Nope, not how to kill snails (for once) but a question on whether anyone's ever run across info on specific pathogens or parasites that affect snails--but not shrimp, scuds or fish.
Last summer I set up a planted vase for a selective breeding project with bladder snails (black and striped shell variations). Gradually, the population explosion waned and I found fewer and fewer succesful hatchings and started seeing a bewildering number of adult snails dead on the substrate. Commonly the shrimp and fish found the dead snails before me and I only found empty shells, but observation eventually turned up a pattern of the snails appearing to have at least partially, if not entirely, left their shells before death, with the bodies lying just outside the shell or with only a small portion of the tail still holding it in. Snails found in the process of dying confirmed this.
I quarantined the vase, did a thorough gravel vac, replaced the hardscape and most of the plants with new trimmings from my main tanks (with healthy snail populations)--but any snail introduced to this vase dies within four days: pond, bladder, nerite, rams horn, even MTS!
While I've maintained a quarantine on plant transfers between tanks, fish taken from the vase and set up in a new tank have apparantly NOT brought the problem with them--as the new tank has a healthy population of ponds, rams and MTS several weeks after the fish being introduced.