Lyme Disease Isn't the Only Tick-Borne Illness That Poses a Threat in the U.S.

Borrelia miyamotoi causes flu-like symptoms similar to Lyme disease, but the condition is harder to diagnose. Kenneth H. Thomas/Science Source

Most people who spend summertime outdoors in the Northeast are well aware of their risk for Lyme disease, a tick-borne illness that's prevalent in the warmer months. But new research suggests that the bacteria that causes Lyme disease isn't the only danger associated with tick bites.

In recent years, health officials in the Northeast report seeing a number of cases of Borrelia miyamotoi (B. miyamotoi), a much rarer tick-borne illness. In the U.S., it is transmitted by the black-legged or "deer" tick (Ixodes scapularis) and the Western black-legged tick (Ixodes pacificus), both of which are known to carry Lyme disease as well anaplasmosis and babesiosis, two other tick-borne illnesses.

According to a paper published online Tuesday in Annals of Internal Medicine, the first known cases of B. miyamotoi in all of North America were diagnosed in the Northeastern U.S. in 2013.

The paper looks at the clinical symptoms of 51 patients diagnosed with B. miyamotoi disease (BMD) in primary care practices, emergency rooms or urgent care facilities between 2013 and 2014. Twenty-four percent of these patients required hospitalization. In that period, diagnoses peaked in August, slightly later than Lyme disease.

In the accompanying editorial, the authors say the bacteria were first discovered in ticks in Japan in 1994 and then detected shortly afterward in rodents and ticks in North America and Europe. However, B. miyamotoi wasn't recognized as a human pathogen until a report from Russia in 2011.

B. miyamotoi causes many flu-like symptoms similar to Lyme disease, including headache, fever, muscle aches and joint pain. Recurring fever is the most common symptom of BMD. Only about 10 percent of patients in this study had a telltale bull's-eye rash around the bite, compared with nearly all people who get Lyme disease.

In immunocompromised patients, B. miyamotoi can also cause meningoencephalitis, a fatal infection in the brain. The New England Journal of Medicine highlighted a case study of an 80-year-old woman who lived on a farm in New Jersey and contracted the tick-borne illness. The woman, also a cancer survivor, stumped doctors when she showed progressive cognitive problems, depression, gait difficulties, hearing loss and decrease in appetite, all caused by the infection. She later developed meningoencephalitis.

To diagnose BMD, physicians use polymerase chain reaction tests, which detect the DNA of the organism. But in the U.S. these tests aren't widely available. According to the U.S. Centers for Disease Control and Prevention, "North American strains of B. miyamotoi have not yet been successfully grown in culture, a common method for identifying bacterial diseases. Blood tests based on detection of antibodies require further validation. Blood tests for Lyme disease are unlikely to be helpful in diagnosis of B. miyamotoi infections."

However, the recent study reports that patients with BMD were treated successfully with doxycycline, amoxicillin and ceftriaxone, all antibiotics that are used to treat patients with Lyme disease.