Researchers at the Cary Institute for Ecosystem Studies, in upstate New York, comb the woods in search of ticks. Photography by Kirsten Luce

Lyme Disease Cases Are Exploding. And It’s Only Going to Get Worse.

Climate change and human sprawl have triggered a pandemic

This story is part of “Tickpocalypse,” a multi-part special report.

KKelly Oggenfuss is walking into the woods. Leading her team of four young researchers through a thicket of slender oak trees, she doles out assignments by letters corresponding to a grid. As early morning light filters through the canopy, Oggenfuss and her colleagues pull on latex gloves then disperse to gather surveillance data.

For 20 years, this has been a post-dawn ritual for Oggenfuss, a senior research specialist at the Cary Institute of Ecosystem Studies in Millbrook, New York, a bucolic town in the state’s Hudson Valley region. Four times a week from April to November — traditionally the most active tick season in the Northeast — she leads a platoon of field researchers as they don white coveralls, drive a pair of old Chevy Tracker SUVs down an overgrown dirt road, and hike to a five-acre tract designated “Henry Control” on the grounds of the institute. Their mission is to seek out and study ticks in one of the most tick-infested areas in America.

Oggenfuss and the others work methodically across a grid of 242 spring-loaded box traps, checking for rodents lured overnight by whole-oat seeds. Sharing updates via walkie-talkie, the team gathers after a squirrel is found in one of the traps. The new researchers transfer the animal to a plastic mesh sleeve and take turns examining it. A similar process unfolds with chipmunks.

Most often, the traps capture mice, which Oggenfuss and her team carry with them, still in the trap, until the grid check is complete. Then the group convenes around a collapsible table. As one researcher records data (grid location, gender, tag number, etc.), the others apply tags to the mice and collect blood, urine, and stool samples. Finally, Oggenfuss and her team meticulously comb the mice with tweezers and blow on their fur, pushing it aside in search of ticks.

Researcher Kelly Oggenfuss tags a chipmunk. Ticks frequently contract the bacteria that causes Lyme disease from small animals, then pass it to humans.

“Look there’s a nymph,” says Oggenfuss. “And I’ve got one, two, three larvae. Can you see them?” She pulls a patch of the mouse’s fur back to reveal a blacklegged tick no bigger than a poppy seed burrowed into its head. The larvae are barely perceptible.

A researcher named Agi holds up another mouse. “Look,” she announces. “That’s a larva on top of that nymph. We have a co-feeding situation here.” The theory is that their feeding sites are so close that pathogens move between them easily, Oggenfuss explains. The potential result is one tick sharing infectious material directly with another through the host mouse as if it were a straw, speeding the spread of disease. “That could have an effect on infection prevalence,” Oggenfuss adds. “It’s one of the things we’re studying.”

Since 1992, the Cary Institute has been compiling a record of tick ecology that they believe to be the longest continuous study of this kind in the U.S. and possibly the world. Mostly its researchers encounter the blacklegged, or deer, tick (Ixodes scapularis), but in recent years, they’ve also been seeing increasing numbers of lone star ticks (Amblyomma americanum), which are native to the American Southeast but now range from northern Mexico to Canada. Over the years, an alarming number of ticks in the surrounding area have been revealed to carry Borrelia burgdorferi, the bacteria that causes Lyme disease, while others have tested positive for the pathogens that cause other tick-borne illnesses, including the potentially fatal Powassan virus.

Because ticks acquire pathogens from hosts, understanding tick-borne diseases means understanding ticks’ so-called disease reservoir, especially mice. If the urban rat was the primary carrier of bubonic plague, the country mouse is it for Lyme disease. And just as the fleas that fed on infected rats spread the plague, ticks that feed on infected mice transmit Lyme.

On this early May morning, the team’s trap yield is relatively modest — four mice, two squirrels, and a chipmunk. “It’s early days still,” says Oggenfuss. In August, during the so-called larval peak, the researchers sometimes catch as many as 220 mice and can find 150 or even 200 tick larvae crawling on a single mouse. It can be an unnerving moment. “When the ticks are looking for a feeding site,” Oggenfuss says, “the mouse fur just seems to move on its own.”

