Freehiking as a Public Health Issue

The Threat

Ticks. If you've ever seen one, that word should make you cringe. Despite their tiny size, many carry a nasty bite with Borrelia burgdorferi, the bacteria that causes Lyme disease.

There is a lot of mystery, controversy, and politics surrounding Lyme disease. On one side, there are organizations like the Centers for Disease Control (CDC), which rely on scientific studies to influence their recommendations for diagnosing and treating Lyme disease. On the other side are organizations like the International Lyme and Associated Diseases Society (ILADS), who listen to those affected by the disease and conduct their own studies.

The CDC [1] and ILADS[2, 3], for the most part, agree on the early symptoms: fatigue, anxiety, chills, fever, headache, muscle aches, and joint aches. They also agree that a “bulls-eye” rash or finding a tick prior or during the symptoms are a tell-tale sign of an infection.

According to the CDC, 70%-80% of people get the “bulls-eye” rash. They recommend performing both the ELISA screening test and the Western Blot test, both of which need to be positive to conclude a positive result. If untreated, a variety of neurological symptoms and joint pain/swelling will come and go. This is called Chronic Lyme Disease. If treated, 10%-20% of patients still get a similar variety of symptoms. They call this Post-Treatment Lyme Disease Syndrome (PTLDS).

ILADS takes a more dire stance. Their research indicates that fewer than 50% of patients recall a tick bite, and fewer than 50% have the “bulls-eye” rash. The ELISA test produces a false-negative 35% of the time, and the Western Blot test has a false-negative 20%-30% of the time. ILADS also believes that treatment sometimes cannot fully eradicate the disease, and questions if PTLDS really is something different.

The CDC maintains that the B. burgdorferi bacteria is primarily transferred through tick bites. ILADS and others believe the bacteria can spread in similar ways that other bacterias spread. Quite frankly, there isn't a lot of research on one side or the other. There is a lot that we don't know about this mysterious bacteria and the disease it causes.

Lyme disease is often called the “great imitator”. Since the symptoms vary widely, and are often similar to other diseases, it's often misdiagnosed. Both the CDC and ILADS suspected that there were more infections than were being reported.

The CDC originally reported about 30,000 cases of Lyme disease per year in America. ILADS, citing some studies in the early 90's, believed that the true amount of new cases was roughly ten times that number. The CDC conducted additional studies and in 2012 announced that the number was actually around 300,000. [4] This puts Lyme disease well beyond more commonly known diseases like HIV/AIDS (around 50,000 new cases per year in America) and even surpasses breast cancer (232,340 new cases in 2013 in America). It also makes one wonder what else ILADS and others have right.

Somewhere between the CDC and ILADS is the truth. It's scary. Living in one of the high-risk zones, and enjoying wilderness recreation, is what prompted me to learn all I can about Lyme disease and the ticks that carry it. What I eventually realized, however, is that the common advice to prevent tick bites isn't ideal.

In order to remain safe while venturing through tick territory, you need the best advice that research can provide. Before that advice, however, are some details that'll make your skin crawl.

Tick Life-Cycle

Ticks go through three stages in their three years of life: larva, nymph, and adult. [5] Each stage requires feeding on blood, and one more feeding as an adult allows it to lay eggs.

Ticks aren't born with Lyme, and receiving a bite from a larva usually isn't a problem. However, the larva tend to feed on small mammals such as mice. If the mouse has Lyme, the tick will become a carrier, and all future targets are at risk.

As the tick feeds on a host, not only is it sucking blood, it's also salivating on your skin. This numbs the skin so the tick can remain undetected for the 3-7 days it needs. It's also how diseases get transferred. After removing a tick, make sure to sanitize the area it was on.

Most applicable to this article is how they hunt for a host. Many people believe they drop out of trees at just the right time or somehow jump onto you. Neither is true. Ticks can sense oder, heat, moisture, and vibration. If a host is nearby, it'll crawl towards it. Otherwise, it'll start “questing”.

To quest, the tick climbs to the top of a nearby plant, hangs on with its back legs and sticks the rest outward. It'll grab on to anything that brushes by.

Fur and Cloth

Researchers have been collecting ticks for various studies for a long time. The best method, still commonly used today, is called “tick dragging”. [6] A researcher pulls a material behind them. Ticks grab on, and the researchers stop to pluck them off every so often. The researchers aren't using the natural choice – fur. They're using cloth.

With that in mind, it seems a little silly that we wrap up in cloth to venture out into the wilderness. Evolution has given us something better.

A 2003 publication by Mark Pagel and Walter Bodmer [7] discusses a unique trait shared by only a handful of mammals: hairlessness. Excluding the mammals which have fur or have thick, tough skin, only two species remain; humans, and naked mole-rats.

