Endemic Strongyloidiasis in Northern Italy: Clinical and Immunological Aspects

Abstract

One hundred and eighteen cases of S. stercoralis infection were detected by stool examination among 4203 patients seen over a period of three years at the Division of Infectious Diseases (IRCCS, San Matteo, University of Pavia) of a University Hospital in Northern Italy. Because chronic strongyloidiasis is often asymptomatic, a 3 per cent prevalence in this selected population indicates that the parasitosis may be much more frequent in the general population of the area. Parasite-specific humoral responses were studied in 48 patients. Strongyloides-specific IgG and IgA antibodies were found by ELISA in the serum of 40 (83.3 per cent) and 43 (89.5 per cent) patients, respectively, and specific IgE antibodies were detected by RAST in 39 (81.3 per cent). The specific IgG antigen recognition patterns of these patients were compared by immunoblotting with those of North and South American and Thai patients, and differences among the groups suggested the existence of separate geographic strains of S. stercoralis. This was further supported by the virtual absence in our patients of the larva currens, a common and highly characteristic sign of strongyloidiasis in subjects infected in southeast Asia. More awareness of the epidemiologic and clinical features of strongyloidiasis, with the use of serologic tests to screen candidates for immunosuppression, may result in the early detection of chronic uncomplicated strongyloidiasis and in the prevention of fatal opportunistic hyperinfections.