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New Deal on Lyme Disease

Braving nasty, needle-sharp thorns on invasive Japanese barberry shrubs that sometimes grow taller than his own sixfoot-eight-inch frame, Guilford’s Scott C. Williams has been wading into prickly thickets in the towns of Lyme and North Branford avoided by even the most leather-hided woodsmen. A Ph.D. wildlife biologist with the Connecticut Agricultural Experiment Station in New Haven, Williams, 38, is sorting out the complex ecological interplay between the Japanese barberry, white-tailed deer, and the black-legged ticks that infect people with the infamous disease
named after Lyme and Old Lyme.

The woods in our part of the world teem not just with ticks but with scientists like Williams who are probing how the abominable little arachnids’ ecological relationships with other animals and plants promote the survival of the spiral-shaped bacterium that causes Lyme disease and its transmission to humans. One reason Coastal Connecticut is ground zero for such research is that it is in the backyard of institutions that were involved in Lyme research from the get-go. Scientists dispatched by Yale University to investigate a weird outbreak of arthritis-like symptoms among people in and around Lyme and Old Lyme during the mid-1970s first brought the disease before the medical world and the public at large. They confirmed the link between Lyme’s characteristic bull’s-eye rash and its symptoms, now known to range from fever and joint pain to neurologic issues
to fatal heart inflammation.

They also created unwanted and enduring notoriety for two upscale Connecticut River towns by attaching their names to a noxious affliction that has scared many people out of forest and field. After ticks of the genus Ixodes, especially the black-legged or “deer” tick, were implicated as Lyme disease’s vector, meaning its carrier and transmitter, researchers from the experiment station put their boots on the ground as well. The experiment station, noted for its entomological research, and Yale have home court advantage in Lyme research, given that Connecticut is a hot spot of Lyme disease, usually tops or close to that in the annual count of cases per state.

Contrary to what many people believe, the disease did not start in Connecticut nor recently, for that matter. Tests show that it afflicted the 5,300-year-old Alpine mummy, Otzi the “Iceman.” Ancient Chinese texts and, later, 19th-Century European medical literature described some of its trademarks, including the rash, even associating it with the bite of ticks. For generations, physicians across the Sound on Long Island treated a
painful joint aliment dubbed “Montauk knee,” probably Lyme disease. In 1970, a physician in Wisconsin, Dr. Rudolph J. Scrimenti, attributed the circular rash that appeared on an extremely ill patient to tick bite and treated it with antibiotics, but his work was lost in the hoopla over the Connecticut outbreak.

A case could be made for Scrimenti, who died last year at 80, as the first to identify the disease, which might have let the Lymes off the hook. Be that as it may, last year the federal Centers for Disease Control and Prevention (CDC) admitted that it understated the incidence of Lyme disease tenfold, estimating the number of cases per year at 300,000, making it the nation’s leading vector-borne illness.

Lyme disease ballooned alongside exploding populations of white-tailed deer, the main host for the adult ticks, although they do not spread the disease itself. The Bambi boom was sparked by forests returning to abandoned farmland, then forest fragmentation by suburbs to create the mix of open space and woods deer adore. Wildlife managers capitalized on the favorable environment to boost herds.

A deer is a veritable singles bar at happy hour for mature ticks, on which the tiny bloodsuckers find free food and hook up with the opposite sex. Immature ticks resulting from such liaisons usually acquire the Lyme bacterium, Borrelia burgdorferi, from previously infected animals, mainly white-footed mice, which are almost as ubiquitous as ants. A tough nut for medicine to crack, B. burgdorferi has thwarted potential vaccines and often confounds diagnosis. The only proven treatment thus far is a blast of antibiotics ASAP after actual or possible infection.

As the attack on Lyme disease by traditional medicine sputters, a second front has been opened, examining ways to minimize risk of disease by understanding the conditions that enable it to thrive in nature and spread to people.

Such research often uses techniques of so-called evolutionary medicine, an emerging field that combines medicine with other disciplines, such as ecology and zoology. Which brings us to why Scott Williams is poking around local woodlands, looking at ticks, deer, and Japanese barberry—a noxious, introduced ornamental running wild in a couple of dozen states. The formula for increasing the potential risk of Lyme disease is more deer equals more ticks; more barberry equals more ticks; more deer equals more barberry and even more ticks. Williams, who captained his crew team at Connecticut
College in New London, is accumulating evidence that the relationship between the barberry and deer has helped tip the ecological balance in favor
of forest-loving B. burgdorferi.

Evolved in Asia, Japanese barberry is foreign to the North American-adapted palate of deer, but they suck up just about everything else growing green in the woodland understory, making more room for barberry and a refuge for ticks. Underneath the umbrella of a barberry patch canopy is tick heaven, says Williams. Like a tropical rain forest, even on hot, dry days it retains the humidity that ticks need to remain active and feed. Barberry patches surveyed by Williams and his cohorts retain 80 percent humidity, which feeding ticks require, for all but an hour in the day. Williams has found ticks are five times more abundant in barberry than among native plants, and the incidence of those carrying Lyme disease is greater by a factor of more than 12. Even worse, there is another strand in the intricate ecological web involving barberry and Lyme disease risk. Its thickets teem with white-footed mice.

In 2012, a University of California Santa Cruz researcher suggested that white-footed mice have increased because coyotes have diminished their key predators, red foxes, a study based largely on computerized models. When their populations increase, white-footed mice move out of forests into edge habitats, like those where suburban lawns meet trees. Of late, based on computer simulations and laboratory experiments, some researchers claim that suburban forest fragmentation reduces the diversity of small animal species, some of which—raccoons and skunks, for instance—otherwise would lure ticks away from the mice. Importantly, these species are not effective carriers of the Lyme bacterium so, according to this train of thought, dilute the risk people will be infected. Intact forest, claim its adherents, contains more diversity. Animal protectionist organizations, opposed to culling deer as a means of controlling Lyme ticks, adore this assumption. However, it flies in the face of myriad studies indicating that the mishmash of development and trees creates multiple habitats for many small species, often more so than in unbroken forest.

“Basically, armchair ecologists still believe that there is more animal diversity in the big woods, when in fact, we are seeing far more diversity in the suburbs,” says Williams, who spends as much time outdoors when off duty as on. “We have all seen animals such as raccoon, opossum, fisher, weasel, chipmunk, squirrel, woodchuck, deer, coyote, and cottontail in or around our backyards. So the risk is actually increased in the big woods and more dilute around our houses.”

Durland Fish of Killingworth, professor of epidemiology and of forestry and environmental studies at Yale, a pioneer of Lyme tick research, found high numbers of infected ticks in a woodland patchwork fragmented by housing in Lyme. Human infections, however, were low there because, Fish opined, the patches were so widely spaced, few people actually entered the woods.

Research by Stanford University suggests that too many unknowns and variables make the impact of biodiversity and forest fragmentation on Lyme difficult to assess. While scientists continue to debate, however, awareness grows that the most effective preventive medicine against Lyme disease may be to focus on its biology on an elemental level, in nature, and go from there.

Meanwhile, most scientists engaged in Lyme disease prevention agree that culling overpopulated deer herds is the best ecologically based tactic for controlling the disease. Case in point: The exclusive private community of Mumford Cove in Groton recorded 30 cases of Lyme annually previous to 2000 when, after trying contraceptives in deer failed to control overpop.ulation, hunters did the job. Ticks virtually disappeared and Lyme disease incidence dropped to two or three cases per year.

Image Credits: Photo courtesy Shutterstock

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