Leeches, Mosquitoes and What Actually Works for Camping in Malaysia

If a leech latches on, the safest action is to wait. Let it finish feeding and drop off. If you cannot wait, dab iodine on the head so it releases. Salt, vinegar, flame and soap are traditional methods, but medical sources advise against them because they make the leech regurgitate its stomach contents into the wound.

The advice below comes from Malaysian health data, peer-reviewed field studies and operator sources, updated September 2026.

Leeches are part of tropical forest camping. They live in humid vegetation, lowland forest and near rivers, and they multiply when the soil is wet. In Borneo, the odds of meeting a tiger leech rose about 5-fold on wet soil. A brown leech rose about 5.6-fold, and encounters doubled after rain. No equivalent study exists for Peninsular forests, so Borneo is the nearest evidence.

When and where the risk rises

Malaysia's northeast monsoon runs November to March. It brings heavy rain to the east coast of Peninsular Malaysia, western Sarawak and the northeast coast of Sabah. On the east coast, November, December and January are the wettest months. June and July are usually the driest. Plan forest camps accordingly.

Two land leech species dominate Borneo rainforests. The tiger leech, Haemadipsa picta, can exceed 6 cm extended. The brown leech, Haemadipsa zeylanica, is only about 2 cm and its bite is often unfelt. Tiger leeches are more common in low-lying, water-retentive forest. Brown leeches appear more often at higher elevations. Neither is found in oil-palm plantations.

Repellents and what the numbers say

DEET is the strongest choice against land leeches. In field tests, DEET gave 88.4% repellency, deltamethrin 73.1%, and plant extracts 62.6% to 82.6%. Apply DEET to skin; permethrin 0.5% is for clothing, shoes and gear, never skin.

DEET also peaks for mosquitoes at about 50% concentration. Higher concentrations do not add much protection time. Products below 10% active ingredient last only 1–2 hours. Children can use DEET, picaridin, IR3535 and 2-undecanone without age limit. Do not use oil of lemon eucalyptus or PMD products on children under three.

Tobacco-soaked socks are sometimes shared online. A Sabah operator described an anecdotal home test, but no peer-reviewed evidence supports tobacco, Dettol, soap or medicated oils as leech repellents. Do not rely on them.

Mosquitoes and dengue

Aedes aegypti and Aedes albopictus bite mainly at dawn and dusk. These are the hours you cook and set up camp. Malaysia reported 122,423 dengue cases in 2024, down slightly from 123,133 in 2023. Selangor alone had 60,364 cases in 2024. Dengue killed 117 people in 2024 and 100 in 2023. It is a year-round, nationwide risk, not only urban.

Use about 50% DEET, long sleeves and permethrin-treated clothing at those hours. Sleep under a net or inside a closed tent. Repair torn mesh before the trip.

Leptospirosis in rivers and floods

Leptospirosis is the third most fatal infection in Malaysia after dengue and malaria. Incidence between 2010 and 2020 was 8.63–17.2 per 100,000 population. The case fatality rate was 0.6–2.4%. Most cases and deaths are linked to water activities.

Cover cuts before wading. Do not swallow river water. Do not camp on freshly flooded ground. Leptospira bacteria survive in rivers, ponds, streams, lakes and flooded areas, and enter through skin cuts and mucous membranes. After the 2014 Kelantan floods, 1,229 cases were identified and cases doubled in the post-flood period.

Pack this kit

• 50% DEET repellent for skin
• 0.5% permethrin spray for clothing, shoes and gear
• Anti-leech socks to seal the ankle gap
• Iodine tincture for leech removal if you cannot wait
• Long sleeves, long trousers and a brim hat for dusk
• A closed tent with intact mesh
• Antiseptic wipes, plasters, antihistamine and a cold pack for bites and stings

Check your body and boots after walks. A leech bite is usually painless, but the wound can bleed for a long time because hirudin in leech saliva stops clotting. Clean the wound with soap and water, then bandage it and apply pressure.

Frequently asked questions

What should I do if a leech bites me?

Let it finish feeding and drop off. If you cannot wait, dab iodine on the head so it releases. Then clean the wound with soap and water, bandage it and apply pressure. An antihistamine helps itching and a cold pack helps pain or swelling. Avoid salt, vinegar, flame and soap; medical sources say they make the leech regurgitate its stomach contents into the wound.

Does DEET work on leeches?

Yes. Field tests on humans in Southeast Asia found DEET gave 88.4% repellency against land leeches. Deltamethrin gave 73.1% and plant extracts gave 62.6% to 82.6%. DEET is the strongest choice.

Do ordinary socks and boots stop leeches?

No. Expedition medicine guidance says socks, trousers and boots provide little protection. Anti-leech socks worn over trousers at the ankle are the most effective chemical-free barrier.

Are mosquitoes a real danger at camp?

Yes. Aedes aegypti and Aedes albopictus bite mainly at dawn and dusk. Malaysia reported 122,423 dengue cases in 2024, with 117 deaths. Selangor alone had 60,364 cases. Use 50% DEET, long sleeves and permethrin-treated clothing, and sleep under a net or inside a closed tent.

Is it safe to camp after heavy rain or floods?

Avoid freshly flooded ground. Leptospirosis cases doubled after the 2014 Kelantan floods, with 1,229 cases identified. Cover cuts before wading and do not swallow river water.