Rickettsia Flashcards
Rocky Mountain Spotted Fever Cause
Rickettsia rickettsii
Rickettsialpox Cause
R. akari
Epidemic typhus (louse-borne typhus) Cause
R. prowazekii
Brill-Zinsser disease Cause
R. prowazekii
Murine typhus Cause
R. typhi
Scrub typhus Cause
Orientia tsutsugamushi
Two types of Ehrlichiosis
Human Anaplasmosis
Human Monocyte Ehrlichiosis
Human Anaplasmosis Cause
Anaplasma phagocytophilium
Ehrlichia ewingii
Human Monocyte Ehrlichiosis Cause
E. chaffeensis
Q fever Cause
Coxiella burnetii
What is the reservoir of R. rickettsii?
Dogs and rodents
What is the vector of R. rickettsii?
Ticks (Dog and Wood)
How is R. rickettsii maintained in the tick population?
Maintained in the tick population by passage from tick to tick through transovarian transmission
What are the manifestations of RMSF?
High fever and headache
Rash most characteristic feature
i. Rash present particularly on hands and feet
ii. Rash moves from extremities to trunk of body
Where does RMSF occur most often?
Main states are NC and OK
Occurs in association with residential and recreational exposure to wooded areas where infected ticks exist
What is the reservoir of rickettsialpox?
Mites (possibly mice)
What is the vector of rickettsialpox?
Mites
How is R. akari maintained in mites?
Transovarian transmission
What are the manifestations of rickettsial pox?
Phase 1: A firm red papule appears at the site of the bite. Papule develops into deep-seated vesicle then black eschar
Phase 2: Systemic spread and after 9-14 days, high fever, severe headache, chills/sweats, myalgias, photophobia develop. A vesicular rash develops (small, blister like lesions filled with clear fluid).
What is the reservoir of epidemic typhus?
Reservoirs include humans and flying squirrels
What is the vector of epidemic typhus?
Lice
How is R. prowazekii maintained in lice?
Lice die after 2-3 weeks, thus preventing transovarian transmission. It is NOT maintained.
How is epidemic typhus spread?
Organisms are present in the feces of the infected lice and enter through the bite would or skin abrasions
What are the manifestations of epidemic typhus?
Fever and headache
Maculopapular rash begins first on the trunk and then spreads centripetally to the extremities (opposite to Rocky Mountain Spotted fever)
What are the manifestations of Brill-Zinsser disease?
Relapse of louse-borne typhus appearing 10-40 years after the primary attack. Rickettsia persist for many years in the lymph nodes of an individual without any
symptoms being manifest.
What is the reservoir of murine typhus?
Rodents
What is the vector of murine typhus?
Fleas
What are the manifestations of murine typhus?
Fever, severe headache, chills, myalgia, nausea
Rash in 50% of cases, typically restricted to the chest and abdomen, but may extend to palms and soles.
Where is scrub typhus found?
Southwest Pacific, Southeast Asia, and Japan
What is the reservoir of scrub typhus?
Mites
What is the vector of scrub typhus?
Mites
What are the clinical manifestations of scrub typhus?
Typical initial lesion, a necrotic eschar at the site of the bite on the extremities, develops in only 50 to 80% of the cases.
Generalized lymphadenopathy
What is the reservoir of HME?
White-tailed deer and dogs
What is the vector of HME
Lone Star Tick
Where is HME found?
HME found in U.S. predominantly in southeastern, mid-Atlantic and south central states; OK has high rate of incidence
What is the reservoir of HA?
Rodents
What is the vector of HA?
Ixodes Tick
Where is HA found?
Human anaplasmosis found in U.S. primarily in northern and central midwestern states and northeast and central Atlantic states.
What are the manifestations of HA and HME?
Fever, chills, headache, myalgia, nausea or vomiting
Typically NO rash
Leukopenia, thrombocytopenia, and elevated serum transaminases develop in majority of patients
What are the manifestations of HME?
Late onset rash in 30-40%
What are the manifestations of HA?
Infection primarily of bone marrow myeloid cells
What is the reservoir of Q fever?
Carried by mammals such as cattle, sheep, and goats
How does infection by C. burnettii occur?
Infection is believed to typically occur through inhalation of dust contaminated with Coxiella or from aerosols in slaughterhouses
What are the manifestations of Q fever?
A mild, dry, hacking cough and patchy interstitial pneumonia may or may not be present.
NO rash
What is the pathogenesis of Q fever?
C. burnetii primarily replicates in the phagosome because it requires low pH.
C. burnetii forms endospores and thus is resistant to drying and other environmental conditions.
How does Coxiella burnetii pathogenesis differ from Rickettsial organisms such as Rickettsia rickettsii?
Coxiella enters via a phagolysosome-like vesicle wheres Rickettsia enters the cytoplasm. The phagosome fuses with endosomes as Coxiella requires low pH for growth.
Outside of the cells Coxiella is viable for years but Rickettsia quickly dies.
What organisms exit the cell by budding?
R. rickettsia and R. typhi
They escape using Phospholipase A and multiply in cytoplasm. R. rickettsia and R. typhi then migrate intracellularly using actin polymerization.
After returning from an extended stay at her Aunt Sarah’s cattle ranch in Oklahoma, 12-year old Susie complains of cold-like symptoms: severe headache, high fever, myalgia, and a persistent cough. You see no signs of rash. Laboratory results indicate the presence of bacteria, but normal white blood cells. You conclude that the causative agent of this disease was transmitted to Susie:
A. By a bite from a blood sucking mite
B. Through exposure to the wood tick Dermacentor andersoni
C. By breathing dust from the cattle.
D. From Aunt Sarah’s persistent cough
E. Through a louse bite
C. By breathing dust from the cattle.
