MilTICK study finds use of permethrin-treated uniforms can reduce tick-borne illness risk

By Douglas Holl, Defense Centers for Public Health-Aberdeen Public AffairsMay 31, 2023

MilTICK study finds use of permethrin-treated uniforms can reduce tick-borne illness risk
Caption: (Jan. 23, 2017) MAYPORT, Fla. - Hospital Corpsman 3rd Class Joshua Nieto of Navy Entomology Center of Excellence (NECE), Jacksonville, Fla., applies the insect repellant permethrin to uniforms at Naval Station Mayport, Fla. Defense Public Health biologists studying MilTICK samples found that ticks submitted by service members using permethrin-treated uniforms were less likely to be engorged, which lowers the chance of passing along an infectious agent that can make someone sick. (Defense Centers for Public Health – Aberdeen graphic illustration by Graham Snodgrass) (Photo Credit: Graham Snodgrass) VIEW ORIGINAL

ABERDEEN PROVING GROUND, Md. – A recent study conducted by biologists who manage the Department of Defense Military Tick Identification/Infection Confirmation Kit, or MilTICK, program, found that ticks submitted to the program by service members wearing permethrin-treated uniforms were significantly less likely to have become engorged.

“The longer a tick stays attached, the more engorged with blood it will be, and the higher the chance of the tick passing along an infectious agent that can make someone sick,” said Dr. Robyn Nadolny, Defense Centers for Public Health – Aberdeen biologist and chief of the Vector-Borne Disease Branch, which manages the MilTICK program.

Clothing treated with the insecticide permethrin protects the wearer from mosquitos, ticks, and other pesky biting arthropods. Army uniforms are factory-treated with permethrin, but its efficacy is known to wane over time. Soldiers are not encouraged to re-treat their uniforms with permethrin since it’s hard to know exactly how much of the chemical remains after wear and washings.

Nadolny says the service members who submitted ticks to the program were likely better protected than the retirees, civilians, and dependents who also submitted ticks, probably because the service members were wearing their uniforms properly and adhering to other elements of the DOD Insect Repellent System.

According to a DCPH-A fact sheet, the DOD Insect Repellent System is a safe and proven method to reduce disease and annoyance associated with insects. The system incorporates:

  • Permethrin on the uniform (factory- or field-treatment methods),
  • DEET or Picaridin repellent on exposed skin,
  • A properly worn uniform, and
  • Using permethrin-treated bed nets when relevant.

Using all elements of this system provides maximum protection and is the safest way to prevent nuisance and disease caused by insect attacks.

“Army and Army National Guard personnel were the most likely to be wearing permethrin than folks from other services, especially the Navy, which does not have routinely treated uniforms,” said Nadolny. People who were bitten while off-duty were also more likely to not be wearing any permethrin-treated clothing, which is to be expected.

Nadolny said the MilTICK team also found that occupationally exposed active-duty service members who were wearing permethrin-treated uniforms submitted an increasing number of engorged ticks over time. This concerning trend could indicate permethrin’s loss of effectiveness over time, reducing Force protection due to the number of old uniforms in circulation.

“Until there is an approved option to re-treat older factory-treated uniforms, we will likely continue to see ticks biting and feeding despite permethrin being worn,” said Nadolny. “We also found that lone star ticks, which can cause ehrlichiosis and red meat allergy; and blacklegged ticks, which can cause Lyme disease and other illnesses; were less affected by permethrin than the American dog tick. More reasons to wear repellent and permethrin to enhance protection, even while off-duty, whenever you’re in tick habitat.”

The DOD MilTICK program is a resource that has been around for more than 20 years and offers free identification and analysis of ticks that have been removed from human patients. The program allows active-duty service members, DOD beneficiaries, as well as contractors and civilians, to submit their ticks for identification and testing without needing to visit a clinic or even order a test kit.

The purpose of this program is to expediently provide tick species identification, engorgement level (an indicator of how long the tick was attached, which correlates with risk of infection), and analysis for the pathogens that cause the following human illnesses: Lyme disease, tick-borne relapsing fever, Rocky Mountain spotted fever and related spotted fevers, ehrlichiosis, anaplasmosis, babesiosis, and Powassan virus, said Nadolny.

Nadolny has seen an increase of samples submitted to the program since it decreased during 2020, the first year of the pandemic, but submissions have not yet returned to pre-COVID-19 pandemic levels.

“Submissions from Army personnel accounted for greater than 80 percent of submissions in 2022, despite all services being supported,” said Nadolny. “The Air Force submitted the second highest number of ticks. We are hoping that with transition to the Defense Health Agency we will be able to actively encourage greater participation from all services.”

Nadolny says climate change can also be a factor in increased risk from tick bites across a wider geographic area.

“Climate change is enabling ticks to colonize new areas and stay active for longer during the year, increasing and expanding the risk of tick-borne diseases,” said Nadolny. “We receive ticks all year round, including in the cold winter months – ticks can be active whenever it’s above freezing and there’s no snow on the ground.”

Nadolny is hoping to see increased submissions from services other than the Army.

“Maryland is also ’over-represented’ in our dataset, since locals tend to know about our program and use it, so we would like to see that level of participation from throughout regions where tick-borne diseases are a big concern, or are expanding,” said Nadolny. “The Midwest, New England, and Mid-Atlantic areas are all big areas of concern for Lyme disease, but we welcome ticks from anywhere in the U.S.!”

For more information on how to submit a human-biting tick, visit MilTICK - Defense Centers for Public Health - Aberdeen.

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