The process for counting ticks not affixed to hosts is called a drag — the researchers pull a one-square-meter sheet of fabric along the ground for 30 meters then tally the number of ticks affixed to it. Oggenfuss holds the Cary Institute record for ticks collected in a single drag: 1,700. As horrifying as that haul was — and it would, by extrapolation, put the tick population on the Cary Institute’s 2,000-acre campus at 2 billion — Oggenfuss is quick to note it was exceptional, and tick density is irregular. Her more conservative calculations of average tick populations, based on drags done during the same time of year (August, the larval peak), are only reassuring by comparison: upward of 20,000 ticks per acre, more than 100,000 on the Henry Control grid, and more than 40 million on the Cary Institute grounds.

Tick “drags,” like the one pictured here, are used to count tick populations. The Cary Institute grounds alone may be home to 40 million of the bugs.

The scary thing is, that’s nothing. Experts say the worldwide tick population is exploding, triggering a dramatic spike in the incidence of Lyme disease and a rise in other tick-borne illnesses, some of which, like Powassan, are far more dangerous than Lyme.

FFirst identified in 1975 in the leafy New England town of Old Lyme, Connecticut, Lyme disease has now reached what experts consider pandemic proportions. According to the Centers for Disease Control and Prevention (CDC), the number of confirmed cases of Lyme disease in the U.S. has more than doubled in the two decades leading up to 2017 (the most recent year for which final figures are available) and increased 17% from 2016 to 2017 alone. More than half the counties in the U.S. are considered high-risk areas for Lyme, according to the CDC, and in some areas, as many as six out of 10 ticks carry the infection.

“It’s been a relentless expansion since the 1980s,” says John Aucott, director of the Lyme Disease Clinical Research Center at Johns Hopkins University School of Medicine. “There may be down years and up years, but the trends are in place, and there’s no indication that they’re going to reverse.”

We now live in a frightening new normal: It’s estimated that 300,000 people contract Lyme every year in the U.S., with victims found not just in traditionally tick-heavy areas like upstate New York and Maine, but also in all 50 states and Washington, D.C. While most people are cured quickly with antibiotics, some go on to experience lingering symptoms characteristic of Lyme, like headaches, fatigue, and joint and muscle pain, for months or longer after they’ve been treated, a condition known as post-treatment Lyme disease syndrome (PTLDS). According to a recent study led by experts at the Brown University School of Public Health, the number of people in the U.S. with PTLDS was estimated to be 1.5 million in 2016 and is predicted to rise to nearly 2 million by 2020.

“There is little doubt that [Lyme disease] is pandemic. It calls for a huge national and concerted international effort to bring it under control.”

Tick populations now exist on every continent, even Antarctica, and Lyme disease can be found throughout most of Europe, where it ranks as the most common vector-borne disease, and beyond. “To me, there is little doubt that it is pandemic,” says Mary Beth Pfeiffer, author of Lyme: The First Epidemic of Climate Change. “It’s in China, Russia, Japan, Australia. It’s moving fast into Canada. It is all across the U.S. It calls for a huge national and concerted international effort to bring it under control.”

The incidence of other tick-borne illnesses is also sharply rising. According to the CDC, the occurrence of those diseases in the U.S. has nearly tripled since 2004 and increased more than 22% from 2016 to 2017. In addition to Lyme, ticks transmit a slew of pathogens, including those that cause babesiosis, ehrlichiosis, anaplasmosis, southern tick-associated rash illness, tick-borne relapsing fever, tularemia, Colorado tick fever, Q fever, Rocky Mountain spotted fever, and Powassan encephalitis. Most of the bacterial diseases are treatable if diagnosed early. Others, like Rocky Mountain spotted fever, are potentially fatal, particularly in children, if not treated quickly. Incidences of spotted fever rickettsiosis, which includes Rocky Mountain spotted fever, increased more than 12-fold from 2000 to 2017 (up from 495 to 6,248). And while more rare still, cases of Powassan virus, which can kill one in 10 people who are infected and for which there is no treatment, are rising as well. In 2008, only two cases were reported. In 2016, that number jumped to 22 and again in 2017 to 33.

“Ticks account for more diseases than all other biting insects and arthropods in the United States,” says Ben Beard, deputy director for the Division of Vector-Borne Diseases at the CDC. “It’s hard to know what the maximum or the ceiling might be. All we can say is that the number of cases is growing every year.”

