Observations on mass production of Calicophoron microbothrium metacercariae from experimentally and naturally infected Bulinus tropicus.

In an attempt to establish an ideal method for mass production of Calicophoron microbothrium metacercariae, a study was carried out to compare the shedding capacities of Bulinus tropicus naturally and experimentally infected with C. microbothrium. A total of 906 F1 B. tropicus between 4 and 5 weeks old were each experimentally infected with two C. microbothrium miracidia and monitored for 12 weeks. The infected snails were fed on dried lettuce and fish flakes and were kept in 1 l plastic aquaria housed in a snail room where temperature, light and humidity were controlled. Seventy-four percent of the experimentally infected snails died during the prepatent period and of the remaining, only 13.2% developed patent infection, while 12.5% were refractory. Snail growth rate was poor and the average shedding rate was 20 cercariae per snail per day. Compared to the experimentally infected snails, 2200 adult B. tropicus, collected from the field and naturally infected with C. microbothrium, yielded high numbers of metacercariae. Eighty-four percent of the snails died within 7 weeks of the study with peak mortality occurring from the 2nd to the 4th week of infection and coinciding with an overall decrease in the number of cercariae shed.