Detection of Scrub Typhus Bacterium in North Carolina Chiggers Raises Public Health Concerns

Researchers in North Carolina have identified the presence of the bacterium responsible for scrub typhus, a severe disease, within local chiggers. This discovery has raised important questions about the origins of the disease and potential health risks, prompting further investigations to evaluate its implications.

A novel study conducted by scientists from North Carolina State University and UNC-Greensboro has revealed the presence of the bacterium that causes scrub typhus in North Carolina. Scrub typhus, a disease not previously reported in the United States, can lead to symptoms such as fever, headache, and body aches and, if left untreated with antibiotics, can be fatal.

It’s crucial to note that scrub typhus has not yet been detected in animals or humans within the state, underscoring the importance of ongoing research to monitor the situation closely.

Research Approach and Key Findings

The researchers from NC State made their discovery while conducting tests on free-living larval trombiculid mites, commonly known as chiggers, in various recreational parks across North Carolina. They sought to determine whether these chiggers carried the Orientia bacterium, the genus responsible for scrub typhus.

Loganathan Ponnusamy, an NC State principal research scholar in entomology and co-author of the research paper, explained their methodology. They placed black tiles on the ground in ten different state parks and collected chiggers as they crossed the tiles. Microbiome studies allowed them to characterize all the bacteria found in the chiggers. Remarkably, one park exhibited a 90% positivity rate for the bacterium, while another displayed an 80% positivity rate. In contrast, other parks showed much lower positivity rates of only 10%.

Chiggers as Disease Vectors

Trombiculid mites are parasitic only during their larval stage and actively seek vertebrate hosts, including humans, to bite. Ponnusamy emphasized that chiggers can transmit bacteria to people or rodents when they bite and can also pass the bacteria to future generations of mites through their eggs.

Resemblance to Rocky Mountain Spotted Fever

The symptoms of scrub typhus closely resemble those of Rocky Mountain spotted fever, a disease traditionally associated with tick bites.

Global Spread and Uncertainties

While scrub typhus is more commonly found in Asia and the Pacific, recent years have seen its emergence in Africa and the Middle East. It remains uncertain whether this spread is a result of human activities or the transportation of goods carrying chiggers from one region to another.

R. Michael Roe, William Neal Reynolds Distinguished Professor of Entomology at NC State and co-author of the paper, highlighted the need to determine whether the bacterium has recently been introduced to the state or if it has been present for an extended period. Additionally, the researchers must establish whether the infected chiggers in North Carolina have the potential to cause disease, a question that requires further investigation.

Ongoing Research and Future Directions

Kaiying Chen, a postdoctoral research scholar at NC State and lead author of the paper, emphasized the importance of monitoring the chigger infection rate in North Carolina to understand whether it is increasing or decreasing. The researchers are conducting resampling efforts at recreational park sites to validate their initial findings.

This study was published in the journal “Emerging Infectious Diseases” and received funding from various sources, including the National Institutes of Health and the Department of the Army. The authors’ findings highlight the need for continued research to assess the potential public health impact of scrub typhus in North Carolina and its broader implications.

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More about Scrub Typhus Bacterium

• Emerging Infectious Diseases Journal