Babesia rossi is an important, tick-borne intraerythrocytic protozoan parasite; however, its natural history and epidemiology is poorly understood. Babesia rossi is the most virulent Babesia sp. in domestic dogs and is generally considered to cause severe babesiosis, which is fatal if left untreated. However, subclinical infections and mild disease from B. rossi have been reported, although the clinical progression of these cases was not reported. Therefore, to better understand B. rossi under field conditions, we evaluated its clinical progression and seroprevalence in an owned, free-roaming dog population in Zenzele, South Africa, where the parasite is endemic and prevention is not routine. The entire dog population in Zenzele was monitored intensively at the individual level from March 2008 until April 2014, primarily for a longitudinal study on rabies control. Subsequent evaluation of B. rossi comprised analyses of clinical and laboratory data collected from the Zenzele dog population during the 6 year study period. A substantial proportion (31% (n = 34)) of 109 dogs (randomly selected from every available dog in February/March 2010 older than ~6-8 weeks (n = 246)) tested by Indirect Fluorescent Antibody Test had seroconverted strongly to B. rossi. All 34 dogs were generally consistently healthy adults, determined from regular clinical examinations between March 2008 and April 2014. Blood smear examinations at multiple time points between July 2009 and February 2011 were also undertaken for almost all of these (34) seropositive dogs and all those tested were consistently negative for Babesia spp. Subclinical infections and mild disease were also the main findings for a separate group of 18 dogs positive for Babesia spp. on blood smear examination and confirmed to be infected with B. rossi by Polymerase Chain Reaction - Reverse Line Blot. Almost all of these dogs were positive at only one time point from repeat blood smear examinations between July 2009 and February 2011. We suggest that these observations are consistent with immunity acquired from repeated, low-level exposure to the parasite, generating transient subclinical infections or mild disease. Should this be the case, the use of tick control, particularly in adult dogs in free-roaming populations in B. rossi endemic regions, should be carefully considered.

中文翻译：

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南非拥有的自由漫游犬的长期跟进活动自然会暴露于罗氏杆菌。

蔷薇虫巴贝斯虫是一种由tick传播的重要的红细胞内原生动物寄生虫。但是，人们对其自然历史和流行病学知之甚少。rossi病菌是最具毒性的Babesia sp.。在家犬中通常被认为会引起严重的贝贝病，如果不及时治疗会致命。然而，尽管没有报道这些病例的临床进展，但已经报道了亚临床感染和来自罗氏沼虾的轻度疾病。因此，为了更好地了解野外条件下的罗氏芽孢杆菌，我们在南非Zenzele的一个自养，自由漫游的狗群中评估了其临床进展和血清阳性，那里的寄生虫是地方性的，并且不是常规的预防措施。从2008年3月到2014年4月，对Zenzele的整个犬只种群进行了严格的个人监测，主要用于狂犬病控制的纵向研究。随后对罗氏沼虾的评估包括在6年研究期内从Zenzele狗种群中收集的临床和实验室数据的分析。通过间接荧光抗体试验检测的109条狗（2010年2月/ 3月约6-8周龄（n = 246）中的每只可用狗随机选出）中有很大一部分（31％（n = 34））经血清转化为强B.罗西。从2008年3月至2014年4月的常规临床检查中确定，所有34只犬总体上都是健康的成年人。几乎所有这些（34）血清反应阳性犬和所有这些阳性犬均在2009年7月至2011年2月的多个时间点进行了血液涂片检查测试的巴贝斯菌属始终呈阴性。亚临床感染和轻度疾病也是另外一组对巴贝斯虫属呈阳性的18只狗的主要发现。进行涂片检查，并通过聚合酶链反应-反向印迹法确认感染了罗氏芽孢杆菌。从2009年7月至2011年2月的重复血液涂片检查中，几乎所有这些狗在一个时间点都呈阳性。我们建议，这些观察结果与反复，低水平接触该寄生虫，产生短暂亚临床感染或轻度疾病。如果是这种情况，应谨慎考虑使用of控制，特别是在罗氏沼虾流行地区自由漫游的成年犬中。进行涂片检查，并通过聚合酶链反应-反向印迹法确认感染了罗氏芽孢杆菌。从2009年7月至2011年2月的重复血液涂片检查中，几乎所有这些狗在一个时间点都呈阳性。我们建议，这些观察结果与反复，低水平接触该寄生虫，产生短暂亚临床感染或轻度疾病。如果是这种情况，应谨慎考虑使用of控制，特别是在罗氏沼虾流行地区自由漫游的成年犬中。进行涂片检查，并通过聚合酶链反应-反向印迹法确认感染了罗氏芽孢杆菌。从2009年7月至2011年2月的重复血液涂片检查中，几乎所有这些狗在一个时间点都呈阳性。我们建议，这些观察结果与反复，低水平接触该寄生虫，产生短暂亚临床感染或轻度疾病。如果是这种情况，应谨慎考虑使用of控制，特别是在罗氏沼虾流行地区自由漫游的成年犬中。我们建议这些观察结果与通过反复，低水平接触寄生虫，产生短暂的亚临床感染或轻度疾病而获得的免疫力是一致的。如果是这种情况，应谨慎考虑使用of控制，特别是在罗氏沼虾流行地区自由漫游的成年犬中。我们建议这些观察结果与通过反复，低水平接触寄生虫，产生短暂的亚临床感染或轻度疾病而获得的免疫力是一致的。如果是这种情况，应谨慎考虑使用of控制，特别是在罗氏沼虾流行地区自由漫游的成年犬中。