BACKGROUND Dogs are vulnerable to pathogens transmitted by brown dog ticks. An epidemic of Rocky Mountain spotted fever (RMSF) is underway in Mexicali, a Mexican city bordering California affecting people and dogs; several human cases have been reported in California residents who travelled to Mexico. To evaluate risks of RMSF, we conducted seroprevalence surveys in Imperial County in 2016 and 2017 using dogs as sentinels. METHODS Blood was collected from 752 dogs and was tested for antibodies against R. rickettsii, E. canis and A. phagocytophilum (as a proxy for A. platys). Samples were considered seropositive to spotted fever group rickettsia (SFGR) if the R. rickettsia titre was ≥1:64 and seropositive to E. canis and A. phagocytophilum if the titre was ≥1:32. Owners provided information on dog age, exposure risks, health status and tick prevention. We assessed associations between SFGR seropositivity and driving distance to the nearest US-Mexico border crossing station, whether proximity to a border crossing increased likelihood of taking dogs across the border, and whether distance to the border was associated with seropositivity. Logistic regression was performed to assess relationships between the titre classes and other predictor variables. RESULTS 12.2% of dogs were seropositive against SFGR. Dogs close to the border were significantly more likely to be taken across the border and to be seropositive. Risk factors that increased seropositivity included owners seeing ticks on the dog (OR = 1.9), being an adult dog, travel to Mexico (OR = 3.0) and living in a rural area (OR = 4.0). There was statistically significant co-exposure to SFGR and Anaplasma spp. CONCLUSION Surveillance for brown dog tick-vectored pathogens can help identify dogs and people at risk for RMSF. Tick prevention, particularly in dogs, and surveillance of tick-borne pathogens can help prevent the spread of rickettsioses and other diseases in this dynamic border region.

中文翻译：

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在美国加利福尼亚州与墨西哥边境附近发现发烧的立克次氏体犬血清监测。

背景技术狗容易受到棕色狗虱传播的病原体的伤害。墨西卡利（Mexicali）正在进行落基山斑点热（RMSF）的流行，墨西卡利（墨西哥）与加利福尼亚州接壤，影响人和狗。据报道，前往墨西哥的加利福尼亚居民有几例人类病例。为了评估RMSF的风险，我们在2016年和2017年使用狗作为前哨在帝国县进行了血清阳性率调查。方法从752只狗中采集血液，并测试其对立克次氏菌，犬埃里希氏菌和吞噬嗜血曲霉的抗体（作为鸭嘴兽的代表）。如果立克次体滴度≥1：64，则样本被认为对点状发热立克次体（SFGR）呈血清反应阳性；如果滴度≥1：32，则样本被认为对犬埃里希氏菌和噬菌体呈血清反应。主人提供了有关狗的年龄，接触风险，健康状况和防tick虫。我们评估了SFGR血清阳性与到最近的美墨边境检查站的行驶距离之间的关联，靠近边境的距离是否增加了带狗越过边境的可能性以及与边境的距离是否与血清阳性有关。进行逻辑回归以评估效价类别与其他预测变量之间的关系。结果12.2％的狗对SFGR呈血清阳性。靠近边境的狗被带走的可能性更大，并且具有血清反应阳性。增加血清阳性的风险因素包括主人看见狗的tick（OR = 1.9），成年狗，去墨西哥旅行（OR = 3.0）和生活在农村地区（OR = 4.0）。SFGR和Anaplasma spp有统计学意义的共同暴露。结论对棕狗tick媒介病原体的监测可以帮助识别狗和有RMSF危险的人。ick虫的预防，尤其是狗的ick虫，以及and虫传播的病原体的监测，可以帮助防止病和其他疾病在这个充满活力的边境地区蔓延。