Investigation of Behavioral Changes Due to the Presence or Absence of Rickettsia in Ticks and Research on Appropriate Utilization of Minocycline

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K17769
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 53050:Dermatology-related
• Research Institution: Mie University
• Principal Investigator: Kondo Makoto 三重大学, 医学部附属病院, 講師 (40464169)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: Japanese spotted fever / Rickettsia / tick / epidemiology

Outline of Final Research Achievements

This study focused on the prevention and epidemiological investigation of Japanese spotted fever (JSF). A total of 500 ticks were collected using flagging methods in both JSF-endemic and non-endemic areas of Mie Prefecture, Japan. Among the collected ticks, 329 specimens were identified using sequencing, and PCR was conducted to detect the presence of Rickettsia within the ticks. A higher number of Haemaphysalis longicornis were captured in JSF-endemic regions, while a variety of tick species, with a slight predominance of Haemaphysalis flava, were found in non-endemic regions. The detection rate of Rickettsia within ticks was higher in JSF-endemic areas. The behavioral patterns of ticks were observed in relation to weather conditions, temperature, and humidity. No significant difference was observed in the detection rates of Rickettsia between ticks treated with minocycline and untreated wild ticks.

Free Research Field

Dermatology

Academic Significance and Societal Importance of the Research Achievements

三重県内でのマダニの分布はまだはっきりとわかっておらず少数マダニの検索ではあるが、日本紅斑熱の流行地域はフタトゲチマダニが多く捕獲された。また非流行地では捕獲されたマダニ種は多種に富んでいたかキチマダニがやや多く捕獲された。日本紅斑熱流行地に生息するマダニの方がリケッチア検出率は高く、また２種のプライマーともPCR産物が増幅されることが多かった。非流行地においても６割程度のリケッチアが検出された。日本紅斑熱流行地域のマダニ種の分布状況やリケッチアの保有状況が判明し疫学的に貢献できたと考える。