Ticks are widely distributed across the globe, and this distribution depends on several environmental and climatic factors [3]. H. longicornis mostly occurs in temperate secondary forests, mountainous and hilly fringe areas, [15] and transmits the virus, bacteria, spirochetes, rickettsia, blood protozoa, chlamydia, and other disease-causing and emerging infectious pathogens [1, 16]. In our research,H. longicornis is the dominant tick species in hilly area in Pingdingshan. Not only in the hilly area we studied, in other hilly areas, such as Shandong Province [17], the hilly area in eastern Liaoning Province [18], the hilly area in Hebei Province [19, 20], southwest forest in Beijing [21], Huichun and Tumen in Jilin Province [22], Huaian in Jiangsu Province [23], Anhui Province [24], Jiangxi Province [25] in China, even in Japan (ref) and South Korea (ref), H. longicornis is the dominant tick species. One common feature of these areas is that they are all hilly areas. Therefore, the distribution characteristics of H. longicornis remind us that the hill area is a unique ecological environment (Habitat), in which H. longicornis was bred. In other words, the hilly area and H. longicornis are a natural pair. Meanwhile, H. longicornis transmits different pathogens, and inhabits the body of livestock close to humans, suggesting it may be a substantial threat to healthy human beings in the hilly area.
R. microplus is also widely distributed in China and abroad (ref ?). We found a small amount of R. microplus in the collected ticks, which is consistent with the report of XX (Ref). We believe that the proportion of R. microplus in this area is relatively small, far lower than that of H. longicornis, so that some research teams have not found the existence of R. microplus in the whole Henan Province, including Pingdingshan (Ref.). In addition, the main hosts we collected were goats and sheep, which were not the main hosts of R. microplus (Ref.), which may be the reason for the low proportion of tick. Therefore, we believe that although R. microplus is not the main tick species in the region, its proportion may be slightly larger than that detected by us. In other words, the tick in the area and the diseases it spreads still cannot be underestimated.
The genus Anaplasma includes six species: A. phagocytophilum, A. marginale, A. centrale, A. bovis, A. ovis, and A. platys. All the Anaplasma members are tick-borne, obligatory, intracellular, Gram-negative bacteria, which infects humans and/or domestic animals [26, 27], culminating in severe infections. Anaplasma phagocytophilum causes granulocytic anaplasmosis (HGA) in humans and anaplasmosis in ruminants, horses, dogs, and cats [26], which is vectored mainly by Ixodes [28], sheep and goat [29, 30]. In the ticks found in China, 16S rRNA gene sequences of A. phagocytophilum were detected in Ixodes persulcatus, Dermacentor silvarum, H. concinna, Dermacentor nuttalli, and H. longicornis [31–33]. In the current study, the A. phagocytophilum infection rate (48.8%) was higher than H. longgicornis in the tick samples found at the border between China and Russia 2.5% (13/515) [34], followed by samples from Hubei Province in China (4.22%) [35], Baoding, Qinhuangdao, Tangshan in Hebei Province, China (14.6%, 39/267) [31], and Laizhou in Shandong Province in China (43.5%) [36]. The infection rate is similar to Yiyuan County in Shandong Province (48.1%) [17]. H. longicornis emerged as dominant tick species, and more than 40% A. phagocytophilum infection rate was seen in Henan and Shandong Province, which may be caused by similar latitude, altitude, and climate, in other words, hilly area. Interestingly, the infection rate in the areas surrounding the Henan and Shandong provinces in China was far less; however, the underlying mechanism remains unclear.
In addition, Anaplasma central (A. central) is a member of the genus Anaplasma. A.central causes a mild form of infectious disease. A. marginale is closely related to A. central, and widely used in immunization and to protect against virulent A. marginale challenge [37]. A. centrale primarily occurs in wild swine, deers [38, 39], sheep [40], and vectored by Ixodes persulcatus [41], Rhipicephalus pumilio, Hyalomma asiaticum [40]. In this study, A. centrale was detected for the first time in H. longicornis in China. These outcomes draw attention to the increased risk of A. centrale infection in the areas where H. longicornis primarily occurs.
Candidatus Rickettsia jingxinensis (Ca. R. jingxinensis) is an uncultured Rickettsia spp. identified in H. longicornis from north-eastern China [42], and its gltA sequence (KU853023) was detected in a human subject. Besides, it was detected in H. longicornis from Japan [43], H. longicornis and rodents from South Korea [44], H. longicornis from Hebei Province [45], Liaoning Province [46] and R. microplus from Wuhan Province of Hubei [47] in China; also H. longicornis was found in Shaanxi Province [4], and H. longicornis in Yunnan Province [48] in China. In our research, 17 kDa and gltA gene sequences of Ca. R. jingxinensis were also detected in H. longicornis ticks. These results indicate that Ca. R. jingxinensis is widely distributed in H. longicornis in hilly area in east Asia and suggests potential health risk to human and animals.