Lyme

The First Epidemic of Climate Change

ISLAND PRESS

Contents

Ticks, Rising

Evolution has endowed the big-footed snowshoe hare with a particularly nifty skill. Over a period of about ten weeks, as autumn days shorten in the high peaks and boreal forests, the nimble, nocturnal hare transforms itself. Where it was once a tawny brown to match the pine needles and twigs amid which it forages, the hare turns silvery white, just in time for the falling of winter snow. This transformation is no inconsequential feat. Lepus americanus, as it is formally known, is able to jump ten feet and run at a speed of twenty-seven miles per hour, propelled by powerful hind legs and a fierce instinct to live. But it nonetheless ends up, 86 percent of the time by one study, as a meal for a lynx, red fox, coyote, or even a goshawk or great horned owl. The change of coat is a way to remain invisible, to hide in the brush or fly over the snow unseen, long enough at least to keep the species going.

Snowshoe hares are widely spread throughout the colder, higher reaches of North America — in the wilderness of western Montana, on the coniferous slopes of Alaska, and in the forbidding reaches of the Canadian Yukon. The Yukon is part of the Beringia, an ancient swath of territory that linked Siberia and North America by a land bridge that, with the passing of the last Ice Age 11,000 years ago, gave way to the Bering Strait. All manner of mammals, plants, and insects ferried east and west across that bridge, creating, over thousands of years, the rich boreal forest. But in this place, north of the 60th parallel, the axiom of life colored by stinging cold, early snow, and concrete ribbons of ice has been upended in the cosmic blink of an eye. The average temperature has increased by 2 degrees Celsius in the last half century, and by 4 degrees in the winter. Glaciers are rapidly receding, releasing ancient torrents of water into Kluane Lake, a 150-square-mile reflecting pool that has been called a crown jewel of the Yukon. Lightning storms, ice jams, forest fires, rain — these things are suddenly more common. Permafrost is disappearing.

Such rapid-fire changes across a broad swath of northern latitudes are testing the adaptive abilities of the snowshoe hare, however swift and nimble it may be. Snow arrives later. Snow melts earlier. But the hare changes its coat according to a long-set schedule, which is to say the snowshoe is sometimes snowy white when its element is still robustly brown. And that makes it an easier target for prey. In 2016, wildlife biologists who tracked the hares in a rugged wilderness in Montana gave this phenomenon a name: "climate change-induced camouflage mismatch." The hares molted as they always had. It's just that the snow didn't come. Survival rates dropped by 7 percent as predation increased. In order to outwit its newest enemy — warmer winters — snowshoe hares would need something on the order of a natural miracle, what the biologists, writing in the journal Ecology Letters, called an "evolutionary rescue." Like the Yukon, this pristine corner of Montana was projected to lose yet more snow cover; there would be perhaps an additional month of bare forest floor by the middle of this century, on which snowshoe hares would stand out like bright white balloons.

In the tally of species that will evolve or perish as temperatures rise, consider now the moose. The lumbering king of the deer family, known for antlers that can span six feet like giant outstretched fingers, faces a litany of survival threats, from wolves and bears to brain worms and liver fluke parasites. But in the late 1990s in many northern states and Canada, something else began to claim adult cows and bull moose and, in even greater numbers, their single or twin calves.

Lee Kantar is the moose biologist for the state of Maine, which means he makes a living climbing the rugged terrain of north-central Maine when a GPS collar indicates a moose has died. A lean man with a prominent salt-and-pepper mustache who wears flannel shirts and jeans to work, Kantar tagged sixty moose in January of 2014 around Moosehead Lake in the Maine Highlands. By the end of that year, twelve adults and twenty-two calves were dead — 57 percent of the group. When biologists examined the carcasses, they found what they thought was the cause. Calves not even a year old harbored up to 60,000 blood-sucking arthropods known as winter ticks. In Vermont, dead moose were turning up with 100,000 ticks — each. In New Hampshire, the moose population had dropped from 7,500 to 4,500 from the 1990s to 2014, the emaciated bodies of cows, bulls and calves bearing similar infestations of ticks. These magnificent animals were literally being bled to death.

Winter ticks have been known to afflict moose since the late 1800s. In a normal year, a single moose might carry 1,000 or even 20,000 ticks. In a particularly harsh winter, when moose are underfed and weak, anemia and hypothermia wrought by ticks can make the difference between life and death. Bill Samuel, a retired University of Alberta biology professor, has spent a career studying the moose of North America. He painstakingly counted 149,916 ticks on a moose in Alberta in 1988. In a 2004 book, he recounts episodes of ticks killing moose in Saskatchewan in the spring of 1916, in Nova Scotia and New Brunswick in the 1930s, and in Elk Island National Park in central Alberta at points from the 1940s through the 1990s. Some of the animals were so infested that there was not a tick-free spot in the arachnids' favored places — the anus, the inguinal area, the sternum, the withers and lower shoulders. In futile attempts to rid the parasite, these pathetic animals had rubbed against trees to seek relief, losing long, lustrous fur and leaving grayish, mottled patches. They are called "ghost moose."

