May 19, 1996
Media Contact: Michael Purdy
Phone: (410) 955-8725
Johns Hopkins researchers have developed a new test that may help probe potential links between Lyme disease and a recently discovered tick-borne illness, granulocytic ehrlichiosis.
Because both diseases are spread by the same tick, the deer tick, and because granulocytic ehrlichiosis symptoms can be mistaken for a flu or Lyme disease, Hopkins investigators say unrecognized ehrlichiosis may be complicating the treatment of some Lyme disease patients.
They say the new test also should help researchers developing better ways to treat and prevent ehrlichiosis, which can be fatal. In one study of Midwesterners with ehrlichiosis, 56 percent of patients were hospitalized and 2 percent died. In serious cases, the body's defense systems weaken and opportunistic viral, fungal and bacterial infections cause fatal complications.
"Patients with ehrlichiosis start with very general, flulike symptoms--fever, headaches, muscle aches, and most doctors say, It's a virus! Go home and get some rest.' That's scary because there's a special antibiotic that can cure patients in 24 to 48 hours if the infection is caught early," says J. Stephen Dumler, M.D., a Hopkins associate professor of pathology. Dumler was a member of the research team that developed the new test and discovered the human form of granulocytic ehrlichiosis.
"We have only isolated human granulocytic ehrlichia from six patients," Dumler says. "By allowing us to isolate more samples of the bacteria, this test should help us identify which forms can cause serious illness and study how they are different from the forms that cause almost no symptoms." These findings could aid development of ehrlichiosis vaccines for persons at risk, such as outdoorsmen, hikers and campers.
As a fellow in the Department of Pathology at the University of Texas in 1990, Dumler examined blood and tissues from the first case of granulocytic ehrlichiosis, a patient from Duluth, Minn. After tracking infections that ranged from a mild, flulike illness to a serious weakening of the body's defenses, Dumler and colleagues identified the bacteria responsible while he was at the University of Maryland in 1993. The research group mass-produced DNA from infected patients, and searched for fragments of bacterial DNA. Clinicians currently use this conventional method to test for granulocytic ehrlichiosis--if they first make the connection between patient symptoms and recent tick bites.
The new test, described by Dumler at this week's meeting of the American Society for Microbiology in New Orleans, cultivates the bacteria by making it reproduce in a tissue culture.
"Ehrlichia can't be grown on lab dishes like most bacteria," he explains. "They belong to a class of organisms that are so highly adapted that they can't grow outside of cells. The new technique solves that problem, and could help us study this whole class of organisms."
Funding for development of the new test was provided by various sources at the University of Maryland.