New Tick-Borne Disease Discovered in Dogs May Pose a Risk to Humans
NEWS | 05 December 2025
Several dogs in the US have died following infections by a newly discovered tick-borne disease from the same genus responsible for 'spotted fever'. Scientists are watching the bacterium closely for fear it could jump to humans. Many of the bacterium's relatives can infect our own species, so the genus "should always be considered potentially pathogenic" to humans, health experts say. Close surveillance is key. Related: There's a Shocking Reason Ticks Are So Dangerous (It's Us) Scientists at North Carolina State University have now successfully cultured the infection from a sick dog, who had symptoms similar to those of Rocky Mountain spotted fever (RMSF, species Rickettsia rickettsii) – also transmitted through tick bites. When the team sequenced the bacterium's genome, they realized it was a whole new species in the spotted fever group. It's been named Rickettsia finnyi – after Finny, the dog whose blood it was found in. "We first reported the novel species of Rickettsia in a 2020 case series involving three dogs," says veterinary researcher Barbara Qurollo from NC State. "Since then, we received samples from an additional 16 dogs – primarily from the Southeast and Midwest – that were infected with the same pathogen." The dangerous infections cause moderate to severe symptoms, including fever, lethargy, and blood platelet deficiencies. Thankfully, most of the dogs recovered after treatment with antibiotics, but one dog died before diagnosis, and another was euthanized. Tragically, there was also a pet that relapsed after treatment and died of nephrotic syndrome. RMSF is one of the most virulent and dangerous of the Rickettsia bacteria, but there are more than two dozen species, several of which can cause disease in mammals. Many species have only been found in recent decades using advanced molecular imaging techniques. Humans and dogs are not considered essential parts of the Rickettsia life cycle, but we and our pets can be occasional carriers. In many parts of the world, human habitats overlap with those of ticks, and each encounter increases the likelihood that we will become opportunistic hosts. Rickettsia bacteria are difficult to culture in the lab because they grow inside other cells, explains Qurollo, but that is the only way to confirm their true identity. A species called Rickettsia parkeri, for instance, can sometimes infect dogs and cows in the southeastern US, but the first human infection was only identified in 2004. There's a chance some diagnoses of RMSF in this part of the nation were actually R. parkeri on the sly. "Until recently, R. rickettsii was the only [spotted fever pathogen] known to cause disease in dogs in North America," write researchers at NC State. Now, it seems there's another. While only a small number of dogs have been confirmed as infected, there's a chance that others are yet to be diagnosed. Its genome alignment shows very few differences from other spotted fever pathogens. In lab experiments, the bacterium was well-adapted to survive in mammalian host cells, growing in canine immune cells for more than 104 days. This suggests that our pets can provide a reservoir for the infection. "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 [that species]," explains Qurollo. Tellingly, the geographic range of this tick species also overlaps with the places where the sick dogs came from. Given the potential for this pathogen to jump between species, identifying its hosts will be essential to preventing public health impacts, researchers at NC State argue. The study was published in Emerging Infectious Diseases.
Author: Carly Cassella.
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