Comparative Tropical Medicine and Parasitology, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität, Leopoldstr, 5, 80802 Munich, Germany.
Parasit Vectors. 2011 Aug 16;4:161. doi: 10.1186/1756-3305-4-161.
Equine Granulocytic Anaplasmosis (EGA) is caused by Anaplasma phagocytophilum, a tick-transmitted, obligate intracellular bacterium. In Europe, it is transmitted by Ixodes ricinus. A large number of genetic variants of A. phagocytophilum circulate in nature and have been found in ticks and different animals. Attempts have been made to assign certain genetic variants to certain host species or pathologies, but have not been successful so far. The purpose of this study was to investigate the causing agent A. phagocytophilum of 14 cases of EGA in naturally infected horses with molecular methods on the basis of 4 partial genes (16S rRNA, groEL, msp2, and msp4).
All DNA extracts of EDTA-blood samples of the horses gave bands of the correct nucleotide size in all four genotyping PCRs. Sequence analysis revealed 4 different variants in the partial 16S rRNA, groEL gene and msp2 genes, and 3 in the msp4 gene. One 16S rRNA gene variant involved in 11 of the 14 cases was identical to the "prototype" variant causing disease in humans in the amplified part [GenBank: U02521]. Phylogenetic analysis revealed as expected for the groEL gene that sequences from horses clustered separately from roe deer. Sequences of the partial msp2 gene from this study formed a separate cluster from ruminant variants in Europe and from all US variants.
The results show that more than one variant of A. phagocytophilum seems to be involved in EGA in Germany. The comparative genetic analysis of the variants involved points towards different natural cycles in the epidemiology of A. phagocytophilum, possibly involving different reservoir hosts or host adaptation, rather than a strict species separation.
马粒细胞埃立克体病（EGA）由细胞内寄生的蜱传专性细菌嗜吞噬细胞无形体引起。在欧洲，它由蓖麻硬蜱传播。在自然界中，大量的无形体遗传变异体循环存在，并在蜱和不同动物中被发现。人们曾试图将某些遗传变异体分配给某些宿主物种或病理，但迄今为止尚未成功。本研究的目的是通过分子方法在 4 个部分基因（16S rRNA、groEL、msp2 和 msp4）的基础上，对 14 例自然感染马的 EGA 致病因子嗜吞噬细胞无形体进行调查。
所有马 EDTA 抗凝血样本的 DNA 提取物在所有 4 个基因分型 PCR 中均产生了正确大小的核苷酸条带。序列分析显示，部分 16S rRNA、groEL 基因和 msp2 基因中存在 4 种不同的变异体，msp4 基因中存在 3 种。在 14 例病例中，有 1 种 16S rRNA 基因变异体与扩增部分引起人类疾病的“原型”变异体相同[GenBank：U02521]。进化分析显示，groEL 基因中的序列与鹿的序列预期分离，如预期的那样，来自马的序列与欧洲反刍动物的变体和所有美国变体分离。
结果表明，在德国，似乎有不止一种无形体变异体参与 EGA。对涉及的变异体的比较遗传分析表明，无形体的流行病学存在不同的自然循环，可能涉及不同的自然宿主或宿主适应，而不是严格的物种分离。