Moose have long died from disease, predators, hunting, and sometimes ticks. But their losses in the early twenty-first century had a different, more threatening, more consequential implication. In 2015, two environmental organizations, alarmed at population trends, petitioned the US Secretary of the Interior to have the Midwestern moose listed as an endangered species. In Minnesota, the number of moose dropped 58 percent in the decade through 2015, similar to losses in New England. Environmentalists believe moose could well be eradicated in the Midwest by 2020, with stocks declining precipitously in Wisconsin, Minnesota, and Michigan.

Lee Kantar knew that ticks were killing his moose in Maine. What's becoming clear is why winter ticks had infested his herd, draining half their blood from every available patch of skin. "The greatest threat confronting the species," declared the Center for Biological Diversity and Honor the Earth in the 2015 petition to help moose, "is climate change." Not hunters. Not habitat loss. Not even pollution, though that is important. Moose like and need the cold. They become sluggish when it's warm, failing to forage as they should and becoming weak and vulnerable. In the warmer, shorter winters of the US Midwest and Northeast, bumper crops of winter ticks are surviving to wake up when the trees burst to life in earlier springs; they have more time in longer falls to cling in veritable swarms on the edges of high bushes, their legs outstretched, waiting for a ranging, unsuspecting, and wholly unprepared moose. When the moose lay in the snow, they leave carpets of blood from engorged ticks. When a baby moose emerges from the womb in Minnesota, a band of thirsty ticks moves from mother to neonate. The moose shed those fat, flush ticks onto fall and winter ground, and the ticks snuggle into the leaf litter rather than freeze in the snow, as they once might have, reducing tick mortality but upping that of the moose.

Bill Samuel is a careful scientist who does not jump to conclusions, and he sees many forces working together to kill off moose in the finely tuned orchestra that is the outdoors. Wolves, liver fluke, brain worms, unmanaged hunting, habitat loss — they are all part of the picture. Because of how it affects and is affected by those other factors, "climate change," he told me, "might be the major one."

"It's the Ticks"

Jill Auerbach knows that the winter ticks attached to dead and dying moose pose little threat as a species to humans, whom they aren't prone to bite. But when news broke of moose losing half their blood to winter ticks, she was horrified and worried. Auerbach, an active woman in her seventies, was bitten in her forties by a small tick that thrives in the woods, thickets, and backyard edges of the county in which she lives, in New York State's Hudson Valley. She lost ten years of her life to that tick, had to retire as a highly rated programmer at the nearby IBM plant, and still suffers the aftermath of a case of Lyme disease that was caught too late. "It brought me to my knees," said Auerbach, among an all-too significant share of people infected with Lyme who suffer long-term symptoms. To her, the rise of winter ticks is one more indicator of an environment out of whack, and so is the more measured, but nonetheless relentless, surge in blacklegged ticks, like the one whose bite haunts her thirty years on.

That other tick, known to scientists as part of the Ixodes genus — in Auerbach's case, Ixodes scapularis, or blacklegged tick — is spreading across the United States and in many other countries with startling alacrity. Canada, the United Kingdom, Germany, Scandinavia, Inner Mongolia in China and the Tula and Moscow regions in Russia: they are all grappling with large and growing numbers of diseaseridden ticks. Infected ticks have been found in urban parks in London, Chicago, and Washington, DC, and in the open, green expanses of Killarney National Park in Ireland's southwest. In Western Europe, where case reporting is not standardized, the official case count is 85,000 per year; a 2016 analysis, published in the Journal of Public Health at Oxford, England, put the number at 232,000. Signs of a burgeoning problem are apparent in Japan, Turkey, and South Korea, where Lyme cases grew from none in 2010 to 2,000 in 2016. When I asked three Spanish physicians in 2017 where Lyme disease was found in Spain, one said, "everywhere," and the others agreed. One of them, Abel Saldarreaga Marín, had treated forestry workers in Andalucía, where he said symptoms are often managed, perilously, with traditional remedies. In the Netherlands, as elsewhere, warnings to protect Dutch hikers, children, and gardeners from bites had failed for years to curb the growing toll, then hit what may simply have been a saturation point, with Ixodes ricinus ticks inhabiting 54 percent of Holland's land.

