Lymnaea tomentosa, the intermediate host of a schistosome which causes schistosome dermatitis in Lake Wanaka, was found to depths of 16 m. The snail recruits in January, lives for up to 21 months, is associated with all water plant species and is found in areas devoid of macroscopic plants. It is host to several trematode species. Avian schistosome infections appear in the spring when echinostome prevalence is low, and a decrease in schistosome prevalence may be correlated with an increase in echinostome prevalence during the summer. A multiple-kind lottery model analysis of parasite species richness implies that interspecific interactions may be occurring in the host snail during the months of December and January.

In response to annual outbreaks of human cercarial dermatitis (HCD) in Lake Wanaka, New Zealand, ducks and snails were collected and screened for avian schistosomes. During the survey from 2009 to 2017, four species of Trichobilharzia were recovered. Specimens were examined both morphologically and genetically. Trichobilharzia querquedulae, a species known from four continents, was found in the visceral veins of the duck Spatula rhynchotis but the snail host remains unknown. Cercaria longicauda [i.e. Trichobilharzia longicauda (Macfarlane, 1944) Davis, 2006], considered the major aetiological agent of HCD in Lake Wanaka, was discovered, and redescribed from adults in the visceral veins of the duck Aythya novaeseelandiae and cercariae from the snail Austropeplea tomentosa. Recovered from the nasal mucosa of Ay. novaeseelandiae is a new species of Trichobilharzia that was also found to cycle naturally through Au. tomentosa. Cercariae of a fourth species of Trichobilharzia were found in Au. tomentosa but the species remains unidentified.

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Waterfowl from Lake Wanaka and the Waitaki Lakes watershed of New Zealand's South Island were surveyed to find natural hosts with adult echinostomes and schistosomes to provide sufficient numbers of eggs for laboratory studies. The Canada goose (Branta canadensis) was found to host an echinostome determined to be a New Zealand strain of Echinostoma revolutum. The New Zealand scaup (Aythya novaeseelandia) concurrently hosts three species of echinostomes (E. revolutum, Echinoparyphium cinctum and E. recurvatum) plus two species of avian schistosomes (Trichobilharzia sp. and Dendritobilharzia pulverulenta). In the Canada goose and the New Zealand scaup, adult gravid echinostomes predominated over juveniles. In other waterfowl surveyed, very few echinostomes were found, with juveniles predominating.

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