Connecticut's War on Lyme Disease
Nearly 40 years after its dramatic emergence in southeastern Connecticut, Lyme disease—an infection caused by the bite of Ixodes scapularis, or black-legged “deer” tick—is epidemic in Connecticut. Though it’s readily curable (primarily with a two to three-week course of doxycycline), we’ve had less luck coming up with ways to prevent the new cases that break out each year. The different strategies that have been undertaken range from encouraging personal responsibility (wearing protective clothing, spraying with the tick repellents DEET and Permethrin, showering after a walk in the woods, building “tick-free” zones in our yards) to broader public health (vaccine development) and policy (culling of deer populations) initiatives—with varying levels of success.
According to certain researchers, Lyme has existed in America for thousands of years. But it wasn’t fully described—or given its name—until 1975, when a cluster of cases in Southeastern Connecticut (including Lyme and Old Lyme), thought to be juvenile rheumatoid arthritis, were investigated by doctors David Snydman and Allen Steere of the Epidemic Intelligence Service (a branch of the federal Centers for Disease Control and Prevention) and others from New Haven’s Yale University. Ten years later, a Lyme disease-testing program conducted by the Connecticut Agricultural Experiment Station and Connecticut Department of Public Health found the greatest prevalence of the disease was still limited to towns east of the Connecticut River.
“Throughout the 1980s, we’d see cases in the high hundreds per 100,000 population in eastern Connecticut, sometimes even more than 1,000,” says state etymologist Kirby Stafford, who’s also vice-director and chief entomologist at New Haven’s Connecticut Agricultural Experiment Station. In the 1990s, however, the disease started moving north and west. “It was like a wave effect,” Stafford says. “For a number of years, the highest reported incidence of Lyme disease was in Litchfield County, while the cases in eastern Connecticut fell to about 300 or so. Now it’s dropped in Litchfield County, too.”
While the disease now affects all parts of Connecticut—as it spread to other states, ours long reported the greatest number of new cases each year—Stafford says we’ve reached “kind of a saturation point. The general trend for many years was upward, but the numbers have actually gone down for a couple of years.”
In September, the Centers for Disease Control (CDC) reported that as of 2011—the last year for which all the numbers are in—the states with the highest incidence of Lyme are Delaware (with 85 cases per 100,000 population) and Vermont (with 76 per 100,000). Connecticut is now ranked at No. 5 (56 per 100,000, as compared to a relatively whopping 134 cases in 2002). But a month earlier, the CDC had already stated how misleading these estimates can be, pointing out that the nationwide incidence of Lyme disease each year is not 30,000, as routinely reported, but closer to 10 times that number.
Attempts to get a grip on accurate case counts are foiled by a number of factors, beginning with whether doctors bother to report their Lyme patients to local health departments. Numbers generally go up when these departments do active surveillance (actually seeking out case reports from labs and doctors) as opposed to passive surveillance (waiting for these reports to come to them). The discrepancy can be striking: “When we did active surveillance,” says Dr. James McDonald of the Rhode Island Department of Health, “we counted about 800 cases a year. Now, it hovers around 150 to 200.”
Compounding the problem is that there’s no reliable diagnostic indicator for Lyme.Peter Wild, executive director of the Lyme Research Alliance in Stamford, notes that the blood test currently in use “is only 65 percent effective.” He adds that the bullseye rash that’s considered a classic “tell” that one has been infected with Lyme-causing bacterium (Borrelia burgdorferi) may or may not appear. In addition, it’s long been known that early symptoms of Lyme disease—fatigue, aches and pains, low-grade fever—mimic the symptoms of other illnesses.
“Not everyone who is treated for Lyme has a blood test,” says Randall Nelson, state veterinarian and senior-level epidemiologist for the Connecticut Department of Public Health. “Oftentimes, doctors who are treating it are doing so simply based upon their best guess.”
