Rocky Mountain Spotted Fever

Introduction. 

Rocky Mountain Spotted Fever (RMSF) is caused by the Gram-negative intracellular pathogen Rickettsia rickettsii. These rod-shaped bacteria are energy parasites that induce host cells (vascular endothelial cells) to internalize then by phagocytosis. The rickettsias then lyse the phagosome and multiply in the cytoplasm of the host cell, eventually killing it. This results in vascular damage, causing blood to leak into the surrounding tissues. Both proteins and blood volume are lost, leading to organ damage. 6 other rickettsias can also cause spotted fevers.

Summary

• Cause: Rickettsia rickettsii
• Microscopy: Gram-negative rods, very small
• Transmission: Tick bite (zoonosis; tick reservoir)
• Symptoms: Fever, chills, headache, myalgia, rash developing from limbs to trunk (rash usually petechial - small hemorrhages)
• Complications: organ damage and failure (encephalitis, renal, GI tract, lungs)
• Pathogenesis: Intracellular replication in vascular endothelial cells damages endothelium, causing plasma to leak.
• Treatment:Tetracycline, chloramphenicol, ciprofloxacin