Alarms are going off all over the globe. South Africa, where tick-bite fever (a form of rickettsias) is common, has seen an increase in incidences of Crimean-Congo hemorrhagic fever (CCHF), which is deadly in 30% to 40% of cases. The tick that carries CCHF, a native of sub-Saharan Africa and eastern Europe, has been found in Spain, Portugal, Germany, and the United Kingdom, where it is believed to have been brought from Africa by migratory birds. Bites from the lone star tick have been shown to cause alpha-gal syndrome, which manifests in rapid-onset allergies to meat, typically beef and pork, that can result in unexplained anaphylactic reactions. There is no treatment, other than eschewing the consumption of red meat.

In North America, news reports in Maine and southern Canada this spring featured a shocking number of sightings of what are called ghost moose — skeletal-looking, malnourished, denuded animals that have rubbed off their fur in response to tick irritation after hosting up to 75,000 feeding ticks through the winter. Many emerged anemic after being the source of so many blood meals, and a number of calves died after losing too much blood to ticks — a vampire-like end to life known as exsanguination.

If Lyme disease has reached pandemic proportions, why haven’t we heard more about it? Because, experts say, Lyme doesn’t strike fear into people’s hearts the way some other illnesses, like Ebola or Zika, do. People respond to dramatic pictures or dramatic mortality, says Aucott. “It’s hard for them to have a perspective on the real impact of Lyme disease because it doesn’t cause visible changes. People with Lyme disease don’t look sick.”

The same dynamic holds true for other tick-borne illnesses, says Beard. “People don’t have to be dying all over for this to be a huge health problem. These are serious illnesses, and some do result in deaths.”

In a report on the dangers of ticks, the Institute of Medicine, the health arm of the National Academies, called ticks “the Swiss Army knife of disease vectors,” emphasizing their remarkable adaptability and efficiency in spreading illness. Although conspiracy theorists have suggested — falsely — that Lyme disease was created in a U.S. military lab, it is true that in the years following World War II, the U.S. employed top German scientists who explored the tick’s potential in biological warfare for Nazi Germany. The researchers were investigating the tick’s ability to spread pathogens across wide areas with the potential to incapacitate entire populations.

Seventy-five years later, the tick timebomb is detonating on its own. Thanks to climate change, globalization, and other factors, ticks are not only proliferating but also becoming more malignant, more aggressive, and more likely to carry infection. A public health crisis is hiding in plain sight, with tick-borne diseases creating millions of sick people at an economic cost running into the billions, and little has been done so far to mount a meaningful defense. On every walk in the woods or picnic in the park, we are encountering more ticks. And as Willy Burgdorfer, the entomologist who identified the bacteria that causes Lyme disease, once proclaimed: “There is no such thing as a clean tick.”

IIt’s late morning when Oggenfuss and her team return to the Cary Institute research building with the field samples they’ve collected and make their way past a room called the Insectary, marked with a large biohazard symbol and the shapes of various tick species, to the lab. The research assistants transfer the mouse blood, urine, and fecal samples they’ve gathered to an Igloo cooler marked “NIH” and send them to be tested for, among other things, the pathogen that causes Lyme disease.

A dozen or so clear plastic canisters labeled “extra ticks” are strewn across Oggenfuss’ desk, all marked with a collection date and grid location. Inside of each, on a bed of plaster of Paris, are groups of ticks, some nymphs, some adults. Oggenfuss reaches up, grabs a pair of high-magnification granny glasses that are resting on a deer skull, and hands them to me.

“Use these,” she says. She hasn’t confirmed the species of each tick yet. “They’re probably all blacklegged, but I’ve been surprised before.”

Taxonomically, the 800-plus species of ticks fall into one of three families — Ixodidae (hard ticks, like the blacklegged tick and dog tick), whose life spans range from one to two years; Argasidae (soft ticks), which can live as briefly as several months or as long as a dozen or more years; and Nuttalliellidae (a single elusive species in sub-Saharan Africa). They are part of the order of Parasitiformes and the classification arachnid (although many varieties emerge as larvae with six legs and develop eight legs as nymphs). Ticks progress through four stages — egg, larva, nymph (argasid ticks will go through up to seven phases of the nymph stage), and adult. Adult female blacklegged ticks have a bright orange-red body; adult males are dark brown to black. Even at their biggest, ticks are small — measuring between three and five millimeters long, or slightly larger than a sesame seed when mature — with a diminutive head on a plump, pear-shaped body. When engorged, they can swell to many times their unfed weight: 200 to 600 times in hard ticks, five to 10 times in soft ticks.

A researcher tags a mouse (left) and examines an embedded tick.

