What are Leeches, Anyway?

Facts about Leeches

With sufficient preparation, travelers can learn to appreciate Madagascar’s leeches as part of the incredible rainforest experience.

Slimy, black, amorphous creatures slink through forest leaf litter, and scamper up tree trunks and branches, awaiting the first sip of mammalian blood they can find. Fossa, lemur, human: any blood will do. A leech’s bite is painless, and, among humans, leeches spread no diseases. They’re easy to remove, and will fall off independently once they’re full. Nonetheless, these harmless critters can be the most repulsive, frightening aspect of jungle exploration. A little knowledge and preparation can dissolve unnecessary fear.

Leeches in Madagascar

Leeches are annelids, closely related to earthworms. They have suction on their anterior to cling to their prey while they pierce the skin and ingest blood with their mouth, on the opposite end. Their body, between either end, is little more than a fluid-filled sac, which can retract and expand as it fills with blood.

Madagascar is home to a wide diversity of leeches. For example, in Ranomafana National Park alone, researchers have recently identified five unique species. These range in size, color, and shape, from a long, dark black hammerhead, to a shorter, brown-bellied tube shape. Compared to aquatic species found in other parts of Africa, Madagascar’s leeches are small: 0.5-4.0 cm, and exist in abundance in any forested area.

What to Do When Leeches Bite

When unperturbed, a leech won’t attach to the first skin it finds. Instead, it searches for softer skin: wrists, elbows, underarms, neck, knees. As it crawls about, it uses only one end as suction, alternating like a slinky, end over end. At this stage, it is easiest to remove. One can simply grab and pull; devoid of blood, it is unlikely to burst. Leeches are stubborn, and logically so. A leech may encounter only one potential source of blood in its lifetime; it’s going to do everything it can to hang on. Local Malagasy have found an excellent solution: if rolled between forefinger and thumb, leeches become disoriented and drop off.

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Once a leech has pierced the skin, there are two possible ways to address the problem: flick it off or ignore it. To remove it, rapidly push a thumbnail beneath the leech’s mouth. This will send it flying. Some describe a mild itching sensation, as the leech may leave behind its mouthparts once it has started sucking. The best alternative is to ignore it! After half an hour, the leech will fall off, engorged, ready to spend the next 3-4 months digesting its meal.

Leeches release a clear fluid, which contains an anticoagulant, to prevent blood clotting, and an anesthetic, which locally numbs the nerves of its prey. Therefore, allowing the leech to consume all the blood it desires won’t hurt, and won’t cause enough blood loss to concern a healthy adult human. The bite may continue leaking for about ten minutes afterward and will leave behind a small purple bruise, but these minor side effects are no reason for alarm. Skin and clothes should be washed with soap and cold water to remove the blood and prevent infection.

How to Prevent Leech Bites

Though painless and free of disease, leech bites can be messy and obnoxious. The best way to prevent bites is to wear lots of clothing. Long-sleeved shirts and long pants, even in the humid summer months, are a practical choice. Leeches can’t crawl through polyester, and wool dries them out. Knee-high nylons are useful above tall socks; the nylons keep leeches from crawling through holes in the socks, while the socks keep leeches from biting directly through tight nylons. Pants can be tucked into the nylons and socks, just as the shirt should be tucked into the pants. Duct or masking tape can be placed over any zippers; otherwise, leeches can crawl through the hole between zipper ends. A brimmed hat impedes leeches falling from tree branches above, and, for the extra-cautious traveler, a mosquito head net, tucked into the top of the shirt, shields the vulnerable neck and face.

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Particularly for the hands, which are not covered by clothing, spray 30-40% DEET, which wards off both leeches and mosquitos. If not reapplied, however, this spray becomes ineffective after a couple of hours of sweating.

How to Overcome Fear of Leeches

Though understandable, fear of leeches is completely unfounded. Especially if foreigners wish to fit in among rural Malagasy, for whom leeches are as common as coffee at breakfast, they should accept the fascinating, diverse critters as a standard asset to adventure in the forest. The fastest way to make peace with the blood-suckers? Hike in shorts and a t-shirt, and leave them be. Handfuls of leeches will render arms and legs a bloody mess, but in the future, a single leech will seem as insignificant and harmless as it really is.

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