Survey of Babesia microti Infection in Field Rodents in Japan: Records of the Kobe‐Type in New Foci and Findings of a New Type Related to the Otsu‐Type

Abstract

Of 247 rodents comprising 5 genera and 7 species collected at 17 sites throughout Japan from 2003 to 2005, Babesia microti was detected microscopically and by polymerase chain reaction (PCR) in 36 rodents comprising 2 genera and 3 species from 12 sites. Based on the analysis of small subunit ribosomal RNA gene (SSUrDNA) sequences, the Kobe‐type, the etiological type of the first Japanese case of human infection was found in Apodemus speciosus and Apodemus argenteus in Aomori, the northernmost prefecture of the Japanese mainland, while the U.S.‐type was found on Hokkaido Island and the Otsu‐type was widely distributed. In addition, a new Otsu‐related type was detected exclusively in Eothenomys andersoni in Nagano, a prefecture in central Japan. The sequences of internal transcribed spacer 1 to 2 (ITS1/2) of the present Kobe‐ and Otsu‐types were almost identical to those of the same types previously identified. The ITS1/2 sequence of the U.S.‐type identified in Hokkaido in this survey was somewhat different from that of the U.S.‐type strain originating from the U.S.A., with approximately 95% identity. This value was similar to the 94% identity found between the ITS1/2 sequences of the Otsu‐type and the new Otsu‐related type. The new Otsu‐related type of B. microti was isolated as the Nagano strain, which was serologically differentiated from the other type strains of B. microti. The divergence and distribution of genotypes are important factors in investigating the epidemiology of human B. microti infection in Japan.

Detection of Kobe-typeBabesia microtiassociated with Japanese human babesiosis in field rodents in central Taiwan and southeastern mainland China

“…In Japan, we have recently found 2 new foci of Kobe-type B. microti in Aomori, the northernmost prefecture on the Mainland of Japan (Honshu Island), significantly distant from Awaji Island (Saito-Ito et al 2007). Thus, the Kobe-type seems to be distributed dispersively in some restricted areas in Japan.…”

“…We also determined the more variable ITS1/2 sequences that were amplified with a primer set of RIB13-RIB3 based on the 3′ portion of the SSUrDNA of Babesia spp. and the 5′-portion of the large subunit ribosomal RNA gene conserved among a variety of eukaryotes, respectively (Zahler et al 1998), as described elsewhere (Saito-Ito et al 2007). To avoid errors caused by the contamination of PCR products, original DNA was extracted, divided into several aliquots and used only in a safety cabinet placed in a room where PCR products had never been treated.…”

“…The Otsu strain (Otsu-type) was provided by Dr T. Shiota of Kyoto Prefectural University of Medicine. The Hachimaki strain (Otsu-type with the ITS1/2 sequence differing by only 1 nucleotide from that of the Otsu strain) had been established in a Syrian hamster by inoculating A. speciosus rodent blood infected with B. microti (AsRK/HM109) from the Rokko Mountains, Hyogo Prefecture (Saito-Ito et al 2004, 2007). The GI strain (US-type) originating from a patient on Nantucket Island in the northeastern US (Piesman et al 1986) was provided by Dr T. N. Mather of the Center for Vector-Borne Disease of the University of Rhode Island.…”

Reservoir Competence of Wildlife Host Species forBabesia microti

“…White-footed mice ( Peromyscus leucopus ) and meadow voles ( Microtus pennsylvanicus ) have been established as reservoir hosts on the basis of seroprevalence ( 16 , 17 ), and P. leucopus mice are known to transmit the pathogen to ticks ( 18 ). Other rodent species, including species in other genera of mice ( Apodemus and Sicista ) and voles ( Eothenomys, Lagurus, and Myodes ) are known hosts in Europe ( 19 – 21 ) and Asia ( 22 – 24 ). B. microti or B. microti –like infection has been observed in other common eastern US mammal species, such as short-tailed shrews ( Blarina brevicauda ) ( 25 ), eastern cottontail rabbits (Sylvilagus floridanus ) ( 17 ), eastern chipmunks ( Tamias striatus ) ( 17 ), raccoons ( Procyon lotor ) ( 26 ) and foxes ( 27 ), and congeneric species in other regions or countries, including Sciurus spp.…”

Case report of the patient source of the Babesia microti R1 reference strain and implications for travelers

“…1,51 Coinfection in tick-borne disease complicates both diagnosis and therapy Ixodid ticks transmit an array of pathogens including A. phagocytophilum, B. microti, B. burgdorferi, Borrelia miyamotoi, Borrelia mayonii, Ehrlichia muris-like agent, and Powassan virus. [54][55][56][57] A single tick can carry more than one agent. Accordingly, several reports have shown evidence of coinfection in reservoir hosts and humans.…”