Piroplasms belong to the phylum Apicomplexa, class Piroplasmea, and order Piroplasmida and include the genera Babesia and Theileria. They are an order of protozoan parasites that live in macrophages, lymphocytes and red blood cells. Piroplasmosis is a human-animal infectious disease caused by piroplasms (Zhang and Li, 2010), with the main clinical symptoms being fever, anemia and swollen lymph nodes. Babesia is widely distributed around the world, and its onset often lacks typical symptoms, making it easy to misdiagnose or overlook. In recent years, the number of reported human cases has been increasing, with the United States, Canada and China having the most reported cases (Yang et al., 2021). The Babesia species that most often infect humans are B. microti, B. venatorum, B. duncani, and B. divergens (Ord and Lobo, 2015). Theileria species are mainly pathogenic to animals and cause serious losses in the livestock industry. Liu et al. (2010) detected Theileria sp. in the blood of a hospitalized patient in Suizhou City, Hubei Province (NCBI Accession: HQ844673.1). Although the paper has not yet been published, this finding suggests that Theileria sp. may be infectious to humans. Since there are relatively few studies on human Theileria infections in China, its study should not be neglected. At this time, none of the canine piroplasm species are zoonotic.

As living standards improve, pet ownership is becoming a normal part of life. Piroplasmosis in dogs and cats can be a chronic or subclinical infection, or it can be a severe acute disease in which the death of infected animals may occur (Irwin and Hutchinson, 1991). When piroplasmosis occurs a subclinical infection in dogs and cats, it is difficult to detect. It is often discovered due to clinical signs such as anemia, fever and lethargy. For example, 36 cases of B. gibsoni were seen in a veterinary hospital in Xi’an, and the signs and symptoms were mainly fever, yellow urine and decreased red blood cells and platelets (Feng et al., 2021). Blood transfusions can have an immediate effect, but they are expensive and there is often a shortage of blood available. Therefore, early identification of the pathogen facilitates the diagnosis and treatment of the disease, reducing the animal’s suffering as well as the medical burden.

However, there are no reports of piroplasmosis in dogs or cats in Guiyang, southwestern China. Therefore, this study aims to investigate the percentage of infections in pet cats and dogs in an animal hospital in Guiyang, and to provide a scientific basis for the prevention and control of piroplasms infections in pets in the region.

The percentage of positives of piroplasms infection in pet dogs in this study was 7.69% (11/143), which was higher than the prevalence of canine-origin piroplasm infections reported in Türkiye (0.13%, 2/757) (Aktas et al., 2015) and China’s Hunan Province (4.30%, 5/115) (Wang J. et al., 2020). This may be related to the different geographic locations where the samples were collected, the sensitivity of the diagnostic technique used, and the different clinical statuses of the dogs studied. To the best of our knowledge, this study is the first to report the detection of T. uilenbergi in the blood of pet dogs in China. The common hosts of T. uilenbergi are sheep and deer (Mans et al., 2015), and host infections may present with fever, diarrhea, respiratory distress and enlarged lymph nodes. However, there are no reports on the pathology and symptoms of T. uilenbergi in dogs, and the clinical significance of this is not known. The vectors of T. uilenbergi have been confirmed to be H. longicornis and H. qinghaiensis (Li et al., 2009), and Xiang et al. (2022) reported that H. longicornis is the dominant tick species in Guizhou, which increases the likelihood of a T. uilenbergi epidemic in the area. The main piroplasms reported to infect dogs in China and abroad are B. canis, B. vogeli, B. rossi, B. conradae, B. vulpes, and B. gibsoni of the genus Babesia (Irwin, 2010; He et al., 2017; Niu et al., 2017). Although Babesia was not detected in the pet dog samples in this study, Colpodella sp. (NCBI Accession: OR226258) was detected in one dog sample, and its pathogenicity requires further investigation. The sequence from the pet dog (NCBI Accession: OR226258) was in close proximity to Colpodella sp. (NCBI Accession: MH012043, OQ540589, MH208619, and OQ540590) detected in ticks (Figure 1). This result suggests that ticks that may carry Colpodella sp. and could be screened for possible Colpodella sp. at this site in the future. The Wudang District of Guiyang has many natural scenic spots, and there are a number of parks with dense vegetation and rich ecology distributed around this hospital. When pet owners walk their dogs in the park, their dogs may be bitten by ticks when brushing against vegetation and may be infected with pathogens carried by ticks during the biting process, posing a threat to the animals’ health.