There’s little argument that historically, the best defense against infectious diseases has been vaccination. In 1998, the FDA approved a Lyme vaccine, LYMErix, which reduced new cases of the disease by nearly 80 percent. Yet, in 2001, manufacturer SmithKline Beecham voluntarily withdrew LYMErix from the market amidst problems with sales and reports by some who were vaccinated that as a result, they developed musculoskeletal ailments including arthritis.
A class-action suit was brought against SmithKline Beecham, claiming that the vaccine was harmful. Dr. Peter Krause, senior research scientist at Yale University School of Public Health—who participated in the development and testing of LYMErix—says, “The data supporting such a claim just isn’t there. Within any immunized population, there will always be a certain percentage of people who will develop the disease in question, which probably would have developed anyway. But because it happened around the time they got the vaccine, these people assume the vaccine was responsible.
“There’s still great interest in developing a vaccine,” he adds, “but it probably won’t appear in the near future.”
Deer are one of the most important links in the cycle that spreads Lyme disease. “Adult female ticks feed on the deer; when engorged, they drop off and lay 2,000-3,000 eggs,” says Stafford.
He points out that one can trace the history of Lyme by charting the ebb and flow of native deer populations since American Colonial times. “There was a Swedish naturalist named Pehr (Peter) Kalm who came to the U.S. around 1750, and for 20 years published a journal of his travels that noted how bad the ticks were,” he says. “A century later, the state etymologist of New York traveled the same route Kalm had and reported that he couldn’t find any ticks. What had happened in the intervening 100 years? Well, the forests were cut down, largely for agriculture, and the deer were hunted out. The best estimate we have for the number of deer we had in Connecticut in 1896 is 12 animals.”
In the 20th century, as farming moved westward and New Englanders began building and heating their homes with fuel sources other than wood, forests gradually returned, and the deer with them. “Now, a lot of people in Connecticut may see more than 12 deer in their back yards any given day,” says Stafford.
The deer population in certain communities seems overwhelming. In 1995, in Groton, it had reached 70 to 80 per square mile. “They were reporting 20 new cases of Lyme a year,” says Howard Kilpatrick, a wildlife biologist (and manager of the deer program) with Connecticut’s Department of Energy & Environmental Protection (DEEP). So, DEEP undertook a project in which the deer population in the area was reduced to 12 per square mile through a controlled hunt, and that number was maintained for five years. “Cases of Lyme dropped to two or three a year,” Kilpatrick says. “They’ve continued to allow hunting in that community.”
Such successful deer-herd culling is not an easy achievement, and it’s one that has to be approved on a town-by-town basis. “There will always be anti-hunting groups that oppose killing deer,” Kilpatrick says. Bringing the herd numbers low enough to affect the spread of Lyme (as indicated by this study) means killing up to 80 or 90 percent. A growing number of municipalities in Connecticut have been willing to make the sacrifice, particularly in Fairfield County. “The towns of Wilton, Ridgefield, Redding and Darien have all opened lands to hunting because of concerns about too many deer. Fifteen years ago, that wasn’t the case,” he says.
DEEP’s current deer study, centered on Mason’s Island, strives to reduce tick populations without killing their hosts. Deer are attracted to feed stations outfitted with paint rollers that apply a tickicide to their heads and necks. Now in its fifth year, the project has reduced tick numbers by half. A similar strategy has been tried with field mice, another critical player in the development of Lyme—they’re the primary incubators for nymph-stage ticks, and carriers of the bacterium that these ticks transfer to other hosts. Mice enter a bait-box and get painted with fipronil (the active ingredient in Frontline tick repellent). For up to a month, any tick that enters their nests is killed. “The downside,” says Stafford, “is that this approach tends to be very expensive, as mice have a very small home-range of a half-acre or so.
“We know we can kill ticks, but trying to demonstrate the impact of that on disease has been much, much tougher,” he adds. “You can reduce their numbers, but it only takes one tick to spread Lyme disease.”