Without doubt, B. burgdorferi barely survives in the more challenging interior of the lone star tick, with which it shares an uneasy coexistence. The pathogen, meantime, thrives aboard blacklegged ticks, the ones that are more apt to hide in the southern shade. But as the next chapter shows, people in states like North Carolina are exposed often to and bitten frequently by lone star ticks. This tick has a far different demeanor and personality than its blacklegged counterpart. It is fierce, if a tick can be called that, and it is plentiful. Herman-Giddens said she found one on her arm once after a brief walk from her door to her car. “They just seem to appear out of nowhere sometimes,” she told me, giving her ten to twenty bites a year. Said Clark, “In some places they are so abundant and attack in such numbers, that they almost seem to be dropping from the trees.” Indeed, it practically rains lone star ticks in the South. That may be all it takes.
CHAPTER 8:
Not Just Lyme
* * *
“Lyme disease is the tip of the iceberg. There are worse diseases coming down the pike.”
—Durland Fish, entomologist at Yale School of Public Health
When a mile-wide tornado ripped through Moore, Oklahoma, in 2013, killing 25 people, a shaken lot of suddenly homeless dogs became subjects in a study of disease spread by ectoparasites, among them ticks. Wandering among the rubble and brush of a battered suburb of Oklahoma City, the canines were like the white flannel flags that researchers sweep over grasses and leaves in efforts to snag and count ticks in the wild. Everywhere the dogs went, ticks, ever alert to body heat and breath, reached out with scabrous forelegs to latch onto bits of whisker or fur, the next meal within grasp. The project of a doctoral student at the veterinary school at Oklahoma State University in Stillwater, the study tested the blood of the forty-four wandering pet dogs and sixty-one others relinquished to a shelter. Fully ninety-two of them, or 88 percent, were infected with at least one tick-borne disease. In all, antibodies to four tick-borne infections were detected in the five-score and five dogs. Ticks have been called “cesspools of infection,” and these tornado-tossed pups and their surrendered brethren showed why.
As is the joy of scientific pursuit, the Oklahoma researchers discovered something else in their study of homeless canines. A single Oklahoma dog was the state’s first documented case of infection with something called Rickettsia amblyommii, a novel pathogen, perhaps up and coming, in the Rocky Mountain spotted fever family and delivered, as ticks go, by a particularly nasty one that you met in the last chapter. The lone star tick, distinguished by the female’s golden crest on her chestnut back, has abilities that a Lyme-toting blacklegged tick can only dream of. Entomologists commonly describe it as “aggressive.” No, they aren’t “hostile or belligerent,” a spokesperson for the US Centers for Disease Control and Prevention responded when I asked for a definition. Rather, “these ticks can actively move toward a warm-blooded host when they detect its presence nearby.” Whereas the blacklegged, aka Ixodes scapularis, tick moves one way—vertically up and down on grasses and twigs in search of a passing mammal meal—the lone star, or Amblyomma americanum, tick can crawl horizontally as well in its quest for a host. While the blacklegged tick in North America or castor bean tick in Europe passively waits for prey, the lone star hunts, stalks even, finding a farmer at work in Missouri, a camper setting up in North Carolina, a white-tailed deer in the tallgrass prairie of eastern Nebraska. One scientist told me it takes seconds for a lone star tick to climb up a pant leg, pass over a shirt, and find its way to the soft nape of the neck or the safety of the scalp.
The United States military with its sprawling bases and outdoor exercises has reason to be concerned about such things and has long kept an eye on resident ticks. At the Aberdeen Proving Ground in Maryland, for example, soldiers in training, who often creep belly to the ground through brush and grass, have encountered up to five hundred nymphal lone star ticks—per soldier, per hour. A nymph is in the second of the lone star tick’s three life stages, when it has already fed once and, therefore, may have picked up any number of infections from its “host” animal, usually small mammals. That was not good for soldier health. Nor was what they found in the ticks.
