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N.C. Dogs Provide Clues About Dangerous Pathogen

A new NC State College of Veterinary Medicine study shines an ever-brightening light on Bartonella by taking a close look at the emerging pathogen’s presence in North Carolina.

The study, published in the journal Vector-Borne and Zoonotic Diseases, creates an activity map of the pathogen Bartonella henselae through samples from dogs obtained between 2004 and 2015. The results showcase ecological and socioeconomic factors associated with exposure to Bartonella henselae, the cause of human cat scratch fever and one of the most common species of Bartonella seen in humans and dogs.

It’s the latest chapter in more than three decades of Bartonella research at the CVM, a world-leading source of research about the bacterium and the increasing number of infectious diseases it causes in humans and animals. Bartonella lives in the lining of blood vessels and causes conditions such as heart valve infections, trench fever and inflammation of the inner lining of the heart. A case study from the CVM published earlier this year adds to the evidence that Bartonella infection can mimic a range of chronic diseases, including mental illness.

Erin Lashnits, the lead author of the new study, has focused much of her research on Bartonella as a Ph.D. student and member of the CVM’s Clinician Investigator Program, which combines a small animal internal medicine residency with a Ph.D. in comparative biomedical sciences.

We spoke with Lashnits about her latest research, co-authored by her mentor, Ed Breitschwerdt, Daniel Dawson and Cristina Lanzas.

When we last chatted about your Bartonella research, you said you were looking forward to going deeper into how the bacterium is impacting North Carolina. What did your new study reveal about its prevalence in the state?

We were able to map dogs’ exposure to Bartonella based on the county that they live in or that their veterinarian is located in, and we found that there was a surprising degree of variation across the state.

More dogs were exposed to Bartonella through the southern and eastern coastal plains and eastern piedmont. In some of those areas, 1 in 10 dogs tested were exposed to Bartonella. In contrast, fewer dogs were exposed in the western mountain counties. In most of these areas, it was less than 1 in 100. The lower levels of exposure in the western part of the state also lined up with some of the ecological factors we found that were associated with lower exposure, particularly deciduous forests and lower humidity.

What did your research suggest about some of the biggest risk factors for Bartonella in North Carolina?

In dogs, it still looks like individual factors are probably the most likely to predict risk of contracting Bartonella. Bartonella is transmitted by fleas and possibly ticks, so certainly preventing exposure to these vectors is a great first step. In dogs, that is usually as easy as getting an effective flea and tick preventative from your vet.

However, Bartonella can also be transmitted by getting scratched by a flea-infested cat, so for people and dogs that might interact with cats it is important to treat the cats for fleas and avoid getting scratched.

Erin Lashnits. Photo by John Joyner/NC State Veterinary Medicine

What surprised you most about your findings?

One association that was somewhat surprising was that in counties with relatively higher levels of income the risk for Bartonella exposure in dogs was lower. This may be reflective of a lack of accessibility to veterinary services for dogs and cats in lower income communities, which is something that as a practicing veterinarian I hope to be able to help with in the future.

While there is a lot we don’t know about Bartonella, we do know simple ways to reduce exposure. In my opinion, that starts with, again, effective flea and tick prevention not just for our dogs, but also for the free-roaming and outdoor cats that are likely serving as a reservoir of infection for both dogs and humans.

There is still a lot to learn about the fundamentals of Bartonella and the diseases it causes, including definitive information on the primary way it is transmitted to dogs. Are you optimistic that over the next few years we’ll be able to fill in more of the blanks?

I hope so and am building my career on it. We have a few exciting upcoming projects on this front, from using sophisticated modeling techniques to try to tease apart transmission at the household level, to creating an experimental model of Bartonella transmission using fleas to study the molecular mechanisms of transmission in a more controlled environment. We’re also studying the microbiome, the community of pathogenic and non-pathogenic bacteria, that lives in fleas in the natural world.

What does it feel like to be at the forefront of investigating Bartonella?

As you said, there’s still so much to learn. When I was a kid, Bartonella wasn’t even on our radar in North America. While it came to the forefront during the AIDS epidemic in humans, it wasn’t until Dr. Breitschwerdt discovered the first dog to be infected with Bartonella here at the CVM in the 1990s that veterinary medicine became aware of this emerging pathogen.

Based on some of the other work going on in our lab on the potential disease manifestations of chronic Bartonella infection, including neuropsychiatric disease and even possibly certain cancers, Bartonella may be contributing even more to chronic disease in humans and animals than anyone expected. If that is the case, understanding and ultimately preventing transmission will prove even more important.

~Jordan Bartel/NC State Veterinary Medicine