Microsurgery: Transplantation and Replantation by Harry J. Buncke, MD, et al.
  Table of Contents / Chapter 40:
The Use of Medicinal Leeches in Microsurgery
  Mann and others9-11 have described the medicinal leech in great detail. The animal is approximately 12 mm long, although it is usually contracted to about one-third of this size at rest. It is a dark brownish green color with black or dark brown stripes running longitudinally. The body is made up of 102 annuli; 5 annuli constitute a segment, except at each end, where the number of annuli per segment is decreased progressively. The body is tapered at each end, the narrower being the anterior sucker, or mouth, and the larger, disc-like end, being the posterior or attachment sucker.

The anterior sucker is equipped with a retractable system of three sharp jaws comprised of semicircular muscular ridges with numerous minute teeth along their edges. The jaws are brought forward, and with a sawing action, create a Y-shaped incision through which a local anesthetic, hirudin, a vasodilator, and other physiologically active substances are instilled. These substances are elaborated by perioral unicellular salivary glands.

Leeches are hermaphrodites, having both male and female pores. They feed infrequently and may live for as long as 200 days without food.11-13 When they do feed, they can take from two to five times their body weight in blood at one meal. The blood is then digested in the gut over a 100-day period, during which water is extracted and excreted through 17 pairs of ventrally located nephridia. No gut proteolytic enzyme has been identified.14-17 The digestion process appears to be carried out by symbiotic bacteria. Original studies of leech digestion identified the predominant leech enteric organism as Pseudomonas hirudinis or Aeromonas liquefaciens.l8-20 Current studies20 identify Aeromonas hydrophila as the predominant organism, and some researchers caution against the use of leeches because they pose a danger of serious infection. As an alternative, based on a single case, Whitlock et al.20 suggests the use of Hirudoid cream, which has purported to have antispasmodic and standardized anticoagulant activity.


Despite these concerns, leeches have been increasingly used without widely reported infection problems. The continued bleeding following leech therapy rinses out the wound and may be an important factor limiting the possibility of wound infection in the patient. Sawyer 21 suggests that this bleeding has adaptive significance in the wild because infection might deplete the number of available hosts, thus jeopardizing the leeches' own survival.

The possibility exists, however, that use of leeches on or near open wounds, macerated tissue, or eschar can result in superficial or invasive Aeromonas hydrophila infection. 22,23

Antibiotics should be considered when leeches are used, especially near compromised tissue. Leeches ingest circulating medication with their host's blood. Antibiotics effective against Aeromonas hvdrophila may therefore sterilize the leech gut and protect host tissue against infection.16 Parenteral antibiotics that are effective against Aeromonas hydrophila include cefoxitin, third-generation cephalosporins (e.g., cefotaxime), and trimethoprim- sulfamethoxasole.24

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