Detection and Phylogenetic Characterization of Anaplasma capra: An Emerging Pathogen in Sheep and Goats in China

Abstract

<i>Anaplasma capra</i> is an emerging pathogen, which can infect ruminants and humans. This study was conducted to determine the occurrence of <i>A. capra</i> in the blood samples of sheep and goats in China. Using nested polymerase chain reaction (nested-PCR) targeting the <i>gltA</i> gene and conventional PCR targeting the heat shock protein (<i>groEL</i>) gene and the major surface protein4 gene (<i>msp4</i>), <i>A. capra</i> was detected in 129 (8.9%) of 1453 sheep and goat blood samples. The positive rate was higher in goats (9.4%, 89/943) than in sheep (7.8%, 40/510) (χ² = 1.04, <i>p</i> > 0.05, <i>df</i> = 1). For sheep, <i>A. capra</i> was found in 17 sites from 2 provinces. The prevalence was 28.6% in sheep from Liaoning province, which was higher than in Henan Province (7.3%). For goats, <i>A. capra</i> was detected in 35 sites from 7 provinces. The prevalence varied from 0 to 19.4% in the goat sites examined. The prevalence rates were 19.4, 19.3, 10, 8.8, 6.8, 1.8, and 0% in goats from Guizhou province, Henan Province, Inner Mongolia Autonomous Region, Shanxi Province, Xinjiang Uygur Autonomous Region, Yunnan province, and Gansu province, respectively. Based on the analysis of the <i>A. capra</i> citrate synthase gene <i>(gltA</i>), two variants were identified. Variant I showed a high sequence similarity to the <i>A. capra</i>, which were previously reported in sheep, goats, <i>Ixodes persulcatus, Haemaphysalis longicornis, Haemaphysalis qinghaiensis</i>, and humans. Variant II was only found in Luoyang, Anyang, and Sanmengxia, of Henan province. To our knowledge, this is the first detection of this variant of <i>A. capra</i> in sheep and goat blood in China. Phylogenetic analysis based on <i>groEL</i> and <i>msp4</i> genes showed that the <i>Anaplasma</i> sp. sequences clustered independently from <i>A. capra</i> and other <i>Anaplasma</i> species with high bootstrap values. We found <i>A. capra</i> DNA in sheep and goats in China, providing evidence that sheep and goats can be infected by <i>A. capra</i>. We also found that this zoonotic pathogen is widely distributed in China. This study provides information for assessing the public health risks for human anaplasmosis.