Difficulties in the Diagnosis and Treatment of Acute Schistosomiasis

To the Editor—We read with interest the recent clinical description of an outbreak of acute schistosomiasis by Leshem et al. in Clinical Infectious Diseases [1]. We have some comments regarding the diagnosis and treatment of acute schistosomiasis in nonimmune travelers. Making a diagnosis of acute schistosomiasis is difficult. In this outbreak, diagnosis relied on positive serologic test results in 15 (68%) of the 22 exposed patients and on the combination of clinical symptoms and eosinophilia in 6 patients. Neither method of diagnosis is sensitive enough. Serologic test results are usually negative at the onset of clinical signs, and tests must be repeated to identify seroconversion, which may appear up to 3 weeks after the onset of symptoms and ∼6 weeks after exposure [2, 3]. At the first encounter with a clinician, serologic test results are positive in ⩽65% of cases [2, 4]. Eosinophilia may also be lacking at the onset of symptoms of acute schistosomiasis; it is only present in 27% of symptomatic patients and may appear up to 3 weeks after onset of fever [2, 5]. In addition, the serologic tests cannot identify the causal species of acute schistosomiasis. For example, reactivity against Schistosoma haematobium was identified in a subset of 3 patients, whereas 1 patient formally received a diagnosis of Schistosoma mansoni infection [1]. In addition, Charcot Leyden crystals were detected in 18% of tested patients, which also points to an intestinal helminthic infection, such as that caused by S. mansoni.