(Section C: Bacteriology) Lecture 24 Flashcards
When was Lyme Disease first recognized?
1975 in rural communities surrounding Lyme, Connecticut
What was Lyme Disease first misdiagnosed as?
Rheumatoid arthritis
* Due to ‘polyarthritis’ symptoms
Borrelia burgdorferi
* Gram stain
* Shape
- Gram negative
- Spirochete
Describe:
Size proportions of Borrelia burgdorferi
Thin (~0.5 μm) and long (>10 μm)
Where is Borrelia found?
Found throughout temperate zones in the Northern Hemisphere
What is the main reservoir for Borrelia burgdorferi?
White footed mice
* Transferred to ticks
What ticks are the primary transmitters?
- Ixodes scapularis
- Ixodes pacifica
What areas do the ticks inhabit?
- I. scapularis: East coast
- I. pacifica: West coast
How do ticks transmit disease?
- Do not fly or jump
- Sit on grasses/shrubs and wait for a host to pass by
Besides humans, what else can get Lyme Disease?
Cat and Dogs
* Deers cannot get Lyme Disease because of their immune system
Can Lyme Disease transmit between person-person?
No evidence
Where are ticks bites often found?
Found often in ‘hard-to-see’ areas
Ixodes life cycle
3 stages
* Larvae
* Nymph
* Adult
Does Borrelia burgdoferi transfer between eggs and larvae?
No transmission between adult to egg
What things can carry B. burgdorferi other than lice?
- Mice
- Squirrels
- Birds
How does Lyme Disease get into the host?
Inserts through a feeding tube with barbs
Why do we not feel tick bites?
The tick secretes a local anesthetic
True or False:
Transmission of Lyme disease occurs in the first 24 hrs
False, the transmission is not thought to occur during the first ~24 hours following bite
What stage of ticks normally transmit disease?
Nymphs
What should you not do when removing ticks?
- Do not squish the tick body
- Do not burn the tick off
- Do not apply petroleum jelly
What must Borrelia burgdorferi do to propagate through it’s life cycle?
Cause disseminated and persistent infection to propagate through it’s life cycle
What is the central event in the development of Lyme Disease?
Hematogenous dissemination
What is the migration of Borrelia burgdorferi in the skin known as?
Erythema migans lesion
* “Bulls eye rash”
How do compounds in tick saliva inhibit dendritic cells?
(4 points)
- Decreased phagocytosis
- Decreased maturation
- Decreased inflammatory mediators
- Decreased antigen presentation
How do Borrelia burgdorferi move?
Moves in a corkscrew like manner due to periplasmic flagella (axial filaments)
What are axial filaments?
Periplasmic flagella
* Axial filaments
* Promotes movement through extracellular matrix of host tissues and invasion of vasculature
What is unusual about the Borrelia burgdorferi outer membrane?
- No LPS
- Many surface expressed lipoproteins that can act as adhesins
Why does Borrelia burgdorferi express so many lipoproteins?
To escape from the blood flow, so that it can invade the endothelium
What is unusual about Borrelia burgdorferi genetic structure?
- ‘Linear’ chromosomes
- Multiple plasmids, some circular and some linear
True or False:
Plasmids vary from strain to strain in Borrelia burgdorferi
True
What are plasmids needed for in Borrelia burgdorferi?
Infection
* Have limited metabolic capability
What are the 4 stages of Lyme Disease?
- Early (Localized) Stage
- Early Disseminated Stage
- Late Disseminated Stage
- Post-treatment Lyme Disease syndrome
Signs/Symptoms:
Early (Localized) Stage
- Bulls eye rash (~25% of patients do not have a rash)
- Flu-like symptoms (fever, chills, fatigue, body aches)
When does the Early (Localized) Stage of Lyme disease occur?
~1-2 weeks after tick bite
Signs/Symptoms:
Early Disseminated Stage
- Multiple rashes
- Pain and swelling of large joints
- Heart palpitations
- Meningitis (severe headaches, neck stiffness)
- Bell’s (facial) palsy
Define:
Heart Palpitations
Interference with heart electrical signals
Define:
Bell’s (facial) palsy
Loss of muscle tone on one or both sides of the face
What mechanism does Borrelia burgdorferi use to traverse the BBB?
Paracellular travel
How long does it take for the Early Disseminated Stage to occur?
Days to weeks
Signs/Symptoms:
Late Disseminated Stage
- Serious long-term disability
- Muscle pain
- Arthritis
- Severe pain and swelling in large joints
- Neurological problems (shooting pains, numbness, tingling in hands and feet, memory)
Approximately what percentage of patients develop neurological problems in the Late Disseminated Stage?
~5%
How long does it take for the Late Disseminated Stage to occur?
Months to years
Signs/Symptoms:
Post-treatment Lyme disease syndrome
- Fatigue
- Muscle and joint pain
- Cognitive defects
- Sleep disturbances
How well do antibiotics work in the Late Disseminated stage?
Work slowly
Approximately what percentage of individuals develop Post-treatment Lyme disease syndrome?
10-20%
What is the cause of Post-treatment Lyme disease syndrome?
Unknown
* May involve an autoimmune response
* Possibly persistent infection
How long does it take most patients to recover from post-treatment Lyme disease syndrome?
After a few months
* Long-term antibiotics are not thought to help
What is the distribution of ticks continuing to spread?
- Migratory birds
- Warmer climates
Prevention of Lyme Disease
- Avoid low lying brush, long grass, wooded areas endemic with Lyme disease
- Stay on paths
- Wear long pants + shirts
- Light colored clothing
- Repellants (containing DEET)
- Check for ticks and remove them
Diagnosis of Lyme Disease
- Symptoms
- Tick bite history
- Anti-B. burgdorferi antibody tests
- Submit tick for testing
Why is the anti-B. burgdorferi antibody test controversial?
False negatives often due occurs (early testing and genetic diversity of B. burgdorferi causes this)
* Sensitivity is not very good
Treatment for Lyme Disease
- Watch for signs and symptoms
- Antibiotic treatment (2-4 week course)
What can happen in Lyme disease without treatment?
- Joint issues
- Heart issues
- Nervous system issues
What is “Chronic Lyme Disease”?
Very controversial
1. Chronic infection by B. burgdorferi
2. Diagnosed without evidence of prior Lyme Disease
What are signs/symptoms of “Chronic Lyme Disease”?
- Fatigue
- Headaches
- Sleep disturbances
- Cognitive dysfunction
- Neurological problems
What treatment was found to be not helpful for “Chronic Lyme Disease”?
Long-term antimicrobial therapy
LYMErix
Outer memberane protein vaccine for Lyme disease
How effective is LYMErix in humans?
75% effective
Why was the vaccine pulled from the markey (LYMErix)?
‘Lack of demand’
* Lawsuits and claims that vaccine caused arthritis (no evidence)
Is the LYMErix vaccine recommended?
“Should be considered” for those in high risk areas
What is the LYMErix vaccine approved for only?
Dogs
