Ticks on the Move

Kelly Oggenfuss hands me a pair of white coveralls like the ones she’s wearing and instructs me to tuck the cuffs of my pants inside my socks. We are going to a tick-infested woodland, and the white fabric will make it easier to detect and remove the crawling black creatures if they try to bite us. Oggenfuss is a biologist at the Cary Institute of Ecosystem Studies in Millbrook, New York. She is part of a team of scientists searching for clues to why ticks—and the sometimes deadly diseases they carry—are spreading to new areas in the U.S.

Kelly Oggenfuss hands me a pair of white coveralls like the ones she’s wearing. She tells me to tuck the pants cuffs inside my socks. Oggenfuss is a biologist at the Cary Institute of Ecosystem Studies in Millbrook, New York. We’re going to a woodland full of ticks. The white fabric will make it easier to see the crawling black creatures. Then we can remove them if they try to bite us. Ticks carry diseases that can be deadly. Now they’re spreading to new parts of the U.S. Oggenfuss is part of a team of scientists trying to find out why. 

As we hike into the forest, Oggenfuss uses a walkie-talkie to call her crew and discuss today’s plan for checking mousetraps. White-footed mice are the preferred host of blacklegged ticks, also known as deer ticks, which carry Lyme disease. This bacterial infection causes headache, joint pain, fatigue, and sometimes a telltale bull’s-eye-shaped rash. Oggenfuss traps and releases mice to track their population from year to year. The institute’s researchers have discovered a pattern: When mice have plenty to eat, their numbers soar. That leads to more ticks—and more cases of Lyme disease.

Thirty years ago, Lyme disease was found only in a small area in the northeastern U.S. But it’s now rapidly spreading throughout the whole region and into the Midwest and southern Canada. Other tick-borne illnesses are on the move too. As a result, more and more people are getting infected.

We hike into the forest. Oggenfuss calls her crew with a walkie-talkie. They talk about today’s plan for checking mousetraps. White-footed mice are the favorite host of blacklegged ticks, also known as deer ticks. These ticks carry Lyme disease. That’s a bacterial infection that causes headache, joint pain, and fatigue. Sometimes it forms a bull’s-eye-shaped rash. Oggenfuss traps and releases mice to track their numbers from year to year. The researchers have discovered a pattern. When mice have plenty to eat, their numbers rise. That leads to more ticks—and more cases of Lyme disease.

Thirty years ago, Lyme disease was found only in a small area in the northeastern U.S. But now it’s quickly spreading through the whole region. It even reaches into the Midwest and southern Canada. Other illnesses carried by ticks are traveling too. The result: more and more people are getting infected. 

Ticks, like spiders, are a type of arachnid. These eight-legged creatures hide in leaf litter or low vegetation in forests. They sit with their front legs outstretched, waiting for an animal to brush by. When that happens, the parasite burrows its mouth into the animal’s flesh and begins drinking its blood—ticks’ only source of food. Ticks need just one of these blood meals between each life stage—egg, larva, nymph, and adult (see The Life Cycle of a Tick).

When a tick bites, it may pick up diseases from the host it’s living on. As a larva, for example, a tick might feed on a mouse carrying a disease. When it’s finished feeding, the larva drops to the ground and begins the nymph stage of its development. The nymph goes looking for its next meal. When it bites this time, it transmits the disease it picked up from the mouse to its new host.

Like spiders, ticks are a type of arachnid. These eight-legged creatures hide in fallen leaves or low-growing plants in forests. They sit with their front legs stretched out, and they wait for an animal to brush by. When that happens, the parasite digs its mouth into the animal’s flesh. Then it starts drinking blood. That’s the only food ticks eat. Ticks need just one blood meal between each life stage—egg, larva, nymph, and adult (see The Life Cycle of a Tick).

When a tick bites, it may pick up diseases from the host. That’s the animal it’s living on. For example, a mouse might carry a disease. As a larva, a tick feeds on that mouse. Then the larva drops to the ground and begins the nymph stage of its growth. The nymph looks for its next meal. When it bites again, it passes the disease that came from the mouse to its new host. 

Different species of ticks carry different types of diseases. “There are hundreds of species of ticks found worldwide,” says Rick Ostfeld, a disease ecologist at the Cary Institute. He studies how climate affects the spread of disease. “Fortunately, in the United States there are only a handful of disease carriers.”

American dog ticks, for instance, can transmit Rocky Mountain spotted fever (see Where Ticks Live). This bacterial infection causes a severe headache, high fever, and a rash. Without medical treatment, it can lead to kidney and heart damage. Lone Star ticks transmit a bacterial disease called ehrlichiosis, which causes flu-like symptoms. But the most infamous species is the blacklegged tick, which can transmit at least six different types of disease. One of them is Lyme disease—the most common tick-borne illness in the U.S.—and a rare virus called Powassan.

