A bacterium historically associated with cat scratch fever and transmitted predominately by fleas may also play a role in human rheumatoid illnesses such as arthritis, according to new research from North Carolina State University.

Bartonella is a bacterium that is maintained in nature by fleas, ticks and other biting insects. It can be transmitted to humans both by these parasites as well as by bites or scratches from infected cats and dogs. The most commonly known Bartonella-related illness is cat scratch disease, caused by B. henselae, a species of Bartonella that can be carried in a cat's blood for months to years.

In collaboration with Dr. Robert Mozayeni, a rheumatologist based in Maryland, and Dr. Ricardo Maggi, a research assistant professor at NC State, Dr. Ed Breitschwerdt, professor of internal medicine at NC State's College of Veterinary Medicine and adjunct professor of medicine at Duke University, tested blood samples from 296 patients for evidence of Bartonella infection. The patients had previously been diagnosed with conditions ranging from Lyme disease to arthritis to chronic fatigue. Since rheumatic symptoms have sometimes been reported following cat scratch disease, the researchers wanted to see if these patients tested positive for B. henselae.

Of the 296 patients, 62 percent had Bartonella antibodies, which supported prior exposure to these bacteria. Bacterial DNA was found in 41 percent of patient samples, allowing investigators to narrow the species of Bartonella present, with B. henselae, B. kohlerae and B. vinsonii subsp. berkhoffii the most prevalent. The study appears in Emerging Infectious Diseases.

"Based upon this one study we can't definitively say that a subset of rheumatoid illnesses have an infectious origin," Breitschwerdt says. "However, our results thus far do implicate Bartonella as a factor in at least some cases. If the link between Bartonella and rheumatoid illnesses is valid, it may also open up more directed treatment options for patients with rheumatoid illnesses."