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Because of previous isolated reports of swimmer’s itch at the stage 1 lake, periodic surveys by sweep netting commenced in July 1990. For each of six localities covering three distinct habitat types (open bays within the lake, along the margins of permanent creeks, temporary ponds), 1 m quadrats containing all vegetation types were scoured for snails. Austropeplea snails were not present in the lake proper until February 1991, but in November 1990 they were first located in ponds along the north-east, east and south-western shorelines. Egg masses were often found attached to the undersides of nardoo (Marsilea mutica) and sometimes wrapped around the stalks and ventral surfaces of the water lily, Nymphaea gigantea. Thus its absence from the lake was attributed to the lack of established vegetation in the stage 2A lake, and from this we developed a working hypothesis that host snails were possibly vegetation-specific. Thus to facilitate recreational use, control of infected Austropeplea could be achieved by simply clearing the appropriate water plant. By July to August 1991, however, schistosome-infected Austropeplea were collected from various types of vegetation along the margins of Ross River, close to the lake. A few Amerianna and Gyraulus gilberti were found in Ti-Tree Bay contiguous with Big Bay and Round Island, which were still negative for snails. By February 1992, planorbids were present in all three habitat types, with Austropeplea in two, i.e. ponds and creeks around the lake. Until 1993, 2,365 snails were dissected to detect both patent and pre-patent Trichobilharzia infection. Four different species of snails were identified, size classed according to shell length or width using vernier calipers. Snails were crushed on a microscope slide or in a Petri dish with a few drops of water under a warm light. A heavy infection of cercariae is evident to the naked eye, but any worm-like animals were removed on to another slide, stained with two to three drops of 0.1 per cent neutral red dye, covered with a coverslip and examined microscopically. Schistosome cercariae are distinctive with their eye spots, forked tail and presence of oral and ventral suckers (see Figure 9.4). Schistosomes were recovered from 4.5 per cent and 1.7 per cent of Austropeplea and Gyraulus gilberti snails, but not from Amerianna nor Thiara. In terms of management solutions, several questions seemed paramount: • Which habitat types presented the greatest (and lowest) risk? • Which time of the year presented the greatest hazard? • Can certain indicators be used to predict infection? Statistical analysis of the presence and abundance of Austropeplea snails did not correlate with any particular vegetation type (Hurley et al. 1995) but was connected with vegetation generally. There was no clear-cut relationship with snail density and physicochemical parameters including temperature, biomass of periphyton or with percentage surface coverage. However, highest densities of Austropeplea lessoni (45/m and Amerianna
DOI link for Because of previous isolated reports of swimmer’s itch at the stage 1 lake, periodic surveys by sweep netting commenced in July 1990. For each of six localities covering three distinct habitat types (open bays within the lake, along the margins of permanent creeks, temporary ponds), 1 m quadrats containing all vegetation types were scoured for snails. Austropeplea snails were not present in the lake proper until February 1991, but in November 1990 they were first located in ponds along the north-east, east and south-western shorelines. Egg masses were often found attached to the undersides of nardoo (Marsilea mutica) and sometimes wrapped around the stalks and ventral surfaces of the water lily, Nymphaea gigantea. Thus its absence from the lake was attributed to the lack of established vegetation in the stage 2A lake, and from this we developed a working hypothesis that host snails were possibly vegetation-specific. Thus to facilitate recreational use, control of infected Austropeplea could be achieved by simply clearing the appropriate water plant. By July to August 1991, however, schistosome-infected Austropeplea were collected from various types of vegetation along the margins of Ross River, close to the lake. A few Amerianna and Gyraulus gilberti were found in Ti-Tree Bay contiguous with Big Bay and Round Island, which were still negative for snails. By February 1992, planorbids were present in all three habitat types, with Austropeplea in two, i.e. ponds and creeks around the lake. Until 1993, 2,365 snails were dissected to detect both patent and pre-patent Trichobilharzia infection. Four different species of snails were identified, size classed according to shell length or width using vernier calipers. Snails were crushed on a microscope slide or in a Petri dish with a few drops of water under a warm light. A heavy infection of cercariae is evident to the naked eye, but any worm-like animals were removed on to another slide, stained with two to three drops of 0.1 per cent neutral red dye, covered with a coverslip and examined microscopically. Schistosome cercariae are distinctive with their eye spots, forked tail and presence of oral and ventral suckers (see Figure 9.4). Schistosomes were recovered from 4.5 per cent and 1.7 per cent of Austropeplea and Gyraulus gilberti snails, but not from Amerianna nor Thiara. In terms of management solutions, several questions seemed paramount: • Which habitat types presented the greatest (and lowest) risk? • Which time of the year presented the greatest hazard? • Can certain indicators be used to predict infection? Statistical analysis of the presence and abundance of Austropeplea snails did not correlate with any particular vegetation type (Hurley et al. 1995) but was connected with vegetation generally. There was no clear-cut relationship with snail density and physicochemical parameters including temperature, biomass of periphyton or with percentage surface coverage. However, highest densities of Austropeplea lessoni (45/m and Amerianna
Because of previous isolated reports of swimmer’s itch at the stage 1 lake, periodic surveys by sweep netting commenced in July 1990. For each of six localities covering three distinct habitat types (open bays within the lake, along the margins of permanent creeks, temporary ponds), 1 m quadrats containing all vegetation types were scoured for snails. Austropeplea snails were not present in the lake proper until February 1991, but in November 1990 they were first located in ponds along the north-east, east and south-western shorelines. Egg masses were often found attached to the undersides of nardoo (Marsilea mutica) and sometimes wrapped around the stalks and ventral surfaces of the water lily, Nymphaea gigantea. Thus its absence from the lake was attributed to the lack of established vegetation in the stage 2A lake, and from this we developed a working hypothesis that host snails were possibly vegetation-specific. Thus to facilitate recreational use, control of infected Austropeplea could be achieved by simply clearing the appropriate water plant. By July to August 1991, however, schistosome-infected Austropeplea were collected from various types of vegetation along the margins of Ross River, close to the lake. A few Amerianna and Gyraulus gilberti were found in Ti-Tree Bay contiguous with Big Bay and Round Island, which were still negative for snails. By February 1992, planorbids were present in all three habitat types, with Austropeplea in two, i.e. ponds and creeks around the lake. Until 1993, 2,365 snails were dissected to detect both patent and pre-patent Trichobilharzia infection. Four different species of snails were identified, size classed according to shell length or width using vernier calipers. Snails were crushed on a microscope slide or in a Petri dish with a few drops of water under a warm light. A heavy infection of cercariae is evident to the naked eye, but any worm-like animals were removed on to another slide, stained with two to three drops of 0.1 per cent neutral red dye, covered with a coverslip and examined microscopically. Schistosome cercariae are distinctive with their eye spots, forked tail and presence of oral and ventral suckers (see Figure 9.4). Schistosomes were recovered from 4.5 per cent and 1.7 per cent of Austropeplea and Gyraulus gilberti snails, but not from Amerianna nor Thiara. In terms of management solutions, several questions seemed paramount: • Which habitat types presented the greatest (and lowest) risk? • Which time of the year presented the greatest hazard? • Can certain indicators be used to predict infection? Statistical analysis of the presence and abundance of Austropeplea snails did not correlate with any particular vegetation type (Hurley et al. 1995) but was connected with vegetation generally. There was no clear-cut relationship with snail density and physicochemical parameters including temperature, biomass of periphyton or with percentage surface coverage. However, highest densities of Austropeplea lessoni (45/m and Amerianna
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