Across the Atlantic Ocean from Holland, the US Centers for Disease Control and Prevention (CDC) in Atlanta issues maps every year showing, by virtue of small black dots, the presence of Lyme disease cases in American counties. The CDC's 1996 map was the first to officially chart US Lyme cases, although the disease was well along by then. Dots on that inaugural map collectively create an unremitting black smudge along the Atlantic shore from Delaware to Cape Cod. New Jersey, Connecticut, Massachusetts and the lower reaches of New York State — where Auerbach contracted her case — are all inky black. A broken shadow runs along the Wisconsin-Minnesota border, too, with a handful of dots in many heartland states.

But it is the change over the course of eighteen years of maps that is telling, depicting the flowering of Lyme in a sort-of cartoon flip book style as it spreads across the Northeast and Midwest of America. North it goes up New York's Hudson River Valley and into the state's Adirondack Mountains, jumping the border to Vermont's Green and New Hampshire's White Mountains. West and south it moves great guns into Maryland and northern Virginia. By 2014, the dots consume much of Pennsylvania and darken New York's Southern Tier to the shores of the Great Lakes and the St. Lawrence River. The Upper Midwest is liberally peppered. Dots appear in many other states too.

In 1996, blacklegged ticks were known to be established — meaning there were enough counted to breed or they already had — in 396 American counties. By 2015, researchers at the Centers for Disease Control reported the ticks were ensconced in 842 counties, an increase of 113 percent. Remarkably, the study's twin US maps chart the forward march of ticks in much the way that the maps of Lyme cases plot the progression of disease. Both are relentless.

Auerbach, who became a Lyme disease expert and advocate after her long-ago bout, has for years ended her emails with, "What's the problem? Well it's the ticks of course!" They must be stopped, she believes, and the 2015 CDC map shows why. In it, ticks are seen moving into places that only a decade before had been considered ill-suited to support them, from the Allegheny Mountains to the Mississippi Valley, from western Pennsylvania south and east across Kentucky and Tennessee. In Minnesota and Wisconsin, I. scapularis "appears to have expanded in all cardinal directions," the CDC researchers reported in language that was sometimes remarkable and alarming. The ticks have "spread inland from the Atlantic seaboard and expanded in both northerly and southerly directions," they wrote, stopped only to the east by the Atlantic Ocean. Tick movement up the Hudson Valley is "recent" and "rapid," the researchers wrote, their expansion overall, "dramatic." Where there had once been a divide between infestations in the Northeast and Midwest, they concluded, ticks merge "to form a single contiguous focus ... a shifting landscape of risk for human exposure to medically important ticks."

On the Move

Lyme disease emerged in coastal Connecticut in the 1970s, where symptoms akin to rheumatoid arthritis were reported in a circle of children unfortunate enough to be trailblazers of a disease in which early treatment is key to recovery. Diagnoses made late can portend long and difficult sieges of illness — fatigue, joint pain, learning problems, confusion, and depression. The parents and guidance counselors of Lyme children, and the children themselves as young adults, have told me of school years lost to the disease. Children five to nine years old have the highest per capita Lyme infection rate in the United States, while people sixty- to sixty-four-years old have the highest hospitalization rates for it, according to a study of 150 million US insurance records from 2005 to 2010.

The story of the emergence of Lyme disease now, of its rise in dozens of countries around the world and of millions made sick, must be told through the lens of a modern society living in an altered environment. In the last quarter of the twentieth century, a delicate array of natural forces indisputably tipped — were tipped, more accurately — to transform Lyme disease from an organism that lingered quietly in the environment for millennia to what it is today: the substance of painful stories shared between mothers; a quandary for doctors who lack good diagnostic tests and clear direction; the object of rancor over studies that discount enduring infection while acknowledging persisting pain.

The US Centers for Disease Control and Prevention defines the word "endemic," which it applies to Lyme disease, as the "constant presence and/or usual prevalence of a disease ... in a population within a geographic area." But while Lyme is firmly rooted in thousands of locales, it is surely not confined there as climate changes, ticks move, and cases mount. The CDC's designation, even if scientifically accepted, is unfortunate. It serves to minimize the import of a disease that yields some 300,000 to 400,000 new cases in the United States each year, is found in at least thirty countries and likely many more, and is growing precipitously around the world. Lyme disease is moving, breaking out, spreading like an epidemic.

The ticks that carry Lyme disease are, like spiders, arachnids not insects. Although they cannot fly or jump, they are, for all practical purposes, climbing mountains, crossing rivers, and traversing hundreds, even thousands, of miles to set up housekeeping. These feats are documented by scientists who are ingenious at finding ways to track and count ticks. They drag white flannel sheets across leafy forest carpets, sometimes infusing them with piped-in carbon dioxide, the mammal gas that makes ticks reach up, forelegs outstretched, to snag a passing meal. They catch avian migrants infested with hitchhiking arachnids. They count ticks on the ears of trapped mice and shrews, sometimes getting bitten in the process. They dissect bird nests, reach beneath leaf litter, and scour grassy sand dunes.