Rickettsia Rickettsii (Rocky Mountain Spotted Fever)
February 8, 2016
Rickettsia rickettsii is the causative agent of Rocky Mountain Spotted Fever (RMSF). The bacteria are Gram-negative, rod shaped intracellular parasites that infect endothelial cells. The pathogen is most commonly spread by the American dog tick, brown dog tick, Rocky Mountain wood tick, and the Lyme disease transmitting Ixodes tick.
Symptoms include fever, rash, headache, nausea, sharp abdominal pain, muscle pain, lack of appetite, and red eyes. A hallmark sign of RMSF is a spotted rash that occurs in 90 percent of patients about two to five days after the onset of fever. It is worth noting that 10 percent of patients may not develop a rash at all. RMSF is a very serious illness that can be fatal within eight days of symptomatic disease if improperly diagnosed. A sign of advanced infection is a red to purple spotted rash that appears around the sixth day of illness in 30-65 percent of patients; for the best outcome, treatment should commence before the appearance of this symptom.
RMSF may lead to the inflammation of blood vessels (vasculitis) because Rickettsia rickettsii infects the endothelial cells that make up their lining. This can trigger bleeding and clotting in vital organs, and fluid leakage in extremities that can lead to amputation.
RMSF is diagnosed symptomatically and confirmed with laboratory tests. Common tests include detection of bacterial DNA through polymerase chain reaction (PCR) and detection of antibodies through the immunofluorescence assay (IFA). Treatment involves the administration of antibiotics and should be provided even if lab results are pending or negative.