How did this unique trait evolve? Pagel and Bodmer put forth a convincing hypothesis that ridding our fur is an adaptation to reduce ectoparasites. (Ectoparasites are parasites which live outside the skin, like fleas and ticks.)

With intelligence, fire, and clothing, human hairlessness became feasible. Since ectoparasites are easily found and removed from hairless regions, being hairless became an advantage. Finally, sexual selection promotes hairlessness since having a parasite-free and disease-free mate is good. Traditionally, males are more selective, which explains why women typically have less body hair.

Similarly, naked mole-rats group together in an always-warm underground environment where ectoparasites are expected to be common. They don't need fur to keep their body temperature regulated, so they lost it. Ectoparasites are relatively rare in these colonies, compared to similar colonies of furry rodents. [8]

Is nakedness still to our advantage when ectoparasites are involved? A different study has the answer, although indirectly.

Tick Psychology

Once a tick hitches a ride on a human host, where does it crawl to in order to feed? The best study I've found [9] comes from Switzerland. Although the Swiss ticks aren't the same species as the the ones in the U.S., they have very similar characteristics, including being a primary vector for Lyme disease.

The purpose of the study was to measure the effectiveness of a typical commercially-available bug repellent containing DEET (15%) and EBAAP (15%) in a real-word setting. The study included 276 volunteer forestry workers and orienteers, and spanned from May to September, 1999. Orienteers, by the way, are people who race through any terrain to finish at a specific spot on a map.

An important aspect that isn't detailed in the study is what clothing the participants wore. The forestry workers were likely wearing long pants, which were not tucked into their shoes or socks. The study mentions that the orienteers typically wore short pants (presumably capri-style) and t-shirts, but doesn't detail if anything was tucked in.

The volunteers were split into two groups, one got the repellent and the other got a placebo. They were given instructions to apply the spray on exposed skin (excluding the face) and the nearby edges of clothing. They logged all ticks they found on them and where they were at.

In total, the placebo group found 335 attached ticks, and the repellent group found 202. The percentages were similar for both groups. The head had the least number of ticks (0.2%-4.0%), with the arms next (13%-14%). At the other end of the spectrum, the legs were attacked 56%-61% of the time, followed by the torso 23%-27% of the time.

Thinking about how ticks quest, most probably land on the shoes along a normal trail. If the person is going through thicker brush, they land on the legs or shirt. From there, they wander around until they find a good warm spot. It makes sense that the legs and torso are most popular.

The study continues with: “75% of the reported attachments were on skin covered by clothing, whereas only 14% were on uncovered skin. For the remaining 11%, it was unclear whether the skin had been covered or uncovered.” From those observations, they conclude that “ticks search for covered skin.”

Lastly, their overall conclusion states that the tick repellent “offers at least moderate protection against tick bites.” Presumably, going naked with tick repellent is the best protection we can get.

Repellents

All repellents on the market are based on a small collection of chemicals. There are two chemicals which stand out.

The first is DEET. In July 2010, Consumer Reports [10] found DEET to be the best repellent for skin. However, remember that it's also toxic, so more isn't better. Their research suggested that 30% strength is ideal. Make sure to reapply as directed, and wash it off when it's no longer needed.

According to the CDC [11], products which combine sunscreen and bug repellent should be avoided. Always apply sunscreen first, followed by insect repellent. The insect repellent should be applied on the outside of clothing. Don't apply it to skin that is covered by clothing.

The second chemical is permethrin, an insecticide applied to clothing. According to a recent study [12], both the manufacturer-treated clothing and the home kits are equally effective. However, the success varied depending on the article of clothing. Treated shirts made it 2.17 times less likely to get a tick bite. Treated shorts made it 4.74 times less likely. Treated shoes and socks, amazingly, made it 73.6 times less likely to get a tick bite. Since most ticks probably grab onto the shoes, it makes sense that few would make it to the bare leg alive.

Staying Safe

No matter where you go to find advice about preventing tick bites, it's basically the same. Here, the “common advice” comes from either the CDC [13] or the Minnesota DNR [14]. Combined, they seem to cover everything. “My advice” is based on the research I discussed in the previous sections and personal experience.

The common advice is to wear light-colored clothing so ticks are more visible, and to tuck pants into boots and shirt into pants. While this may be good to keep ticks outside your clothing, it'll be extremely warm. Sweat attracts more bugs and makes repellent lose effectiveness quicker. Wearing loose clothing to stay cool allows ticks to sneak in. My advice is to go naked when weather permits. This keeps you comfortably cool and gives ticks no place to hide.

