In vivo and in vitro studies on the viability and the infectivity to coots, Fulica americana, of Cyclocoelum mutabile metacercariae from three species of snails

The host response to and the viability and infectivity of metacercariae of Cyclocoelum mutabile were examined in three species of pulmonate snails, Stagnicola elodes, Gyraulus parvus, and Promenetus exacuous. Host response was generally similar among snail species at 8 weeks post infection. Host responses increased with age of infection in S. elodes. There was no difference in the excystment success of metacercariae from each species at 8 weeks post infection. The mean excystment time in vitro was greater for metacercariae from S. elodes than for those from either G. parvus or P. exacuous at 8 weeks post infection. There were no differences in either excystment success or mean excystment time of metacercariae from 5-, 8-, and 30-week-old infections from S. elodes. The mean infection success of metacercariae from S. elodes was lower than that of metacercariae from G. parvus and P. exacuous in juvenile coots. Adult coots were less susceptible to infection than juveniles. There was no difference in the infection levels established in naive and previously infected adult coots.