Scientists scramble to forecast where and when the disease-carrying ticks pose the most danger.
In the 1970s, an epidemic of mysterious arthritis-like symptoms began spreading among children in the lushly wooded area around Lyme, Connecticut. Scientists traced the cause to tick bites and named it Lyme disease, but why it had suddenly appeared there was a mystery.
Similar symptoms had been documented on Long Island, New York, years before. Doctors there called it “Montauk spider bite” or “Montauk knee.” It would take until 1990 before scientists found museum specimens of ticks from Long Island and were able to connect the same tick-borne bacteria to both locationsand suggest how Lyme disease might have started its modern spread.
As a researcher who studies how disease travels based on geography, I have been following Lyme disease’s spread for nearly four decades. Over that time, Lyme disease cases increased from a few hundred reported in 1982 to more than 33,000 in 2018. The U.S. Centers for Disease Control and Prevention estimates the actual number of Lyme disease cases is about 10 times greater than those reported. For people infected, the symptoms can be debilitating, including fever, fatigue and muscle and joint pain that can last for months or years after treatment, and in some cases cause neurological disorders and heart infections.
Every year people are diagnosed with and treated for tick-borne illnesses such as Lyme disease, anaplasmosis and Rocky Mountain spotted fever. For Lyme disease alone, the annual figure is nearly half a million, according to estimatesfrom the U.S. Centers for Disease Control and Prevention. And that number is expected to rise as many tick species continue to expand their ranges. jIn the U.S., confirmed cases of Lyme disease rose 44 percent from 1999 to 2019, according to the Centers for Disease Control and Prevention.
The CDC has also started developing its own probability models to predict where ticks are likely to be found in significant numbers—and where they are likely to spread infection—Eisen says. “We generate these statistical models to come up with what defines a good habitat for the tick or the pathogen,” she says. These models help the government agency allocate its limited resources and zero in on new locations where ticks are likely to be found, either now or in the future. They use mostly county-level geography, climate and vegetation data. “The resulting maps help us to identify areas where it looks like environmental conditions are suitable for the tick or pathogen to persist,” Eisen adds, “but where we haven’t yet found records of the tick or pathogen.” Then they go looking for evidence of ticks and tick-borne illnesses in those locations. Such efforts are helpful, but most researchers who work on this issue acknowledge that a true forecast—one that could predict not only where ticks are likely to be but whether those specific ticks are likely to spread illness—is still out of reach. Data collection is one piece of that puzzle, but another is a better understanding of how ticks interact with host species, both human and nonhuman, and how the arthropods act as conduits for disease.
There’s no vaccine for Lyme disease currently available. According to the CDC, the Lyme disease vaccine once on the market for a few years was discontinued by its maker because of “insufficient consumer demand.” Some vaccines for Lyme disease, including one from Yale researchers that deploys mRNA technology, are being considered. If you do have that telltale rash, that’s considered a “home run” diagnosis, Bran said, and a dose of the antibiotic Doxycycline is used to treat the disease. “If you have the rash, you don’t need any expensive testing,” Bran added. “You need Doxycycline.”
Many cases of Lyme disease can be cured with a course of antibiotics. Some people, however, may develop lasting symptoms after a Lyme infection, including pain, fatigue, difficulty thinking, mental health issues and other symptoms that interfere with daily life. The CDC refers to illness that lasts longer than six months after treatment as Post-Treatment Lyme Disease Syndrome. The agency says some experts believe the bacteria that causes Lyme disease can trigger an autoimmune response, resulting in symptoms that last well after the infection is gone. There is also some research that suggests the bacteria that causes Lyme disease can stay alive in the body after initial treatment.CNET