Rickettsial pox

Definition 
Rickettsial pox is an infectious disease transmitted by a mite and characterized by a “chickenpox-like” rash.

Causes, incidence, and risk factors 

Rickettsial pox is caused by Rickettsia akari. It is commonly found (endemic) in the US in New York City and other urban areas. It also has been recognized in South Africa, Korea, and Russia. It is transmitted by the bite of a mite which lives on mice (Liponyssoides sanguineus).

The disease begins at the site of the mite bite as a painless, firm, red nodule that develops into a vesicle (fluid-filled blister) which then bursts and crusts over. This lesion may be large - almost up to an inch across.

Several days later, the patient develops a fever and chills with sweating (diaphoresis), and muscle pain (myalgia). Over the next 2 to 3 days, a rash develops with many small versions of the initial lesion which resemble the chickenpox rash. These lesions clear up within a week.

Symptoms  

     
  • Initial large (up to 1 inch) nodule that forms a vesicle  
  • Fever and chills  
  • Sweating (diaphoresis)  
  • Muscle pain (myalgia)  
  • Generalized vesicular rash resembling chicken pox  
  • Discomfort when in bright light (photophobia)

Signs and tests 
Physical examination confirms the presence of a rash that resembles chicken pox.

Tests include:

     
  • Serologic studies demonstrate antibody titers to Rickettsia akari  
  • CBC

Treatment  
The goal of treatment is eradication of the infection. Medications used include chloramphenicol, tetracycline and doxycycline.

Expectations (prognosis) 
Full recovery is expected.

Complications 
There are usually no complications if the disorder is treated.

Calling your health care provider 
Call your health care provider if your child has symptoms suggestive of rickettsial pox.

Prevention 
Sanitary measures, especially with regard to control of mice and their parasites, will prevent spread of rickettsialpox.

Johns Hopkins patient information

Last revised: December 3, 2012
by Gevorg A. Poghosian, Ph.D.

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