Schistosome dermatitis in the Swan Estuary, Western Australia
Appleton, C.C.; Lethbridge, R.C.
Medical Journal of Australia 1(5): 141-145
1979
ISSN/ISBN: 0025-729X PMID: 449750 Document Number: 144260
A survey of gastropod molluscs from the Swan River estuary, Western Australia, revealed that one of the most abundant species, Velacumantus australis, was releasing schistosome cercariae. A maximum of 9% of the snails was infected. The cercarae emerged in greatest numbers between 10 a.m. and 12 noon and emergence commenced at a water temperature of 23 deg C. Adult schistosomes identified as Austrobilharzia terrigalensis were recovered from the mesenteric veins of chickens and a fledgling Larus novaehollandiae 25 to 67 days after they were exposed to cercariae. 10 of 13 adult L. novaehollandiae from Carnac Island were naturally infected with this parasite and examination of faecal pellets deposited by this gull revealed an infection rate of 69.6%. A. terrigalensis is concluded to be 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 5 to 14 years old were most frequently affected. Most cases of dermatitis were contracted between 11 a.m. and 12 noon. Exposure times varied considerably, but were generally between 30 and 90 min, with dermatitis appearing 12 to 24 hours later. The lesions, which were sometimes widespread over the body and itched severely, persisted for one to 2 weeks and longer if they were secondarily infected. Approximately 38% of affected people consulted doctors about their condition.