Oliva Alec, Kreisler Rachael, Romkema Andrea, Madsen Soren, Furman Haley, Maag Christopher, Schaefer Charles, Hernandez Jose A, Lee Jung Keun, Quinlan Michael, VandenBrooks John
Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, USA.
Department of Primary Care, Shelter and Community Medicine, Midwestern University College of Veterinary Medicine, Glendale, Arizona, USA.
Zoonoses Public Health. 2025 Aug 28. doi: 10.1111/zph.70009.
Rocky Mountain spotted fever (RMSF), a rapidly progressing febrile disease caused by the bacterium Rickettsia rickettsii, is the deadliest tick-borne disease in the world. Human infection initially results in non-specific symptoms and, if untreated, can result in death in up to 35% of cases. Rhipicephalus sanguineus (brown dog tick) was discovered to spread RMSF in Arizona and Northern Mexico in the early 2000s, and the disease is now considered endemic in areas of the Southwestern United States. This study investigates the relationship between canine spotted fever group rickettsial (SFGR) seroprevalence and human RMSF case rates in Arizona.
Canine serum samples were opportunistically collected from 12 counties in Arizona between February 2018 and November 2022. Immunofluorescence assays were employed to determine the anti-SFGR antibody titers in each of the samples, with dilutions ≥ 1:64 considered positive. An exponential nonlinear regression was used to determine the association between canine SFGR seroprevalence and human RMSF case rates per 100,000 as reported by the Arizona Department of Health Services.
Of the 423 dogs sampled, 21% (89/423) were found to be positive for anti-SFGR antibodies. Eight of the 12 counties had seropositive dogs. Geometric mean titers ranged from 64 to 464, with a median of 179. A nonlinear regression model demonstrated a strong association between canine SFGR seropositivity and human RMSF case rates, with the best-fitting model employing RMSF case rates lagged by 1 year. A similar model also showed a significant association between canine SFGR geometric mean titers and RMSF case rates.
Canine SFGR seroprevalence correlates with human RMSF case rates, with RMSF risk rising exponentially as canine SFGR seroprevalence increases. This lends support to the potential use of canine SFGR serology as an epidemiological tool for forecasting RMSF.
落基山斑疹热（RMSF）是一种由立氏立克次体细菌引起的快速进展的发热性疾病，是世界上最致命的蜱传疾病。人类感染最初会出现非特异性症状，如果不进行治疗，高达35%的病例可能会死亡。21世纪初，在亚利桑那州和墨西哥北部发现血红扇头蜱（棕狗蜱）可传播RMSF，现在该疾病在美国西南部地区被认为是地方病。本研究调查了亚利桑那州犬类斑点热群立克次体（SFGR）血清阳性率与人类RMSF发病率之间的关系。
在2018年2月至2022年11月期间，从亚利桑那州的12个县机会性地收集犬类血清样本。采用免疫荧光测定法确定每个样本中的抗SFGR抗体滴度，稀释度≥1:64被视为阳性。使用指数非线性回归来确定犬类SFGR血清阳性率与亚利桑那州卫生服务部报告的每10万人中人类RMSF发病率之间的关联。
在423只采样犬中，21%（89/423）被发现抗SFGR抗体呈阳性。12个县中有8个县存在血清阳性犬。几何平均滴度范围为64至464，中位数为179。非线性回归模型显示犬类SFGR血清阳性与人类RMSF发病率之间存在很强的关联，最佳拟合模型采用滞后1年的RMSF发病率。类似的模型还显示犬类SFGR几何平均滴度与RMSF发病率之间存在显著关联。
犬类SFGR血清阳性率与人类RMSF发病率相关，随着犬类SFGR血清阳性率的增加，RMSF风险呈指数上升。这支持了将犬类SFGR血清学作为预测RMSF的流行病学工具的潜在用途。
