Actually, we've come quite a bit further than leeches today. There are specialized pieces of equipment called needles and syringes, when properly applied, can extract a relatively precise amount of blood in a short period of time. Seriously, the use of leeches in surgical therapy is restricted more to traumatic wounds in which there is interrupted or diminished venous outflow (such as crushing injuries). The leech helps in these situations by removing a portion of the congested venous blood, as well as releasing natural anticoagulants and anti-inflammatories locally - substances that are primarily release for its feeding, but also have beneficial effects in these wounds. P. vera is largely a neoplastic proliferation of the red blood cells. In these cases, the blood becomes so thick that it can actually sludge in the small vessels of the body, resulting in hemorrhage and infarction of these tissues. Periodic bleeding is needed simply to keep the level of the RBCs at a normal level. This is an unusual case, and it will be interesting to monitor over time to see how effective periodic phlebotomy (still the primary mode of treatment in humans) works in this ferret. With kindest regards, Bruce Williams, dVM [Sukie note: I am not the one with the ferret that has Polycythemia vera, but I was the one to ask about leeches! :-) ] [Posted in FML issue 3470]