Content continues after advertisement

Novel Rickettsia Species in Dogs

Susan Little, DVM, PhD, DACVM (Parasitology), Oklahoma State University

Infectious Disease

November/December 2021

Sign in to Print/View PDF

In the Literature

Wilson JM, Breitschwerdt EB, Juhasz NB, et al. Novel Rickettsia species infecting dogs, United States. Emerg Infect Dis. 2020;26(12):3011-3015. 


Although tick-borne infection is commonly encountered in veterinary medicine, identifying the specific pathogen responsible can be difficult. Emergence of novel agents that can induce similar and, at times, severe disease increases the challenge. Diagnostic tests for tick-borne infection have been developed and validated to identify known, established organisms, but a diverse array of potential pathogens cycle in nature.

This study describes a novel spotted fever group of Rickettsia spp that caused severe disease in 3 dogs infected in the central and southern United States. Although attempts to culture the organism were unrewarding, researchers sequenced identical Rickettsia-specific targets from the blood of the 3 patients. All sequences were identical to each another and unique from other known Rickettsia spp.

The dogs shared a history of tick exposure in a region with heavy tick populations and were presented in the summer with fever, lethargy, and thrombocytopenia, leading to suspicion of tick-borne illness. All 3 patients were seropositive for antibodies reactive to Rickettsia spp on immunofluorescent assay (IFA) testing. One dog also had neutrophilic polyarthritis, which is occasionally reported in dogs with Rocky Mountain spotted fever. 

One dog had protein-losing nephropathy and was euthanized after developing nephrotic syndrome. The remaining 2 dogs recovered after receiving doxycycline, prednisone, and supportive care. The novel organism was identified via PCR and sequencing of Rickettsia-specific nucleic acid targets from the blood of all 3 patients. 

Studies like this are critical to understanding the diversity of tick-borne pathogens that threaten canine health. Spotted fever group Rickettsia spp cause cross-reacting antibodies detected on IFA tests, leading to a suspicion that as-yet-unrecognized agents like the one described here may be widespread. 

Dogs are important sentinels for tick-borne infection risk in humans. The potential zoonotic risk posed by this agent warrants further consideration.


Key pearls to put into practice:


Novel tick-borne agents continue to be described. Recognizing classic clinical signs may allow for a successful outcome, even if the disease is caused by an unrecognized organism.



Ticks transmit a wide variety of infectious organisms. Focusing on consistent tick preventives and avoiding areas with intense tick populations can help limit risk for disease and protect dogs from infections.


Spotted fever group Rickettsia spp also infect humans. Novel infections provide another opportunity to raise awareness among pet owners about the zoonotic risk of tick-borne pathogens.

Suggested Reading

For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

All Clinician's Brief content is reviewed for accuracy at the time of publication. Previously published content may not reflect recent developments in research and practice.

Material from Clinician's Brief may not be reproduced, distributed, or used in whole or in part without prior permission of Educational Concepts, LLC. For questions or inquiries please contact us.


Clinician's Brief:
The Podcast
Listen as host Alyssa Watson, DVM, talks with the authors of your favorite Clinician’s Brief articles. Dig deeper and explore the conversations behind the content here.
Clinician's Brief provides relevant diagnostic and treatment information for small animal practitioners. It has been ranked the #1 most essential publication by small animal veterinarians for 9 years.*

*2007-2017 PERQ and Essential Media Studies

© Educational Concepts, L.L.C. dba Brief Media ™ All Rights Reserved. Terms & Conditions | DMCA Copyright | Privacy Policy | Acceptable Use Policy