Molecular Survey ofBabesia microti, EhrlichiaSpecies andCandidatusNeoehrlichia mikurensis in Wild Rodents from Shimane Prefecture, Japan

Abstract

A significant number of patients are diagnosed with “fevers of unknown origin” (FUO) in Shimane Prefecture in Japan where tick‐borne diseases are endemic. We conducted molecular surveys for Babesia microti, Ehrlichia species, and Candidatus Neoehrlichia mikurensis in 62 FUO cases and 62 wild rodents from Shimane Prefecture, Japan. PCR using primers specific for the Babesia 18S small‐subunit rRNA (rDNA) gene and Anaplasmataceae groESL amplified products from 45% (28/62) and 25.8% (16/62) of captured mice, respectively. Of the 28 18S rDNA PCR positives, 23 and five samples were positive for Hobetsu‐ and Kobe‐type B. microti, respectively. In contrast, of the 16 groESL PCR positives, eight, one and seven samples were positive for Ehrlichia muris, Ehrlichia sp. HF565 and Candidatus N. mikurensis, respectively. Inoculation of selected blood samples into Golden Syrian hamsters indicated the presence of Hobetsu‐ and Kobe‐type B. microti in four and one sample, respectively. Isolation of the latter strain was considered important as previous studies suggested that the distribution of this type was so far confined to Awaji Island in Hyogo Prefecture, where the first case of transfusion‐associated human babesiosis originated. DNA samples from 62 FUO human cases tested negative for B. microti 18S rDNA gene, Anaplasmataceae groESL gene, Rickettsia japonica 17K genus‐common antigen gene and Orientia tsutsugamushi 56K antigen gene by PCRs. We also conducted seroepidemiological surveys on 62 human sera collected in Shimane Prefecture from the FUO patients who were suspected of carrying tick‐borne diseases. However, indirect immunofluorescent antibody tests using B. microti‐ and E. muris‐infected cells detected IgG against E. muris in only a single positive sample. This study demonstrates the presence of several potentially important tick‐borne pathogens in Shimane Prefecture and suggests the need for further study on the causative agents of FUOs.

Detection of Two Zoonotic Babesia microti Lineages, the Hobetsu and U.S. Lineages, in Two Sympatric Tick Species, Ixodes ovatus and Ixodes persulcatus, Respectively, in Japan

“…Kobe lineage occurs in wild rodents in a few narrowly defined focal areas in Japan (26,31,34). Three tick species, I. ovatus, H. flava, and I. turdus, were collected (Table 1) at Sumoto on Awaji Island, where two lineages, Kobe and Hobetsu, are reported to coexist in Apodemus mice at an equal incidence (29%) (31,34).…”

“…Other taxa, such as the Munich taxon in Europe and B. microti in Alaskan voles, are believed to be maintained only in wild animals. All of these lineages are found naturally parasitizing a variety of wild mammalian species in the rodent subfamilies of the Murinae, Arvicolinae, and Sigmodontinae and, occasionally, in the Soricidae shrew (9,11,12,26,30,32,34,37,38).…”

“…In these regions either of the two taxa overlaps in geographic distribution with the U.S. taxon by adaptation to the same or similar reservoir hosts (2,37). The Kobe lineage, also found in Apodemus and Ruttus spp., occurs only locally in a few narrowly defined areas such as Mikura Island in the Izu-Ogasawara (Izu-Bonin) Trench, Awaji Island near Osaka, and Daito-town on the western tip of the main island of Japan (26,34), where the Hobetsu parasites have been shown to coexist in similar reservoir hosts. (On Mikura Island, the Kobe parasite was detected by chance from a wild rat despite the fact that local surveillance data have not been reported.…”

A Molecular and Serological Survey of <i>Rickettsiales</i> Bacteria in Wild Sika Deer (<i>Cervus nippon nippon</i>) in Shizuoka Prefecture, Japan: High Prevalence of <i>Anaplasma</i> Species

“…Recently, Anaplasma phagocytophilum infection and coinfection with Rickettsia japonica in humans have been confirmed in central to western parts of Japan (3,4), where infected ticks were present (5). In the past decade, tick-associated Rickettsiales bacteria have also been identified in wild mammals, including deer, boar, Japanese serows, field mice, and wild rats in Japan (2,(6)(7)(8)(9)(10)(11)(12)(13)(14). In particular, wild deer are thought to be one of the most likely reservoirs and/or wide-spreading hosts for tick-associated Rickettsiales bacteria.…”

<i>Ehrlichia canis</i> Infection in Two Dogs that Emigrated from Endemic Areas

“…DNA was purified from each sample using DNeasy Blood & Tissue Kit (QIAGEN, Valencia, CA, U.S.A.), according to the manufacturer's instructions. Nested PCR for detecting the partial 16S ribosomal RNA (rRNA) gene of E. canis and groEL gene of anaplasmataceae bacterium were performed as described previously, except for modifying the annealing temperature from 60 to 63°C for the amplification of 16S rRNA gene [10,11]. The PCR products were electrophoresed on 1.5% agarose gels.…”