Biology 216 - Lect 32 (Rickettsia)
Hans Zinsser - Rats, Lice and History - Typhus
Final Study Guide in Lab book and Website
Rickettsia: Obligate intracellular; Arthropod vectors;
	 Diseases - typhus, RMSF, Q-fever (rash, fever, headache)
	Know one (pick your favorite) in detail - 
		Disease, etiology, vector, disease symptoms.
	Know general pathogenesis for Rickettsiae
Ehrlichiosis - Ehrlichia - tick transmission, Similar to RMSF
I. General Rickettsia
	A. Bact - Small Gm negative coccobacilli, Obligate intracellular, 
		Used to be discussed in Virology: PG, LPS, ribosomes,
			culture in embryonated eggs (candle, Montana)
		Vary intracellular location: Cytoplasm/nucleus
			 (escape phagosomeby phospholipase), 
			Phagolysosome (Coxiella)
		Transmission: Arthropod (most) - louse, flea, tick, mite....
	B. Pathogenesis (all similar except for Coxiella) - 
		Less than 1000/yr in US, Most RMSF
		1. Cycle in nature between rodent and arthropod vector. 
			(Mild to asymptomatic in rodent - adapted)
		2. Transmitted to human by bite of arthropod (except Coxiella)
		3. Induce phagocytosis into endothelial cells; 
			Multiply in capillary endothelia; 
			Destroys cells; hypertrophy of cells; inflammation; 
				vasculitis; leakage; occlusion; necrosis; clotting
		4. Effects of vascular damage and LPS:
			Headache - meningeal damage; 
			Unresponsive to analgesics
			Fever - LPS induced
			Rash - destruction of small capillaries; 	
			Manifestation helpful in diagnosis.
			Hepatosplenomegaly
		5. Humoral (increase intracellular killing) and CMI helpful. 
			Mortality varies with each disease
	C. Diagnosis - Clinical and history of contact with arthropod
		1. Rarely culture (eggs)
		2. Serodiagnosis
			Weil Felix agglutination: Shared Ag between 
				Proteus vulgaris O-Ag and Rickettsia

Disease	OX-19	OX-2	OX-K
Epidemic typhus	++++	+	0
Brill-Zinsser	0	0	0
Scrub typhus	0	0	++++

		Problem with false positive from other diseases
		Specific Rickettsial tests: IFA, Indirect HA
	D. Treatment - Antibiotics; fluids; 
	E. Prevention - vector control.
II. Epidemic typhus - R. prowazekii; Vector - human louse 
		(never person to person)
	Pre-antibiotic era - millions of deaths associated with 
		war time (louse infestations); Most virulent Rickettsia
	A. Pathogenesis - Transmission by human head or body louse.
		1. Acute disease - Headache, fever, rash 
		(trunk then spread out, seldom soles, palms, face)
			Death by vascular collapse, renal failure.
		2. Recrudescence (Brill-Zinsser disease) - 
			Relapse years later.
			Rickettsia dormant in endothelia; 
				Age depressed immunity; 
				Same as acute except milder.
			Classic: WWII east Europeans (Russian and German)
III. Q-fever (Query since etiology was unknown) - Coxiella burnetii
	Resists dessication (spore-like form); Airborne transmission to 
		humans from infected animals (domestics)
	A. Pathogenesis - Cycle in nature is tick -> 
			animal (asymptomatic) -> tick
		Organisms shed in milk, placenta (10(9)/gm tissue), feces
		Humans inhale or ingest
		Organisms survive in phagolysosome (opt pH 4.5)
		Clinical - asymptomatic, flu-like, endocarditis, no rash, 
			no Weil-Felix, benign unless compromised.
	B. Serodiagnosis
	C. Prevention: Endemic in domestic cattle and sheep
		Pasteurization - 62 C/30 min (used to be 60 C) 
			or 71.5 C/15 sec.