CDC to Start Tracking Ticks as Diseases Rise

Bara Vaida

March 28, 2019

The CDC for the first time will be monitoring the nation's tick population and the diseases the pests may be carrying.

The effort comes as the number of people diagnosed with serious diseases caused by things like ticks, fleas, and mosquitoes has more than doubled over the past few decades. Ticks caused the vast majority of those diseases.

Its aim is to assess where Americans might be most likely to get a tick-borne illness.

"For the first time this year, the CDC is funding states to conduct widespread surveillance of ticks and the pathogens they can transmit, in addition to funding human disease surveillance and education and prevention," says Anna Perea of the National Center for Emerging and Zoonotic Infectious Diseases' Division of Vector-Borne Diseases. "Taken together, the data can help define areas where ticks are spreading, the infectious pathogens that they carry, and where risk of tick-borne disease is increasing."

Richard S. Ostfeld, PhD, a disease ecologist with the Millbrook, NY-based Cary Institute of Ecosystem Studies, called the CDC's step "great news."

"The CDC will be able to paint a picture of where risk is occurring, and it will provide us with better data than we have ever had before with geographic coverage of the ticks, where they are moving, and how infection prevalence is changing," he says.

In 2017, the number of tick-borne disease cases reported to the CDC rose 22%, to 59,349. But the number of Americans with tick-related diseases was likely much higher — closer to 300,000 to 400,000 — because not all Lyme disease cases are reported to the CDC, says John Aucott, MD, chairman of a national tick-borne disease working group, supported by the U.S. Department of Health and Human Services.

"It is hard to predict what will happen in any given year, but the long-term trends are obvious," says Aucott, who's also director of the Johns Hopkins Lyme Disease Clinical Research Center. "There are more tick-borne disease [cases] every year."

The most common illness caused by a tick bite is Lyme disease. In 2017, there were 42,743 cases of Lyme disease, up 17% from 2016, according to the CDC. Lyme represented 72% of all tick-borne diseases reported in 2017. Ticks carry other diseases, such as anaplasmosis, ehrlichiosis, Rocky Mountain spotted fever, babesiosis, tularemia and Powassan virus, but these diseases are rarer than Lyme.

Lyme is carried by the blacklegged tick (also called the deer tick) and traditionally was found in the Northeast, mid-Atlantic, North-Central U.S., and parts of Northern California. People living in these regions had been the most at risk of contracting Lyme, says Aucott. Now, the blacklegged tick is found in more than half the country.

"In 1996, we used to say no Lyme disease south of the Potomac [River, which separates Washington, D.C., from Virginia and Maryland]," says Aucott. "But it has moved south. It has spread to west of the Pennsylvania border, and to Michigan and surrounding states."

Ticks are spreading across the country for many reasons, experts say. They include changing land use, destruction of forest, residential building near woods, and the warming climate, says Ostfeld. The institute forecasts how severe tick season will be in the Northeast.

"Traditionally, May has been Lyme disease awareness month in preparation for June [when ticks are at the height of feeding]," he says. "But I have been advocating for Lyme disease awareness month to begin in April because ticks are out in full force in May. People need to be aware, ticks are coming out earlier in the year, advancing the dates of greatest risk."

Ostfeld predicts 2019 will be an "average" to "slightly below average" tick season. Still, he says the risk for becoming ill from Lyme disease is the same as in previous years. His forecast is based on the region's population of white-footed mice, which carry the bacteria that cause Lyme and are a favorite tick host. Ticks need blood to live and tend to feed in May, June, September, and October, making these months among the riskiest times of the year for contracting a tick-borne disease, says Aucott.

This year, public health officials are also warily watching the growing range of a new tick species — the Asian longhorned tick — first reported in New Jersey in 2017. The tick doesn't need a mate to reproduce and has already spread to at least nine states, mostly in the Northeast and mid-Atlantic. Though the tick hasn't yet been found to carry a pathogen dangerous to humans, it has carried potentially deadly diseases in other countries.

"The Asian longhorned tick has everyone very concerned," says E. Oscar Alleyne, DrPH, chief of programs and services for the National Association of County and City Health Officials. The organization represents local health officials charged with disease prevention.

"It is new, invasive, and shouldn't be here...and has the potential to be yet another tick that could wreak devastation," Alleyne says.

Public health officials say the best way to prevent a tick-borne disease is to cut the chances of getting bitten. Here are some of their tips:

  • Limit exposure to tall grass, and walk in the center of trails. Ticks hang on to the edge of grass and latch onto your body when you walk by.

  • Mow the lawn frequently. Remove leaf litter and tall grass brush from around your home and the edge of your yard.

  • When hiking, gardening, and spending time in the outdoors, wear long pants and socks treated with permethrin — a chemical used to treat lice in children — to ward off ticks. Many outdoor companies now sell clothing already treated with this chemical. You may also use a bug repellent like DEET. The CDC has a list of approved insect repellents

  • Once you've been outside where ticks might live, do a full body check when you go back inside. Throw your clothing into a dryer turned to high heat for 10 minutes. The dryer will kill the ticks.

  • If your pet goes outdoors, use tick collars, spray shampoos, and medications to prevent ticks. Also check your pet for ticks when they return inside. Don't sleep with your pet.

Be aware of what ticks look like so you can detect them. If you find a tick, remove it with tweezers. If you get a rash (and often it won't look like the typical "bull's-eye" rash), call your health care provider right away. If treated early, you can prevent Lyme disease.

SOURCES:

Anna Perea, policy and communications lead, Bacterial Diseases Branch, National Center for Emerging and Zoonotic Infectious Diseases' Division of Vector-Borne Diseases, CDC.

CDC: "Vital Signs: Trends in Reported Vectorborne Disease Cases — United States and Territories, 2004-2016."

CDC: "Lyme Disease Maps: Historical Data."

CDC: "What you need to know about Asian longhorned ticks — A new tick in the United States."

E. Oscar Alleyne, DrPH, chief of programs and services, National Association of County and City Health Officials.

John Aucott, MD, director, Johns Hopkins Lyme Disease Clinical Research Center.

Richard S. Ostfeld, PhD, disease ecologist, Cary Institute of Ecosystem Studies.

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