A recent study involving over 32,000 people in Tamil Nadu in India has flagged that scrub typhus may affect up to 10 per cent of rural populations each year and is a leading yet often overlooked cause of hospitalisations due to fever across the country.
The research, published in the New England Journal of Medicine, was a collaboration between the London School of Hygiene & Tropical Medicine (LSHTM) and Christian Medical College Vellore, India.
Scrub typhus is a potentially deadly infection caused by the bacterium Orientia tsutsugamushi, part of the rickettsia family. It spreads through the bite of infected chiggers (larval mites), which are commonly found on grass, plant litter, and bare soil in rural parts of Asia. Chiggers usually feed on small mammals like rats and shrews.
Symptoms of scrub typhus include fever, headaches, body aches, and a rash, which typically appear about 10 days after infection. A characteristic blackening of the tissue around the bite can also help doctors diagnose the condition.
If untreated, scrub typhus can lead to severe complications such as acute respiratory distress syndrome (ARDS), shock, meningitis, and kidney failure, which can be fatal. Treatment with antibiotics like doxycycline or azithromycin is effective, but there is currently no vaccine to prevent the infection.
The study was conducted in 37 rural villages in Tamil Nadu, where scrub typhus is known to be common. Between August 2020 and July 2022, the team visited households regularly to collect blood samples and record symptoms of illness. Blood samples from individuals with fever were tested for scrub typhus.
The findings revealed a high rate of infection, with almost 10% of the population affected annually. While most cases were asymptomatic, 8% to 15% of those infected developed fever, often leading to hospitalisation due to the severity of the infection. Five deaths occurred during the study as a result of scrub typhus complications.
The researchers noted that underreporting of fever was a significant limitation of the study, suggesting that the actual number of scrub typhus cases may have been higher. Additionally, the study was conducted during the COVID-19 pandemic when quarantine measures were in place.
Wolf-Peter Schmidt, the principal investigator of the study and Clinical Assistant Professor at LSHTM, asserted that scrub typhus is a major concern in India, particularly during the August to February period when infections are most common. He pointed out that while five deaths occurred due to scrub typhus, no deaths from malaria, dengue, or typhoid fever, typically thought to be the leading causes of severe fever in India, were recorded in the study.
Carol Devamani, lead author of the study and MD in Community Medicine at Christian Medical College Vellore, highlighted that scrub typhus accounted for nearly 30% of fever-related hospitalisations in their study after COVID-19. Despite being common and treatable, scrub typhus is often overlooked when diagnosing fever, especially in rural areas where diagnostic tests may not be readily available. She stressed the need for better community awareness and improved diagnostic capabilities to reduce unnecessary hospitalisations and prevent fatalities.
“Despite cases being very common and treatable, scrub typhus is often overlooked as a possible cause when patients present with a fever. Diagnostic tests are available at major hospitals but not in the community.
“Our study highlights a need to inform communities about the possible dangers of scrub typhus infection, and to improve diagnostic capabilities in the community for timely treatment. Only by doing so will we reduce the number of unnecessary hospitalisations and fatal cases.” The study was funded by the UK Medical Research Council.