In order to survive, ticks must feed on hosts, which can be mammalian, avian, amphibian, and reptilian, a minimum of three times — once at every stage after they hatch from the egg — before adult males die and females lay eggs, between 2,000 and 5,000 of them. Depending on the species, ixodid ticks will feed on either one, two, or three separate hosts in the course of their life cycle; argasids will feed on more depending on how many nymphal stages they undergo. Multihost ticks present the greatest risk: On each feeding after the first, either on a different host species or a different member of the same species, a tick can transmit bacteria and viruses from one host to the next. Hence, ticks, like mosquitoes, are known as disease vectors.

According to some researchers, ticks veered off from the mite family tree as far back as 450 million years ago; other scientists date their emergence to the Cretaceous period, approximately 100 million years ago. Thanks to specimens trapped in amber, we know ticks were feeding on feathered dinosaurs 99 million years before they began being featured on identification charts in veterinarian’s offices and in hiker’s handbooks.

Some scientists date ticks’ emergence to the Cretaceous period, 100 million years ago.

Contemporary ticks “don’t look much different at all from those preserved specimens,” says Rick Ostfeld, a distinguished senior scientist at the Cary Institute, the leader of the Tick Project, and arguably the country’s preeminent researcher into the ecology of tick-borne diseases. “They are very conserved morphologically throughout their evolutionary history, more so than most groups.”

The tick’s early adaptations have aged well, starting with its barbed feeding tube, called a hypostome, which penetrates the host’s skin and is moored in place by a glue-like secretion produced by the salivary glands. Tick saliva itself contains an almost alchemist’s mix of elements: Pain-killing enzymes called kininases make bites barely, if at all, noticeable to hosts; anti-inflammatory compounds keep the wound site from becoming irritated and the tick from being detected during its sometimes days-long feeding period, and anticoagulants keep the blood meal flowing freely all the while. Over time, ticks have become adept at sensing hosts when questing for a blood meal, learning to detect movement, body heat, odor, moisture, respiration, and carbon dioxide. Some species can even detect shadows cast by nearby creatures.

The characteristics that have helped ticks endure for eons — surviving numerous periods of warming and ice ages (including the 2.5-million-year Pleistocene ice age), mass extinctions, and years of plenty and years of famine thousands of times over — also help them from season to season. “They have massive reproduction, they have super long lives, especially for a parasite, they don’t need to feed often, they’re very tiny, and they are very resistant,” Ostfeld says. “They are able to escape nasty conditions. They just go into suspended animation in the cold. They have antifreeze molecules they mobilize seasonally. They don’t need much oxygen — a close to zero rate of respiration when not feeding — so they can be underwater for a few days, even a few weeks.” Although they are deceptively easy to kill in a lab with extreme heat or cold — or at home by putting tick-covered clothes in the dryer or freezer — in the outdoors, ticks are adept at finding shelter in the leaf cover or soil to insulate themselves from severe temperatures.

It seems surprising Hollywood hasn’t tried to mine the star power of relentless, blood-eating, disease-spreading creatures that reproduce by the thousands and can’t be killed off. “I’m not an expert in that area,” Beard says, “but it seems like you could create a pretty good horror film out of all that.”

IIt’s a common trope of such cinema that mankind’s actions will trigger the tragic consequences visited upon it. While the relationship between changes to the climate and the spread of ticks and tick-borne disease is complex — tied to host populations and hosts’ food supplies, among other factors — this much is clear: Human-driven climate change is making tick season longer and tick country larger. As winters get warmer and shorter, ticks become dormant later in the year (if at all should it fail to fall below freezing) and active earlier. Ostfeld has observed the timing of spring nymphs move up by a month in the past two decades. Lyme Disease Awareness Month, May, now arrives after Lyme-carrying blacklegged tick nymphs do in the Northeast U.S.

Tick maps are changing as fast as the calendars, as species like the deer tick have spread northward from temperate zones to regions with boreal forests. This helps explain why the Public Health Agency of Canada only began tracking cases of Lyme disease in 2009. From that year through 2017, Lyme cases in Canada increased more than 14-fold, from 144 to 2,025. In 2017, Maine had the highest per-capita incidence rate of Lyme of any state in the U.S. and reported a 23% year-over-year increase in cases.

There was a time when human impact on the environment helped suppress the threats posed by ticks. The radical clear-cutting of forests and overhunting of deer in the 19th and early 20th centuries lowered the transmission of Lyme disease. In recent decades, however, changes in land use, reforestation efforts, and other factors have combined with warming temperatures to exacerbate it. “You’ve got climate change moving it north, you’ve got suburban growth into wooded areas, you’ve got rebounding deer populations,” says Beard.

