest.

Strongyloidiasis is a neglected but widespread parasitic disease caused by infection with the nematode Strongyloides stercoralis and to a lesser extent by the zoonotic species Strongyloides fuelleborni.It is common in tropical and subtropical areas, where heat and humidity favour the growth of geohelminths in general. However, endemic-sporadic transmission can also be observed in some temperate countries, such as the USA,Japan,Italy,France,and Spain.

2. Case presentation

A 17-year-old French woman of Spanish origin (through her parents), born and residing in the Bordeaux area of south western France, was referred to our department by her general practitioner (GP) for chronic abdominal pain, involuntary weight loss, diarrhoea, cough, pruritus, and a mild fever at 38.0 °C. Prior to her admission, hypereosinophilia at 16.9 × 109/l (normal <0.7 × 109/l), which had not been noticed before, was found on biological investigations. For this reason, stool examinations by Telemann and Bailenger methods (diphasic enrichment techniques, using acetic acid solution and acetic acid/sodium acetate buffer, respectively, for the concentration of helminth eggs and larvae) were prescribed by the GP and rare S. stercoralis rhabditoid larvae were found.

On questioning, the patient acknowledged chronic intermittent abdominal pain and discomfort, with a possible initial gastroenteritis-like episode following a recreational stay in western Spain, near the Portuguese border (district El Payo, Castilla y Leon) in which she had walked barefoot on a riverside before swimming, about 8 years ago. Over time, the episodes of abdominal pain had become increasingly frequent and severe and were accompanied by diarrhoea. She had also experienced episodic urticaria for 1 year and bronchial hyper-reactivity.

The patient had never travelled outside occidental Europe, but had travelled to Spain on several occasions with her family. Between 1995 and 2005, she had stayed each summer on the Mediterranean coast in the district of Safor, near Valencia. She went to western Spain near the Portuguese border in 2004 and 2005, where she reported walking barefoot on muddy banks before swimming in rivers and in an antique Roman pool with thermal waters (district El Payo, Castilla y Leon). Thereafter, she visited coastal Galicia near La Coruña and Santiago de Compostella in 2006, during which time she had also walked barefoot before swimming in rivers and brackish lakes.

The treatment she received consisted of oral ivermectin at a dosage of 200 μg/kg, repeated twice, 1 week apart. This was well tolerated and all the symptoms improved rapidly. Multiple stool examinations with Baermann enrichment method performed 1 month after the second intake confirmed the eradication of S. stercoralis larvae. Moreover, her eosinophil count returned to normal values within a few weeks. No serological testing could be performed. More than 2 years after treatment, there has been no clinical or biological evidence of relapse.