L 80 Rickettsial Infections Flashcards
What type of pathogen is Rickettsia?
Obligate intracellular parasites
Characteristics of rickettsiaceae
Gram (-) very small
Induce phagocytosis to enter host cells and grow in cytoplasm or nucleus
Vectors of rickettsiaceae
Many different vectors:
Ticks, Mites, Louse
Remember that these are also hosts for the rickettsiaceae
Where do rickettsiaceae like to multiply in the body?
Often multiply in the endothelial cells of small blood vessels of the skin and other organs => necrotizing vasculitis
Also causes INCREASED MICROVASCULAR PERMEABILITY
This causes damage and consequences in tissues highly dependent on blood flow
Rickettsial vasculitis leads to what symptoms?
Rash, headache, encephalitis, nephritis, myocarditis, lesions in lungs and liver and GI
What is the most common first set of Sx for rickettsia infection?
High fever and Severe headache
What are the 4 species of rickettsia to know, their associated diseases, and worldwide distribution?
R. rickettsii: RMSF, western hemisphere
R. akari: rickettsialpox, worldwide
R. prowazekii: Epidemic typhus, worldwide
R. typhi: murine typhus, worldwide
What are the reservoir hosts of R. rickettsii? What are the vectors?
Mammaliam reservoirs: wild rodents and other small mammals
Vectors: american dog tick, rocky mtn wood tick, brown dog tick (AZ)
R. rickettsii incubation and SSx
Incubation 2-14d
Fever and severe headache
Rash 2-5d after fever often starts at wrists and ankles and works inward (Centripetal)
R. rickettsii complications
Myocarditis, CNS dysfunction, renal failure, gangrene, pneumonia
All come from vascular damage
Early treatment essential
R. akari epidemiology, reservoirs and vector
Mild disease
Found in urban areas like NYC
House mice and rats reservoir
House mouse mite vector
R. akari disease
Rickettsialpox:
Mild disease
Incubation 7-10d
1st phase: red papule at bite site becomes vesicular and forms eschar
2nd phase: 3-7d later, sudden fever and severe headache, chills, rigors, sweating, myalgia
Rash 2-3d after fever onset
Generally self-limited even without treatment
R. prowazekii epidemiology
Louse-bourne typhus, serious disease that causes lots of death
Worldwide: prison camps, refugees, crowding and poor hygiene
In US: usually exposure to fleas from flying squirrels, or among the homeless who get lice
Humans are reservoir
Human body louse vector
Infection of R. prowazekii in humans
Human body louse bites and then defecates. Getting the feces into the wound or a scratch causes the disease.
R. prowazekii disease
Very serious disease
Incubation 7-14 days
Sudden fever and severe headache, tachypnea, myalgia
Rash 4-7d after fever begins on trunk and goes to extremities (centrifugal)
R. prowazekii complications
CNS dysfunction, myocarditis, pneumonia, renal failure, gangrene, multi organ system failure
Early treatment important
R. prowazekii long term effects
If survive the disease, the bug may remain for decades and come back to cause Brill-Zinnser disease: symptoms less servere
Sylvatic epidemic typhus
Symptoms less severe
Eastern USA
Southern flying squirrels reservoir
Squirrel flea vector
R. typhi epidemiology
Causes endemic or murine typhus Worldwide Reservoir: rats, mice, cats, opossums Vectors: fleas Seen in coastal port areas, also Texas Transmission through flea feces
R. typhi disease
Incubation 7-14d
Similar to epidemic typhus (this is endemic) nut less severe and shorter
Rickettsiosis diagnosis
Fever, headache, rash, etc.
Hx of arthropod bites
Serology, rash biopsy
Rickettsiosis treatment
Doxycycline
Chloramphenical if doxy contraindicated
Rickettsiosis prevention
Tick control and precautions
Control rodents, mass delousing
Characteristics of Anaplasmataceae
Gram (-)
Like to target cells of hematopoietic origin–especially leukocytes
Multiply within membrane-bound structures called morulea within the cells (they are dark spots within the cells)
Anaplasmataceae vectors
Lone star tick and blacklegged tick
Ehrlichia chafeensis epidemiology
Worldwide distribution
SE to SCentral USA
White-tailed deer reservoir
Lone star tick vector
Ehrlichia chafeensis disease
Incubation 5-21d
SSx: fever, headache, myalgia, rash
Complications: CNS, meningitis, renal failure, myocarditis
A. phagocytophilum epidemiology
Worldwide, upper midwest and NE states
Reservoir: wild rodents
Vector: blacklegged ticks
A. phagocytophilum disease
Incubation 7-14d
SSx: fever, headache, myalgia, rash
Complications: ARDS, renal failure, TSS, myocarditis, serious opportunistic infections (from low leukocyte counts)
Diagnosing ehrlichioses and anaplasmosis
History, area, blood tests–leukopenia, low platelets, MURULAE in stained leukocytes
ehrlichioses and anaplasmosis treatment
Doxycycline or rifampin