To compound matters, ticks themselves are undergoing a simultaneous, seemingly unrelated evolutionary change. Disease ecologists have observed the ascendance of a particularly aggressive genetic population, or clade, of blacklegged ticks that are overtaking more docile clades in the southern U.S. “This northeastern clade moving southward is causing more cases of human Lyme disease,” Beard says, “because these ticks’ behavior is changing. They’re more likely to bite people.”

When Aucott joined Johns Hopkins in 1996, Lyme disease had been a mounting concern for a number of years, but conventional wisdom held that the illness would not spread south of the Potomac River. However, he soon began seeing case referrals from first northern then southern Virginia. Lyme is now endemic in North Carolina and has moved westward to Tennessee, Kentucky, and Ohio.

“It jumped,” Aucott says. “We also know there’s no geographic barrier to the spread of Lyme disease south of Maryland and literally out through to the Mississippi River Valley.”

In early May, the United Nations’ Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services released a devastating report that concluded that 1 million species of flora and fauna face extinction due to human activity. Disease ecologists who study ticks say biodiversity is critical in curbing the spread of Lyme disease: “High diversity dilutes transmission,” says Ostfeld. “As you lose diversity, the species that remain typically are the ones that amplify the disease.” Among the species sure to survive the coming die-off are ticks and the rodents that serve as disease reservoirs for them. “We’ll never lose mice,” Ostfeld explains. “Mice are cockroaches with fur.” So even as the biome is depleted, ticks will not only survive, but will become more likely to carry disease.

Globalization is also heightening the threat posed by ticks. Although U.S. Department of Agriculture officials screen livestock traveling internationally for parasites, they do not screen pets, migratory birds, planes, boats, or people for them. Among the CDC’s greatest concerns is non-native and invasive tick species that have the potential to spread across the country unabated. One already has.

In October 2017, Andrea Egizi, a research scientist with the Monmouth County, New Jersey, Tick-Borne Disease Lab, was one of a team of experts who investigated an unusual infestation of ticks. A resident in nearby Hunterdon County had become covered in larval ticks while shearing one of her sheep. “The reason this raised a red flag,” Egizi recalls, “was because there were just so, so many ticks.” There were hundreds on the sheep in question and more than 1,000 more in the paddock — an inordinately high count for the type of ticks normally found in the region, none of which these specimens resembled under a microscope.

Sure enough, Egizi couldn’t find the tick on any of the taxonomic keys that identify species from the region. She and her colleagues contacted the Smithsonian for help to no avail. “We were pretty sure it was something exotic, but we didn’t know what,” Egizi says. “Then I did the DNA barcode.”

Her sequencing search returned with a match to Haemaphysalis longicornis, the Asian longhorned tick. It was the first time the tick had been reported in the United States. Egizi, who had never heard of the species, began doing additional research. “That’s when I realized it could be a big problem.”

The Asian longhorned tick transmits an emerging hemorrhagic fever found in China, Korea, and Japan called severe fever with thrombocytopenia syndrome. Experts suspect it spreads Rickettsia japonica, which causes Japanese spotted fever. The species previously spread to New Zealand and Australia, where it has wreaked havoc on livestock populations, particularly cattle (it is a vector for a frequent condition called fatal bovine theileriosis). What’s more, in Asia, the longhorned tick carries pathogens that are also present in North America, including forms of anaplasma, babesia, borrelia, ehrlichia, and rickettsia. As of now, it has not been found to feed on rodents or carry human pathogens in the U.S., although CDC research on its so-called vector competence is ongoing.

“It may just be a matter of time,” Beard says. “Then it gets to the issues of how much does it feed on rodents? How much on people? What is the relative risk to humans? It’s hard to know whether it will be a game changer or if it will just incrementally to add to the concerns we already have. The jury is still out.”

The particular strain of Asian longhorned tick found in New Jersey is parthenogenetic — that is, it can reproduce without mating. A single female can lay 2,000 genetically identical eggs every six months as opposed to every two years for most North American ticks. That may explain the startling numbers of tick larvae found on the sheep. Scientists generally refrain from using the term “self-cloning,” but it is hard to avoid in this case.

In less than two years since Egizi’s discovery, there have been more than 50 reports of Asian longhorned ticks around the United States. Most were found on wildlife and domestic animals, but two were found on humans. The species has been reported as far north as Connecticut and as far south as Arkansas, and Egizi says the tick is likely to have spread elsewhere. “There are definitely places where no one’s found it yet,” she says, “because no one’s looked.”