In samples from thirty-three sites on the base’s 72,500 acres on the Chesapeake Bay, Aberdeen researchers found “widespread distribution” of ticks infected with the bug that causes human monocytic ehrlichiosis, a disease that infects about 1,500 Americans annually and can be fatal if not treated promptly. By 2012, the Army researchers had concluded the lone star was no longer the “nuisance pest” it had long been regarded. Instead, it now carried three varieties of the pathogen that caused ehrlichiosis, and its role in two sometimes fatal diseases, Rocky Mountain spotted fever and tularemia, was “being re-examined.”
To that point, Lyme disease from Ixodes ticks was known to be widespread in the military, reported at 120 military bases, from West Point in New York to Landstuhl in Germany and in every region of the United States except Hawaii. Cases topped 3,200 from 2001 to 2008, although the true number was likely much higher, using the CDC’s tenfold undercounting yardstick. Soldiers had reported Lyme cases that led to discharge when they could no longer do the job. Now, the tick-borne menace was growing, in size and scope, and not only for the military. In Oklahoma, where the tornado-tossed pups were studied, historical records unearthed from libraries and government archives had shown lone star ticks living in eighteen counties. By 2015, researchers found the ticks in sixty-eight counties, 88 percent of the state’s total. This then is the future of tick-borne disease: more ticks in more places with more pathogens.
In 2015, scientists from four US government agencies assembled data to predict that future, to model how far, in the latter half of the twenty-first century, the lone star tick might move, driven by the winds of climate change. First, they studied conditions in the places the tick currently lived. The model looked at how much snow there was in October; the temperature at the wettest and driest times of year; the difference between high and low temperatures; the benchmarks of warmth that help farmers predict the emergence of insects and blooms; and last, the vapor pressure, a measure of humidity. For ticks, which desiccate and die in hot, dry conditions, the humidity factor was by far the most significant for lone star survival. Then the scientists plotted where conditions favorable to lone stars might emerge in a warmer United States, circa 2061 to 2080. Disturbingly, they found vast swaths of new territory for A. americanum, which had once been relegated to the southern United States, Central America, and northern South America.
In coming decades, they predicted, the lone star tick would follow the pioneers who moved north into the Great Plains and the Ohio River Valley and the Scandinavians who settled the cold Midwest two hundred years earlier. But the ticks would be driven by something other than frontier spirit; they would thrive amid more humidity and more warmth. And that, the scientists found, meant “considerable increases in the proportion of suitable habitat in Iowa, Illinois, Indiana, and Ohio. With greater warming, southern and central portions of South Dakota, Minnesota, Wisconsin, and Michigan are also likely to increase in suitability.”
Studies often note that some places might become too warm to support ticks, but this should be slim comfort. East Texas and coastal areas of Florida and Alabama, lone-star research speculated, might become climatically unattractive to the lone star. But the scientists were far less certain about what kills ticks off than what propels them forward. “We don’t feel we can say that ticks won’t occur in areas in the future,” one of the model’s designers, Catherine Jarnevich of the US Geological Survey in Fort Collins, Colorado, told me. Other scientists agree this is not a zero-sum game, with ticks gained here but lost there. What is clear is that there will be more places for the lone star to live, thrive, and bite, a trend, the report said, “almost certainly driven by warming and the accompanying changes in humidity, particularly during spring and summer months.” A year after that study, the US government’s c
limate change assessment predicted that ticks loaded with Lyme disease and other pathogens “will show earlier seasonal activity and a generally northward expansion in response to increasing temperatures.”
Tale of Two Continents
September Norman was a trim, blonde woman of fifty-four who liked hiking and lived in a leafy Tennessee city that juts into Old Hickory Lake known as Hendersonville. During a round of late-spring gardening in 2014, Norman had a chance meeting with a lone star tick, sustaining one of many bites she’d had over the years. This bite, however, would change her life in a strange and frightening way, one that would not become clear for another six weeks. That was when Norman awoke at 2 a.m.—in the middle of the woods on a camping trip—clawing furiously at an intense pain in her foot, in just the spot where she had last been bitten. She consumed copious amounts of water to flush her system, to no avail. Within a couple of hours, her tongue and lips had swelled; she was covered in hives, and her head looked to her husband like a giant red balloon. Ambulance attendants arrived as her throat was closing, and she was perhaps thirty minutes from suffocating. It would not become clear until she had another incident and was taken to Vanderbilt University Hospital in Nashville what had triggered the response. Both times she had eaten meat, first beef then pork. And she had been bitten previously by a lone star tick.
