Emergent reuse leech therapy: a better method.

Tissues threatened by venous congestion often can be saved by timely leech therapy. Methods to restimulate sated leeches, particularly emergently, are only poorly described in the nineteenth-century literature. Sated leeches were purged of their blood meals by (1) posterior crop incision, (2) hypertonic saline (3 percent) immersion, (3) gentle finger pressure emesis, or (4) wood ash exposure. Their ability to reattach and refeed with or without serotonin stimulation was evaluated. All 20 leeches (100 percent) purged by posterior crop incision reattached, with 75 percent refeeding. After purging again, 87 percent of these refed leeches reattached, with 46 percent refeeding for a third time. Those leeches which did not initially refeed were exposed to serotonin 10 microM with 100 percent reattaching and 40 percent refeeding. None of the leeches purged by hypertonic saline immersion regurgitation reattached or refed. A single leech purged by finger pressure emesis reattached (20 percent) but did not refeed. After exposure to serotonin, two (40 percent) of each saline and finger pressure group reattached, with neither of the hypertonic saline group refeeding, while both finger pressure-purged leeches refed, consuming a meal 38 percent (+/- 29 percent) of original meal. None of those leeches which refed would reattach or refeed a third time. None of the wood ash-purged leeches reattached or refed even with serotonin exposure. The best method of purging leeches of their blood meals for emergent reuse is by posterior crop incision. Additional refeeding behavior can be achieved by immersion in serotonin 10 microM for 20 minutes.