Section 6: Rickettsiae Flashcards
What are the characteristics of Rickettsiae
• Very small Gram negative coccobacilli
• Obligate intracellular parasites-needs cell for materials to synthesize A TP
• Unable to metabolize glucose
• Can be grown in the laboratory in chick embryo yolk sacs
• Some Rickettsiae share antigens with Proteus strains
-Historically use Weil-Felix test to diagnosis Rickettsiae, no longer used-insensitive
What are the 2 types of Rickettsial diseases
Group I -Typhus
GroupII - Spotted fevers
What is Rickettsia prowazeki
Epidemic Typhus
What is the vector for Rickettsia prowazeki
- Vector is lice, associated with poor sanitation -
- Reservoir in U.S. is flying squirrels -last epidemic was 70 yrs. Ago
What is the pathology of Rickettsia prowazeki
- Clinical symptoms due to bacteremia
- High fever, chills, muscle pain
- Macular rash (not on soles or palms)-only in 40% of patients
- Generally resolves in 3 weeks, but is occasionally fatal
How is Rickettsia prowazeki diagnosed
IFA test (indirect fluorescent antibody)
What is Brill-Zinsser Disease
Hans Zinsser discovered that those NOT treated with antibiotics retain R. prowazeki in a latent state
- Occasionally breaks out oflatent state to cause Brill-Zinsser disease, milder form of epidemic typhus
- No skin rash
What is Rickettsia typhi
endemic Typhus
What is the vector for Rickettsia typhi
fleas, rodents are primary reservoir
What is scrub typhus
Caused by Orientia (formerly Rickettsia) tsutsugamushi
- Transmitted by larva of mites (chiggers which live in soil)
- Rodent reservoir
- Affected soldiers in WWII and Vietnam
What is the pathology of scrub typhus
High fever, severe headache
-Eschar (resembling a cigarette burn) forms at initial bite site followed by maculopapular rash
What is Rickettsia rickettsii
Rocky Mountain spotted fever
What is the epidemiology of Rickettsia rickettsii
Vector is the spotted wood tick
What is the pathology of Rickettsia rickettsii
- Fever
- Severe headache
- Maculopapular rash-with discolored spots from small hemorrhages
- Rash seen first on palms, soles of feet and wrists. Then spreads over body
What are Rickettsialpox caused by
Rickettsia akari
What is the vector for Rickettsia akari
mites that love on house mice
What are the symptoms for Rickettsia akari
Mild chills and fever
• Initial bump at bite, turns into vesicle
• Vesicles spread over body (similar to chickenpox)
What is trench fever
Rickettsia Quintana
What is the epidemiology of Rickettsia Quintana
- Only member of this genus grown in lab
- Most prevalent disease among Allied troops serving in the trenches during WWI.
- Current incidence is unknown, occurs in homeless population
- The body louse, Pediculus humanus, transmits classic trench fever
What is the pathology of Trench fever
- Fever can reach I 05°F ( 40.5°C) and stays high for five to six days at a time. The temperature then drops, and stays down for several days, usually recurring in five-to six-day cycles. An individual may experience as many as eight cycles of fever with the illness
- Skin rash is common
What is Q Fever
Coxiella burnetii
What is the epidemiology of Q fever
- Not transmitted by an arthropod
- Unusual because has an endospore form
- Cattle, sheep, and goats are the primary reservoirs of C. burnetii
- Bacteria are excreted in milk, urine, and feces of infected animals.
- Most importantly, during birthing bacteria are shed in high numbers within the amniotic fluids and the placenta.
- Endospores are resistant to heat, drying, and many common disinfectants.
- Inhale endospore from contaminated air
What is the pathology of Q fever
- Fever, chills, headache
- Develop atypical pneumonia
- NO skin rash
- Q fever outbreaks have resulted mainly from occupational exposure: veterinarians, meat processing plant workers, sheep and dairy workers, livestock farmers, and researchers at facilities housing sheep
