Illustration: Rebecca Zisser/Axios

The spread of ticks in the U.S. — and a rise in cases of the diseases they carry — is putting the tiny tick in the sights of Congress and spurring calls for better tools to track and control them.

Why it matters: Ticks spread bacteria that cause Lyme disease and more than a dozen other pathogens. Nearly 43,000 confirmed and probable cases of Lyme disease were reported in the U.S. in 2017 — triple the number in the late 1990s — but the CDC suspects the actual number of cases each year could be about 300,000.

Driving the news: The increase in tick-borne illnesses moved New Jersey Rep. Christopher Smith to introduce an amendment — passed by the House last week — to investigate whether the Department of Defense experimented with weaponizing ticks with Lyme disease and released them between 1950 and 1975.

Reality check: There's evidence the Lyme disease-causing bacterium — Borrelia burgdorferi — has been in North America for 60,000 years.

  • The bacteria and the tick would make "a lame bioweapon," says Rick Ostfeld, who studies the arachnids at the Cary Institute of Ecosystem Studies.
  • Among the reasons: Lyme disease isn't communicable. Ticks themselves don't move much in their entire lives, and each new generation has to bite the right infected host to maintain that infection.

The big picture: "The world is getting tickier for sure. That's especially true for the U.S.," Ostfeld says, referring to the arrival of a new tick species in the U.S. and the fact that ticks are expanding their range.

  • Climate change, reforestation in the Northeast, development that drives out predators of mice that harbor the disease, and a boom in deer that are hosts to ticks are all thought to be creating opportunities for ticks to expand their range and spread disease.
  • That tick species typically lives for 2 years. Unlike mosquitoes that can cause epidemics and then die out, longer-living ticks — like the blacklegged or deer tick that spreads Lyme disease — can produce a chronic, steady, infectious vector risk, says the CDC's Paul Mead. "Their biology affects the patterns of illness we see."

He and Ostfeld say there's a need for new prevention tools, including vaccines and tick control measures.

What to watch: Ostfeld co-leads the Tick Project, an ongoing 5-year study looking at whether a fungus that kills ticks can be used to control and reduce cases of tick-borne disease in neighborhoods.

  • Researchers are also in the early stages of experimenting with controlling the spread of Lyme disease by editing the genes of mice so the rodents don't transmit disease-causing bacteria to ticks.
  • Six federal departments are drafting a national strategy to "combat the growing threat of vector-borne diseases," which includes those carried by ticks.
  • A CDC spokesperson tells Axios it is expected to be finalized later this summer.

Go deeper: Illnesses from ticks and mosquitos tripled over 13 years

Go deeper

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Photo illustration: Sarah Grillo/Axios. Photo: Roy Rochlin/Getty Images and BRENDAN SMIALOWSKI/AFP via Getty Images

If you want to understand the rhetorical roots of Trump's Independence Day speech at Mount Rushmore, go back and watch Tucker Carlson's monologues for the past six weeks.

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Illustration: Aïda Amer/Axios

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Bolton's hidden aftershocks

Photo illustration: Sarah Grillo/Axios. Photo: Justin Sullivan/Getty Images

The news media has largely moved on, but foreign government officials remain fixated on John Bolton's memoir, "The Room Where It Happened."

Why it matters: Bolton's detailed inside-the-Oval revelations have raised the blood pressure of allies who were already stressed about President Trump's unreliability.