Glossary of Micro - vector-borne bacteria
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- What is the intrinsic incubation time? Extrinsic incubation time?
- *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?
- *Borrelia burgdorferi
- 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?
- Where is Lyme disease most prevalent? During what time of year?
- *the Northeast and upper Midwest
*spring and summer months
- What are four reasons for the increase in Lyme disease prevalence?
- *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?
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.
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?
*erythema migrans - bullseye rash
*lymph node swelling
There is no definitive tick bite history in over 50% of Lyme disease cases.
- If left untreated, in 1-2 weeks Lyme disease may become systemic. What are the symptoms of this?
- *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?
- What are the means of diagnosing Lyme disease?
- *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?
- 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?
- *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
- *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?
- *small coccobacillus
*envelope similar to G-
*obligate IC pathogen
- What cell types does R. rickettsii target? How does it enter these cells?
*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?
- *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?
3.petechial rash that begins at the extremities (not always present on adults)
- Describe the pathogenesis of R. rickettsii.
- *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?
- *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?
- *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?
- *human granulocytic erhlichiosis
- What is a "morula"?
- A vacuole filled with ehrlichia or anaplasma.
- What are 4 diseases carried by the black-legged tick?
- *Borrelia b. (Lyme disease)
*Anaplasma phagocytophila (HGE)
*Tick-borne encephalitis virus
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