Studies on Schistosome Dermatitis

A novel schistosome species hosted by Planorbella (Helisoma) trivolvis is the most widespread swimmer's itch-causing parasite in Michigan inland lakes

“…1 ). Lakes and sites were selected to include locations throughout MI's lower peninsula where SI had been documented in past scientific studies (McMullen and Brackett, 1948 ; Jarcho and van Burkalow, 1952 ; Kulesa et al ., 1982 ; Rudko et al ., 2018 , 2019 ), news reports (Durham, 2018 ) or historical state-wide reports of copper sulphate treatment permits and SI control efforts in MI between 1929 and 1976 (Newton and Fetterolf, 1967 ; Seeburger, 1969 ; Michigan Bureau of Land and Water Management, 1976 ). These sites represented a wide range of lake sizes (approximately 30–19 000 acres), shoreline types (e.g.…”

“…For analytical purposes, we separated sites into northern (north of Thompsonville), mid-latitude and southern (south of Grand Rapids) regions, roughly corresponding to regions defined by McMullen and Brackett ( 1948 ) in their historical state-wide SI survey (see Fig. 1 ).…”

“…Early reports from the Division of Water Itch Control indicated that ‘from 1939 to 1942 Michigan had the most extensive endemic areas of schistosome dermatitis in the world’ (Cort, 1950 ), and implicated the single species Trichobilharzia stagnicolae as causing ‘most of the swimmer's itch so prevalent on the bathing beaches in northern Michigan’ (Cort et al ., 1940 ). Perhaps due in part to this early assessment, studies from 1940 to 2018 focused mostly on the biology of T. stagnicolae (hosted by Lymnaea catescopium = Stagnicola emarginata ; Walter, 1969 ; Burch, 1989 ; Correa et al ., 2010 ) in northern MI inland lakes (McMullen and Brackett, 1948 ; Keas and Blankespoor, 1997 ; Muzzall et al ., 2003 ; Coady et al ., 2006 ; Gordy et al ., 2018 ; Rudko et al ., 2018 ; McPhail et al ., 2021 ). Lymnaea catescopium is largely restricted to northern MI (Wall, 1976 ), which may help explain why SI surveys of snails tended to focus on this region despite reports of SI cases from throughout the state (Clampitt, 1972 ; Wall, 1976 ).…”

“…; Cort, 1950 ; Muzzall et al ., 2003 ) or to the distribution of snail-borne parasites further south (but see McMullen and Brackett, 1948 ; Najim, 1956 ; Guth et al ., 1979 ; Kulesa et al ., 1982 ; Laman et al ., 1984 a ; Strohm, 1979 ) despite increasing reports of SI cases in south MI after 1950 (Clampitt, 1972 ; Wall, 1976 ). To our knowledge, only 2 studies to map state-wide gastropod distributions have been conducted in MI, including a survey of SI-producing snails by McMullen and Brackett ( 1948 ) and a study that mapped snail observations based on museum specimens (Wall, 1976 ). Both studies focused on Lymnaea and Physa .…”

“…Almost no historic studies of SI in MI reported screening Planorbella snails (e.g. McMullen and Brackett, 1948 ; Wall, 1976 ; Muzzall et al ., 2003 ; but see Strohm, 1979 ), despite this being one of the first documented host snails for schistosomes in the state (‘ Cercaria elephantis ’ from Douglas Lake; Cort, 1917 ). Cercaria elephantis did not cause human dermatitis in initial tests (Cort, 1928 ), but an early study outside MI confirmed that Planorbella sp.…”