New Tick-Borne Disease on the Rise in Some Areas

Medically Reviewed by Jacqueline Brooks, MBBCH, MRCPsych
From the WebMD Archives

July 17, 2000 (Atlanta) -- Ehrlichiosis, a sometimes-fatal disease spread by ticks, appears to be erupting in areas already hardest hit by Lyme disease, according to a report here at the International Conference on Emerging Infectious Diseases. Other reports suggest that the disease can cause long-lasting symptoms -- and that getting the disease once doesn't protect against getting it again.

"We actually do think infection is increasing in Connecticut," researcher Peter D. Guarino, MPH, tells WebMD. "All of a sudden we are seeing an explosion of cases." Guarino is a researcher with the Department of Veterans Affairs Cooperative Studies Program in New Haven, Conn.

Guarino's colleague, Yale University researcher James Meek, MPH, is more cautious. "I think ehrlichiosis is on the rise, but that has to be taken with a grain of salt," he tells WebMD. "We may just now be recognizing it more -- but it is possible that the [number] of the ticks is increasing."

In January 1995, Meek, Guarino, and colleagues began a laboratory-based surveillance program that included widespread public service announcements describing the symptoms of ehrlichiosis and warning of the danger of tick bites. Annual cases of ehrlichiosis increased from about 37 confirmed and probable cases in 1995 to 338 cases in 1998.

Most people who get ehrlichiosis get better without treatment, the researchers say. "We believe the normal immune system usually can handle this," Guarino says. "There probably are a lot more infections, but they aren't serious enough to cause people to go to the doctor and get blood drawn."

Ehrlichiosis comes in two forms -- human granulocytic ehrlichiosis (HGE) and human monocytic ehrlichiosis (HME) -- caused by two slightly different bacteria. HGE is spread by the same deer ticks that carry Lyme disease. Indeed, some individual ticks carry the bacteria that cause both diseases. HME is spread by the lone star tick.

Infection is difficult to diagnose and often requires a blood test. Symptoms appear three to 16 days after a tick bite and include fever, severe headache, muscle and joint pain, chills, cough, nausea, vomiting, and/or lack of appetite. Rash is uncommon and does not resemble the distinctive bull's-eye rash that marks Lyme disease.

Only about one in 10 infected people are thought to get symptoms. But more than half of those who do require hospitalization, and up to 5% will die if not treated promptly. The good news is that the disease can be cured by prompt treatment with the antibiotic doxycycline.

Still, another conference presentation reports that ehrlichiosis may cause long-lasting health effects. Edward Belongia, MD, and colleagues collected basic health information and blood samples from 85 patients with the HGE form of the disease an average of 24 months after they first became ill. They compared these findings to those of 102 people who had not had ehrlichiosis, matched for age and sex.

People who had supposedly recovered from ehrlichiosis reported more symptoms than those who never had the disease: 5.4 times more fevers, 4.5 times more chills, twice as much fatigue, and three times more sweats. They also reported significantly more bodily pain and rated their relative health lower than the normal people. But there was no difference in physical function, impairment of daily activities, general health, or vitality.

"One possibility is that people do have chronic HGE infection," Belongia tells WebMD. He says that it may be that even once they are treated, Ehrlichia lingers in the body's tissues. However, Belongia -- a researcher at Marshfield Medical Research Foundation in Madison, Wis. -- notes that there are other explanations. The patients who had HGE once may have been more likely to get HGE again. Or maybe patients who had recently gotten over a serious illness were more sensitive about their health, and thus more likely to report symptoms than other people.

In another conference presentation, Allison Liddell, MD, of Washington University in St. Louis, reported the first case history of a person who got HME twice. The man, a liver-transplant recipient taking drugs that suppress the immune system, came down with the disease in June 1997 and again in May 1999. Both times, he quickly got better after treatment with antibiotics.

Liddell says she doesn't think the immune-suppressing drugs made the man more likely to be infected. "We've now got a large number of patients with HME," she tells WebMD. "I can't say that the immunocompromised patients do any worse."

Can normal people get the disease more than once? Liddell says there should be an answer very soon. "We currently have many people in our area who have had ehrlichiosis and -- despite our warnings -- continue to get bitten by ticks," she says. "They don't think anything of it, so we'll see."