Recent studies on permethrin effectiveness against ticks

[Rex Sanders]

Repellent Clothing Protects You From Ticks, Wired.com:
http://www.wired.com/2014/05/repellent-clothing-protects-you-from-ticks/

The whole article is worth reading, including the creepy diagram of tick bite locations on people who volunteered to get bitten!

Highlights:

… treated clothing reduced tick bites by 83% in workers that spent a lot of time in prime tick habitat.

The results of this study suggest that longevity of control is more related to time; all the [commercially] treated clothes used in this study lost their punch after one year, but didn't always get laundered 70 times.

Subjects wearing permethrin-treated sneakers and socks were 73.6 times less likely to have a tick bite than participants with untreated shoes.

More tidbits from one of the base studies:
Long-lasting Permethrin Impregnated Uniforms, American Journal of Preventive Medicine, May 2014:
http://dx.doi.org/10.1016/j.amepre.2014.01.008

No statistically significant differences in number of tick bites were detected between commercial permethrin treatment (19.33%) and the do-at-home permethrin application method (24.67%).

The success of permethrin-treated clothing in reducing tick bites varied depending on the specific article of clothing. Subjects wearing permethrin-treated sneakers and socks were 73.6 times less likely to have a tick bite than subjects wearing untreated footware. Subjects wearing permethrin-treated shorts and T-shirts were 4.74 and 2.17 times, respectively, less likely to receive a tick bite in areas related to those specific garments than subjects wearing untreated shorts and T-shirts.

— Rex

[Dave @ Oware]

Permethrin quickly loses it effectiveness against malaria mosquitoes in Africa. Just a few years. Will be the same in ticks?

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3655544/

"Evolution of resistance to the chemotherapeutic is a common outcome of effective (and ineffective) vector or parasite control programs. Although this is often viewed as a failure of the program, it is better regarded as an almost inevitable consequence because history has repeatedly shown that intensive interventions lead to the emergence of physiological (biochemical) resistance due to the high selective pressure exerted on the targeted population. The emergence of resistance in the vector has not only developed against all four classes of insecticide licensed to control adult mosquitoes for public health purposes (World Health Organization 1970; Ranson et al. 2011), but also in the malaria pathogen against the most widely used antimalarials, starting with chloroquine, the standard drug of treatment during the Global Malaria Eradication Campaign (GMEC) (Najera 1999). Indeed, resistance was one of the reasons cited for ending the GMEC in the late 1960s (Najera 1999). At that time resistance to DDT had developed in 14 anopheline species. The recent emergence of artemisinin drug resistance in South East Asia (World Health Organization 2011b; Phyo et al. 2012) makes clear that this is not simply a problem of the past, nor one confined to insecticides."

[Bruce Tolley]

@ Rex
I am not seeing in the main body of the AJPM paper the comparative conclusion of self treated vs commercially treated clothing.

Is the conclusion from some other study?

[Jerry Adams]

83% and 73% reduction doesn’t seem to be that much of an improvement, still useful though

73.6 times fewer bites seems better

(those seem inconsistent : )

Regardless, that makes sense, first treat shoes because that’s where the ticks are, then pants and gaiters.  I don’t even bother treating my shirt.

Spraying on Sawyer permethrin is so easy, it could be done several times a year.

[Todd T]

The success of permethrin-treated clothing in reducing tick bites varied depending on the specific article of clothing. Subjects wearing permethrin-treated sneakers and socks were 73.6 times less likely to have a tick bite than subjects wearing untreated footware. Subjects wearing permethrin-treated shorts and T-shirts were 4.74 and 2.17 times, respectively, less likely to receive a tick bite in areas related to those specific garments than subjects wearing untreated shorts and T-shirts.

That’s a horribly worded paragraph that leaves me uncertain what it means.  It seems pretty clear that the stats quoted for shorts and t-shirts are for ticks “in areas related to those specific garments.,” but the article doesn’t include that specificity for shoes/socks.

If such specificity is intended, the much larger effect for shoes/socks seems plausible at first blush.  Socks are always tight against the skin, forcing ticks to nuzzle up against the treated fabric to get to an area “specific to those garments.”  But shorts and shirts are generally looser, which may give ticks a better chance of finding an attractive feeding spot with less contact with the garment. But in the dozens of tick bites I’ve had in my life, not one has been on an ankle or foot, so I have trouble believing they could even have enough foot bites to calculate (changes in) likelihood of a bite there.

So if the first sentence really means what it says–that whole-body tick probability is reduced by a factor of 73.6–that’s a bit surprising but is very good news.

It’s also unclear whether the shorts/shirt subjects did or didn’t also have treated shoes/socks and vice-versa, at least from that isolated paragraph.  Like @btolley, I’m unable to find anything in the cited study.

Not sure I know any more than I did.

[Steve M]

Can’t I just drink the Permethrin–you know, to disinfect inside….and take care of any COVID-19 problems??  :o

(Sorry, I couldn’t help myself…after seeing our “president’s” recent medical ‘advice’ video)

[Jerry Adams]

“That’s a horribly worded paragraph…”

Not to worry – bottom line is clear – treat shoes, then pants, maybe shirt,… – ticks are way reduced although you still need to check…

[Todd T]

Not to worry – bottom line is clear – treat shoes, then pants, maybe shirt,…

Well, no, it’s not clear, not to me anyway.  If they’re saying that treated shoes/socks reduce the probability of a tick bite to my feet by 73% (or shoot, even by 100%) it’s not worth bothering with.  But if they’re saying it reduces the probability of a bite to any part of my body by 73%, that’s a big deal.

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