Comparative Evaluation of the Vector Competence of Four South American Populations of the Rhipicephalus sanguineus Group for the Bacterium Ehrlichia canis, the Agent of Canine Monocytic Ehrlichiosis.
Comparative Evaluation of the Vector Competence of Four South American Populations of the Rhipicephalus sanguineus Group for the Bacterium Ehrlichia canis, the Agent of Canine Monocytic Ehrlichiosis.
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DOI：
10.1371/journal.pone.0139386
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Labruna MB
中科院分区：
文献类型：
--
作者：
Moraes-Filho J;Krawczak FS;Costa FB;Soares JF;Labruna MB
本研究比较了血根头蜱群4个种群对犬单核细胞埃利希体病病原犬埃利希体的传播能力。来自巴西东南部<s:1>圣保罗州（BSP）、巴西南部南里约热内卢大德州（BRS）、阿根廷（ARG）和乌拉圭（URU）四个种群的蜱虫（幼虫和蛹）通过食用实验感染犬伊氏绦虫的狗而暴露于犬伊氏绦虫感染。让充血的蜱虫（幼虫和若虫）分别蜕皮为若虫和成虫，通过分子分析（犬E. canis-specific PCR assay）进行检测，并用于感染naïve犬。通过将成年蜱虫侵染naïve犬只，以感染犬只获得若虫后，发现只有BSP种群为犬只易感染载体，即只有感染BSP成年蜱虫的犬出现临床疾病，血清转化为犬只，并通过PCR获得犬只DNA。这一结果经两次独立重复证实，与流行病学数据一致，因为BSP蜱来自CME高度流行的巴西<s:1>圣保罗州。另一方面，BRS、ARG和URU蜱虫来自一个地理区域（南美洲南锥），在那里CME从未得到适当的记录。对蜕皮后30天未喂食的成年蜱的分子分析支持这些传播结果，因为BRS、ARG和URU蜱都没有PCR阳性，而1%的BSP若虫和31.8%的BSP成年蜱含有犬e的DNA。我们的结论是，由于南美南锥体的狗伊螨导致的CME病例的缺失或稀缺是由于在南美这部分地区盛行的狗伊螨群蜱的媒介无能的结果。
This study compared the vector competence of four populations of Rhipicephalus sanguineus group ticks for the bacterium Ehrlichia canis, the agent of canine monocytic ehrlichiosis (CME). Ticks (larvae and nymphs) from the four populations—one from São Paulo state, southeastern Brazil (BSP), one from Rio Grande do Sul state, southern Brazil (BRS), one from Argentina (ARG), and one from Uruguay (URU)–were exposed to E. canis infection by feeding on dogs that were experimentally infected with E. canis. Engorged ticks (larvae and nymphs) were allowed to molt to nymphs and adults, respectively, which were tested by molecular analysis (E. canis-specific PCR assay) and used to infest naïve dogs. Through infestation of adult ticks on naïve dogs, after nymphal acquisition feeding on E. canis-infected dogs, only the BSP population was shown to be competent vectors of E. canis, i.e., only the dogs infested with BSP adult ticks developed clinical illness, seroconverted to E. canis, and yielded E. canis DNA by PCR. This result, demonstrated by two independent replications, is congruent with epidemiological data, since BSP ticks were derived from São Paulo state, Brazil, where CME is highly endemic. On the other hand, BRS, ARG, and URU ticks were derived from a geographical region (South America southern cone) where CME has never been properly documented. Molecular analysis of unfed adults at 30 days post molting support these transmission results, since none of the BRS, ARG, and URU ticks were PCR positive, whereas 1% of the BSP nymphs and 31.8% of the BSP adults contained E. canis DNA. We conclude that the absence or scarcity of cases of CME due to E. canis in the South America southern cone is a result of vector incompetence of the R. sanguineus group ticks that prevail on dogs in this part of South America.