By Sean Henahan, Access Excellence

BALTIMORE As tick season begins, researchers are putting increased focus on granulocytic ehrlichosis, a potentially fatal disease spread by the same tick that spreads Lyme disease. A newly developed cell culture test should help researchers understand and treat the disease.

Photo: Ixodes scapularis (John VanDyk)

Hikers and campers are at risk for both diseases. This complicates diagnosis and treatment because the symptoms of ehrlichiosis can be mistaken for Lyme disease. In one study of Midwesterners with ehrlichiosis, 56 percent of patients were hospitalized and two 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, flu-like 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., associate professor of pathology at Johns Hopkins University.

"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."

Dr. Dumler's team is the first to identify the species of the genus Ehrlichia of the family Rickettsiaceae that causes Ehrlichosis. The obligate, intracellular bacteria are found within white blood cells. Ehrlichiosis in humans was first reported in 1986. A canine form of the disease was recognized earlier. It has similar symptoms to Lyme disease, except without the characteristic rash. And, like Lyme disease, the infection can be treated effectively with common antibiotics.

Dumler and colleagues 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, they identified the bacteria responsible.

"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."

Lyme disease is caused by the spirochete Borrelia burgdorferi. The white-footed mouse is the primary animal reservoir for the nymphal and larval ticks, with deer the preferred host for the adult ticks. Dogs can also host these ticks.

The new test was announced May 20, 1996 at the annual meeting of the American Society for Microbiology.

Related information on the Internet

Ehrlicosis Home Page

B. burgdorferi Molecular Genetics Server

Tick Preparedness