Department of Veterinary Pathobiology, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK.
Department of Veterinary Pathobiology, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK.
J Equine Vet Sci. 2022 Nov;118:104135. doi: 10.1016/j.jevs.2022.104135. Epub 2022 Oct 3.
Although ticks are known vectors of pathogens across a range of hosts, there is limited research on emerging tick-borne diseases of horses in the United States. Tick surveys from other regions suggest Rickettsia spp. and Ehrlichia spp. may be clinically relevant in horses. To better understand the transmission risk of these tick-borne rickettsial disease agents to horses, ticks were collected from horses in Oklahoma. Ticks for the current study (306 Amblyomma americanum, 20 Dermacentor albipictus, 19 D. variabilis, and 7 A. maculatum) were evaluated for Rickettsia spp. and Ehrlichia spp. using polymerase chain reaction and sequence analysis. Serum samples from infested and noninfested horses were evaluated for antibodies to R. rickettsii using indirect fluorescence antibody testing and Ehrlichia spp. and Anaplasma spp. using a commercial enzyme-linked immunoassay. Of the horses with tick infestations, 71.4% hosted at least one tick with a rickettsial agent detected. Rickettsia spp. were identified in 25.9% (91/352) of the ticks tested with R. amblyommatis (80.2%; 73/91) most often detected. Ehrlichia spp. were identified in 2.8% (10/352) of the ticks tested with E. ewingii most often identified. Serologic screening revealed no horses with antibodies to R. rickettsii or Anaplasma spp., but 29.6% of the examined horses had circulating antibodies to Ehrlichia spp. Together, these results demonstrate the presence of Rickettsia spp. and Ehrlichia spp. in equine ticks and evidence of past or current infection with Ehrlichia spp. in Oklahoma horses which strongly suggests there is a need to explore the relationship between these agents and equine health.
尽管蜱虫已知是多种宿主的病原体传播媒介，但在美国，对马类新兴蜱传疾病的研究有限。来自其他地区的蜱虫调查表明，立克次体属和埃立克体属可能与马类具有临床相关性。为了更好地了解这些蜱传立克次体病病原体感染马类的传播风险，研究者从俄克拉荷马州的马匹身上采集了蜱虫。目前的研究中采集的蜱虫（306 只美洲钝眼蜱、20 只白足硬蜱、19 只草原革蜱和 7 只肩突硬蜱）通过聚合酶链反应和序列分析，评估了立克次体属和埃立克体属的情况。通过间接荧光抗体试验评估了感染和未感染蜱虫的马血清样本中针对 R. rickettsii 的抗体，使用商业酶联免疫吸附试验评估了埃立克体属和无形体属的抗体。在有蜱虫感染的马匹中，71.4%至少有一种携带检测到的立克次体病原体的蜱虫。在所检测的 352 只蜱虫中，有 25.9%（91/352）检测到立克次体，其中 R. amblyommatis（80.2%；73/91）最为常见。在所检测的 352 只蜱虫中，有 2.8%（10/352）检测到埃立克体，其中 E. ewingii 最为常见。血清学筛查未发现感染 R. rickettsii 或无形体属的马匹，但 29.6%的受检马存在循环埃立克体属抗体。综上所述，这些结果表明马类蜱虫中存在立克次体属和埃立克体属，并且俄克拉荷马州的马类存在过去或当前感染埃立克体属的证据，这强烈表明有必要探索这些病原体与马类健康之间的关系。
