A disease that kills up to 70 percent of people it infects has been detected in the United States for what appears to be the first time.
The bacteria that causes scrub typhus was found in mites living in half of the national parks in North Carolina, according to a Centers for Disease Control and Prevention (CDC) study.
It can be transmitted to humans via bites, triggering symptoms including rashes that cover the limbs and dark, scab-like, marks around bites. In serious cases, it can also impair the function of the lungs and heart, leading to death.
Scientists at North Carolina State University, who led the research, warned further surveillance was needed in case the disease had spread to other states. It comes after warnings that malaria had reached the US for the first time in two decades.
The above map shows where sampling took place in North Carolina and where mites were detected carrying the disease. Darker colors indicate a higher proportion of mites carrying the disease
Pictured above is the scab that can be caused by scrub typhus (left) and a larval and adult mite that can carry the disease and transmit it to humans via a bite (right). The mites are shown on top of a pinhead
Scrub typhus is native to an area called the Tsutsugamushi Triangle — named after the bacteria that causes the disease — which stretches from Pakistan to far eastern Russia and Australia, where it causes 1million cases a year.
But it has recently started to crop up in other areas including the Middle East, southern Chile and Africa, which prompted researchers to search for it in the US.
The Virginia Department of Health says scrub typhus is ‘not seen in the US’, except for sporadic cases where it has been picked up by travelers.
Scrub typhus, also known as bush typhus, is caused by an infection with the bacteria Orientia tsutsugamushi which can be carried by mites.
About 10 to 12 days after being infected a reddish or pinkish lesion appears at the site of the mite bite.
The patient may also start to suffer from a headache, fever, chills, muscle pains and have a sore emerge on the skin with a ‘punched out’ appearance.
About a week later, a pinkish rash may also appear on the skin around the abdomen that may then extend to the arms and legs.
Without treatment, the disease can also lead to abnormalities in the heart, lungs and blood — which could lead to death.
Treatment includes doses of the antibiotic doxycycline to kill off the bacteria causing the infection.
Scientists at the University of Texas say between 30 to 70 percent of patients die if they do not receive appropriate treatment.
For the study, published today in the Morbidity and Mortality Weekly Reports (MMWR), scientists checked mite populations in ten national parks in North Carolina.
Mites were collected by placing a tile on the ground, which generally measures a meter by a meter, and searching the area within them for the arthropods.
At nine of the sites, ten mites were collected, while at one only five mites were collected.
All the mites were then tested for whether they were carrying the bacteria that causes scrub typhus.
Testing showed that nine out of ten mites in Lumber River State Park were infected with scrub typhus.
Eight out of ten in Kerr Lake State Recreation Area carried the bacteria behind the disease, as well as one out of ten in Falls Lake State Recreation Area and Morrow Mountain State Park.
One out of the five from Merchant Millpond State Park was also infected.
Dr Kaiying Chen, an entomologist who led the study, and her team said in the paper: ‘This result is… significant because it indicates… circulation of [scrub typhus] in chiggers [mites] collected within the continental United States.’
It was not clear how the disease had reached the US, but it could be the case that a person who was infected with it arrived in America. This person may then have been bitten by a mite, transmitting the disease.
Alternatively, mites carrying the disease could have found their way to the US on an airplane or via an import on a ship.
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