What is Rickettsia?
Rickettsia infections are spread through ticks, mites, fleas or lice. Rickettsial infections include: anaplasmosis, ehrlichiosis, and Q fever, Rickettsia parkeri infection and Rickettsia species 364D . The most deadly of the infections in the United states is Rickettsia rickettsii infection (Rocky Mountain spotted fever [RMSF]). Most of these cases occur in children ages 5-9 . The risk factors and severity of the disease depend on factors such as delay or lack of treatment, age, Native American decent, G6PD or glucose-6-phosphate dehydrogenase deficiency and immunocompromised states.
RMSF typically presents itself with fever, headache and a rash. "This triad is present in only 3% of early infections, but the prevalence increases to 60% to 70% by 2 weeks after the tick bite." Other initial symptoms include generalized malaise, weekness and myalgia. Without the appropriate treatment, death can ocur 7-15 days after onset. Fever typically subsides within 24 - 48 hours of starting treatment. Failure to clinically improve within 48 hours suggests a different diagnosis. Long term effects of the infection can include: hearing loss, blindness and gangrene which can lead to amputations of digits and extremities.
The principal diagnostic test for RMSF is serologic testing with an immunoflourescence antibody assay. "Paired testing (during the acute and convalescent phases) has a sensitivity of 94%. A 4-fold or greater increase in antibody titer (with a minimum titer of 1:64) between acute and convalescent samples is considered diagnostic of acute infection."
According to the review article published in the Clevlan Clinic Journal of Medicine, " doxycline for 7 days is the treatment or choice for RMSF, Rickettsia parkeri infection, or Rickettsia species 364D infection, “including in pregnant patients with life-threatening disease and in children.”1. While these are all rickettsial infections, which is the most common and most likely to cause death if left untreated?
B. Rickettsia species 364D infection
C. Rickettsia rickettsii infection (Rocky Mountain spotted fever [RMSF])
2. All of the following statements are true about RMSF EXCEPT:
B. Without appropriate antibiotic therapy, the case-fatality rate with RMSF is over 20% and death occurs 7 to 15 days after symptoms onset
C. Fever, headache, and a rash make up the classic triad of RMSF
D. Most cases of RMSF occur in adults ages 25 to 35
3. Any of the following diagnostic tests can be performed in patients suspected to have RMSF, Rickettsia parkeri infection, or Rickettsia species 364D infection, but which is considered the principal diagnostic test?
B. Cell culture in a biosafety level 3 laboratory
C. Immunohistochemical staining of a skin biopsy or autopsy specimen
D. Serologic testing with an immunofluorescence antibody assay
4. While all of the following agents can be used in the treatment of RMSF, Rickettsia parkeri infection, or Rickettsia species 364D infection, which is the treatment of choice?
5. How many hours after starting treatment does fever typically subside in patients with RMSF?
B. More than 72 hours
C. More than 72 hours
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If you have bitten by a tick within two weeks, call us and you are eligible for free testing as part of a study. We will draw and ship your blood and you will receive the results. 845 358-8385.
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1. C. Rickettsia rickettsii infection (Rocky Mountain spotted fever [RMSF])
2. D. Most cases of RMSF occur in adults ages 25 to 35
3. D. Serologic testing with an immunofluorescence antibody assay
4. B. Doxycycline
5. C. Within 24 to 48 hours
For complete information, see:
“Tickborne diseases other than Lyme in the United States.”