Bleeding in human volunteers from the bite of the American medicinal leech Macrobdella decora compared with its European counterpart Hirudo medicinalis

Abstract

In this paper the effectiveness of the so-called American medicinal leech Macrobdella decora in overcoming human haemostasis is compared to that of the European medicinal leach Hirudo medicinalis. Thrombin-clotting times indicated that M. decora prevents coagulation of human blood by means of anti-thrombin activity. Our findings suggest that its role is similar to that of hirudin. In human volunteers, the duration of bleeding from the bite of M. decora (mean = 73 min; n = 18) is significantly shorter than H. medicinalis (mean = 600 min; n = 15). The mean concentration of anti-thrombin units in each specimen of M. decora and H. medicinalis is 100 and 285 AT-U, respectively. These findings support the concept that H. medicinalis is more advanced in terms of haematophagous predation. Despite similar feeding durations by both species of leech (means = 68 min and 70.5 min by M. decora and H. medicinalis, respectively), the mean increase in body weight of M. decora was only 58% compared to 460% in H. medicinalis.