Rickettsial infections

Question 1

Rocky Mountain Spotted Fever

Answer 1

• Tick-borne, caused by Rickettsia rickettsii , Gram (-) coccobaccilus.
• obligate intracellular pathogen
• Serious, life-threatening illness.
• Early presentation is non-specific, febrile.
• 2-5 days after fever
• Maculopapular or petechial rash spreading from limbs toward trunk.: from infection of vascular smooth muscle and endothelium of large and small vessels
  
  • microthrombi–infarction + dic from hemorrhaging of blood vessels–fatalities
• other symptoms: pulmonary edema,

Question 2

Epidemic (Louse-Borne) Typhus

Answer 2

• Caused by Rickettsia prowazekii,
• Transmitted by lice, often during disasters, war, or in prisons; human pool.
• Obligate intracellular pathogen–endothelial cells
• Early stage = Febrile
• Later = A rash begins on the chest (infects capillary endothelial cells) about five days after the fever appears, and spreads to extremities (from trunk).
• vasculitis from invasion of enothelial cells–severe
• typhus nodules on liver and spleen.

Question 3

Endemic (Murine) Typhus

Answer 3

• Caused by Rickettsia Typhi
• Transmitted by flea; rodent pool.
• Similar phenotype to epidemic louse-bourne typhus, but less dangerous.

-Flea feces can be inhaled–pulmonary infection

Question 4

Scrub Typhus

Answer 4

• Orientia tsutsugamushi, a Gram-negative α-proteobacterium of Rickettsia family.
• Transmitted by Chigger (mites) bite, leaving a black eschar that helps with diagnosis.
• Endemic to parts of Russia, Korea and Japan.
• Generalized lymphadenopathy
• Can be fatal without treatment.
• Similar effects to those above.–obligate intracellular pathogen–infects endothelial cells–hemorrhaging and intravascular coagulation
• myocarditis, meningioencephalitis other complications

Question 5

Q Fever

Answer 5

• Coxiella burnetii
• From animals–inhalation of aerosolized dropletts
• phagocytosed and proliferation inside macrophages.
• focal bronchopneumonia–atypical pneumonia (from immune response to granulomas
• Typically a self-limited systemic infection, particularly lungs and liver.
• Granulomatous hepatomegaly.