Anaplasmosis in New England: The Other Tick Disease Rising Fast

Most people in Maine know the bull’s-eye rash by now. They check for it after a hike, scan the kids at bath time, and breathe easier when nothing shows up. The problem is that the deer tick carries more than Lyme, and one of its other passengers does not announce itself with a rash at all. Anaplasmosis has been climbing faster than almost any tickborne illness in the state, and in 2024 it hit a record.

What anaplasmosis actually is

Anaplasmosis is a bacterial infection caused by Anaplasma phagocytophilum, according to the U.S. Centers for Disease Control and Prevention. In the eastern United States it spreads through the bite of the blacklegged tick, the same deer tick (Ixodes scapularis) responsible for Lyme disease and babesiosis. On the West Coast a different species, the western blacklegged tick, does the job. For New England readers, the takeaway is simpler than the Latin: the tick already living in your backyard can carry it.

That overlap matters. A single bite can deliver more than one infection at once, which is part of what makes these diseases tricky to sort out. If you want the wider picture of the regional tick problem, our complete Maine and New Hampshire tick and Lyme guide lays out the full landscape.

The symptoms, and why they are easy to miss

Here is the part that catches people off guard. Anaplasmosis rarely comes with a rash. The CDC notes that when a rash does appear, it may actually point to a coinfection with something else, like Lyme. So the one sign most Mainers have been trained to look for is usually absent.

What shows up instead looks a lot like a bad case of the flu, typically within one to two weeks of the bite. Fever. Chills. A severe headache. Aching muscles. About one in five people also get gastrointestinal symptoms, the CDC says, meaning nausea, vomiting, diarrhea, or loss of appetite. None of that screams “tick disease.” In July, plenty of people would shrug it off as a summer bug.

Two things make it harder still. Many people never remember being bitten, because the deer tick in its nymph stage is roughly the size of a poppy seed. And the disease leaves its fingerprints in bloodwork rather than on the skin. The CDC’s clinical guidance lists low platelet counts, low white blood cell counts, mild anemia, and elevated liver enzymes as common laboratory clues. A doctor who suspects a tickborne illness can often spot the pattern, but only if anaplasmosis is on the radar in the first place.

Why cases are climbing fast in Maine and New Hampshire

The national trend is steep. Reported anaplasmosis cases rose more than sixteenfold across the country, from 348 in 2000 to 5,762 in 2017, according to research published in the CDC’s journal Emerging Infectious Diseases. The disease clusters hard in the Northeast and upper Midwest. Just six states, New York, Connecticut, New Jersey, Rhode Island, Minnesota, and Wisconsin, account for roughly 90 percent of reported cases.

Maine sits right in that hot zone, and its recent numbers are striking. The Maine CDC counted 777 anaplasmosis cases in 2023. In 2024 that figure jumped to about 1,284 confirmed and probable cases, a roughly two-thirds increase in a single year and an all-time high. State health officials have tied the broader surge in tickborne disease partly to a run of mild winters.

New Hampshire has watched the same curve bend upward. NH state surveillance data show anaplasmosis climbing from 88 cases in 2013 to 317 in 2017. The Granite State’s health department points to the same culprit Maine does: the blacklegged tick that already spreads Lyme and babesiosis is spreading anaplasmosis too.

Scientists connect the rise to a warming climate. Milder winters and longer warm seasons let blacklegged ticks survive and push their range north, into parts of Maine that were not established tick habitat in the early 2000s. One 2025 study in Global Change Biology measured the leading edge of the tick’s range expanding at roughly 48 kilometers a year. The ticks are not just more numerous. They are moving.

What the UMaine Tick Lab data shows

The clearest local snapshot comes from the University of Maine Cooperative Extension Tick Lab in Orono, which tests ticks that residents mail in from across the state. In 2024 the lab analyzed 4,776 submissions, 3,650 of them deer ticks, sent from 398 towns spanning all 16 counties. That is a lot of ticks pulled off a lot of Maine ankles.

Of the deer ticks tested, 9.7 percent carried Anaplasma phagocytophilum. For comparison, 41.5 percent carried the bacterium behind Lyme and 12 percent carried Babesia microti, the parasite that causes babesiosis. So Lyme is still the most common find by a wide margin, but nearly one in ten deer ticks here is carrying anaplasmosis. That is not a fringe risk.

The geography tells its own story. UMaine researchers have identified the midcoast, specifically Waldo, Knox, Hancock, and Lincoln counties, as carrying the heaviest burden of Lyme, anaplasmosis, and babesiosis. They have called the region the state’s current tick “epicenter.” If you live, garden, or hike along that stretch of coast, the odds are simply higher.

How it is diagnosed and treated

Anaplasmosis is treatable, and the treatment is well established. The CDC names doxycycline as the treatment of choice for anaplasmosis in adults and children of all ages, and it works best at preventing serious complications when it is started early. There is an old worry that the drug stains children’s teeth, but the CDC says a short course does not cause that staining. None of this is a do-it-yourself project. Diagnosis and any prescription belong to a clinician who can read your bloodwork and your history.

