Ticks Now Found to Carry a New Infectious Agent Related to the Lyme Disease Bacteria

The pin dot-sized deer ticks responsible for more than 100,000 cases of Lyme disease nationwide are now found to carry yet another new and infectious organism, a Yale researcher has found.

“We report here, for the first time, the existence of a previously unrecognized Borrelia species transmitted by (Ixodes scapularis) ticks,” said Durland Fish, associate professor of epidemiology in the Department of Public Health at Yale School of Medicine and senior author of the study. “This discovery represents the fifth transmissible agent associated with this tick species in the Northeast.”

The organism was detected in mice during a routine experiment designed to investigate transmissible pathogens in a tick/rodent model. Fish said the organism, as yet unnamed, closely resembles a spirochete found in ticks in Japan, Borrelia miyamotoi, and is a close cousin to Borrelia burgdorferi, the spirochete that causes Lyme disease.

“It is not yet known if the bacteria can infect humans, but we do know that all the other organisms that this tick transmits to mice can also infect people,” he said.

The study was published this month in the inaugural issue of a new journal, Vector Borne and Zoonotic Diseases, of which Fish is editor.

In addition to the new bacteria and Borrelia burgdorferi, deer ticks also are carriers of Ehrlichia phagocytophila, which causes ehrlichiosis; Babesia mircoti, which are malarial like organisms; and a virus which can cause encephalitis.

The new organism was observed in nymphs derived from larvae that had fed upon mice that were not infected with Borrelia burgdorferi.

“Some of our experiments were getting some bizarre results,” Fish said. “We were finding infected ticks in experiments where we did not expect them. We sequenced a portion of the DNA to determine what it was and it turned out to be a spirochete that is related to relapsing fever spirochetes rather than the Lyme disease spirochete.”

Fish said the new organism has been found in about two percent of the nymphs tested in four states: Rhode Island; Lyme, Conn.; Westchester County in New York, and in northern New Jersey. It was previously thought that all of the spirochetes found in deer ticks were Borrelia burgdorferi, but these findings show that up to 20 percent of the infected ticks are carrying this new organism instead.

“It is completely cryptic, which means there is no way to diagnose it,” Fish said. “None of the Lyme disease tests would detect an infection by this organism. We’re anxiously studying this organism to develop diagnostic techniques and to determine whether or not it infects people. If it does, it’s likely that the same treatment for Lyme disease would be effective against this organism.”

The principal investigator of the study was Glen Scoles, a former post doctoral student who worked with Fish and is now at the USDA Animal Disease Research Unit, Washington State. Co-authors were Michele Papero, research associate, and Lorenza Beati, M.D., associate research scientist.

The work was supported by an American Lyme Disease Foundation Research grant and the Yale School of Medicine Brown-Cox Fellowship to Scoles, as well as by grants to Fish from the USDA Agricultural Research Service and the G. Harold & Leila Y. Mathers Charitable Foundation.

Vector Borne and Zoonotic Diseases publishes original research papers dealing with infectious diseases that pose serious threats to public health in the U.S. and worldwide. The journal examines geography, seasonality, and other risk factors that influence the diagnosis, management, and prevention of these diseases.

The publisher, Mary Ann Liebert, Inc., publishes peer-reviewed journals in new and promising areas of science and biomedical research.