Molecular-phylogenetic analyses of Babesia and Theileria species from small mammals and their ticks in northern China suggest new reservoirs of bovine and equine piroplasms.

Molecular analyses of Babesia and Theileria species in small mammals and their ticks in northern China reveal new potential reservoir hosts for piroplasms that typically infect cattle and horses.

Background and Objective

• Babesia and Theileria species are tick-borne protozoan parasites causing infections in humans, wildlife, livestock, and companion animals.
• Previous molecular studies on these parasites in wild small mammals and their ticks are limited, especially in Asia.
• The study aimed to extensively survey small mammals and their ticks in northern China for the presence of various Babesia and Theileria species to better understand their diversity and potential reservoir hosts.

Sample Collection and Screening

• A total of 907 liver samples and 145 ixodid ticks were collected from 16 species of small mammals belonging to orders Rodentia, Lagomorpha, and Eulipotyphla.
• Samples were gathered from 13 different cities and counties across northern China.
• DNA was extracted from these samples and initially screened for the piroplasm 18S rRNA gene, a common genetic marker used in identifying Babesia and Theileria.
• Samples testing positive for 18S rRNA were further analyzed for other genetic markers: the mitochondrial cox1 gene and the ITS1-5.8S rDNA-ITS2 region, offering finer phylogenetic resolution.

Findings: Identification of Piroplasm Species

• Various piroplasm species were identified, including:
  • Babesia sp. tavsan2
  • Babesia occultans
  • Theileria sp. Xinjiang
  • Theileria equi
  • Theileria sp. Kalecik
• Theileria sp. Xinjiang was the most prevalent species found across samples.
• Babesia sp. tavsan2 was detected in the tick Rhipicephalus sanguineus collected from the Yarkand hare, matching pathogen DNA found in the hares themselves.
• Theileria sp. Kalecik was found in the tick Hyalomma asiaticum from the long-eared hedgehog, also corresponding with pathogen presence in the hedgehog.

Significance: Discovery of New Reservoirs and Geographical Records

• DNA of typically livestock-associated piroplasms, Babesia occultans (usually in cattle) and Theileria equi (usually in horses), was found in small mammals—suggesting these mammals may act as previously unrecognized reservoirs.
• Theileria sp. Kalecik and Babesia sp. tavsan2 were reported for the first time in China, marking new geographical records for these species.
• This indicates an expansion in known host and geographic ranges and underscores the importance of small mammals in the ecology and epidemiology of these parasites.

Implications and Conclusions

• The presence of Babesia and Theileria DNA in both small mammals and their ticks highlights complex host-vector-pathogen interactions that could influence disease emergence and transmission.
• Small mammals may serve as important reservoirs contributing to the maintenance and spread of piroplasms that impact livestock health.
• This knowledge can inform disease control strategies and tick-borne parasite surveillance efforts in northern China and possibly other regions.
• The study expands the molecular and phylogenetic understanding of piroplasm diversity in wildlife hosts and their ectoparasites in Asia.