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Rickettsialpox

(Vesicular Rickettsiosis)

By

William A. Petri, Jr

, MD, PhD, University of Virginia School of Medicine

Last full review/revision Jul 2020| Content last modified Jul 2020
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Rickettsialpox is a rickettsial disease that is caused by Rickettsia akari and spread by chiggers (mite larva) or adult mites.

  • Symptoms of rickettsialpox, which are mild, include a fever with chills and sweating, a headache, sensitivity to light, muscle pains, and a rash.

  • To diagnose the infection, doctors test a sample of the rash and sometimes do blood tests.

  • Rickettsialpox is treated with an antibiotic.

Rickettsiae are a type of bacteria that can live only inside the cells of other organisms. The rickettsiae that cause rickettsiosis usually live in house mice (the host).

Rickettsialpox occurs in many areas of the United States and in Russia, Korea, and Africa. The rickettsiae are transmitted to people when they are bitten by a chigger (mite larva) or an adult mite. The mites may also transmit the bacteria to house mice.

Symptoms of Rickettsialpox

Symptoms of rickettsialpox are mild. A small buttonlike sore covered by a black scab (eschar) appears at the site of the bite. It develops into a small sore that leaves a scar when it heals.

About a week later, other symptoms develop. They include a fever with chills and sweating, a headache, discomfort in the eyes when they are exposed to light, muscle pains, and a widespread rash. Nearby lymph glands may be swollen.

Diagnosis of Rickettsialpox

  • A doctor's evaluation

  • Biopsy and testing of the rash

  • Blood tests

The diagnosis of rickettsialpox is suggested by symptoms.

To confirm the diagnosis, doctors may do an immunofluorescence assay, which uses a sample from the rash. Or they may use the polymerase chain reaction (PCR) technique to enable them to detect the bacteria more rapidly.

Doctors may do blood tests that detect antibodies to the bacteria. However, doing the test once is not enough. The test must be repeated 1 to 3 weeks later to check for an increase in the antibody level. Thus, antibody tests do not help doctors diagnose the infection immediately after someone becomes ill but can help confirm the diagnosis later.

Prevention of Rickettsialpox

Prevention of rickettsialpox involves controlling the mice population and using pesticides to kill the mites.

Making the environment less appealing to mice can help. For example, people can remove wood piles, leaf litter, and trash and clear tall grasses and brush around homes. Mice can hide and nest in such places. Holes and other openings where mice can enter homes should be blocked. All food should be stored in mice-proof containers.

Treatment of Rickettsialpox

  • An antibiotic

Treatment of rickettsialpox consists of an antibiotic, usually doxycycline taken by mouth for at least 5 days.

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