Micro - vector-borne bacteria
Terms
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- What is the intrinsic incubation time? Extrinsic incubation time?
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*intrinsic = time required for an infected host to become infectious
*extrinsic = time required for the vector to become infectious - What is the "grace period"?
- The time required for transmission of a pathogen from a vector to a human.
- What bacteria cause Lyme disease? What does it look like?
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*Borrelia burgdorferi
*spirochete - What is the arthropod vector for the causative agent for Lyme disease?
- Black-legged tick (2 species)
- What is the grace period for Lyme disease?
- 48 hours
- Lyme disease is usually transmitted when its vector is in what stage of life?
- Nymph
- Where is Lyme disease most prevalent? During what time of year?
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*the Northeast and upper Midwest
*spring and summer months - What are four reasons for the increase in Lyme disease prevalence?
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*amt of forested land has increased
*human population has increased
*more people are living in wooded areas
*increased outdoor recreation - What is the main reservoir host for the causative agent of Lyme disease?
- Mice
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T/F:
The bacteria that causes Lyme disease mediates pathogenesis by an LPS reaction. - False: Borrelia does not have LPS. Immune response is mediated in part by TLR-2 binding to lipoprotein though.
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T/F:
The agent that causes Lyme disease has a large number of plasmids, and ~10% of its genome codes for outer membrane components. - True: Borrelia has 25-30 plasmids.
- What are the characteristic symptoms of Lyme disease?
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*H/A
*fever
*erythema migrans - bullseye rash
*lymph node swelling -
T/F:
There is no definitive tick bite history in over 50% of Lyme disease cases. - True.
- If left untreated, in 1-2 weeks Lyme disease may become systemic. What are the symptoms of this?
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*infection of CNS and PNS causes numbness, weakness, memory and mood problems
*joints and tendons may be infected
*infection of CV system causes weakness and arrhythmia - What are the three stages of untreated Lyme disease?
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1.Skin
2.Blood
3.Organs - What are the means of diagnosing Lyme disease?
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*culture from skin scrapings
*Serology: ELISA, Western blot - What is the cause of treatment-resistant Lyme arthritis?
- Believed to result from autoimmune damage directed towards cross-reactive epitopes.
- What are two ways the agent for Lyme disease evades immune response?
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1.Antigenic variation through DNA recombination
2.Phasic expression of surface proteins - What are the two most prominent vectors of R. rickettsii in the US?
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*dog tick (east)
*rocky mountain wood tick (west) - How is R. rickettsii transmitted between ticks? Where in the tick does it live? What implications does this have
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*via small mammal intermdiate host
*vertical transmission in eggs and larvae
*lives in salivary glands
*grace period shortened to 10-24 hrs - What are the bacterial characteristics of R. rickettsii?
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*small coccobacillus
*envelope similar to G-
*obligate IC pathogen - What cell types does R. rickettsii target? How does it enter these cells?
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*endothelia
*taken up by endocytosis, secrete lysin which allows escape to the cytoplasm - How does R. rickettsii move in the human host? What benefit does this give the bacteria?
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*actin-based motility
*polymerizes host actin to effect movement to adjacent cell
*results in a double-walled vacuole which the bacteria is then able to lyse
*avoids contact with extracellular space - What are 3 early symptoms of RMSF?
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1.Fever
2.sore throat
3.petechial rash that begins at the extremities (not always present on adults) - Describe the pathogenesis of R. rickettsii.
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*attacks and damages endothelial cell membrane
*platelets stick to altered membrane leads to DIC
*blood leakage contributes to edema and shock - How is RMSF diagnosed?
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*Serology: IFA and latex agglutination
*Tx should begin based on clinical findings - What disease is caused by Erhlichia chaffeensis? What is the vector for this bacteria? What cell type is infected?
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*Human Monocytic Erhlichiosis
*lone star tick
*macrophages and monocytes - What disease is caused by Anaplasma phagocytophila? What is the vector for this bacteria? What cell type is infected?
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*human granulocytic erhlichiosis
*black-legged tick
*neutrophils - What is a "morula"?
- A vacuole filled with ehrlichia or anaplasma.
- What are 4 diseases carried by the black-legged tick?
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*Borrelia b. (Lyme disease)
*Anaplasma phagocytophila (HGE)
*Babesia
*Tick-borne encephalitis virus