Leeches may seem creepy, but they are fascinating creatures that deserve more admiration. I know many people freak out when they see a leech on them, but I hope that we can learn to appreciate these amazing creatures - maybe even grab a selfie with them. Yeah, I know, that seems crazy.

I have the great privilege of living near a popular bushwalking trailhead. I often witness the amusing "leech dance" performed by walkers as they discover leeches upon returning to their cars. Arms flail, occasional screams fill the air, and sometimes people abandon their leech-infested shoes. I've seen individuals accidentally injure themselves in a frantic attempt to remove a tiny leech. But do these little creatures truly warrant such dramatic reactions?

Text Matt McClelland

Leech on leafPavel Kirillov, CC BY-SA 2.0

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Leech on mossDoug Beckers, CC BY-SA 2.0

Contrary to popular belief, leeches don't bite; they latch onto your skin using suction. Most people don't feel a leech feeding until they see the blood afterwards. Leeches can cause itchiness for a few hours or even a day, but removing them calmly and safely can minimise discomfort.

Habitat and distributionLeeches thrive in diverse environments, from freshwater bodies to wet rainforests and marine settings. Terrestrial leeches are often found in moistened areas of drier forests or burrowed in soil, while freshwater leeches prefer still or slow-moving water. Some leeches, considered amphibious, can be found in both terrestrial and aquatic habitats. Leeches are found in various habitats across Australia, except for permanently arid regions.

Feeding and dietMost leeches feed on the blood of different hosts, including humans, mammals, fish, frogs, turtles, and birds. Depending on their feeding mechanism, leeches can be categorised into three groups: jawed leeches, jawless leeches, and worm leeches. Leeches can ingest several times their body weight in blood and can survive long fasting periods due to slow digestion.

Hungry leeches are highly sensitive to light and mechanical stimuli, constantly changing positions and exploring their surroundings. They respond to disturbances from potential hosts by "inchworm crawling" until they make contact with the host and attach themselves. Aquatic leeches display more "pursuit" behaviour, while land leeches often attach to hosts accidentally.

BiologyLeeches belong to the segmented worm family and share similarities with earthworms but display unique physical and behavioural traits. With more than 500 leech species globally, leeches can be found in freshwater, marine, and terrestrial environments.

What sets them apart? Leeches have muscular bodies that are usually flat and segmented. Their body shapes and sizes can vary significantly, ranging from elongated worm-like forms to broad, pear-shaped figures. Leeches have two suckers: one at their mouth end (oral sucker), and a larger one at their tail (Caudal sucker). The tail sucker is not as strong, but it allows them to walk. Unlike other segmented worms, leeches don't have leg-like structures or bristles except for Acanthobdellida.

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TypesThe two main types of leeches are like different families within the leech world: “true” leeches are the most common, while Acanthobdellida leeches are a bit different. Among “true” leeches, there are two groups: one with a nose-like structure called a proboscis (Rhynchobdellida), and another without it (Arynchobdellida).

Leeches in actionLeeches breathe through their body walls, with slow undulating movements assisting in gas exchange. Their sensory organs detect changes in light, temperature, vibration, and chemicals, helping them navigate their environment. Some leeches can change colours, though the purpose of this behaviour remains unknown. Leeches move through either wavy swimming motions or inch-worm-like crawling using their suckers.

The leech lifecycleLeeches are hermaphroditic, possessing both male and female sex organs. Mating involves intertwining their bodies and exchanging sperm. Fertilised eggs are deposited in a gelatinous cocoon, and after hatching, the young emerge as miniature adults. Leeches typically die after one or two reproductive cycles.

Minimising Leech EncountersAlthough leeches are amazing creatures, you may still want to avoid them hitching a ride or feeding off your blood. Prevention is a good starting point.

We know leeches are typically found in warm, moist areas and use heat and carbon dioxide sensors to locate hosts. They usually wait on the ground or plants, attaching to passing people and migrating to places with softer skin. Being aware of that will help, but two other steps that can help are thinking about clothing and repellents.

ClothingWearing long pants tucked into socks or using anti-leech socks and gaiters can help prevent leeches from finding soft skin to latch onto. However, covering up also makes it harder to spot a leech if it does attach.

RepellentApplying insect repellent before heading out can discourage leeches from latching on. Some clothing can be treated with repellent, and it can also be applied to the skin. However, using repellent to remove a leech is not recommended due to the risk of infection from regurgitation.

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Leech (Haemadipsa zeylanica)Bernard Dupont, CC BY-SA 2.0

Removal rationaleThere isn't much medical research on the best techniques for leech removal. Using methods harmful to the leech, like applying salt, fire, pulling, or sprays may cause the leech to regurgitate. A leech regurgitating into a wound, especially before removal, may increase the risk of infection. Breaking the suction with a fingernail or credit card can remove the leech more quickly without giving it time or reason to regurgitate. There is no rush; when you find a leech, chances are it has been attached for a while, deep breath and take a few seconds to check it out. Grab a selfie - there are bonus points if your leech has yellow stripes.

First aid for leech "bites"

DRSABCD: Follow standard initial first aid procedures.

Reassure: Calm the person, as the sight of a leech can cause anxiety. Talking to the person with the leech through doing these steps themselves can help some people. If they can stop and admire it, then great, but if not, then now is not the best time to try.

Taut skin: Gently pull the skin under the leech until it's taut, and maintain for the next step.

Slide a fingernail: Gently slide a fingernail under the leech's mouth to separate it from the skin. Encourage the person to use their own fingernail to remove the leech, but if they can’t, then consider using a credit card or the back of a knife (not the sharp edge) to avoid the risk of infection. Alternatively, you can wait for the leech to fall off naturally, which usually takes about 30 minutes.

Flick away: Flick the leech away in a few seconds before it reattaches.

Clean the wound: Wash the wound with water and apply an antiseptic to help avoid infection.

Cover the wound: Use a simple adhesive pad; if blood soaks through, add another absorbent pad and bandage.

Monitor: Seek medical aid if there are signs of allergy or infection. Itchiness is common after removal; avoid scratching the site.

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