First relapsing fever outbreak in Montana identified

August 26, 2003

A 2002 outbreak of tick-borne relapsing fever in Montana--the first confirmation of relapsing fever in the state--has led to the discovery of a bacterium and species of tick not known previously to exist in Montana.

In the September 2003 issue of the journal Emerging Infectious Diseases, investigators at Rocky Mountain Laboratories (RML) in Hamilton, Montana, and their collaborators describe this outbreak and the results of laboratory and clinical investigations.

"Given the 100-year history of research into ticks and tick-borne diseases in Montana, we are gratified to have helped solve the mystery of this outbreak and to have identified a focus of this disease as well as the bacterium and tick in our back yard," states Tom G. Schwan, Ph.D., lead investigator of the study. RML, which began by conducting pioneering studies in Montana on Rocky Mountain spotted fever, is part of the National Institute of Allergy and Infectious Diseases (NIAID), a component of the National Institutes of Health in Bethesda, MD.

"This investigation demonstrates once again the potential for diseases to emerge unpredictably in areas where they have not been recognized previously," notes Marshall Bloom, M.D., associate director of RML. "These findings will also alert health care providers in this region that relapsing fever bacteria may cause a recurrent febrile illness, which is curable when recognized and treated promptly with antibiotics."

The mystery presented itself between July and August 2002, when five of 20 people became ill during or after visiting a cabin on an island in Flathead Lake in western Montana. RML investigators and tick experts Dr. Schwan and Paul Policastro, Ph.D., worked with physicians in Seattle; Montana State Epidemiologist Todd Damrow, Ph.D.; the Lake County Health Department; and the curator of the U.S. National Tick Collection to determine the cause of the outbreak.

The patients, between 5 and 54 years old, experienced a variety of signs and symptoms including high fever, headache, joint and muscle pain, vomiting, diarrhea and rash. One individual had a second onset of illness, or relapse, which gives this illness its name. Large numbers of the bacteria circulate in the blood, giving rise to recurrent episodes of illness interspersed with periods of feeling well. All the patients eventually recovered.

Blood samples from four patients who had returned home to Seattle were sent to RML. There Dr. Schwan and his group isolated and identified the cause of the illness as Borrelia hermsii, a spiral-shaped bacterium or spirochete. Drs. Schwan and Damrow then visited the cabin where the individuals had become infected. In the attic, they discovered the species of tick that is known to transmit this bacterium in other regions of the western United States.

The bacteria that cause relapsing fever are related to those bacteria that cause Lyme disease. The illnesses, however, are quite different, and the ticks that transmit relapsing fever spirochetes have a strikingly different lifestyle compared with the ticks that transmit Lyme disease spirochetes.

For example, while Lyme disease is usually acquired from ticks in an outdoor setting, most people who develop relapsing fever become infected while sleeping in rodent- and tick-infested cabins. Because the ticks feed quickly and only at night, most people are not aware of having been bitten. In nature, the bacteria--which infect rodents such as pine squirrels and chipmunks--are transmitted among these animals by the ticks that live in or near their nests.
NIAID is a component of the National Institutes of Health (NIH), which is an agency of the Department of Health and Human Services. NIAID supports basic and applied research to prevent, diagnose, and treat infectious and immune-mediated illnesses, including HIV/AIDS and other sexually transmitted diseases, illness from potential agents of bioterrorism, tuberculosis, malaria, autoimmune disorders, asthma and allergies.

Reference: Schwan TG et al. Tick-borne relapsing fever caused by Borrelia hermsii, Montana. Emerging Infectious Diseases 9(9):1151-54 (2003). Available online at: .

Press releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at

NIH/National Institute of Allergy and Infectious Diseases

Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to