About a decade before, Scott Commins was an allergist at the Asthma and Allergic Diseases Center in the University of Virginia Health System when he and his colleagues started to see people like September Norman—patients with severe, sometimes life-threatening, allergic reactions. That’s not so unusual in an allergy center except that, in these new cases, the response occurred after the patients had eaten mammal meat. Anaphylaxis, as the response is called, usually occurred almost immediately after exposure to a potential toxin, such as bee venom; these new reactions began three to eight hours later. Half a world away, Sheryl van Nunen, an allergist and medical school professor, had charted the same alarming trend at Royal North Shore Hospital in St Leonards, a city near Sydney on Australia’s east coast. Van Nunen had seen her first case in 1987. As cases rose, she dutifully performed skin prick tests with raw meat and took extensive case histories. When a thread emerged linking meat consumption and the bite of a tick, the dynamic was so unusual that she remembers saying to herself, “This is indeed happening, and I am not imagining it.” When she posited her theory, in an abstract for a conference in 2007, it broke the mold on the well-established immediate anaphylaxis reaction, not to mention the cause. The theory, she wrote in an email to me, had “most of my colleagues thinking at that time that I might have slipped my trolley wheels!” Today, knowing how ticks are masters at manipulating human immune response—that is, after all, what an allergic response is—she said it makes far more sense.
It would be Scott Commins and his colleague, Thomas Platt-Mills, who would publish a paper in 2009 in which they identified a carbohydrate in mammal meat called alpha-gal as the cause of the intense and life-threatening response. Then, in 2011, they and other scientists reported what van Nunen had suspected in Australia: “Tick bites are a cause, or possibly the only cause” of the allergy in the United States. Their conclusion marked the first report of “an ectoparasite giving rise to an important form of food allergy,” and a validation of van Nunen’s work. The eerie parallels between the work of these physician-researchers, so far apart in geography, speak volumes about the worldwide nature of tick-borne havoc and the schedule on which diseases and, in this case, an emergent allergy are making their unwelcome debuts. For Commins in the United States, the culprit was the lone star tick. For van Nunen in Australia, it was the Australian paralysis tick, Ixodes holocyclus.
When Commins described the first cases of so-called alpha-gal meat allergy in the United States in 2009, he was aware of twenty-four of them. By the time September Norman was bitten in Tennessee five years later, Commins had amassed 1,000 cases in Virginia alone, and he estimated there were 5,000 in the Southeastern United States in all. Cases were subsequently reported in France, Spain, Germany, South Korea, Sweden, Switzerland, Costa Rica, South Africa, and Japan, though the numbers were small. Many children were also affected. In a study published in 2013 in the journal Pediatrics, researchers reported the profiles of fifty-one children in Lynchburg, Virginia, aged four to seventeen, who had severe, unexplained allergies. Of the fifty-one, forty-five harbored antibodies to alpha-gal. More than 90 percent had been bitten by ticks in the previous year.
The question, for researchers, was, why now? It has long been the same question asked about the emergence of Lyme disease, and the answer was, oversimplified to be sure, that there were more ticks. In Australia, surging numbers of bandicoots, a mouse-like marsupial, and small mammals that support the life cycles of ticks were believed to have played a key role. In the American Southeast, more white-tailed deer enabled vastly more tick procreation and more clashes with people. This was undoubtedly part of it. So were the ways people interacted with nature and the rise of communities that prized small parks and forest patches, which provided habitats for those mammals to thrive. But the fuel for the tick-disease engine, of which alpha-gal syndrome is but one small working part, is climate change. As the US government report on climate change confidently predicted, ticks move and multiply in a warming world, affecting more places and people. “I see ticks every day, all day,” said Andrew Lucas, an emergency department physician at Macksville District Hospital in New South Wales on Australia’s east coast. If he sees thirty people in a shift, Lucas said, four will have come in for tick bites. “People get 200 ticks on them all the time.” For Lucas, who I met in 2016 at a Philadelphia conference of doctors who treat tick-borne diseases, the threat was personal. His wife had suffered for two years from what he believed to be Lyme disease, an illness not officially recognized in his country and for which she could get only ancillary care.