My favorite bit of common advice is to bathe or shower as soon as possible after coming indoors to wash off and find ticks. Why not start that way? From my own experience of textiled hiking, the commute back home with ticks crawling all over is the worst. It gives them extra time to find a spot and bite. I believe all of my bites stem from not being able to get out of my clothes fast enough.

Although the common advice to do a full-body check, wash clothing, and check gear is good, my advice is much more simple. Keep your clothes sealed in a plastic bag or in the car, and do the full-body check before getting dressed. A shower and a double-check for ticks at home is a good idea, but you'll already be confident that you're tick-free. There's no need to rush home, so you can grab some food and continue the day normally. 

 

For optimal protection, the common advice is to apply the minimum amount of DEET to exposed skin and clothing. I recommend 30% strength, which lasts up to 7 hours. If trails are nice and wide and you don't brush up against anything, you could skip the DEET.

Don't skip the permethrin though. The common advice is to treat everything you wear. If you're hiking naked, I recommend treating a good pair of solid boots and some shin-high socks at a minimum. Backpacks and hats are good too.

I'd like to offer a few additional pieces of advice. These aren't typically found in the common advice, but they probably should be.

Find a hat that keeps ticks out of your hair. If it has holes in it, ticks might find their way in. Also, if ticks can hide in your body hair, you should consider trimming it down.

It's best to hike with others. Take turns leading so others can “watch your back”. I've gotten into the habit of running my hands across most of my skin every so often. If there are any ticks, they get brushed off or I feel that they've recently bitten.

Conclusion

With Lyme disease impacting such a large number of people, I believe the best advice that research can provide should be promoted as a matter of public health. In a high-risk area during the warm months, wearing clothing significantly increases your chances of getting Lyme disease through a tick bite.

In a growing number of states, a nursing mother can breastfeed openly in public. Laws allow the “nudity in public” since public health takes priority. Freehiking in the wilderness should someday be accepted on the same basis.

References:

[1] Centers for Disease Control (2012, Aug. 27). Signs and Symptoms of Lyme Disease. Retrieved from http://www.cdc.gov/lyme/signs_symptoms/index.html

[2] International Lyme and Associated Diseases Society (2009). Top Ten Tips to Prevent Chronic Lyme Disease. Retrieved from http://www.ilads.org/lyme_disease/lyme_tips.html

[3] International Lyme and Associated Diseases Society (2006, April 15). Basic Information about Lyme Disease. Retrieved from http://www.ilads.org/lyme_disease/about_lyme.html

[4] Centers for Disease Control (2013, Aug. 19). Press Release – CDC Provides Estimate of Americans Diagnosed with Lyme Disease Each Year. Retrieved from http://www.cdc.gov/media/releases/2013/p0819-lyme-disease.html

[5] Centers for Disease Control (2012, Sept. 9). Tick Life Cycle and Hosts. Retrieved from http://www.cdc.gov/ticks/life_cycle_and_hosts.html

[6] Falco, R. C., Fish, D. (1992). A comparison of methods for sampling the deer tick, Ixodes dammini, in a Lyme disease endemic area. Experimental & Applied Acarology, 14(2), 165-173.

[7] Pagel, M., Bodmer, W. (2003). A naked ape would have fewer parasites. Proceedings of the Royal Society, Biological Sciences, 270, 117-119.

[8] Scharff, A., Burda, H., Tenora, F., Kawalika, M., & Barus, V. (1997). Parasites in social subterranean Zambian mole‐rats (Cryptomys spp., Bathyergidae, Rodentia). Journal of Zoology, 241(3), 571-577.

[9] Staub, D., Debrunner, M., Amsler, L., & Steffen, R. (2002). Effectiveness of a repellent containing DEET and EBAAP for preventing tick bites. Wilderness & Environmental Medicine, 13(1), 12-20.

[10] Consumer Reports (2010, July). Best ways to keep bugs at bay. Retrieved from http://www.consumerreports.org/cro/magazine-archive/2010/july/health/insect-repellent/overview/index.htm

[11] Centers for Disease Control (2012, Aug. 27). West Nile Virus Q&A Insect Repellent Use and Safety. Retrieved from http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm

[12] Miller, N. J., Rainone, E. E., Dyer, M. C., González, M. L., & Mather, T. N. (2011). Tick bite protection with permethrin-treated summer-weight clothing. Journal of medical entomology, 48(2), 327-333.

[13] Centers for Disease Control (2011, Nov. 15). Preventing Tick Bites. Retrieved from http://www.cdc.gov/lyme/prev/on_people.html

[14] Minnesota Department of Natural Resources (2013). Deer Ticks. Retrieved from http://www.dnr.state.mn.us/insects/deerticks/index.html

Comments and feedback can go on the Preface.