Tyranny of Monsoon Leeches

Sanguivorous leeches thrive during wet conditions, vying for a trekker’s 10 pints of blood. During the monsoon, they are abundant in forests above 4000 feet (1200 m)…and the author once became attached to one at over 12,000 ft (3700 m). These jawed, terrestrial parasites (Gnatbobdellida of the suborder Hirudiniformes) are sensitive to light and attracted to movement, warmth, and by-products of respiration. Leeches can drop from vegetation or “crawl” in inch-worm fashion (by using suckers at each end of the body) up from the ground as well as attach from leaves or rocks. Leeches find hosts by detecting shadows, mechanical stimuli of vibrations and heat as well as chemicals (carbon dioxide and skin oils).

As ecto-parasites, they attach themselves by means of tiny teeth with sharp cutting edges. Although leeches feed off the blood of a host, bites usually go unnoticed because a concomitant anesthetic is released. They also disperse an anticoagulant (the peptide hirudin is in their saliva) to keep the prey’s blood flowing and eventually, will drop off once sated. This may take twenty to forty minutes or longer, in which time the leech can swell, bloated on the blood feast, many times in size.
A single feeding is enough to sustain a leech for several months and they burrow into the ground to survive long dry periods. Leeches are hermaphroditic and deposit eggs in a cocoon after copulation and exhibit advanced care of young not usually seen in the phylum Annelida. They also have modern day medical relevance and can be used during recovery in plastic and reconstructive surgery cases and are helpful in the drainage of pooled blood, especially to relieve venous congestion and maintain circulation.

To remove a leech in the wild, use the leading edge of a fingernail (or other flat object) scraped along the skin to dislodge the thinner, anterior end at the attachment site. Keep the wound clean. Other means of removal—such as pulling or using heat, salt, alcohol, or insect repellent—can cause the leech to release the contents of its stomach which contain bacteria and may infect the bite area. Jawed leeches are not known to be transmitters of disease, however, because of anticoagulants there might be considerable blood flow. Control the minute lesion with pressure, and watch for signs of infection later. Rarely, some people have an anaphylactic or other allergic reaction to leech bites, requiring serious medical attention.

If embarking on a monsoon trek, certain items of equipment are essential: a waterproof pack cover, sheets of plastic for porter loads, plastic bags for gear inside the pack, an umbrella, a hat with a brim, a walking stick, footwear with good traction and especially leech protection. The best preventive to bites is to cover the skin. However, leeches often find a way through clothing. Some insect repellents work when applied to boots, lower legs and exposed skin. “Anti-Leech Oil,” a potent elixir of five oils, is available in some pharmacies and shops in Kathmandu and at the Kathmandu Environmental Education Office (KEEP) in Kesar Mahal, Thamel. Other options include eucalyptus oil, lemon juice, or, in a pinch, smearing bath soap over dry skin. Leech-proof socks could be worn over regular socks. With preparation, a foray into the leech infested heights can be relatively terror free!