An examination of previously unidentified samples done after the discovery of the Asian longhorned tick in New Jersey revealed that the species had actually been in North America years before 2017. One specimen found at the USDA’s National Veterinary Services Laboratories was collected from West Virginia in 2010. That was deeply unsettling, says Beard. “That, of course, raises the question: Is it possible we have other invasive species here that we’ve not even recognized yet?”

It’s also possible they are present but not able to proliferate — yet. One working hypothesis at the CDC is that the Asian longhorn tick had been in the U.S. in low numbers but only began to spread rapidly after adapting to its new environment.

Meanwhile, Egizi is comparing the DNA of her sample with those of specimens around the world, trying to find the most likely population from which it came. The goal is to determine just how it arrived. “It’s a concern how vulnerable our systems are,” she says. “For example, the fact that dogs are not checked for extra parasites when they come into the country, that is shocking to me. There’s also concern about ticks expanding their distribution within the U.S. or within North America. It’s not just from overseas that we need to be concerned about.”

That very scenario is playing out on the U.S.-Mexico border in Mexicali, where a particular clade of brown dog tick has caused a massive outbreak of Rocky Mountain spotted fever, which can be fatal in up to 30% of cases and causes more deaths than any other tick-borne disease in North America. This tick, a tropical variety, differs from the common temperate clade of its type found in North America, which almost exclusively feeds on canine hosts. “The one in Mexicali is a very aggressive tick that is more predisposed to bite people,” says Janet Foley, a professor of veterinary medicine and epidemiology at University California, Davis who specializes in disease ecology. “If it spreads to the United States in numbers, that’s dangerous.”

As of 2018, three years after the Mexican Ministry of Health declared an epidemiologic emergency, more than 4,000 people had been diagnosed with Rocky Mountain spotted fever in Mexicali, which has a population of approximately 700,000. Several hundred have died, including, according to reports, at least four who were infected in Mexicali and later crossed into the U.S. Foley co-authored a study with researchers at Universidad Autónoma de Baja California that concluded the epidemic is not contained — it has spread to other parts of Baja California and is moving into the United States. The most immediate fear is an outbreak in a major city like Tijuana, with a population of more than 2 million. “Hundreds of people have already died, and millions more are at risk,” says Foley. The tick is already there and has already moved north. Recently it’s been reported in San Diego and Los Angeles.

While ticks need moisture to survive, the common brown dog tick requires far less than most. This particular clade takes that to the extreme, suggesting its spread could be hastened by climate change. “This tick needs it hot and it needs it dry. This tick is rooting for global warming and drought,” Foley says. As places like California and Arizona become hotter and drier, the tick’s reach will expand, she says. To compound matters, research has shown that the hotter the temperature, the more aggressive this tick becomes. “You can actually do experiments and bring the temperature up and increase the bite rate of that tick,” Foley says.

She remembers driving through Mexicali with a local tick expert and being struck by the lack of leaf cover. When she asked where the ticks were found, he pointed not at vegetation but a patch of dirt in a front yard and mentioned they also like the stucco on the sides of houses. Foley experienced it herself, standing in an infested courtyard. “The ticks sense that there’s a body there,” she recalls, “and they start to crawl out of cracks in the walls. It’s unnerving.”

WWhile Lyme disease may not be as lethal or communicable as Ebola or SARS, its impact shouldn’t be underestimated.

Lyme can be difficult to diagnose. To identify it, doctors generally rely on symptoms (the bull’s-eye rash) and circumstances (having been in a tick-infested area) rather than a blood test because the antibodies that indicate the presence of the disease can take weeks to appear in tests, resulting in false negatives. The lack of a reliable test means people often go untreated longer than necessary.

The headaches, fever, muscle and joint pain typical of the illness’s early stages are comparable to flu symptoms and, if the disease is left untreated, can become severe. In rare cases, the bacteria that causes Lyme disease can enter the heart, blood, or brain, and people may experience irregular heartbeat, nerve pain, or dizziness. In extremely rare cases, Lyme can be fatal.

“This disease has been very much underestimated. We don’t have a good test. We have treatments that fail. We seem to have very little urgency to respond.”

PTLDS is both physically and psychologically debilitating. Some people’s symptoms can leave them in pain for months or years, and the lack of effective treatments and skepticism among some people that their condition is real can leave people feeling anxious and depressed.

