Acute schistosomiasis occurs during the invasion and migration stages of the parasite’s life cycle.
- often seen in travellers or immigrants to schistosome endemic regions who are infected with the antigen for the first time
- in the case of S japonicum it is also associated with either a superinfection or a hypersensitivity reaction in previously infected people
- symptoms are mediated by the immune complexes which usually begin with the deposition of schistosome eggs into host tissues (1,2,3).
Four acute presentations have been recognised:
- swimmer's itch
- occurs when the parasites initially enter the skin
- this is a local inflammatory, hardly visible wheal at the site of penetration
- duration and reaction of this reaction may vary with the duration of schistosomular stay in the dermis
- cercarial dermatitis
- a temporary itchy maculopapular skin eruption, comprising discrete, 1 cm to 3 cm erythematous raised macules
- may develop at the site of entry of the parasite
- pathogenetically similar to the ‘‘swimmers itch’’
- is not a sequela of acute schistosomiasis, but develops in sensitized people when they are re-infected by schistosomal species that do not colonize in humans
- bronchopneumonia
- bronchial hyper-reactivity with radiologically demonstrable pulmonary infiltrates may occur during the migration of schistosomulae through the pulmonary capillaries
- may also occur with superinfection in previously infected people
- Katayama fever/ Katayama syndrome -
- this is an allergic response and usually develops 1-2 months after contact with contaminated water.
- is characterised by - fever, arthralgia and vasculitic skin eruption
- generally self-limiting and patients recover spontaneously after 2–10 weeks.
- some may develop persistent and more serious disease with weight loss, dyspnoea, and diarrhoea, diffuse abdominal pain, toxaemia, hepatosplenomegaly and widespread rash
- Katayama fever is more noticeable in S. japonicum infection than other forms
- serological testing and stool and urine testing will be negative in this phase of the illness. Worms take six to ten weeks to start egg production and so screening tests for schistosomiasis should be delayed until about 12 weeks after last exposure (1,4).
- further clinical features depend whether the infection leads to urinary schistomiasis (S. haemotobium) or intestinal schistosomiasis (S. mansoni, S. japonicum, S. intercalatum, S. mekongki)
Note that the majority of travellers with acute infection will be asymptomatic, the most commonly reported symptom being tiredness (4).
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