Permethrin: the solution to biting bugs

By Ruth Anderson, travel health nurse, Travelvax Australia.

If you are one of those people mosquitoes just love to bite, your first line of defence should be a long-lasting personal insect repellent. You knew that, right?
But, did you know that there’s a second line you can throw up in the battle against the veritable army of disease-carrying insects?
It’s called permethrin and it’s cheap, fast-acting – and deadly!
Permethrin is a contact insecticide which has been in use for over 30 years. A pyrethroid, it’s a synthetic version of pyrethrum, which is extracted from the Chrysanthemum. The flower’s insecticidal properties were first recognised in the 18th century.
Permethrin kills virtually all insects, including those that have the greatest impact on travellers – mozzies, fleas, ticks, bedbugs, chiggers, spiders, and flies.
When added to water, permethrin can be used to impregnate or ‘treat’ almost any material, from the bed net you sleep under to the shorts, shirts, hats, socks and other items of clothing you wear during the day or put on when biting bugs are at their fiercest – either at night in the case of malaria-carrying Anopheles mosquitoes, or around dawn and sunset for the dengue and Chikungunya-transmitting Aedes species.
Any insect that lands on the treated material – even briefly – dies before it can bite you and pass on any infection it may be carrying.

A deadly encounter for insects

Why bother treating clothes? Because several of the larger and aggressive mosquito species (including our very own Hexham Grey) can bite through light fabric, while ticks crawl over your socks in their quest for a place in your groin area or armpit to bite. In Africa, the tsetse fly, which spreads debilitating African trypanosomiasis or ‘sleeping sickness’, can deliver its painful bite even through heavyweight material.
Because the tiny invader dies on contact with the permethrin-treated material, there’s no chance of it heading off to feast on a less protected friend or family member, as it would if it encountered an untreated bed net or personal insect repellent.
A study found that a treated bed net is at least twice as effective as an untreated one at preventing bites from mosquitoes that can carry diseases like malaria, yellow fever, dengue fever and the Chikungunya and Zika viruses in tropical regions, as well as ‘home grown’ diseases like Ross River virus in Australia.
Instead of biting your skin through the holes in the netting, they’re quickly dispatched. (It’s VERY satisfying seeing their corpses scattered around the edges of your bed each morning, knowing you didn’t lose a drop in the bloodless nocturnal battle!)
In the bigger picture, the widespread use of long-life treated bed nets has significantly reduced malaria rates among children living in malaria-plagued African and Western Pacific countries. Nets not only protect young sleepers but keep on killing the mozzies that spread malaria.

Why it’s such a great solution

Here’s a few other reasons why you should consider adding permethrin to your insect-fighting arsenal, especially if your summer travel plans could consistently put you at the top of the ‘mozzie menu’ in a tropical country overseas or while camping in Australia.
Permethrin is:
EFFECTIVE & FAST ACTING - It kills any insects that come into contact with material treated with it in minutes.
LONG LASTING - A permethrin-impregnated mosquito net is effective for 3-6 months of regular use. (Slightly more expensive are Long-life Insect Nets (LLIN) such as the WHO-accredited PermaNet, which are available online directly from our supplier, Equip. LLINs are factory-treated with the insecticide deltamethrin, which is incorporated into the net’s fibres and remains effective for the life of the net.) 
WATERPROOF – Treated clothes continue to be effective for 5-10 normal washes in hot or cold water. (As long as clothes can absorb the solution it can be treated and the clothes can be ironed, too.) 
SAFE – Permethrin is odourless, vapour-free, and safe for all ages – including kids. In humans, permethrin is metabolised and excreted as inactive metabolites in urine faster than it can be absorbed through the skin, so tissue retention and storage is not a factor. (It’s rare, but some people occasionally develop a minor skin rash after wearing permethrin-treated clothing. If that was to occur, discontinue wearing the treated clothing until the solution has been washed out.)  

Just don’t forget the repellent…

Not everyone needs the extra protection of permethrin. We recommend it for travellers who will be staying in areas where they can expect heavy infestations of insects or will be travelling in rural areas during a peak season for insect-borne diseases – especially if they will be staying in budget accommodation with no screens on windows or doors, and no air-conditioning.
It’s also important to note that wearing clothes impregnated with permethrin won’t stop mozzies and other insects biting unprotected skin.
Treated clothing should be worn as well as – not instead of – a personal insect repellent containing the recognised active ingredients, such as DEET, Picaridin, IR3535, or oil of lemon eucalyptus.
Treated nets in single and double sizes are available online from Travelvax Australia or from our travel clinics, as are DIY treatment kits to treat your own bed net and/or clothing. 

How to use your DIY kit

Once you have your kit, follow these steps to treat your net or clothing.
1. Choose a well-ventilated, shaded area outside. 
2. Assemble everything you’ll need, including: The items to be treated, a large non-tip bucket, a stirring stick, and plastic sheet (ideally on a table) to lay out the net and garments on as they dry. (It’s best if they don’t drip dry as some of the potency is lost.)
3. Put on your rubber gloves and safety glasses.
4. Permethrin is added to cold water at specified ratios for different types of materials. The 20ml in the DIY kits is enough to treat 2 nets and at least one set of clothes (depending on their size). 
5. Measured out the volume of water into the bucket. Don’t overfill the bucket – it will only spill out when you add the net or clothing to be treated.
6. If you’re not using the full 20ml in the bottle, use the syringe provided with the kit to draw up the appropriate amount of permethrin from the container. Add it to the water and use your stick to mix the solution thoroughly.
7. Carefully lower your net or item of clothing into the solution, using your stick to ensure it is completely submerged without causing the solution to spill over the sides. Leave each item to soak for 2 minutes.
8. Remove each item from the solution, gently squeezing out the excess liquid from top to bottom while holding the item over the bucket to catch drips.
9. Lay the item on the plastic sheet to dry by evaporation away of direct sunlight. (Evaporation leaves the permethrin in the fibres while sunlight breaks down the insecticide, making the net or clothes less effective. Your items may take 24-48 hours to dry, so allow enough time before travel).
10. When you have finished, wash your hands with soap and water. 
STORAGE: Even after you’ve begun using them, store the treated items in plastic bags to retain their insect-killing potency.

Dispose of thoughtfully

Permethrin is dangerous to fish, so DO NOT dispose of used or unused solution in storm water drains, sewers, streams, rivers or other waterways. 
Used and unused prepared solution can be disposed of by pouring around non-food producing gardens. Follow the kit’s Storage and Disposal instructions to dispose of other items used in the dipping process.
You’ll also find several ‘how-to’ clips on treating bed nets and clothing with permethrin on YouTube.
NOTE: Permethrin is harmful if swallowed and can irritate eyes and skin. If swallowed, do NOT induce vomiting – give a glass of water, then contact a doctor or the Poisons Information Centre in your state for further advice.
Used in conjunction with an effective insect repellent and other bite avoidance measures, permethrin offers extra protection against biting insects. Think of it as ‘insect bite insurance’. 

Travelling overseas? Get more advice on treated bed nets and DIY permethrin kits, along with other tips for avoiding insect-borne diseases during your overseas holiday from Travelvax Australia’s travel health information service on 1300 360 164 (toll free from landlines within Australia). We also provide vaccinations and personalised advice at our travel health clinics.