Symptoms may be discreet and comprise an urticarial rash and/or angio-edema, medium grade fever, a non-productive cough, abdominal pain, and diarrhea.5,10,19–22 In most patients of this cluster, symptoms were mild and had already resolved before treatment was given. In practice, AS is usually not recognized by primary
health care providers who are not familiar with tropical pathology. When the first symptoms appear, eosinophilia may not yet be raised.10 As illustrated with this cluster, eosinophilia will however increase rapidly in the course of the following days to levels rarely seen in other parasitic PTC124 diseases. Diagnosis is thus likely when at least one of the above symptoms appears in association with a clearly raised eosinophil count and with a primary exposure to schistosomiasis up to 90 days prior, pending confirmation of schistosome infection.1,23,24 In the early disease stage, diagnosis cannot be reliably confirmed by antibody tests or parasite detection methods.6,25 However, by the time patients are referred to a travel clinic, evidence of schistosomiasis
is found in most, mainly by serum antibody detection and/or ova detection in feces or urine.6,10,23,25 The current techniques for the laboratory diagnosis of AS have some shortcomings. Antibody production against adult worm and egg antigens starts only after schistosomules in the liver have been matured and after oviposition has started around the perirectal or perivesical venous plexus. This occurs at the earliest FDA approved Drug Library 6 weeks after infection, when symptoms may have largely subsided. Serological techniques used in clinical practice do not distinguish active infection from past exposure nor provide reliable information on parasite burden, and are not species-specific. Most routine techniques detect IgG, IgM, or IgE against soluble worm antigen (SWA) or soluble egg antigen (SEA) by ELISA, HAI or immunofluorescence. When combining assays using different sets of antigens in parasitologically confirmed infection, sensitivity may exceed 90% while retaining specificity at over
97%, but is less in AS.10,11,26,27 In this cluster, seroconversion failed to happen in three patients during the follow-up period, one parasitologically confirmed and two with symptomatic AS. Whether this is due to early treatment, a low parasite burden, or host Cyclic nucleotide phosphodiesterase immune response factors is unclear. In most travelers and migrants, established schistosomiasis infection is predominantly asymptomatic and with a low parasite burden, so that eggs are often not found in excreta.28,29 Nevertheless schistosome eggs were detected in feces of nearly all (6/7) symptomatic patients of this cluster. This may be due to low average age of patients, as well as to the relatively long average time lapse between exposure and diagnosis.30 There is thus a need for a more sensitive qualitative diagnostic test that confirms schistosomiasis infection at an earlier stage.