Steven Kutcher is Hollywood's top bug wrangler.
Here is the email Shaz received from him:
I worked with live leaches. kept one as a pet Larry the leach. He would
have dinner with us . We would feed him raw meat. The Scene was shot on stage in a heated water cave set. The gag was the science character was supposed to shock the leaches off. by using two wires from a battery they had. We had live and fake leaches. Steven Spielberg helped me a bit by handling some. We had trouble making them stay on I seem to recall. It was fun and the actors were great.
All the best,