The reason early treatment matters is that the window counts. Because the symptoms are so generic and the rash is usually missing, the danger is delay, not the disease being untreatable. A doctor who knows you were outdoors in tick country, or who sees the telltale dip in platelets and white cells, can act quickly. That is why it helps to mention recent time outside, even if you never saw a tick.

Who faces the highest risk

Most people who get anaplasmosis recover. The overall case fatality rate is low, under 1 percent in national surveillance, but the illness is not trivial: roughly a third of reported cases end up hospitalized. The serious outcomes cluster in specific groups.

• Adults 65 and older
• Anyone whose treatment is delayed, often because the diagnosis was missed
• People with weakened immune systems

In rare cases, severe anaplasmosis can progress to respiratory failure, bleeding problems, organ failure, or death, according to the CDC. Those outcomes are uncommon, and they become less likely with prompt care. For older Mainers who spend summers in the garden or on the trails, the practical lesson is to take a sudden summer fever seriously rather than waiting it out.

Prevention and what to do after a bite

The defenses against anaplasmosis are the same ones that protect against every other deer-tick disease, which is convenient. Cover up on wooded trails. Use an EPA-registered repellent. Do a careful body check after time outside, paying attention to the warm, hidden spots where nymphs like to settle. Throw clothes in a hot dryer when you get home.

If you do find an attached tick, remove it promptly and consider saving it. The UMaine Tick Lab will test a mailed-in tick for a fee, which can tell you whether the tick that bit you was even carrying anything. That does not replace watching your own health, but it adds useful information.

Then keep an eye on how you feel for the next couple of weeks. A summer fever with chills and a pounding headache, especially without an obvious cause, is worth a call to your doctor, and worth mentioning the tick. Anaplasmosis is not the only thing the deer tick carries either. Babesiosis, covered in our guide to the malaria-like tick disease, and the rare but serious Powassan virus ride along on the same insect. Knowing all three exist is half the battle in a state where the tick season keeps getting longer.

Sources

• U.S. Centers for Disease Control and Prevention. About Anaplasmosis. 2024. https://www.cdc.gov/anaplasmosis/about/index.html
• U.S. Centers for Disease Control and Prevention. Clinical Signs and Symptoms of Anaplasmosis. 2024. https://www.cdc.gov/anaplasmosis/hcp/clinical-signs/index.html
• U.S. Centers for Disease Control and Prevention. Clinical Care of Anaplasmosis. 2024. https://www.cdc.gov/anaplasmosis/hcp/clinical-care/index.html
• CDC Emerging Infectious Diseases. Epidemiology and Spatial Emergence of Anaplasmosis, New York, USA, 2010-2018. 2021. https://wwwnc.cdc.gov/eid/article/27/8/21-0133_article
• American Journal of Tropical Medicine and Hygiene (PMC). Human Granulocytic Anaplasmosis in the United States from 2008 to 2012: A Summary of National Surveillance Data. 2015. https://pmc.ncbi.nlm.nih.gov/articles/PMC4497906/
• National Library of Medicine / NCBI Bookshelf. Anaplasma Phagocytophilum (StatPearls). 2023. https://www.ncbi.nlm.nih.gov/books/NBK513341/
• Maine CDC (Maine Tracking Network). Tickborne Diseases (annual Lyme, anaplasmosis, and babesiosis case counts). 2025. https://data.mainepublichealth.gov/tracking/tickborne
• Maine Public. Maine reported record-high number of tickborne disease cases last year. 2025. https://www.mainepublic.org/health/2025-01-03/maine-reported-record-high-number-of-tickborne-disease-cases-last-year
• New Hampshire Department of Health and Human Services. Tickborne Diseases. 2024. https://www.dhhs.nh.gov/programs-services/disease-prevention/infectious-disease-control/tickborne-diseases
• New Hampshire Charitable Foundation. Tick-borne diseases on the rise. 2018. https://www.nhcf.org/what-were-up-to/tick-borne-diseases-on-the-rise/
• University of Maine Cooperative Extension. 2024 Surveillance Report from UMaine Extension Tick Lab highlights tick-borne disease risk. 2025. https://extension.umaine.edu/2025/04/17/2024-surveillance-report-tick-lab-highlights/
• Ticks and Tick-borne Diseases (PMC). Changes in the geographic distribution of the blacklegged tick, Ixodes scapularis, in the United States. 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10862374/
• Global Change Biology (PMC). Rapid Northward Expansion of the Blacklegged Tick, Ixodes scapularis, in Response to Climate Change. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12590538/
• University of Maine. UMaine Extension’s Tick Lab releases research showing elevated activity in midcoast counties. 2025. https://umaine.edu/news/2025/06/umaine-extensions-tick-lab-releases-research-showing-elevated-activity-in-midcoast-counties/
• Bangor Daily News. The midcoast is Maine’s new tick “epicenter.” 2025. https://www.bangordailynews.com/2025/07/14/midcoast/midcoast-environment/maine-midcoast-ticks-population-disease-umaine-study/

This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before making any health decisions.