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46 Cards in this Set
- Front
- Back
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What are rickettsiae?
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Obligate intracellular parasites that divide by binary fission within host cells.
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What are three reasons rickettsiae are not considered viruses?
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Contain both DNA and RNA
Synthesize own proteins Susceptible to antibiotics |
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What molecule does rickettsiae require for growth?
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ATP
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What lipopolysaccharides do Rickettsia and Proteus share?
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OX-2
OX-19 OX-K |
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What is the implication of Rickettsia lipopolysacchaides?
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Agglutination in the Weil-Felix test
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What are three rickettsial diseases?
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Rocky Mountain Spotted Fever
Typhus Lyme disease |
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What is the classic triad of symptoms from rickettsial infection?
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Headache
Fever Rash |
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How does the rash in typhus spread?
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Outward from the runk to the extremities.
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How does the rash in Rocky Mountain Spotted Fever spread?
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Inward form the extremitits to the trunk.
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What type of cells do rickettsiae have tropism for?
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Endothelial cells that line blood vessels
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What does rickettsial infections tropism for endothelial cells lining blood vessels cause?
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Vasculitis resulting in a rash with small, petechial hemorrhages.
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What is the treatment for most rickettsial infections?
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Doxycycline, tetracycline, or chloramphenicol.
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What are rickettsiae transmitted?
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Arthropod vector
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What disease and most common vectors are associated with R. rickettsii?
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RMSF: tick
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What disease and most common vectors are associated with R. typhi?
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Endemic typhus: flea
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What disease and most common vectors are associated with R. prowazekii?
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Epidemic typhus: human body louse
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What serological tests are used to diagnose rickettsial disease?
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1) ELISA
2) Indirect immunofluorescence 3) Weil-Felix test |
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What does the Weil-Felix reaction detect.
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Antirickettsial antibodies
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Is the Weil-Felix reaction positive in RMSF?
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YES
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Is the Weil-Felix reaction positive in Typhus?
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YES
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How are rickettsiae cultured?
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Inoculated into chick embryo yolk sac or cell culture.
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What is the causative organism in RMSF?
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Rickettsii
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Is there Human-to-Human RMSF transmission?
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NO
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Why is there no human-to-human RMSF transmission?
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R. rickettsii must complete its lifecycle in the tick (vector).
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How is RMSF transmitted and give two examples?
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Arthropod vector
Wood Tick (Dermacentor andersoni) Dog Tick (Dermacentor andersoni) |
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What number of rickettsial diseases are caused by RMSF in the US?
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95%
+/- 1000 |
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What time of year do most cases of RMSF occur?
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Spring and early summer (when ticks are most active).
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Where in the US is RMSF usually found?
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East coast (applachian and ozark mountains)
NOT IN THE ROCKIES |
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What are three symptoms of RMSF?
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Rash
Headache Fever |
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How does the RMSF rash appear?
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Migrates from the palms and soles to the wrists, ankles, and trunk.
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What are two other infectious causes of a rash on the palms and soles?
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1) Syphilis caused by Treponema pallidum
2) Hand-foot-and-mouth disease aused by coxsackievirus (Picornaviridae). |
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What are six complications of RMSF?
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Edema
Delirium DIC Shock Coma Death |
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What is the treatment for RMSF?
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Docycycline
Tetracyclie Chloramphenicol |
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What is the prognosis for someone with RMSF?
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Potentially fatal if untreated, total cure if diagnosed and treated promptly.
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What kind of vaccine is used to protect against RMSF?
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NONE
there is no vaccine against RMSF. |
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What is the differenct between typhus and typhoid fever?
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Typhus is a rickettsial disease with an arthropod vector.
Typhoid fever is an enteric fever accompanied by bacteremia caused by Salmonella enterica. |
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What is the causative organism of typhus?
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R. typhi
R. prowazekii |
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How is typhus transmitted?
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Arthropod vector (human skin louse)
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What is the reservoir for R. typhi or R. prowazekii?
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Only humans, there are no animal reservoirs.
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What are four symptoms of typhus?
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1) Centrifugal maculopapular rash (spreads outward from trunk)
2) Sudden onset chills 3) Fever 4) Headache |
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What are six complications of typhus?
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1) Bacterial pneumonia
2) Severe meningoencephalitis 3) Delerium 4) Shock 5) Coma 6) Death |
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What sequence of events leads to typhus?
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1) Human body louse bites a bacteremic individual and ingests the bacteria.
2) Bacteria multiplies in louse gut epithelium 3) Excreted in feces of the louse during act of biting the next person. 4) Autoinoculated by the person while scratching the bite. |
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What is the treatment for typhus?
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Doxycycline, tetracycline, or chloramphenicol.
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What is Brill-Zinsser disease?
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A milder, recurrent form of epidemic typhus that occurs 10-40 years after initial infection.
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What kind of vaccine is used to protect against typhus?
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Formalin-killed R. prowazekii
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Who gets vaccinated for typhus?
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Restricted for military use.
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