Peer-reviewed veterinary case report
Exposure to four zoonotic rickettsia infections in dogs near
By Rubino, Francesca et al.·Published in PLoS neglected tropical diseases·2026·Department of Medicine and Epidemiology, United States·View original on PubMed →
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Original publication title: Simultaneous serological assessment of four zoonotic rickettsiae among dogs near the United States-Mexico border.
Plain-English summary
A study found that nearly half of the dogs tested near the U.S.-Mexico border showed signs of exposure to various rickettsial infections, which can affect both pets and humans. Out of 779 dogs, 41.2% had antibodies for at least one type of rickettsia, with the most common being Rickettsia felis. The research also revealed that certain rickettsiae often appeared together in the same dogs, suggesting they might share transmission routes. This information is crucial for understanding the health risks these infections pose to both dogs and their owners.
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Abstract
Obligately intracellular rickettsiae cause a broad spectrum of disease in humans and animals, ranging from mild illness to life-threatening infections. Multiple species co-circulate along the southern United States of America-northern Mexico border, yet their seroprevalence in susceptible hosts remains incompletely understood. Dogs serve as key amplifying hosts for several of these pathogens, including Rickettsia rickettsii and Rickettsia massiliae, and have been shown to be infected by flea-borne Rickettsia typhi and Rickettsia felis. To better characterize exposure and potential co-infection patterns, we conducted a large binational seroepidemiologic study of 779 dogs from urban households and shelter settings across seven subregions along both sides of the border. Using a custom multiplex micro-immunofluorescence assay, we simultaneously screened for antibodies to R. rickettsii, R. massiliae, R. typhi, and R. felis. Overall, 41.2% of dogs were seroreactive to at least one pathogen, with the highest seroprevalence for R. felis (19.3%), followed by R. massiliae (15.7%), R. typhi (14.5%), and R. rickettsii (9.8%). Co-seroreactivity was common, particularly between R. typhi and R. felis, with 34.2% of R. typhi-seroreactive samples also seroreactive to R. felis, and 16.7% exhibiting high titers to both. In contrast, R. rickettsii and R. massiliae showed limited overlap (15.2% co-seroreactive; 6.4% with high titers), suggesting possible cross-protection or competitive exclusion. Spatial analyses revealed distinct geographic patterns: R. massiliae predominated in western Baja California, R. rickettsii was concentrated in Mexicali and the Rio Grande Valley, and R. felis was widely distributed. Seroreactivity patterns were generally consistent across age and sex but varied modestly between shelter and neighborhood dogs, particularly for R. typhi. These findings highlight the complex ecology of rickettsial pathogens in a binational context, underscore the importance of dogs as sentinels for human risk, and provide a foundation for future studies on vector-host-pathogen interactions, cross-protective immunity, and spatial epidemiological risk.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/41838685/