ABSTRACT
Wild deer are one of the important natural reservoir hosts of several species of
Ehrlichia
and
Anaplasma
that cause human ehrlichiosis or anaplasmosis in the United States and Europe. The primary aim of the present study was to determine whether and what species of
Ehrlichia
and
Anaplasma
naturally infect deer in Japan. Blood samples obtained from wild deer on two major Japanese islands, Hokkaido and Honshu, were tested for the presence of
Ehrlichia
and
Anaplasma
by PCR assays and sequencing of the 16S rRNA genes, major outer membrane protein
p44
genes, and
groESL
. DNA representing four species and two genera of
Ehrlichia
and
Anaplasma
was identified in 33 of 126 wild deer (26%). DNA sequence analysis revealed novel strains of
Anaplasma phagocytophilum
, a novel
Ehrlichia
sp.,
Anaplasma centrale
, and
Anaplasma bovis
in the blood samples from deer. None of these have been found previously in deer. The new
Ehrlichia
sp.,
A. bovis
, and
A. centrale
were also detected in
Hemaphysalis longicornis
ticks from Honshu Island. These results suggest that enzootic cycles of
Ehrlichia
and
Anaplasma
species distinct from those found in the United States or Europe have been established in wild deer and ticks in Japan.
A novel bacterium that infects laboratory rats was isolated from wild Rattus norvegicus rats in Japan. Transmission electron microscopy of the spleen tissue revealed small cocci surrounded by an inner membrane and a thin, rippled outer membrane in a membrane-bound inclusion within the cytoplasm of endothelial cells. Phylogenetic analysis of the 16S rRNA gene sequence of the bacterium found in R. norvegicus rats and Ixodes ovatus ticks in Japan revealed that the organism represents a novel clade in the family Anaplasmataceae, which includes the Schotti variant found in Ixodes ricinus ticks in the Netherlands and the Ehrlichia-like Rattus strain found in R. norvegicus rats from China. The novel clade was confirmed by phylogenetic analysis of groESL sequences found in R. norvegicus rats and Ixodes ovatus ticks in Japan. No serological cross-reactivity was detected between this bacterium and members of the genera Anaplasma, Ehrlichia or Neorickettsia in the family Anaplasmataceae. It is proposed that this new cluster of bacteria should be designated ‘Candidatus Neoehrlichia mikurensis’.