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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?
2.sore throat
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
*black-legged tick
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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