Scrub typhus is a rickettsia-like bacterial infection caused by Orientia tsutsugamushi bacteria and spread by chiggers (mite larvae).
People become infected when they are bitten by an infected mite.
People with scrub typhus have sudden fever, chills, and a headache, followed by a rash several days later.
To diagnose the infection, doctors test a sample of the rash and do blood tests.
The antibiotic doxycycline is used to treat spotted fevers.
Orientia tsutsugamushi bacteria can be passed between people and animals and cause infections. Infections that can be passed between people and animals are called zoonotic diseases, or zoonoses (see Introduction to Diseases Spread Between Animals and People (Zoonoses)).
The bacteria that cause scrub typhus, like rickettsiae, can live and multiply only inside the cells of a host organism, such as an animal or a person, and cannot survive on their own in the environment. Orientia tsutsugamushi bacteria live in mites (the host), so mites are both the vectors and the hosts.
Scrub typhus occurs worldwide and is rare in the United States.
The infection is transmitted to people when they are bitten by an infected chigger (mite larva).
Symptoms of Scrub Typhus
Symptoms of scrub typhus begin about 7 to 10 days after a chigger bite. They include sudden fever, chills, a severe headache, and swollen lymph nodes.
PDC/SCIENCE PHOTO LIBRARY
Fever rises during the first week, often to 104 to 104.9° F (40 to 40.5° C). People may have a cough during the first week of fever, and may develop lung irritation the second week.
In some people, a rash appears on the trunk about 5 to 8 days after the fever starts. The rash often spreads to the arms and legs.
Chigger bites look like hard, red bumps. The bumps eventually develop small, fluid-filled blisters that break open and become covered with a black scab. Sometimes a thicker, crustier scab-like covering forms at the bite site if dead tissue from the wound dries out and hardens. This thicker covering is also black and is called an eschar.
In scrub typhus (tsutsugamushi disease), a black scab (eschar) forms at the site of a chigger bite (top). A rash develops later (bottom).
Images courtesy of Yoshiki Taniguchi, MD, and the Dermatology Online Journal.
The black scab seen in this photo is called an eschar. It can develop in people who have been bitten by a chigger and develop scrub typhus.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Other symptoms may develop in people who have a severe infection:
Delirium and stupor
Muscle twitches
An enlarged spleen
Heart damage
Increased pulse and low blood pressure
High fever that lasts 2 weeks or longer
Diagnosis of Scrub Typhus
A doctor's evaluation
Biopsy and testing of the rash or eschar
Blood tests
Doctors base the diagnosis on symptoms such as fever, rash, and eschar in people who have recently been to an area where scrub typhus occurs and have participated in outdoor activities, such as camping or visiting farms, which could expose them to chigger bites.
To confirm the diagnosis, doctors do an immunofluorescence assay, which is a blood test that detects antibodies to the Orientia tsutsugamushi bacteria.
Doctors may also do the polymerase chain reaction (PCR) technique. The PCR technique makes copies of the bacteria's DNA, so that the bacteria can be detected more rapidly. For this test, doctors take samples of the rash or an eschar (biopsy) and test if for antigens produced by the bacteria. See also Tests That Detect Antibodies to or Antigens of Microorganisms.
Treatment of Scrub Typhus
An antibiotic
Doctors typically give people the antibiotic doxycycline, which is taken by mouth. People take this antibiotic until they improve, have not had a fever for 48 hours, and have been taking the medication for at least 7 days. With treatment, people recover quickly.
Doctors give azithromycin to people who are pregnant or who have a severe doxycycline allergy.
Although doxycycline can cause tooth staining in children younger than 8 years old, a short 5- to 10-day course in children of all ages is recommended by the American Academy of Pediatrics and can be used without causing tooth staining or weakening of tooth enamel.
Prevention of Scrub Typhus
Prevention involves clearing brush and spraying infested areas with insecticides to eliminate or decrease the chigger population.
If people are likely to come in contact with chiggers, they should use insect repellents such as DEET (diethyltoluamide).
Drug Information for the Topic
