Up-close tick encounters are nothing new to Peter Krause. As a tick-borne disease researcher, he’s conducted fieldwork where these parasites live. After one trip to Block Island, off the coast of Rhode Island where ticks are endemic, Krause had the jarring experience that’s become all too common for many others, too.
“I came back, and the next morning noticed what I thought was a little freckle on my chest, so I didn’t do anything about it,” recalls Krause, a senior research scientist in the Department of Epidemiology of Infectious Diseases at the Yale School of Public Health. “The next day, I looked again, and it was a bigger freckle, so I knew it was a tick attached to me.”
As spring deepens into summer, ticks — those blood-sucking, microbe-transmitting vectors — are back on the radar. Forecasting how prevalent they’ll be is tricky. Will a mild winter make for an exploding tick population in spring? Does a winter with little snowfall cut down their numbers? While Krause says predicting the population in any given season can be difficult, one thing is for sure: Ticks are proliferating and spreading, and they’re bringing their diseases with them.
In rural or suburban areas, where large deer and mice populations maintain the deer tick population, there’s no escaping their crawly presence. But there are steps people can take to avoid ticks, keep calm, and summer on.
In a Q&A, Krause explains what’s spreading, what’s rare but dangerous, and how to stay safe this summer.
Peter James Krause
What tick-borne diseases are most prevalent?
Peter Krause: Ticks transmit disease microbes while taking a blood meal when they release organisms into a victim’s bloodstream. There are 15 or so disease microbes transmitted by a variety of ticks in different regions of the U.S. In the Northeast, the Ixodes scapularis tick, or deer tick, transmits seven diseases, including what are known as the “big three.” Lyme disease is far and away the most prevalent. Over 89,000 cases of Lyme disease were reported by the Centers for Disease Control and Prevention [CDC] in 2023 in the U.S. And there’s some evidence that the real number is much greater, with an estimated 476,000 cases per year. We have a good surveillance system, but many people with tick-borne disease are not diagnosed or are not reported.
Three life stages of the deer tick — larval, nymph and adult.
The second most common deer-tick transmitted disease is anaplasmosis. It’s caused by the anaplasma microbe, which infects white cells and causes systemic illness. It’s easily treated with antibiotics. The third most common is babesiosis. Babesiosis is a little parasite that infects red blood cells and can cause a host of clinical symptoms. About 5,000 or 6,000 anaplasmosis cases and about 2,000 to 3,000 babesiosis cases are reported to the CDC each year. As with Lyme disease, however, the actual numbers of both diseases are thought to be much greater.
And babesiosis carries the greatest risk?
Krause: It can cause very serious disease, and the mortality rate is much higher for babesiosis than the other two diseases. One to 3% of people with a normal immune system die from this disease. The figure jumps to as high as 20% for people who are immunocompromised. Those folks need to be especially careful to try to avoid tick bites if they live or travel in babesia endemic areas [including the Northeastern and Upper Midwestern U.S.], and to be aware of the disease.
Contact the Connecticut Agricultural Experiment Station for more information on ticks, mice, and deer, and on how to install effective tick control environmental measures in a yard or anywhere on private property. You may also submit ticks to the station for testing to determine the presence of pathogens.
What are some of the less common tick diseases?
Krause: Of the other deer tick-borne diseases, Powassan virus disease is of greatest potential concern. Powassan virus is very uncommon. We’re talking maybe 60 cases a year. But unfortunately it’s increasing. The health impact of this disease can be severe because it can cause severe brain damage. About 50% of people who’ve been reported as infected to date have had evidence of brain damage, and the mortality rate is about 10%. It’s a really nasty bug. If this disease ever becomes widespread and infection rates increase, there will likely be increased efforts to reduce deer numbers, as deer are responsible for greatly amplifying the deer tick population. The efficacy of deer reduction is not clear, and reducing the herd is difficult.
Is climate change making ticks more virulent or more numerous?
Krause: Global warming has had a measurable effect on ticks. It’s been well documented that there’s a northern expansion of deer ticks. Ticks can’t survive in climates that are too hot or too cold. As temperatures rise, Canada is experiencing an increase in deer tick transmitted diseases. Our lab is currently working with a group of scientists at the Public Health Agency of Canada regarding the recent increased incidence of babesiosis in Canada.
