Mammals in Chile are represented by nine orders and 150 species, with Rodentia being the order with the highest diversity, comprising 31 genera and 67 native species. This constitutes the highest specific diversity of mammals in Chile, accounting for 61.3% of species richness (1–4). The Cricetidae is the most diverse family of rodents in Chile with 39 species (2). Despite their vast diversity, recent studies of pathogens among rodents in Chile are predominantly focused on searching for gastrointestinal and ectoparasites (5–12), in addition to Trypanosoma cruzi (13), and “Candidatus Orientia chiloensis” infection (14, 15), with few studies on Borrelia (16, 17), Anaplasmataceae (18), and Piroplasmida (19).

Borrelia is a genus of spirochete bacteria, including both pathogenic and non-pathogenic species that affect a variety of hosts, primarily transmitted by ticks. Borrelia burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii are species that are known to cause Lyme disease in humans in the northern hemisphere; this disease is primarily transmitted by ticks of the genus Ixodes (20). Other Borrelia species are primarily associated with Ornithodoros spp. and are the agents of tick-borne relapsing fever in humans (21).

Anaplasmataceae is a family of obligate intracellular gram-negative alphaproteobacteria belonging to Rickettsiales. These bacteria can infect ticks and vertebrates, and multiply within host cells, typically in leukocytes or endothelial cells of the blood vessels (22, 23). Diseases caused by bacteria of the Anaplasmataceae family affect humans and animals, and their geographic distribution is often linked to arthropod vectors (22, 23). This family includes Anaplasma, Ehrlichia, Neorickettsia, “Candidatus Neoehrlichia,” and Wolbachia, among other genera (24).

The order Piroplasmida comprises a group of obligate intracellular parasitic protozoa belonging to the phylum Apicomplexa. Ticks transmit these organisms and affect mammals and birds (25, 26). A prominent genus within Piroplasmida is Babesia, which includes various species with distinctive characteristics. Babesia microti is a major cause of human babesiosis in regions such as the Nearctic, while Babesia divergens and Babesia bovis affect bovine livestock in Europe and the Neotropics, respectively (25, 26). Genetic variability and host-specific adaptations present challenges in understanding those diseases.

Rodents play a crucial role as reservoir hosts. At least 2,017 of the 2,777 rodent species described harbor 66 zoonotic agents (27, 28), and cricetid rodents exhibit a higher propensity to carry infectious agents with zoonotic potential (28). Thus, considering the need to understand the distribution of these tick-borne infectious agents (TBIAs) in cricetid rodents in Chile, the objective of this study was to assess the presence of Borrelia, Anaplasmataceae, and Piroplasmida in cricetid rodents in Central and Southern Chile.

A total of 207 rodents belonging to six species and four genera were captured (see Supplementary Table S2 for details). The most abundant species was Abrothrix olivacea, with 93 individuals, followed by Abrotrix hirta, with 77 individuals, and Oligoryzomys longicaudatus, with 31 individuals. The highest number of rodents were collected at Conguillio National Park and Sendero Bosque Piedra, with 47 rodents at each location (Supplementary Table S2). PCRs targeting the GAPDH gene produced amplicons of the expected size in all samples, confirming successful DNA extraction. All samples presented optimal DNA purity ratios (an A260/A280 DNA ratio within the 1.6–2.0 range). However, screenings for Borrelia, Anaplasmataceae, and Piroplasmida yielded negative results in all rodent samples while DNA in positive control was successfully detected.

Recognizing infectious agents in wildlife is crucial for understanding disease dynamics, which is essential for both preserving biodiversity and preventing disease transmission to humans and domestic animals (34). Hence, continuous surveillance of these rodent species is imperative for public and animal health, as well as for ecosystem management (35).

To the best of our knowledge, this study represents the first assessment of the presence of DNA from Borrelia and piroplasmids, and the second assessment of Anaplamataceae bacteria in cricetid rodents from Central and Southern Chile, with screenings yielding negative outcomes among all cricetid rodent samples. The absence of DNA from these TBIAs in the surveyed rodents may arise due to multiple factors, including potential compromises in DNA extraction quality (32), the non-presence of DNA from screened TBIAs, or the lack of suitable vectors in the sampled areas (36, 37). However, the first statement was dismissed since all samples showed optimal DNA purity ratios, conducive to effective PCR amplification (32). This, coupled with successful internal control amplification, validated the DNA extraction process (33).

The non-detection of DNA of TBIA in the samples examined in this work contrasts with prior findings in other Chilean regions, where the DNA of Borrelia, members of the Anaplasmataceae family, and the Piroplasmida order have been reported in various tick genera, including Ixodes (16, 19, 38–40), and Ornithodoros (38, 41–43), as well as in their associated hosts (17–19, 39, 44, 45).