The study that predicted widespread movement of the lone star tick suggested, optimistically, that the research had served a valuable purpose. It helped point to “areas where public health information campaigns could be initiated proactively and where field studies of tick ecology…might be conducted.” In truth, we have little else but warning people and studying ticks, both of which have nonetheless been done in spare and inadequate measure. And both have failed to stop or slow the pandemic.
Because of that single tick, September Norman cannot have fish cooked on the same grill as steak, or any dairy products at all, so vicious is her allergy to that one mammal molecule. She and thousands like her, currently and yet to come, are left with allergies that could be set off by a bit of beef broth dropped into a soup or some bacon drippings used in a gravy, a tick-borne legacy that lasts a lifetime. The lone-star’s ability to impart a lifelong allergic response is significant and unprecedented in the annals of immunology. But it is not the only new discovery in the lone-star arsenal and is part of a growing list of pathogens and problems that ticks, lone star and otherwise, can cause.
The Next Big Thing
On a farm in central North Carolina in 2010, a sixty-one-year-old man found a tick in his right armpit. Within a week, he developed body pain, headache, nausea, and a fever of 103 degrees Fahrenheit. The man, who ran a small beef cattle farm, removed the guilty arachnid, a beautifully preserved-in-alcohol, engorged, male lone star tick. The farmer, it seemed, was also a leading researcher of tick diseases, based at the College of Veterinary Medicine at North Carolina State University, Raleigh. In a study of his case published in 2011, Edward Breitschwerdt and his colleagues concluded they had documented, through molecular testing, the first infection from a lone star tick of Rocky Mountain spotted fever, a nasty illness normally delivered by the dog tick, Dermacentor variabilis. “If you don’t treat for Rocky Mountain spotted fever by the fifth day of illness,” a researcher at the US Centers for Disease Control, Kenneth Dahlgreen, told NPR Radio in 2015, “there’s a really good chance you’re going to die. And it’s an ugly, ugly death, t
oo.”
Breitschwerdt recovered well. Moreover, his case helped explain a strange new trend in tick spread and disease. Since the late 1990s, health authorities had watched the number of spotted fever cases soar, from around 350 nationwide in 1993 to about 2,000 by 2010. On the upside, as cases rose, the share of people who died, namely the fatality rate alluded to by Dahlgreen, had dropped sharply—another indicator that something new was happening. So Dahlgreen and his colleagues at the CDC plotted where cases had grown and fatality rates had dropped. It was when they added one more variable—where the lone star tick was prevalent—that the picture became clear. “The expanding range of A. americanum is associated with changes in epidemiology” of Rocky Mountain spotted fever, the researchers reported in 2015. More lone star ticks in more places, they concluded, meant more Rocky Mountain spotted fever.
Breitschwerdt, to be sure, got there first. Though he contracted an infection that the CDC states “can be a severe or even fatal illness,” he was nonetheless jubilant over his luck. That tick tucked in his armpit, he told me after a round of baling hay on his farm, was nothing less than a bit of “medical serendipity,” the kind of thing science is sometimes built on. “If I was not a vector-borne disease researcher, I would not have saved the tick and perhaps we would still not know if the lone star tick could transmit RMSF to a dog or human,” he said.
After thirty years of studying ticks, Breitschwerdt was less concerned about spotted fever—though it most certainly was a growing threat—than about another infection he believed would eclipse even Lyme disease in size, scope, and significance. It often accompanies Lyme as one of several leading coinfections that vastly complicate diagnosis, care, and recovery. But tagging it onto Lyme disease failed to accord this bug its proper due. Decades of study had convinced Breitschwerdt that this pathogen would stand alone in the pantheon of emerging human diseases: Bartonella.
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