Different kinds of ticks carry different kinds of diseases. “There are hundreds of species of ticks found worldwide,” says Rick Ostfeld. He’s a disease ecologist at the Cary Institute, and he studies how climate affects the spread of disease. “Fortunately, in the United States there are only a handful of disease carriers.”

For example, American dog ticks can carry Rocky Mountain spotted fever (see Where Ticks Live). This bacterial infection causes a bad headache, high fever, and a rash. It can lead to kidney and heart damage if it isn’t treated. Lone Star ticks spread a bacterial disease called ehrlichiosis. It causes flu-like symptoms. But the blacklegged tick has the worst reputation. It can carry at least six different kinds of disease. One of them is Lyme disease—the most common tick-borne illness in the U.S. Another is a rare virus called Powassan. 

“Many people who become infected with the Powassan virus do not develop symptoms,” says Rebecca Eisen, a research biologist with the Centers for Disease Control and Prevention in Atlanta, Georgia. “However, the virus can lead to rare but serious problems, including encephalitis [inflammation of the brain] and meningitis [inflammation of the membranes that surround the brain and spinal cord].”

“Many people who become infected with the Powassan virus do not develop symptoms,” says Rebecca Eisen. She’s a research biologist with the Centers for Disease Control and Prevention in Atlanta, Georgia. “However, the virus can lead to rare but serious problems, including encephalitis and meningitis.” That first condition involves swelling of the brain. The second involves swelling of the tissue layers around the brain and spinal cord. 

As tick populations expand, more people become infected with the diseases they carry. Confirmed cases of Lyme disease, for example, have tripled since the late 1990s to nearly 30,000 a year. Ostfeld says there are a few reasons this might be happening.

As ticks spread, more people get the diseases they carry. For example, known cases of Lyme disease number nearly 30,000 a year. That’s three times as many as in the late 1990s. Ostfeld gives a few reasons this might be happening. 

“One is a warming climate, which allows the ticks to invade areas that were once too cold for them to live out their entire life cycle.” Another factor is people clearing sections of forests to make way for houses and cities. “This process, which we call forest fragmentation, reduces predators like owls, foxes, and bobcats,” says Ostfeld. That’s great for mice and for the ticks that live on them, he explains. Fewer mice are eaten, and ticks have more hosts. “But it’s not so good for us because we’re more likely to get Lyme disease,” he says.

“One is a warming climate, which allows the ticks to invade areas that were once too cold for them to live out their entire life cycle.” Also, people clear parts of forests to make room for houses and cities. “This process, which we call forest fragmentation, reduces predators like owls, foxes, and bobcats,” says Ostfeld. That’s great for white-footed mice, he explains. It’s also great for the ticks that live on them. Fewer mice are eaten, and ticks have more hosts. “But it’s not so good for us because we’re more likely to get Lyme disease.” 

Ostfeld is one of the researchers heading a five-year study called the Tick Project. It aims to test preventive measures that could protect people from tick-borne diseases.

Ostfeld and other researchers are heading a five-year study. It’s called the Tick Project. It aims to test ways of protecting people from tick-borne diseases.

One method involves the use of a product called Tick Control System—a small box that attracts rodents. When one enters the box, it rubs against a low dose of a liquid chemical that kills any attached ticks. That interrupts the life cycle that spreads Lyme disease.

A second method involves a fungus found naturally in soils in Northeastern forests that has been shown to kill ticks. A commercially developed strain of the fungus is being sprayed on vegetation to kill ticks looking for a blood meal.

One way involves a product called Tick Control System. It’s a small box that attracts rodents. When one enters the box, it rubs against a liquid chemical. It’s a low dose of the chemical, but it kills any ticks on the rodent. That breaks the life cycle that spreads Lyme disease.

A second way involves a fungus found in soils in Northeastern forests. This fungus has been shown to kill ticks. A business has developed a strain of the fungus. It’s being sprayed on plants to kill ticks looking for a blood meal. 

People can also take steps to protect themselves from the tiny bloodsuckers. Precautions include wearing insect repellent and remembering to check themselves for ticks if they’ve been outside. Such precautions can reduce the risk of contracting a tick-borne illness, says Ostfeld. There’s no reason to avoid the benefits of being outdoors for fear of ticks, he says.

If you have been bitten by a tick and start to experience symptoms, like a rash, fever, or headache—especially in summer months outside of flu season—see your doctor as soon as possible. “When treated early, most tick-borne diseases are fairly easy to cure,” says Ostfeld.

People can also take steps to protect themselves from the tiny bloodsuckers. One step: Wear insect repellent.  Another step: Check yourself for ticks if you’ve been outside. These actions can lower the risk of getting a tick-borne illness, says Ostfeld. There’s no reason to miss the benefits of being outdoors for fear of ticks, he says. 

What if you’re bitten by a tick? Watch for symptoms, like a rash, fever, or headache—especially in summer months outside of flu season. If symptoms start, see your doctor as soon as possible. “When treated early, most tick-borne diseases are fairly easy to cure,” says Ostfeld.