Regarding cricetid rodents, surveys in northern Chile have detected Borrelia DNA in blood samples from Oligoryzomys longicaudatus and Phyllotis xanthopygus collected in Bosque Fray Jorge National Park and Socoroma, respectively (17). Additionally, Borrelia DNA was detected in Ixodes sigelos group ticks on Phyllotis darwini and Abrothrix longipillis in Bosque Fray Jorge National Park and Isla Mocha National Park (38), and in Ornithodoros sp. ticks feeding on P. darwini in Río Los Cipreses National Reserve (41). In southern Chile, Borrelia chilensis DNA was found in Ixodes stilesi from O. longicaudatus in Valdivia (16). Collectively, these findings point to the prevalence of three genotypes and a unique genospecies, B. chilensis, within the Lyme Borrelia group, in addition to three genotypes from the Relapsing fever Borrelia group, thereby underscoring the Borrelia diversity associated with these rodents and their potential role as a reservoir host for the Borrelia species (16, 17).

Conversely, the detection of Anaplasmataceae DNA in cricetid rodents is limited, with records primarily involving “Candidatus Neoehrlichia chilensis” found in the tissue of Abrothrix rodents captured in the Corral commune in Valdivia (18), and in I. sigelos ticks from P. darwini in Bosque Fray Jorge National Park (38). Notably, DNA of “Ca. N. chilensis” has been predominantly detected in Ixodes ticks (46) and their associated hosts (18, 47). This suggests that “Ca. N. chilensis” could be transmitted by widespread Ixodes species among cricetid rodent populations in Chile. Thus, the involvement of Abrothrix rodents and I. sigelos in the epidemiology of “Ca N. chilensis” is highlighted (18, 38).

In 2022, the Piroplasmida order was associated with cricetid rodents in Chile for the first time (19); the DNA of Babesia was detected in the blood samples of Abrothrix jelskii collected in Parinatoca and P. darwini in Llanos de Challe National Park. Interestingly, despite being collected ~1,122 Km apart, two samples each from A. jelskii and P. darwini shared the same Babesia haplotype. This finding suggests a ubiquitous vector for this genotype, which is part of a novel Babesia group associated with South American small mammals (19, 48, 49). Additionally, a distinct Babesia genotype found in P. darwini from Llanos de Challe National Park aligns with the Babesia microti group, underscoring the emerging diversity of Babesia in Chilean cricetid rodents (45).

In addition to rodents, records of the evaluated TBIAs in wildlife in Chile include the detection of A. platys DNA in fox species Lycalopex culpaeus and Lycalopex griseus in central and northern Chile (44). Notably, A. platys primarily associates with ticks from the Rhipicephalus sanguineus group, which are common on canids (50). Other reports include DNA detections of Babesia sp. “Pudui” and the Anaplasma phagocytophilum “Patagonia” variant in both mainland and insular populations of the cervid Pudu puda, and in I. stilesi ticks that infest them in southern Chile (39, 45). Although I. stilesi commonly parasitizes the rodent O. longicaudatus (51) and is considered a potential vector of these infectious agents, the Babesia sp. “Pudui” and A. phagocytophilum “Patagonia” variant seem to have specific vertebrate host preferences (52, 53), primarily for P. puda in Chile (39, 45). This host specificity might account for our inability to detect the DNA of these TBIAs in O. longicaudatus samples.

The lack of TBIA DNA in our samples raises important hypotheses regarding the dynamics of these agents in the studied rodent populations: Is there an undetected low prevalence of the evaluated TBIAs in the sampled areas, or are these TBIAs absent in the surveyed rodent populations? Unpublished data from our sampling indicate a very low prevalence of ticks, a fact that supports the first hypothesis, given that the presence of the vector would imply the circulation of the TBIAs. Further studies focusing on the temporal and spatial variability of TBIAs in Chilean cricetid rodents, the frequency of these TBIAs in vectors, and the factors affecting the presence of these infectious agents in rodents will be insightful in answering these questions.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

The animal study was approved by the Bioethics Committee of the School of Veterinary Sciences, Universidad de Concepción: CBE 47–2017; CBE-51-2019. The study was conducted in accordance with the local legislation and institutional requirements.

MA: Conceptualization, Writing – original draft, Writing – review & editing. RT: Investigation, Methodology, Writing – review & editing. AS: Conceptualization, Methodology, Writing – review & editing. MS-dF: Methodology, Writing – review & editing. SM-L: Funding acquisition, Methodology, Writing – review & editing. CL-A: Conceptualization, Funding acquisition, Methodology, Writing – review & editing. AH: Conceptualization, Methodology, Writing – review & editing.