South Carolina study spotlights RMSF risk in lame dogs

A study published in Veterinary Sciences puts Rocky Mountain spotted fever back into focus for small-animal clinicians by looking at dogs seen in a South Carolina veterinary lameness and performance referral setting, a population where infectious disease may not be the first explanation for reduced performance or musculoskeletal complaints. The paper’s premise is straightforward but important: RMSF, caused by Rickettsia rickettsii, can be severe in dogs and humans, yet it may be missed when dogs present with subtle signs and when point-of-care screening panels don’t routinely include it. (cdc.gov)

That framing fits the broader epidemiology. CDC says RMSF is transmitted primarily by infected American dog ticks, Rocky Mountain wood ticks, and brown dog ticks, and while the disease name suggests a western footprint, a large share of reported U.S. human cases comes from the South Atlantic and south-central regions. CAPC similarly identifies the southern Atlantic states, including South Carolina, as a core area of concern, underscoring why a referral center in that region may be well positioned to detect exposure patterns that general screening can miss. (cdc.gov)

The study also lands in a diagnostic gray zone that veterinarians know well. RMSF can overlap clinically with other tick-borne diseases, and lameness is not unique to R. rickettsii infection. Merck lists fever, petechiae, lymphadenopathy, polyarthritis, edema, neurologic signs, and thrombocytopenia among common findings in canine RMSF, while also noting that PCR on blood may be positive only early, because organisms later localize in endothelium. CDC’s human-facing diagnostic guidance echoes a similar principle: early treatment should not wait for confirmatory results, and paired serology is preferred because acute samples can be negative in the first week. (merckvetmanual.com)

That matters because seropositivity and active disease are not always the same thing. CAPC notes that canine exposure can signal environmental risk for people, and a broader MDPI review on dogs as sentinels found that canine serosurveys can reflect the geographic prevalence of spotted fever group rickettsiae and may alert handlers and physicians to local pathogen circulation. In other words, even when a study is centered on dog patients, the implications extend beyond the exam room into public health and community tick awareness. (capcvet.org)

There doesn’t appear to be a major external press release or broad industry reaction tied to this paper, but the surrounding expert literature points in the same direction. A 2022 review in Vaccines called a canine RMSF vaccine “an unmet One Health need,” arguing that dogs have epidemiologic importance because of their close contact with people and their role in tick ecology. That review also stressed the lack of an accurate point-of-care test and the consequences of delayed recognition, themes that align closely with the South Carolina study’s rationale. (mdpi.com)

Why it matters: For veterinarians, especially in the Southeast, the practical takeaway is less about a single prevalence number and more about case recognition. Dogs referred for lameness, poor performance, or vague inflammatory signs may still warrant a tick-borne disease workup that goes beyond the usual in-clinic panel. RMSF should stay on the list alongside ehrlichiosis, anaplasmosis, Lyme disease, immune-mediated polyarthritis, and other causes of fever of unknown origin or shifting-leg lameness. In suspected cases, clinicians may need to lean on history, geography, platelet counts, follow-up serology, and empiric doxycycline rather than wait for a clean, immediate diagnostic answer. (merckvetmanual.com)

The study may also be useful as a reminder that referral populations can reveal surveillance gaps. A sports-medicine or lameness caseload can capture dogs whose main complaint is decreased performance rather than overt systemic illness, which may broaden how the profession thinks about RMSF presentation. If that pattern holds in future work, it could support more tailored testing strategies in endemic areas and more communication with pet parents about year-round tick prevention and shared human-animal exposure risk. (merckvetmanual.com)

What to watch: The next question is whether follow-on studies validate these findings in larger, multi-center populations, and whether diagnostic companies or clinicians respond by incorporating RMSF more deliberately into tick-borne disease screening pathways in endemic regions. (mdpi.com)