Schistosome dermatitis in the Swan Estuary, Western Australia.

The avian blood fluke, Austrobilharzia terrigalensis (Trematoda: Schistosomatidae), is recorded in Western Australia for the first time, and is implicated as the cause of dermatitis among users of the Swan estuary in Perth. Quantitative data provided by a questionnaire sent to affected people showed that infection occurred from November to March in the shallows throughout the "middle" estuary and that children from five to 14 years old were most frequently affected. Most cases of dermatitis were contracted between 11 a.m. and 12 noon--the time of day when the emergence of A. terrigalensis cercariae from the intermediate host, Velacumantus australis, reaches a peak. Exposure times varied considerably, but were generally between 30 and 90 minutes, with dermatitis appearing 12 to 24 hours later. The lesions, which were sometimes widespread over the body and itched severely, persisted for one to two weeks and longer if they were secondarily infected. Approximately 38% of affected people consulted doctors about their condition. These results are discussed in relation to findings on the ecology of the parasite's intermediate and definitive hosts.