Fire & Ticks: The Impacts of Long-term Prescribed Fire on Tick Populations & Tick-borne Disease Risk

Approx. 1 hour

Published on Mar 29, 2018

This webinar by Dr. Liz Gleim, Assistant Professor of Biology & Environmental Studies from Hollins University explores the impacts of long-term prescribed fire on ticks & tick-borne disease risk and what appears to be some promising results linking fire & reducing disease risk.

Webinar found on the NAFSE website, www.firesciencenorthatlantic.org.

https://madisonarealymesupportgroup.files.wordpress.com/2018/04/4101b-gleim_tick26fire_webinar_final.pdf

(slide show in link)

The research conducted in southwest Georgia concerned four tick species (slide 2):

  • Lone Star Tick – known for causing Human Monocytic Ehrlichiosis (HME), Ehrlichiosis ewingii (STARI)
  • Gulf Coast Tick – known for causing Rickettsiosis
  • American Dog Tick – known for causing Rocky Mountain Spotted Fever (RMSF)
  • Black Legged Tick – known for causing Lyme Disease (LD), Human granulocytic anaplasmosis (HGA), and Babesiosis

Prior research (slide 5) have shown a discrepancy regarding whether or not controlled fire reduces tick abundance over time.  Gleim found that these prior studies did not take into account “real-world” management practices such as they were conducted in small areas and consisted of single-burns.

Gleim’s study consisted of 21 Total sites in 4 different categories (slide 7):

  1. 8 burned sites surrounded by burned areas
  2. 5 burned sites surrounded by unburned areas
  3. 5 unburned sites surrounded by unburned areas
  4. 3 control unburned sites surrounded by unburned areas

The study went for 2 years in which they did monthly tick surveys, took weather data, and did vegetative and host surveys (slide 8).  In the two years they collected over 47,000 ticks.

Tick abundance was in the following order (slide 10):

  1. Lone Star Tick
  2. Black Legged Tick
  3. Gulf Coast Tick
  4. American Dog Tick

Regarding fire on tick populations, they found the burned areas “flatlined” the tick populations whereas the control sites had typical tick abundance (slide 11) .  

Greater than 95% leaf litter = 2X more ticks (slide 12)

High tree density = 6X more ticks

Regarding black legged ticks:

Burning reduced the black legged tick population by 78%

High tree density = 17X more ticks

Recent precipitation = 2X more ticks

Gleim was concerned about the effects of red imported fire ants (RIFA) on the ticks (slide 14 & 15)

Ticks:  Evidence has shown that Imported fire ants reduce populations of certain tick species by preying on engorged female ticks filled with blood and eggs or small hatching ticks. Non-engorged ticks freeze in place and “play possum” when examined by a foraging ant, thus escaping their fate as ant food!   http://articles.extension.org/pages/60922/what-do-fire-ants-eat

There is limited data only the effects of RIFA on Lone Star Ticks.

So they did 3 treatments (slide 16) putting engorged Lone Star & Gulf Coast Ticks as well as nymphs into each enclosure and releasing them them during months that they were determined to be naturally active (slide 17):

  1. Burned habitat with Fire Ants
  2. Burned habitat without Fire Ants (this doesn’t happen naturally)
  3. Unburned habitat without Fire Ants (this doesn’t happen naturally)

They found (slide 18) no significant effect of RIFA on either tick species and that Gulf Coast Ticks did better than the Lone Star Ticks in the burned habitat with higher temperatures and the Lone Star Ticks did better in the unburned habitat.  The ticks did not have to survive burning; however, they had to survive the habitat after the vegetation was alive and well.

They found (slide 19) that burning gave an open canopy with sunlight being able to reach through to the forest floor causing higher temps and lower humidity.  The unburned sites conversely had closed canopy with a leaf litter understory causing lower temps and higher humidity which is more conducive for tick populations.

In essence – fire causes a forest structure that is less conducive to tick populations and lowers ticks and pathogen prevalence (slide 20).

The bottom line is they found (slide 21):

No Borrelia burgdorferi in the black legged ticks they collected.

  • .02 infected ticks per hour in all burned sites
  • .70 infected ticks per hour in unburned sites

Burning gave a 98% reduction in ticks.

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**Comment**

Well, now we know. Burning SIGNIFICANTLY REDUCES TICKS.  Let there be no question.

I’m very thankful for this work as it lays to rest the idea that burning isn’t worth it.  I would say that a 78-98% reduction in ticks to be worth it!

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0112174   These data indicate that regular prescribed burning is an effective tool for reducing tick populations and ultimately may reduce risk of tick-borne disease.

Those of you in states where funding is increasing for tick reduction, copy this off and get it to your representatives.  Burning is not toxic like pesticides often used to reduce ticks.  It also works.  I have to think it’s economical compared to many other options as well.