Sunday, August 16, 2020

How to avoid the bite

While lions and tigers and bears (Oh my!) may be fearsome predators, humankind is at much more risk from critters at the other end of the size scale: mosquitos and ticks! World-wide, malaria, carried by anopheles mosquitos, caused 228,000,000 cases and 405,000 deaths in 2018. While malaria has been largely banished in North America, mosquitos also carry the viruses causing Eastern Equine Encephalitis, Zika, West Nile, Dengue and chikungunya: diseases that are serious and often fatal.

Ticks carry Lyme disease, Babesiosis and Rocky Mountain spotted fever among others. Since many of these illnesses have no treatment, prevention is key. Prevention means not getting bitten by mosquitos and ticks. Is this possible? Yes, by using a combination of simple measures: avoidance and deterrence.

Mosquitos tend to be most active feeding between dusk and dawn, so when mosquito-borne illnesses are around, it is wisest to avoid being outdoors at that time. Barbecues at noon are lower risk; barbecues at 7 PM much higher, so have the friends over in the afternoon, not the evening. Drain any pools of free-standing water (where mosquitos breed) – and do not forget such mosquito havens as gutters. Be sure your screens are in good repair and fit snugly. If you use window air conditioners, be sure to seal around them.

Clothing can be protective: do not walk barefoot through the grass, where ticks are lurking and ready to latch on. Wear long pants and long-sleeve shirts when mosquitos are around.

Finally: use effective repellants. The news media recently carried banner stories about a new “natural” insect repellant, nootkatone, found in minute quantities in grapefruit skin and Alaska yellow cedar trees. You had to read the small print to learn that while it has been approved, it will not be commercially available until 2022. Until then, several effective products are widely available.

Best known is DEET (dimethyl-m-toluamide), available in lotions, sprays and wipes. While DEET products can contain from 5% to 99% of the active ingredient, at least 20% is recommended, and concentrations above 50% add little. DEET can cause skin irritation, but is generally very safe, and can be used on children and infants over 3 months.

An alternative product with similar efficacy is picaridin, available in concentrations of 5-20%. 10% is a good compromise and is safe for children.

A slightly less effective product is IR3535. Be careful to get a product that has 20% concentration; the 7.5% product has been found ineffective.

For those inclined to “natural” products, there is oil of lemon eucalyptus (whose products often use the word Botanicals in the name). It is somewhat more likely than the others to cause skin irritation and should not be used on children under 3.

Citronella oil-based products are less effective and are not recommended unless nothing else is available.

Finally, consider use of permethrin on clothing and footwear. It kills mosquitos and ticks on contact. You can spray it on not only clothing, but on tents, sleeping bags and mosquito nets. Permethrin-impregnated clothing is commercially available and remains active for several weeks, though multiple launderings.

While you may see wearables such as wrist bands with insect repellants, none of these are of much benefit.

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