Updated distribution of anopheline mosquitoes in Hokkaido, Japan, and the first evidence of Anopheles belenrae in Japan

Kyoko Sawabe,Kenji Takai,Yukiko Higa,Mutsuo Kobayashi,Nozomi Imanishi-Kobayashi,Kyeong Soon Kim,Keita Hoshino,Toshihiko Hayashi,Naoko Nihei,Yoshio Tsuda,Yoshihide Maekawa,Takeshi Kurihara

doi:10.1186/s13071-021-04995-w

Abstract

BackgroundIn Hokkaido, northern island of Japan, at least seven cases of falciparum malaria were reported by 1951. A survey conducted at that time was unsuccessful in implicating any mosquito species as the possible vector. Although active anopheline mosquito surveillance continued until the middle of the 1980s, there is very limited information on their current status and distribution in Japan. Therefore, this study is an update on the current status and distribution of anopheline mosquitoes in Hokkaido based on a 15-year entomological surveillance between 2001 and 2015.MethodsA survey of mosquitoes was conducted at 22 sites in Hokkaido, Japan, from 2001 to 2015. Adult mosquitoes were collected from cowsheds, lakesides, shrubs, and habitats ranging from open grassland to coniferous forest using a Centers for Disease Control and Prevention (CDC) miniature light trap enhanced with dry ice, aspirators, and sweeping nets. Larvae were collected from lakes, ponds, swamps, stagnant and flowing rivers, and paddy fields. All specimens were morphologically identified and subjected to polymerase chain reaction (PCR)-based sequence analysis of the internal transcribed spacer 2 ( ITS2) region of rDNA. Phylogenetic trees were reconstructed using the neighbor-joining method with the Kimura 2-parameter model on MEGA X version 10.2.2.ResultsA total of 46 anopheline specimens were used for the phylogenetic analysis. During the survey, a new member of the Anopheles hyrcanus group, An. belenrae, was discovered in eastern Hokkaido in 2004. Anopheles belenrae has since then been consistently found and confirmed to inhabit only this area of Japan. Four members of the An. hyrcanus group, namely An. belenrae, An. engarensis, An. lesteri, and An. sineroides, have been found in Hokkaido. The results also suggest that An. sinensis, formerly a dominant species throughout Japan, has become a rarely found species, at least currently in Hokkaido.ConclusionThe updated distribution of anopheline mosquitoes in Hokkaido, Japan, showed considerable differences from that observed in previous surveys conducted from 1969 to 1984. In particular, areas where An. sinensis was previously distributed may have been greatly reduced in Hokkaido. The phylogenetic analysis revealed a novel An. hyrcanus group member identified as An. belenrae, described in South Korea in 2005. It is interesting that An. belenrae was confirmed to inhabit only eastern Hokkaido, Japan.Graphical abstract

Highlights

In Hokkaido, northern island of Japan, at least seven cases of falciparum malaria were reported by 1951
The collected specimens were classified into four anopheline species of the An. hyrcanus group: An. belenrae, An. engarensis, An. lesteri, and An. sineroides (Table 1)
internal transcribed spacer 2 (ITS2) sequence divergence revealed the current distribution of the An. hyrcanus group mosquitoes in Hokkaido, demonstrating great differences from surveys conducted between 1969 and 1984

Summary

Introduction

In Hokkaido, northern island of Japan, at least seven cases of falciparum malaria were reported by 1951. Previous surveys conducted in Japan from 1970 to 1986 revealed that An. sinensis was the dominant anopheline species in Japan, including Hokkaido; An. lesteri was commonly found in Hokkaido, with only a few An. sineroides [3,4,5,6]. These surveys found a new member of this group, An. engarensis [3,4,5]. Several DNA barcoding projects have been conducted on mosquitoes in Japan, and a small number of genomic data on anopheline mosquitoes were included [7,8,9] These studies were not specific to malaria vector mosquitoes

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