The percentage of positives of blood piroplasms in pet cats in this study was 4.27% (7/164), which was lower than the 8.00% (2/25) infection rate reported in Hunan Province (Wang J. et al., 2020). In this study, the pet cat pathogens were more diverse, containing not only T. uilenbergi, but also T. luwenshuni, Colpodella sp. and two unknown species of gene sequences. Reports of piroplasm infections in domestic cats and wild felines include the species such as B. felis, B. cati, B. leo, B. hongkongensis, B. gibsoni, and Cytauxzoon sp. (Hartmann et al., 2013; Palmer et al., 2022; Yin et al., 2022), but there have been no reports on the detection of T. uilenbergi and T. luwenshuni in blood samples from pet cats. This may be related to the fact that piroplasm in cats is often an asymptomatic infection (Wong et al., 2012), resulting in a lack of research and underreporting. T. uilenbergi and T. luwenshuni are common Theileria in China and are the more pathogenic species (Hao, 2020). They are often found in mixed infections. Studies have reported that T. luwenshuni can infect a wide range of host animals, such as goats, sheep, deer and sheepdogs (Ge et al., 2012; Li et al., 2014; Gholami et al., 2016), and it is evident that it may have a wider distribution range. For example, Zhong et al. (2019) and Wang K. L. et al. (2020) investigated the infection of cattle and sheep with T. luwenshuni in Aba Prefecture, Sichuan Province and Linyou County, Shanxi Province and found that the infection rates were as high as 75.00 and 61.20%, respectively. The rare Colpodella sp., a tick-borne pathogen that has been detected in Qinghai Province (Hu et al., 2022), was also detected in the blood samples of pet cats. Colpodella sp. is also a zoonotic pathogen, with the first case of a Colpodella sp.-like pathogen infecting a human found in Kunming, Yuan et al. (2012). Colpodella sp. was also detected in horses from Jingxi and Napo, Guangxi (Xu et al., 2022; Zhou et al., 2022), as well as being recently detected in the blood of Amur tigers (Chiu et al., 2022). Cui (2013) also amplified Colpodella sp. sequences in the blood of febrile patients and in the cerebrospinal fluid of in-patients with neurological symptoms (Jiang et al., 2018). The cat sample Colpodella sp. sequence (NCBI Accession: OR226256) clustered with the reference strain ATCC50594 and was closer to the gene sequences of the currently published patients (NCBI Accession: MF594625), with a higher sequence identity (99.60%). The possibility of zoonotic disease transmission to humans in this region cannot be excluded. In this study, it should be noted that Colpodella is not a piroplasm. Colpodella is a sister group to an apicomplexan clade (Kuvardina et al., 2002). The initial aim of the study was to investigate blood carriage of piroplasms in cats and dogs with 18S rRNA amplification sequencing, but we inadvertently discovered Colpodella, which is a significant finding. Therefore, it is not unusual that Colpodella was amplified unintentionally with these common primers, which is similar to what has been observed in previous studies (Jiang et al., 2018; Xu et al., 2022). The Colpodella sp. pathogen and whether it can infect humans remains controversial and requires further confirmation. The taxonomic statuses of the gene sequences of two unknown species also need to be confirmed.

The PCR molecular biology technique used in this study addresses the morphological difficulty of distinguishing parasites in the blood when the quantity is low. It is able to accurately detect the presence of pathogens. However, there are some limitations to the study, which failed to collect basic information regarding the pet dogs and cats during the sample collection process and failed to analyze the epidemiological characteristics of the hosts in a comprehensive manner. According to the current detection results, the tick-borne pathogens Theileria and Colpodella sp. were found in the blood samples of dogs and cats. The data suggest that Theileria and Colpodella sp. were existent in dogs and cats in Guizhou. The Theileria and Colpodella sp. found in the study are different in their treatments. At the present stage, there is no highly efficient drug for the treatment of piroplasmosis caused by T. uilenbergi and T. luwenshuni, and the more commonly used drugs include Imidocarb, Diminazene Aceturate, Acriflavine, Atovaquone, Azithromycin, Clindamycin, Quinine, etc. (Hao, 2020). Colpodella has been reported in fewer cases in host animals and humans. The paucity of case reports makes it difficult to draw conclusions regarding treatment. For example, the patient reported by Yuan et al. showed some common features with Babesia cases and responded well to treatment with Atovaquone and Azithromycin (Yuan et al., 2012). The patient reported by Jiang et al. (2018) exhibited neurological symptoms and was treated with Doxycycline. Neculicioiu et al. (2021) found that a combination regimen of Ceftriaxone and Metronidazole was effective against urinary contamination due to Colpodella sp.

In conclusion, this study is the first report of pet dogs and cats infected with T. uilenbergi, T. luwenshuni, and Colpodella sp. in Guiyang, southwestern China, which provides scientific data for the diagnosis of the common piroplasmosis in pet dogs as we as decision-making in the management of animal health and public health.

The data presented in the study are deposited in the NCBI repository, accession numbers OR016205, OR016425, OR226256, OR226257, OR226255, OR016208, and OR226258.

The animal studies were approved by the Animal Care Welfare Committee of Guizhou Medical University. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent was obtained from the owners for the participation of their animals in this study.

SW: Conceptualization, Data curation, Formal analysis, Investigation, Validation, Visualization, Writing – original draft, Writing – review and editing, Project administration. JM: Investigation, Supervision, Writing – review and editing, Project administration. FY: Funding acquisition, Supervision, Writing – review and editing, Project administration. CZ: Supervision, Writing – review and editing, Project administration. BY: Supervision, Writing – review and editing, Project administration. XC: Supervision, Writing – review and editing, Project administration. GY: Supervision, Writing – review and editing. YS: Supervision, Writing – review and editing. WC: Supervision, Writing – review and editing. JJ: Project administration, Supervision, Writing – review and editing, Validation. JW: Funding acquisition, Project administration, Supervision, Writing – review and editing. LZ: Funding acquisition, Investigation, Project administration, Supervision, Writing – review and editing, Methodology.