Scrub Typhus in Northern Thailand: Exploring Preventative and Diagnostic Challenges in the Field

Scrub typhus is a highly neglected tropical disease caused by the obligate intracellular bacterium Orientia tsutsugamushi. It is estimated to cause hundreds of thousands of infections yearly. Lack of awareness and of reliable field-deployable tests, however, leads to delays in specific treatment and to severe outcomes. My thesis will focus on promoting prevention and awareness as well as improving diagnostic strategies. I will start by reviewing vector ecology and risk factors, followed by original findings on antibody prevalence and its relationship with environmental exposure and preventative behaviour. This will introduce the community engagement chapter, in which I will present our experience in successfully raising knowledge and awareness of scrub typhus using a community engagement approach. The second section will begin with a comprehensive summary of scrub typhus diagnostics followed by a systematic review on the relative performance of PCR and serology for acute diagnosis. Original findings from the “Scrub Typhus Antibiotic Resistance Trial” up to early 2025 will then be presented, highlighting the limitations of immunochromatographic tests and the superiority of nucleic acid detection for acute identification in endemic settings. To overcome the limitations of current tests, I designed the “Quick and Easy Scrub Typhus diagnostics” study, which compares single-gene target primers to newly developed ones targeting repeated parts of the O. tsutsugamushi genome. The latter were tested on real-time PCR and on a highly automated insulated isothermal PCR machine, better suited for small hospitals. In the first year of recruitment the newly developed primers detected 38% more cases than the traditional ones. The potential for simple anamnestic and clinical information to direct diagnostic choices will also be discussed. In the final chapter, I will summarise the salient findings, discuss their relevance and limitations, and suggest potential future developments.