Researchers at North Carolina State University have identified a new species of Rickettsia bacteria found in dogs, naming it Rickettsia finnyi. The discovery builds on previous work that first detected the pathogen in 2018 and was later described in a 2020 case series involving three clinically ill dogs.
Barbara Qurollo, associate research professor at NC State and corresponding author of the study, stated, “We first reported the novel species of Rickettsia in a 2020 case series involving three dogs. 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.”
Rickettsia finnyi is associated with symptoms similar to those caused by Rocky Mountain spotted fever (RMSF), including fever, lethargy, swelling, rash, and pain. While these symptoms are known to affect both dogs and humans when caused by other Rickettsia species, there have been no reports so far of R. finnyi infecting humans.
Qurollo explained some challenges faced by researchers: “Rickettsia species are difficult to culture because these organisms grow inside of cells. 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 process for naming a new bacterial species required culturing the organism, sequencing its genome, publishing those results, and depositing cultures into biobanks for further study by other scientists. The team named this bacterium after Finny, the first dog identified with this infection.
“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 said.
The findings were published on December 2, 2025 in Emerging Infectious Diseases. The research was supported by a grant from the American Kennel Club Canine Health Foundation (grant number 02983). Co-first authors include Praveen Korla and Michael Karounos; additional contributors from NC State are Sarah Clarke, Cynthia Robveille, James Wilson, Edward Breitschwerdt and Adam Birkenheuer.
According to their analysis, genetic sequencing showed that Rickettsia finnyi has about 96.87% identity to Rickettsia raoultii based on average nucleotide identity analysis. Phylogenetic analysis placed this bacterium as its own branch within the spotted fever group.
The researchers observed fever and thrombocytopenia among abnormalities seen in all seventeen naturally infected dogs they studied—highlighting possible health concerns for canine populations and potential relevance for public health.