Steps to avoid ticks
• Minimize time spent in the woods or tall grass
• If you go into the woods, wear light-colored long pants and a long-sleeve shirt, tuck your pant cuffs into your socks
• Wear topical tick repellent on your skin and/or pesticides on clothing
• Perform thorough tick checks of your body after spending time in high-risk areas
• Keep your yard free of brush or wood piles
• Use tick repellent on pets
• Treat your yard with tick sprays
• Remove ticks embedded in skin as soon as possible, preferably with tweezers
How widespread are tick-borne diseases in the U.S?
Krause: Tick-borne diseases are reported from every state in the U.S., but they vary in type and number. Deer tick-borne diseases are most common and most prevalent in the Northeast and the Upper Midwest. They are reported in the Far West, although the numbers there are much smaller. And, again, we’re talking about deer tick-transmitted diseases, but there are other ticks that transmit disease. One example is the Lone Star tick, Amblyomma americanum, that has recently come up from the South, and global warming is probably at least partly responsible. It’s gotten into New England, and is associated with several diseases, including the alpha-gal syndrome, which is an allergic reaction to ingestion of red meat.
Somebody finds a tick on them. What should they do?
Krause: If it’s crawling around, you should consider placing it in a small container and showing it to scientists at The Connecticut Agricultural Experiment Station or your primary care practitioner. They can identify the tick species, determine whether the tick is infected, and if so with what pathogen(s).
If a tick is attached, remove it as soon as you can. The best way is to take a pair of tweezers, grasp the tick, and pull it out. You can also try using your hand and pulling it out, but tweezers are best.
It’s best to place the tick in a small container for possible identification. If it’s not a deer tick, you don’t have to worry about Lyme disease. Ticks feed for about three to five days. So, if you pull the tick off within 36 hours of its attachment, you’re not going to get Lyme disease or babesiosis. Powassan, though, is different as transmission can occur within 15 minutes.
What about looking for the telltale Lyme rash?
Krause: Not everyone develops it. Estimates vary between 70 and 80%. The erythema migrans rash is an expanding red rash; round or oval, five centimeters [two inches] or more in diameter, with or without a bulls-eye/target appearance. The presence of the rash meets the CDC surveillance definition of Lyme disease. Many times, when you have the rash, you have accompanying symptoms like fever, fatigue, or joint and muscle aches. Some people only have the systemic illness symptoms, so you have to be aware of that. When someone in an endemic area, like Connecticut, develops a viral-like illness during the summer, you need to consider Lyme disease (as well as anaplasmosis and babesiosis).
What are the best ways people can protect themselves from a tick encounter?
Krause: The most effective way is to stay out of the woods and stay away from tall grass areas. If you minimize walking through the woods or tall grass areas, your risk for developing a tick-borne disease is going to go down. If you do walk in woods, stay on the trail. Don’t go into the grassy areas or brush. Ticks are going to be sitting there. You can also take personal protective measures. Wear light-colored, long pants and a long-sleeve shirt, tuck the cuffs of your pants into your socks, so a hidden tick can’t crawl up your leg.
There are also acaricides that kill ticks, like permethrin, which you put on your clothing or repellents, including DEET, which you put on your skin. Another practice that can decrease tick-borne disease risk is checking for ticks on your body after you’ve been in wooded or tall grass areas. You will need a partner to check your back and scalp.
What about treating outdoors areas?
Krause: Spraying acaricide on your property is effective. Mice are ubiquitous, but they like to live in stonewalls. If you have one, cementing it over will prevent mice from nesting there. Woodpiles present the same problem. If your property abuts a wooded area, you should know that one of the favorite places of deer is the edge — the transition area where the lawn ends and the woods begin. Ticks are particularly abundant there, so that’s an area to avoid. Deer-proof fences also work but need to be at least 7 or 8 feet high.
Do pets put people at greater risk for Lyme disease?
Krause: It hasn’t been terribly well studied, but earlier observations concluded there was no association between pet ownership and Lyme disease. More recently, there is some evidence that there is a positive correlation, so pets probably do put people at some risk. But there are effective anti-tick products for pets that help. Ticks that make it into your house can pose a risk, but indoor air is very dry compared to the moist environment ticks require. If ticks fall off a pet in the house, most will just dry out and die. And if they’ve completed a meal on a pet, and they’re all filled up with dog blood, they’re not going to be interested in you.
