Affiliation:
1. Management Department of Biosafety, Laboratory Animal and Pathogen Bank, National Institute of Infectious Diseases, Tokyo, Japan
2. Rishiri Town Museum, Hokkaido, Japan
3. Department of Pathology, National Institute of Infectious Diseases, Tokyo, Japan
4. Asahikawa Medical College, Hokkaido, Japan
5. Department of Veterinary Medicine, Okayama University of Science, Okayama, Japan
Abstract
ABSTRACT
Rishiri Island, towering toward the Sea of Japan, has been volcanically dormant for approximately 8,000 years. This small inhabited island is free of middle- to large-sized wildlife and a crucial stopover for wild birds migrating along various routes of the East Asian Flyway. A 5-year survey was conducted to explore the biogeography of ticks and tick-borne microorganisms. By flagging vegetation,
Ixodes pavlovskyi
(Pomerantzev, 1948), distributed in limited spots in the Far East, was predominantly collected (60%–80% collection) throughout the survey period. The
I. pavlovskyi
consisted of two haplogroups, Asahikawa-type and Rishiri-type, with the prevalence and nucleotide diversity of Rishiri-type being over 90% and 0.068, respectively. A survey of wild animals revealed that red-backed voles and wild birds, including Oriental greenfinches and black-faced buntings, are their hosts for blood feeding. Furthermore, the red-backed voles were infected with tick-borne
Candidatus
Ehrlichia khabarensis (5/21, 24%). Till date, microorganisms with identical gene sequences have only been reported from Khabarovsk and Vancouver.
Ca
. E. khabarensis gene has also been detected in host-seeking adult
I. pavlovskyi
. These results indicated that Rishiri Island is a refuge for both
I. pavlovskyi and I. pavlovskyi
–borne microorganisms. Additionally, the
Babesia microti
US lineage, which is vectored by
Ixodes persulcatus
in the Far East, appears to be maintained between
I. pavlovskyi
and wild rodents. Various factors have influenced the unique ecosystem of the island. The historical and ecological biogeography of Rishiri Island helps us understand the origin, evolution, and expansion of ticks and associated microorganisms.
IMPORTANCE
Understanding the ecology of ticks and tick-borne microorganisms is important to assess the risk of emerging tick-borne diseases. Despite the fact that the
Ixodes pavlovskyi
tick bites humans, we lack information including population genetics and the reason for the inadequate distribution in Japan. A 5-year survey revealed that Rishiri Island, the main stopover in the East Asian Flyway of wild birds in the northern Sea of Japan, was a refuge of
I. pavlovskyi
. The
I. pavlovskyi
included two haplogroups, which were supposed to diverge a long time before the island separated from the continent and Hokkaido mainland. The detection of microorganisms from wildlife revealed that wild birds and rodents play a role in diffusion and settlement, respectively, of not only
I. pavlovskyi
but also
I. pavlovskyi
–borne microorganisms including
Candidatus
Ehrlichia khabarensis and
Babesia microti
US lineage. Various island-specific factors control
I. pavlovskyi
dominance and tick-borne pathogen maintenance. The results may enable us to explain how tick-borne infectious microorganisms are transported.
Funder
Osimo Foundation
Japan Agency for Medical Research and Development
MEXT | Japan Society for the Promotion of Science
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology