Detection of Tick-Borne Microorganisms, Anaplasmataceae and Piroplasmida, in Sorex spp. in Hokkaido, Japan

The habitats of shrews substantially overlap with those of rodents, which are well known as reservoirs for many tick-borne diseases. However, the ecological role of shrews (Mammalia: Eulipotyphla: Soricidae) remains poorly understood. We examined 103 Sorex spp. (S. unguiculatus, S. gracillimus, S. caecutiens) from Kushiro, Hokkaido, Japan, to investigate their relationships with ticks and tick-borne microorganisms, including Piroplasmida and Anaplasmataceae. Pathogen screening revealed Babesia microti Hobetsu lineage (9.7%), Neoehrlichia mikurensis (26.2%), Ehrlichia japonica (13.6%), and E. muris (0.97%). These intracellular protozoa and bacteria, typically associated with rodents, are recognized zoonotic agents or have zoonotic potential. Detection rates were highest in S. caecutiens (62.5%, 10/16), followed by S. unguiculatus (45.3%, 24/53) and S. gracillimus (23.5%, 8/34). Co-infections were observed between N. mikurensis and B. microti (n = 3) and between N. mikurensis and E. japonica (n = 4). Immature stages of Ixodes ovatus and I. persulcatus were collected from the body surface of shrews, and transstadial transmission of N. mikurensis was suggested by its detection in a molted I. ovatus nymph. These results indicate that shrews act as feeding hosts for immature ticks and reservoirs for multiple tick-borne pathogens. Shrews should be considered important reservoirs for tick-borne diseases.