Molecular Detection and Phylogenetic Analysis of <i>Anaplasma phagocytophilum</i> and Related Strains in Cattle from Henan, China

<i>Anaplasma phagocytophilum</i> is a zoonotic pathogen transmitted by arthropod vectors. The pathogen infects various vertebrate hosts, causing mild to severe illness. Molecular studies have demonstrated that <i>A</i>. <i>phagocytophilum</i> exhibits a high level of genetic diversity, with two <i>A. phagocytophilum</i>-related variants identified in several countries. This study represents the first application of PCR amplification and restriction fragment length polymorphism (PCR-RFLP) in conjunction with DNA sequencing to investigate the frequency and phylogenetic relationships of <i>A. phagocytophilum</i> and its related strains in cattle from China. A total of 662 bovine blood samples were collected from diverse regions within Henan Province, China, and pathogen DNA was detected in 75 samples, comprising 11.33% of the total. PCR-RFLP analysis identified three strains with frequency rates of 2.87% (19/662) for <i>A. phagocytophilum</i>, 11.33% (75/662) for <i>A. phagocytophilum</i>-like 1, and 3.22% (22/662) for <i>A. phagocytophilum</i>-like 2. Additionally, co-infections involving <i>A. phagocytophilum</i> and <i>A. phagocytophilum</i>-like 1 were observed as well as between <i>A. phagocytophilum</i>-like 1 and <i>A. phagocytophilum</i>-like 2. <i>Anaplasma phagocytophilum</i>-like strains 1 and 2 should be considered when diagnosing bovine anaplasmosis. Despite recent molecular studies of <i>A. phagocytophilum</i>-related strains, there remains a shortage of data concerning vector capability, the epidemiology of the disease, clinical signs, and genetic diversity of the pathogens. Thus, large-scale investigations involving animals and tick vectors are necessary to obtain more detailed information concerning the etiology of anaplasmosis.