Clinical Trial: The Clinical Epidemiology of Scrub Typhus in Humans, Chiggers and Rodents

Study Status: Not yet recruiting
Recruit Status: Not yet recruiting
Study Type: Observational

Official Title: The Clinical Epidemiology of Scrub Typhus in Humans, Chiggers and Rodents

Brief Summary: This study to collect and identify rodents and mites across transects through diverse habitats used by the human community from a localised area identified as a scrub typhus 'hot spot'.

Detailed Summary:

Study design:

The project will undertake a detailed investigation of one human community, and its environment, at risk of scrub typhus:

Chiggers, Rodents & Habitat Study:

Transects across diverse habitats determining spatial distribution of species of chiggers and rodents. This will be performed 3x/year.

High-resolution habitat mapping. Comparison of genomes of O. tsutsugamushi detected in different environments, using attempted WGS.

Village Cohort Study:

Follow a cohort of villagers over 2 years screening all febrile patients for scrub typhus and determining seroconversion rates and infecting O. tsutsugamushi genotypes.

Procedures:

  • Mites:

Working with ecology/GIS collaborators, the environment of the community will be mapped and transects laid across the diverse habitats used by the community. Free-living mites will be collected with black plastic plates and black cloth21, from soil using Berlese funnels and from rodents. Trombiculid mites will be identified to genus and a subset to species.

DNA will be extracted from individual chiggers, and qPCR screening for O. tsutsugamushi-positivity performed (real-time PCR targeting 47kDa-gene). A proportion of confirmed positives will undergo genotyping by attempted whole-genome sequencing (WGS).

  • Rodents:

Rode
Sponsor: University of Oxford

Current Primary Outcome:

  • determine the diversity of O. tsutsugamushi genotypes infecting rodents and mites and link these to their geographical distribution and associated habitat characteristics. [ Time Frame: up to 24 months ]
  • Correlate the frequency of O. tsutsugamushi in mites and rodents with habitat characteristics, to define interactions between distribution and transmission dynamics. [ Time Frame: up to 24 months ]
  • Identify key mite vectors and rodent hosts involved in scrub typhus natural history, human infection, and disease virulence [ Time Frame: up to 24 months ]


Original Primary Outcome: Same as current

Current Secondary Outcome:

  • Determine changes in scrub typhus antibody titres over time and identify acutely infected scrub typhus cases [ Time Frame: up to 24 months ]
  • Identify human-derived O. tsutsugamushi genotypes to define genomic relationships between human, rodent and mite-derived genotypes. [ Time Frame: up to 24 months ]
  • Identify putative determinants of human infection/virulence [ Time Frame: up to 24 months ]
  • To interlink the distribution of O. tsutsugamushi positive mites, rodents and humans with habitat characteristics to propose interventions to reduce the risk of human disease. [ Time Frame: up to 24 months ]


Original Secondary Outcome: Same as current

Information By: University of Oxford

Dates:
Date Received: August 18, 2016
Date Started: September 2016
Date Completion: December 2019
Last Updated: August 22, 2016
Last Verified: August 2016