Resumen de Actualización en la epidemiología de la estrongiloidiasis
Strongyloides stercoralis (S.stercoralis) causes estrongiloidiasis, a disease with a wide clinical spectrum and a heterogeneous global distribution. Direct skin contact with contaminated soil is the main factor for transmission, what is more frequent in areas with poor access to sanitation, and in tropical, subtropical and temperate areas. Indeed, strongyloidiasis was once endemic in some wetlands of the Spanish Mediterranean coast. In the last decades, this infection has reemerged due to imported cases. Thus, the classical patient profile seems to have changed.
Strongyloidiasis seems to be mainly asymptomatic, although some comorbidities (especially those affecting the immune system) can lead to severe and often fatal outcomes. Factors associated with disease development remain unknown in immune-competent hosts, along with its frequency and clinical presentation.
Diagnosis has been based on direct parasite identification through traditional direct microscopy, what is highly specific but has very poor sensibility, often around 30%. Serology has recently been proved to be useful in diagnosis, as it is also highly specific, simple and practical in a routine basis. Nevertheless, it can cross-react with other helminths and its sensitivity might decrease in immunosuppressed individuals.
The main objective of this thesis is to assess the epidemiological trend of strongyloidiasis in Spain, its impact in the health system and the potential role of migration, alongside with risk factors for disease development.
A systematic review of published cases in Spain was initially carried out, showing that strongyloidiasis is reemerging due to imported cases. The first study in this thesis aimed to estimate the impact of strongyloidiasis in our sanitary system. Data were obtained from the Conjunto Mínimo Básico de Datos (CMBD). Hospital admissions reached from 0.01 to 0.10 x 100.000 person/years in 15 years, with an average cost of 17 122 ± 97 968 euros. Crude mortality was 7.9%. The second study aimed to describe the clinical and epidemiological profile of severe cases,. A retrospective review of all the severe cases attended at reference centers was performed. In every case, larvae were identified by optic microscopy techniques or at necropsy. Serology was performed in half of the patients, with 100% sensitivity. 94.4% of the cases were imported. Corticoid use and/or a retrovirus coinfection were present in most of them. Mortality was 11.1%. The third work in this thesis is a case-control study aiming to identify factors associated with simple estrongiloidiasis. Cases were matched according to the service/department were they were screened. Abdominal pain, epigastralgia, eosinophilia and raised IgE levels, along with coming from Latin America were associated with estrongiloidiasis, although these associations were less evident in those immunosuppressed. The appropriate time needed to determine treatment response might be longer than six months.
We conclude that strongyloidiasis incidence has increased by tenfold in our country, what has a high cost and huge mortality. Autochthonous cases are rare. People coming from endemic areas should be screened, especially those from Latin America and those presenting with an immunosupression condition. Disease should be suspected in the presence of gut symptoms, eosinophilia and raised IgE levels, although these last manifestations might be more infrequent in immunecompromised individuals.