Because children are especially vulnerable to Lyme disease (kids tend to spend more time outdoors than adults and are less cautious about where they venture), the threat of the illness is a source of widespread anxiety among parents. Studies have shown that tick-borne diseases disproportionately affect the rural poor, people employed in manual and farm labor and other outdoor vocations, and people with limited access to health care. Lyme also contributes to the overuse of antibiotics and the rise of drug-resistant bacteria, which is a serious public health threat of its own.

Recent studies estimate the medical costs of Lyme disease at $1.3 billion per year. When accounting for indirect costs, including loss of work, that figure is thought to be between $50 billion and $100 billion. But that number doesn’t factor in PTLDS cases. “That is a tiny fraction of the true cost,” says Pfeiffer. “It only reflects [people who] are diagnosed and treated quickly. Those aren’t the ones for whom treatment failed or who don’t get diagnosed or who get diagnosed with something else.”

What’s more, Pfeiffer says, the Lyme outbreak is being badly mismanaged. “This disease has been very much underestimated. We don’t have a good test. We have treatments that fail. We seem to have very little urgency to respond. That lack of urgency means we simply have not spent the money needed on this epidemic.”

AAfter the morning’s lab work is complete, Oggenfuss and her team make their way to the Cary Institute auditorium for the final talk in a seminar series called “Forecasting Outbreaks of Infectious Diseases,” a presentation being given by Jeffrey Shaman, director of the Climate and Health Program at Columbia University’s Mailman School of Public Health. In the hall, Oggenfuss, Ostfeld, and the others listen intently to the process of building a predictive computer modeling system for the flu.

Later, Ostfeld and Shaman meet to discuss similar methods for forecasting the spread of Lyme disease. Although the expression is “mighty oaks from little acorns grow,” mice too survive on the tree seeds. Ostfeld’s field teams are creating a model that links high annual acorn production to a surge in the mouse population through the summer and fall, which in turn leads to spikes in the number of Lyme-infected nymphs the following spring. It’s light-years from Shaman’s detailed weekly predictions for 108 U.S. cities. But that model is for the flu, which caused the most severe pandemic in modern history from 1918–1920 and is now the subject of concerted and coordinated worldwide health efforts. Each year, the WHO Global Influenza Surveillance and Response System selects the strains of the influenza virus to target with its seasonal vaccine, which is manufactured and distributed worldwide. In the U.S., it is administered free in many workplaces and widely available at local pharmacies.

Lyme and other tick-borne diseases have yet to receive anything like that sort of attention. In 1998, the Food and Drug Administration approved a Lyme disease vaccine called Lymerix, administered in a three-injection cycle, that reduced infections in adults by nearly 80%. But it was discontinued three years later after sales bottomed out, due in large part to public fears driven by negative news reports over its side effects (most notably arthritis) and a class-action lawsuit whose claims were debunked. It was an early victory for the anti-vaccine movement, which gained momentum thanks to a now-retracted study linking autism to the measles-mumps-rubella vaccine that was released the same year as Lymerix.

“That actually scared me,” says Joyce Sakamoto, an entomologist at the Center for Infectious Disease Dynamics at Pennsylvania State University who has researched public engagement strategies to improve tick-borne disease literacy. “That was a case where the anti-vax community was able to effectively kill something entirely without a lot of scientific evidence.”

For now, the only vaccines in use for humans against tick-borne diseases target viral, not bacterial, infections (for instance, tick-borne encephalitis, which is endemic in central Asia as well as Europe, where widespread vaccination has proven effective). Over the past 10 years, however, there has been increasing scientific inquiry into a one-stop shop — a vaccine that would inoculate against all tick-borne diseases by targeting the proteins in tick saliva to block the transmission of pathogens. This would be a game changer, but the research is still in early stages.

More immediately, a new Lyme vaccine called VLA15, developed by French biotech firm Valneva, is undergoing clinical trials in Europe. Although it was given fast-track status by the FDA and seems likely to be approved in the United States, there is no guarantee it will be adopted by the public. As a result of low demand and anti-vaccine agitation, there is a chance the drugmaker will choose not to distribute it in the U.S. “I don’t know how that’s all going to work out. They are trying to address the potential PR fail that could happen, even if you have a really good product,” says Sakamoto. “If the risk of disease outweighs the risk of the side effects — and this is true of any drug — people are more likely to take the drug. But if they feel like it’s something they can survive, it’s not a big deal, they’re going to disregard it.”

