Published Feb 24, 2026 | 9:00 AM ⚊ Updated Feb 24, 2026 | 9:00 AM
Scrub typhus test. (iStock)
Synopsis: A recent study suggested that scrub typhus is becoming more common in villages than in surrounding agricultural fields. The findings challenge long-held assumptions about who is most at risk and where transmission is likely to happen. In simple terms, bacteria may be circulating more intensively around homes than in farmland.
For years, scrub typhus, a bacterial infection spread to humans through the bite of infected larval mites, commonly called chiggers, has been seen as a disease of the fields — something farmers pick up while working in crops after the monsoon.
However, new research from Tamil Nadu suggests the infection may be much closer to home.
A study published in the February 2026 issue of Emerging Infectious Diseases found that infected chigger mites were more common in villages than in surrounding agricultural fields.
The findings challenge long-held assumptions about who is most at risk and where transmission is likely to happen.
The researchers noted that “chigger numbers found on small mammals and the prevalence of O tsutsugamushi infection in chiggers were higher within human settlements than in the land surrounding them.”
In simple terms, bacteria may be circulating more intensively around homes than in farmland.
The research was conducted in 25 villages in Vellore and Ranipet districts of Tamil Nadu between August 2022 and September 2023. Scientists trapped 883 small mammals and collected over 90,000 chigger mites for analysis.
One species, Leptotrombidium imphalum, stood out. It was the most common mite and the only one clearly associated with infection by Orientia tsutsugamushi, the bacterium that causes scrub typhus.
The overall prevalence of infection in these mites was 3.6 percent, but it was more than twice as high in village centres and edges compared to fields.
The study concluded that its findings “corroborate studies in South India suggesting human settlements as the setting in which most infestation with chigger mites infected with O. tsutsugamushi occurs.”
In other words, the peridomestic environment — areas around the home — may be a key risk zone.
Researchers also used a measure called the “chigger index,” which means the average number of mites per animal. They found that this index was far higher inside villages.
As the number of L. imphalum mites on an animal increased, the probability of infection in the mite pool also rose. This suggests that dense mite populations within settlements may be driving transmission.
The researchers said the findings “suggest a causal chain” in which large numbers of small mammals within settlements support dense chigger populations, encouraging the spread of O. tsutsugamushi. In short, high rodent density inside villages may be sustaining transmission.
They suggested bacterial spread may intensify when mites cluster, possibly through co-feeding — larvae feeding side by side on the same host — or through infected animals.
However, firm evidence exists only for vertical transmission, where bacteria pass from parent mite to offspring.
Infection in spleen tissue was sometimes higher in field-caught animals, which the authors attribute to possible immune differences.
They observed that host infection appeared to plateau at lower mite loads, suggesting repeated exposure may limit bacterial persistence.
Seasonal patterns differed between settings. Rodent trapping in fields correlated with reported human cases, but village trapping did not.
The study noted that chiggers can complete their life cycle inside rodent burrows, potentially independent of broader seasonal changes.
Infection was also clustered, with some villages showing higher concentrations of infected mite pools, indicating uneven risk across settlements.
The researchers recommended sampling “questing chiggers” — free-living larvae — within villages and integrating ecological findings with human behaviour data to better estimate exposure.
Overall, the findings call for a shift in focus: from treating scrub typhus primarily as an occupational risk to addressing environmental transmission within village settlements.
Dr Sarika N Holla, Consultant General Physician at Kinder Hospitals in Bengaluru, explained to South First that warm and humid climates favour mite breeding.
“Earlier, it was seen commonly in agricultural workers and mainly after the monsoons. But it has now become a home threat,” she said.
According to her, rural households with shrubs, bushes and nearby vegetation are particularly vulnerable. Children playing in grassy areas or people walking barefoot in fields can get exposed to the mites.
She added that overcrowding and poor sanitation increase the risk, while “clean house, cleaner surroundings” and wearing footwear can help prevent infection.
From a clinical perspective, doctors said early symptoms are often ignored.
Dr Pradeep Selvaraj, Assistant Professor of Preventive and Social Medicine at Chettinad Hospital and Research Institute in Chennai, said most patients do not seek care during the first few days of fever.
“Usually, patients will not come to any hospitals or primary health centres with complaints of fever in the first stage,” he told South First. “They take paracetamol by themselves.”
He explained that any fever lasting more than three to four days without another clear cause should raise suspicion. A classic sign is the black scab at the bite site, known as an eschar — a dark, crusted sore. However, he noted that this is seen only in about 35–40 percent of cases.
Most patients, he said, present with persistent high fever, severe body ache, headache and poor appetite.
As the illness progresses, dehydration and electrolyte imbalance can develop, sometimes requiring admission for intravenous fluids.
Dr Holla added that the common clinical features include fever, headache and joint pain. “When left untreated, it can cause multi-organ failure and respiratory failure,” she warned.
Since laboratory confirmation can take time, Dr Pradeep said doctors often start treatment based on suspicion.
He said that in cases of persistent fever beyond three to four days, “we usually take it as a scrub typhus only, where we give a dosage of doxycycline,” even before test reports arrive. Doxycycline is an antibiotic commonly used to treat infections.
If transmission is indeed happening within villages, prevention strategies may need to shift focus.
Dr Pradeep stressed the importance of environmental cleanliness. Bushes, tall grasses and piles of dry leaves around homes should be cleared. Wet areas, manure heaps and rodent burrows need attention because they attract rats and shrews that host the mites.
He also highlighted personal protection. Wearing full-sleeved clothes while working outdoors, avoiding sitting or resting on damp grass and washing up after fieldwork can reduce exposure. Animal sheds, he suggested, should be kept slightly away from the main house.
Dr Holla echoed similar advice. “Good hygiene, less overcrowding and proper disposal of waste are essential.”
Wearing footwear, especially for children playing outdoors, is a simple but effective measure, she added.
The study’s findings do not mean agricultural exposure is irrelevant. Rather, they suggest that the risk may be more widespread than previously thought. In villages where people live in close contact with small mammals and vegetation, the line between field and home may not be very clear.
If scrub typhus is indeed a disease that thrives just outside the doorstep, awareness and early treatment could make the difference between a manageable fever and a life-threatening illness.
(Edited by Muhammed Fazil.)
