Researchers have detected the bacteria that cause scrub typhus, a serious disease, in scrub typhus in North Carolina. The discovery has raised concerns about the origins and potential health risks of the disease, and further research is currently underway to assess its impact.
A bacterium that causes scrub typhus has been discovered in North Carolina and has not been previously reported in the United States, according to a new study by researchers at North Carolina State University and UNC-Greensboro.
Researchers stressed that scrub typhus causes fever, headache and body aches and can be fatal if not treated promptly with antibiotics, but the disease has not yet been found in animals or people in the state.
Researchers at North Carolina State University detected this bacterium - the genus Orientia in the family Rickettsiaceae - at high frequency while testing free-living, larval (biting) tumor mites, commonly known as chiggers, at several different recreational parks in North Carolina.
"In the past, we have not had diagnostic tools to detect this specific bacterium at the genus level," said Loganathan Ponnusamy, principal research scholar in entomology at North Carolina State University and co-corresponding author of a paper describing the study.
"We set up a black tile on the ground at 10 different state parks in North Carolina, and we caught scrub typhus as they moved through the tile. Microbiome studies allowed us to characterize all the bacteria within the scrub typhus. One park had a 90 percent positive rate (9 out of 10 scrub typhus caught); another had an 80 percent positive rate (8 out of 10 scrub typhus caught). Other parks had a positivity rate of just 10 percent."
Chiggers are parasitic only in their larval stage. They seek out vertebrate hosts, including humans, to bite. Chiggers spread the bacteria when they bite people or rodents, but they also pass the bacteria on to subsequent generations of mites through their eggs.
Researchers say symptoms of scrub typhus are similar to Rocky Mountain spotted fever, a disease usually caused by tick bites.
Scrub typhus is more common in Asia and the Pacific, but in recent years the disease has also been found in Africa and the Middle East. It is still uncertain whether the spread of scrub typhus is caused by people or cargo carrying scrub typhus from one place to another.
"We don't know if this was a recent introduction to the state, or if the bacteria have been here for years," said co-author R. Michael Roe, William Neal Reynolds Distinguished Professor of Entomology at North Carolina State University. "We also don't know if infected scrub typhus found in North Carolina actually causes disease; that will have to be determined in future work."
"We don't know whether scrub typhus infection rates are declining or rising," said Kaiying Chen, a postdoctoral researcher at North Carolina State University and first author of the paper.
Researchers at North Carolina State University and the University of North Carolina at Greensboro are resampling scrub typhus in recreational parks to determine if reported results remain consistent.
Compiled source: ScitechDaily