A bacterium causing scrub typhus, a deadly form of typhus disease spread through chigger bites, has been detected for the first time in the U.S.

According to a study conducted by the Centers for Disease Control and Prevention (CDC), chiggers or larval forms of mites infected with Orientia tsutsugamushi, the bacteria that causes scrub typhus were found in several recreational parks in North Carolina.

Scrub typhus is a life-threatening infectious disease that may cause severe multiorgan failure and bleeding when left untreated. The fatality rate of the disease is up to 70% without medical attention.

The symptoms of scrub typhus appear six to 21 days after the infected chigger bite.


  • Fever and chills
  • Headache and body pain
  • Scab at the site of chigger bite, also known as eschar
  • Rash on the trunk that often extends to the arms and legs
  • Enlarged lymph nodes
  • Cough

As the infection gets worse, patients may face muscular twitching, high pulse rate and a drop in blood pressure. In severe cases, the patients may develop confusion and coma. The use of doxycycline is usually prescribed for treating the disease.

Most cases of scrub typhus infections are reported from rural areas of Southeast Asia, Indonesia, China, Japan, India and northern Australia.

"We wanted to see if chiggers in the United States carried Orientia. We haven't in the past had the diagnostic tools to test for this specific bacterium at the genus level," said Loganathan Ponnusamy, co-corresponding author of the research paper.

Researchers evaluated the chiggers picked up from 10 different North Carolina state parks as they crossed a black tile set on the ground. They then identified all types of bacteria found in them.

"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%," the researchers said.

Chiggers not only infect people or rodents through bites but also can pass to future generations of mites through their eggs, the researchers said.

"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," noted R. Michael Roe, co-author of the paper.