Researchers from North Carolina State University have confirmed that a species of Rickettsia first seen in dogs in 2018 is a new species of bacteria. The new species, dubbed Rickettsia finnyi, is associated with symptoms similar to those of Rocky Mountain spotted fever (RMSF) in dogs, but has not yet been found in humans.

Rickettsia pathogens are categorized into four groups; of those, spotted-fever group Rickettsia (which is transmitted by ticks) is the most commonly known and contains the most identified species. There are more than 25 species of tick-borne, spotted-fever group Rickettsia species worldwide, with R. rickettsii – which causes RMSF – being one of the most virulent and dangerous.

Symptoms of RMSF in dogs and people are similar, including fever, lethargy and symptoms related to vascular inflammation, like swelling, rash and pain.

“We first reported the novel species of Rickettsia in a 2020 case series involving three dogs,” says Barbara Qurollo, associate research professor at NC State and corresponding author of the new study.

“Since then we received samples from an additional 16 dogs – primarily from the Southeast and Midwest – that were infected with the same pathogen. We were also able to culture the new species from the blood of one of the naturally infected dogs in that group.”

To name a new Rickettsial bacterial species, the bacteria must be cultured, its genome sequenced and published, and the cultures must be deposited in two biobanks so that other researchers can also study it. Qurollo’s group successfully cultured the new species from the infected dog.

“Rickettsia species are difficult to culture because these organisms grow inside of cells,” Qurollo says. “While we haven’t been able to confirm which tick species transmit it yet, we think it may be associated with the lone star tick, because a research group in Oklahoma found R. finnyi DNA in a lone star tick.”

The researchers named the new species Rickettsia finnyi, after Finny, the first dog they found it in.

“By naming it after an individual dog, we wanted to honor all companion dogs that have contributed to the discovery of new pathogens that could cause serious illness in both dogs and humans,” Qurollo says.

The work appears in Emerging Infectious Diseases and was supported by the American Kennel Club Canine Health Foundation (grant number 02983). Praveen Korla and Michael Karounos, both researchers at NC State, are co-first authors. Other NC State contributors include Sarah Clarke, Cynthia Robveille, James Wilson, Edward Breitschwerdt and Adam Birkenheuer.

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