BIOL334- Lyme Disease Flashcards
1
Q
What is Lyme disease?
A
Lyme disease is an infection caught from the bite of an infected tick.
- Most common tick borne disease in US/ Europe
- 300,00 Americans and 85,000 Europeans get Lyme disease
- Can affect people all ages
2
Q
What causes Lyme disease?
A
Borrelia burgdoferi (spirochete bacteria)
3
Q
Do patients recover from Lyme disease?
A
- When treated with antibiotics early enough patients recover fully
- But if left untreated can spread to joints, heart and NS.
4
Q
Describe Borellia burgdoferi
A
- Spiral shape (spirochete) bacteria
- Periplasmic flagella (internal flagella)
- Bundles of flagella wind around the flexible rod shaped cylinder- flagella control movement in blood stream
- Can move along sides of the blood vessels without getting swept away by bonds called catch bonds
5
Q
How can Borellia burgdoferi move through the bloodstream
A
- Borrelia can move along the sides of blood vessels to spread throughout the body without getting swept away by blood by blood catch bonds called BBK32.
- Catch bonds allow borrelia to keep moving, one bond gets broken as another stays attached and the load moves forward in a stepwise motion.
- The formation of these bonds allows Borrelia to keep moving forward and infect other organs- it is a virulence trait
6
Q
How does the flagella allow Borrelia to infect other organs?
A
- Flagella to control movement in the blood stream, the flagella wrap around the bacteria to propel forward.
- This allows Borrelia to control entry and exit and can therefore go on to infect other organs
7
Q
Describe how Borrelia burgdoferi has a unique genome
A
- One large linear chromosome ~850 encoding genes
- Also contains 21 other linear and circular plasmids
- The genomic organisation of Borrelia is unique due to the high number of plasmids. Some strains lacking a complete set of plasmids are unable to successfully infect their host.
- Plasmid Ip25 is necessary in Borellia infection.
- Sequenced genome do not contain any obvious genes encoding for pathogenesis therefore the mechanisms are unknown.
- Lacks iron containing enzymes and iron containing proteins in the ETC so it uses Manganese instead- overcomes the problem of having to scavenge for iron.
8
Q
What type of ticks carry Lyme disease?
A
- European
- Black legged
- Rocky Mountain Tick
9
Q
Describe the B.burgdoferi life cycle
A
- Uninfected larval ticks acquire Borrelia by feeding on infected small animals such as rodents
- Spirochetes multiply and persist in midguts of infected ticks through the moult to nymphal stage
- When infected nymphal ticks feed, the spirochetes migrate from the midgut to the salivary glands
- When the tick takes a blood meal from the human host spirochetes (Borrelia) is transferred to the human
10
Q
Explain why Lyme disease is seasonal
A
- Ticks reproduce better and are more active in the summer months
- Higher levels of human outdoor activity results in increased exposure to ticks
11
Q
Describe the major reason for an increase in ticks
A
- More deer (carry ticks)
- Suburbanisation (living closer to animals) means we are more exposed to deer and the ticks they carry
- Climate change (helps ticks reproduce and. live in more areas of the UK).
12
Q
Describe the 2 stages in Lyme Disease
A
Stage 1:
- Flu like symptoms (7-14 days)- headache, fever, muscle and joint pain, dizziness
- Transient inflammatory skin rash known as Erythema Migraines (EM)- spirochetes are localised to the skin
Stage 2:
- Weeks or months after bite
- Involves organs to which spirochetes have disseminated, including joints, heart, NS and include arthritis, carditis and neuropathies (meningitis-rare)
- Can develop chronic systems that are unresponsive to antibiotics
13
Q
What happens if Lyme disease is not treated?
A
- If Lyme disease is not treated, you can get progression into stage 3 of the disease with chronic arthritis, neuroborreliosis (disorder of CNS) and skin disorders
14
Q
How does Lyme disease enter the body and spread?
A
- Borrelia spirochetes are inoculated into the skin by bites of infected ticks and initially establish a localised infection, that causes a painless rash called erythema migrans (EM).
- As spirochetes migrate from the site of the tick bite they penetrate vessels and transiently present in the blood, in which they disseminate throughout the body (can do this because of catch bonds BBK32).
- Spirochetes subsequently exit the blood and various tissues and organs where they can establish persistent infections- heart, joints, skin, bones
15
Q
Infection cycle of Borrelia (how does Borrelia migrate from the gut to salivary glands)
A
- As an infected tick feeds, Borrelia migrates to the salivary glands and is transmitted via saliva to the host
- At the same time, Borrelia involves a dramatic switch in major surface proteins (from OspA to OspC).
- The Borrelia encounters the tick protein Salp15 in the salivary glands and Salp15 binds to OspC.
- In the presence of neutralising antibodies, from immune hosts, Borrelia with both OspC and Salp15 can survive.
