North Carolina Chiggers Host Disease-Causing Bacteria

Researchers from North Carolina University found Orientia — a bacterium that causes scrub typhus — in trombiculid mites at several of the state's recreational parks.

Trombiculid mites, also known as chiggers, are tiny red mites that lurk in moist grassy, weedy, and brushy areas. Though common worldwide, in the United States, chiggers are primarily found in the South, Southeast, and Midwest.

Chigger bites leave itchy welts on the skin, usually around the ankles, backs of the knees, or under the beltline. However, in the U.S., chiggers aren't associated with the transmission of scrub typhus, as the disease is mainly found in rural areas of Indonesia, Asia, and Northern Australia.

Now, a new study published July 12 in Emerging Infectious Diseases has found evidence that chiggers living in North Carolina may carry Orientia, the bacterium responsible for scrub typhus.

Curious as to whether chiggers in the U.S. could carry Orientia, North Carolina State University and University of North Carolina-Greensboro researchers collected the mites at ten different state parks.

After extensive testing, the scientists found that many captured chiggers tested positive for the bacterium.

"One park showed a 90% positivity rate for the bacterium (nine out of 10 chiggers captured); another showed an 80% positivity rate (eight of 10 chiggers captured). Other parks showed positivity rates of just 10%," explains corresponding author Loganathan Ponnusamy in a news release.

However, so far, no cases of scrub typhus have been identified in humans or animals in the state.

Co-author R. Michael Roe, a William Neal Reynolds Distinguished Professor of Entomology at N.C. State says, "We don't know if this is a recent introduction into the state or if the bacterium has been here for years. We also don't know if the infected chiggers found in North Carolina actually will cause disease; this has to be determined in future work."

For now, the scientists are retesting chiggers in the recreational parks to determine if the initial findings remain consistent.

However, because the chiggers tested positive for Orientia, the scientists recommend that healthcare providers in North Carolina be on the lookout for possible human cases of scrub typhus.

What is scrub typhus from chigger bites?

Scrub typhus is a potentially fatal disease transmitted through the bite of an infected chigger in the larval stage. Symptoms of scrub typhus usually appear within 10 days of being bitten and may include:

• Headache
• Fever and chills
• Body and muscle aches
• Enlarged lymph nodes
• Rash
• Eschar, a dark scab at the center of the chigger bite
• Mental changes ranging from confusion to coma

Scrub typhus can also lead to organ failure and bleeding, which can be fatal. However, healthcare providers can treat the disease with the antibiotic doxycycline. When treated early, most people recover without incident.