# Molecular detection and genetic diversity of Anaplasma in ticks from southeastern and central Shanxi, China

## TL;DR

This study found high rates of Anaplasma infection in ticks from Shanxi, China, and identified four species with varying genetic diversity.

## Contribution

The study reports the genetic diversity and high prevalence of Anaplasma species in ticks from specific regions in Shanxi, China.

## Key findings

- 246 out of 350 ticks tested positive for Anaplasma, with infection rates exceeding 66% in most regions.
- Four Anaplasma species were identified: A. phagocytophilum, A. ovis, A. marginale, and A. bovis.
- A. phagocytophilum and A. ovis showed higher haplotype diversity compared to A. bovis and A. marginale.

## Abstract

Anaplasma is an obligate intracellular gram-negative bacterium belonging to the family Anaplasmataceae and the order Rickettsiales, which is primarily transmitted by the bite of ixodid ticks. To investigate the prevalence risk and genetic diversity of Anaplasma in southeastern and central Shanxi, China, Ixodid ticks were sampled from sheep and cattle host animals in 11 different geographic regions during 2022–2024. These tick samples were then subjected to Anaplasma detection via nested PCR combined with partial 16S rRNA gene sequencing. The analysis revealed that 246 of 350 ticks were positive for Anaplasma. Among the survey areas, the prevalence rates of Anaplasma infection were 67.50% (27/40) in Wangjiazhuang Village, 74.19% (46/62) in Baitupo Village, 52.38% (11/21) in Daxigou Village, 66.67% (26/39) in Matian Town, 80.95% (34/42) in Zhuanghe Village, 75.00% (30/40) in Siyuan Village, 68.75% (11/21) in Xiwangyong Village, 70.83% (17/24) in Dongsitou Village, 76.19% (16/21) in Taling, 73.68% (14/19) in Houbu Village, 66.67% (14/21) in Shipan Village. The prevalence of Anaplasma is significantly higher in female ticks compared to males (89.73% vs 11.49%, χ2 = 191.614, p < 0.001). Sequencing results revealed that this study identified four species of Anaplasma namely Anaplasma phagocytophilum, Anaplasma ovis, Anaplasma marginale and Anaplasma bovis. Meanwhile, four strains belonging to the order Rickettsiales were also detected and named “Uncultured Rickettsiaceae bacterium”. Phylogenetic tree analysis examined the clustering and genetic relationships between the identified four Anaplasma species and other Anaplasma species available in the NCBI database. The Rickettsiaceae bacteria obtained in this study were also included in the phylogenetic tree construction, and they were found to form the out group as the root of the tree. Haplotype phylogeographic dynamics provided an in-depth exploration of the subtle evolutionary differences among the same species of Anaplasma and revealed their evolutionary pathways. It was shown that the evolutionary paths of A. phagocytophilum, A. ovis, and A. bovis were more complex compared to that of A. marginale. The 110 A. phagocytophilum sequences obtained in this study were classified into 13 haplotypes, while the 36 A. ovis sequences were grouped into 10 haplotypes. A. bovis and A. marginale each exhibited a single haplotype, as only one sequence has been obtained for each of them. In conclusion, a high prevalence of Anaplasma infection was observed in ticks from southeastern and central Shanxi, China. This finding lays a theoretical foundation for the formulation and implementation of relevant prevention and control measures in the study area. Continuous monitoring and epidemiological surveys of pathogens in host animals will be required in the future.