According to the National Institutes of Health database, there are eight ongoing trials involving Lyme disease, and there have been 59 since its cause was identified in 1982. Lyme advocates say that’s far too few. “There is a very solid case to be made that Lyme disease deserves a lot more attention and a lot more money,” says Pfeiffer. “It’s a source of great consternation to me and to a lot of other people.”

In 2016, Congress passed the 21st Century Cures Act, which authorized the Health and Human Services Department to establish a Tick-Borne Disease Working Group to advise Congress and the secretary of HHS on research priorities and coordination. In late May, Sens. Susan Collins of Maine and Tina Smith of Minnesota, both of whose states are now hotbeds of Lyme disease, introduced S.1657, a piece of legislation called the Ticks: Identify, Control, and Knockout (TICK) Act, which allocates $100 million over the next several years for the study of tick-borne disease and new treatments. Although a companion bill was recently introduced in the House of Representatives, the legislation is currently languishing in committee, and its prospects remain unclear.

Those whose jobs it is to foresee and prepare for real-life disasters and apocalyptic events, the Department of Defense and DARPA Defense Advanced Research Projects Agency, are acting more decisively. Along with the EPA, they are funding Ostfeld’s research into the links between ticks and climate change.

Through the Tick Project, Ostfeld is also investigating tick control methods. Historically, most tick eradication efforts have done as much harm as good — the Soviet Union’s widespread use of DDT, for instance — largely because chemical agents that kill ticks also exterminate all other bugs and endanger water supplies. Ostfeld and the Tick Project are focusing on environmentally sensitive bioagents that kill ticks but affect as few other creatures as possible. “We’re using a naturally occurring native fungus,” Ostfeld says, “and it is pretty specific to ticks.”

To be exact, he and his team are studying a type of pathogenic fungus called Metarhizium brunneum strain F52, which is applied to foliage and soil. Its spores then attach to passing ticks, penetrate their exoskeletons, and reproduce inside them until they die.

The compound is not some closely held secret — it’s sold commercially as MET52. When Ostfeld had to halt research last year after being unable to order an adequate supply, it was not because a foreign government or the World Health Organization had started stockpiling it. “California pot growers were buying up huge amounts,” he says, noting that it control whiteflies and other crop-eating insects. “They can use it and still sell their pot as organic.” At least as Ostfeld envisions it, the bioagent would not be carpet-bombed across large regions, but rather used to create buffer zones around homes, woods-adjacent communities, and the like. That is the same application Ostfeld envisions for another product he is testing called the Tick Control System — a small box that attracts mice and other small mammals to enter, then applies a small dose of fipronil, the active ingredient in Frontline, which is widely used to kill ticks on dogs and cats.

Other, more high-tech ways to stop the spread of Lyme, such as an attempt by MIT researchers to genetically engineer Lyme-resistant mice, are being investigated but are years from being deployed, if it turns out they work at all. In the meantime, experts recommend prevention and treatment measures like wearing long pants and long-sleeve shirts in areas where ticks proliferate and conducting frequent tick checks.

The Cary Institute sells “I Brake for Opossums” bumper stickers. The decals don’t do anything to curtail tick-borne diseases themselves, but preserving opossums populations can. Unlike mice, opossums are not so-called “permissive hosts,” Ostfeld explains. They are efficient at eating ticks while grooming and are not a disease reservoir. Unfortunately, Ostfeld explains as we sit in his office, mice are far more numerous than possums, and they are like magnets to tick larvae.

“Look, a larva would be lucky to crawl from me to you across this table in five hours, right? But it’s likely to find a mouse passing on the forest floor,” says Ostfeld, walking his finger slowly across his desk toward me. Once that larva feeds on a mouse, or any infection-carrying host, everything changes, he says. The tick is effectively weaponized.

We’re already losing the war on ticks and Lyme disease, Ostfeld says; most of us just don’t realize it. “People ask me all the time, when they find out what I do, whether we’ll live to see the age of the tick. We’re already in it. The real question is, what do we do now?”

A researcher counting ticks. Scientists are investigating everything from naturally occurring fungi to gene-altered mice to help stop the spread of the bugs.

This story is part of “Tickpocalypse,” a multi-part special report.

Journalist and writer. A contributing editor at WSJ. magazine whose work appears in numerous other publications. Raised in Brooklyn, lives in Los Angeles.

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