Image Based Question-65815

A patient complained of chills and fever following a bite 2 weeks before by the insect vector shown in the picture below.

He had rashes which started initially over the trunk and then peripherally and was delirious at the time of presentation to the hospital and subsequently went into coma.

A provisional diagnosis of vasculitis was made. Which one of the following can be causative agent ?

A. Rickettsia typhi.

B. Rickettsia rickettsiae.

C. Rickettsia prowazekii.

D. Rickettsia akari.

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Correct Answer » C Explanation

Ans:C. Rickettsia prowazekii.

The parasite shown in the picture above represent Louse.

History of a louse bite with rashes all over the body and vasculitis is suggestive of epidemic typhus, caused by Rickettsia prowazekii.

Epidemic Typhus

• Epidemic typhus (also called “Epidemic louse-borne typhus,”and “louse-borne typhus”) is a form of typhus so named because the disease often causes epidemics following wars and natural disasters.

• The causative organism is Rickettsia prowazekii, transmitted by the human body louse.

• Rickettsia parasitize the endothelial cells of the small venous, arterial, and capillary vessels. The organisms proliferate and cause endothelial cellular enlargement with resultant multiorgan vasculitis.

Symptoms :

• The incubation period for the disease is 10 to 14 days, on average.

• Fever is characterized by abrupt onset and high grade.

• Headache is characterized by abrupt onset and is unremitting.

• A maculopapular/petechial rash occurs on days 4-7 and may begin on the axilla and trunk and spread peripherally. Other symptoms may include rigors, myalgias, malaise, and CNS symptoms (ranging from mental dullness to coma).

• The infection is treated with antibiotics like Tetracycline, Chloramphenicol, and Doxycycline.