Lyme Disease Flashcards
What type of infection is Lyme disease? How is it transmitted?
Zoonotic infection: ticks are its primary host
ixodid tick species are the vectors for Lyme
-ixodes scapularis is the species in northeastern and Midwestern Canada and U.S.
At what stage in the I.scapularis life cycle are they more likely to transmit the disease?
Nymph:infected
They are small and therefore difficult to detect
Who are the hosts for ticks?
1-rodents
2-white tailed deer are critical for tick survival
Birds most likely spread ticks over different geographic locations
Who are the dead end hosts for Lyme disease?
Domestic animals
Humans
Ticks cannot get Lyme disease from us
What spirochete causes Lyme disease?
Borrelia burgdoferi in North America
Europe and Asia: b. Afzelii and b.garinii
What is the risk of getting Lyme disease from ticks?
1-unengorged ticks pose essentially no risk
2-overall risk in endemic(greater than 20% of ticks infected) area is 1-3%
-this risk increases with degree of engorgement-10-25%
3-risk equates with duration of attachment, generally needs to be on you more than 36 hours
What Areas of NS are endemic for Lyme disease?
southern shore
- lunenberg
- more and more in HRM
What are the clinical manifestations of Lyme disease in the early localized stage of infection? (Stage 1)
What is the duration of stage 1?
duration: 3-30 days post bite
1-flu like symptom
2-erythema migrants:bull eyes rash , normally on the torso
What are the clinical manifestations of Lyme disease in the early disseminated stage of infection? (Stage 2)
What is the duration of stage 2?
Duration: days to months post bite Gets in the skin, injects bacteria and then you can get more systemic rashes 1-malaise, fatigue 2-diffuse erythema, malar rash 3-infects heart-AV block 4-polyarthritis 5-head and neck pain 6-May have no neurological findings
What are the characteristics of the erythema migrans that would make you think it is Lyme disease?
1-should be greater or equal to five centimetres is diameter for secure diagnosis
2-size normally expands over 24-48 hours
3-can vary in appearance
4-typically seen within a week to two weeks after the bite
What are the common manifestations of late stage Lyme disease? Stage 3
If untreated leads to:
1-neurologic, although uncommon in North America
2-rheumatologic:
-arthritis, typically in the knee
-inflammatory synovial fluid
-84% of individuals do not recall the tick bite**
What are the symptoms of post Lyme disease syndrome?
-can last more than 6 months after resolution of objective manifestations with therapy
-can be fatigued and have pain
But there is no chronic Lyme disease
-little or no evidence of b.burgdorferi infection after being on antibiotics for 1 month
How is Lyme disease diagnosed?
Controversial
-early localized Lyme disease: predominately a clinical one. See someone with erythema migrans from endemic area-Treat them! Don’t test
- serology-two tiered approach:screening ELISA(sensitive) and confirm positive by western blot
- clinical information is helpful when interpreting and ordering tests
What shows a positive test for western blot if Lyme disease? Who should have a western blot done?
5 of 10 IgG bands
Patients with symptoms greater than 4 weeks duration except if they were already treated
How accurate is the serology test?
Accurate during late stages of the disease
Does not work in acute setting
Neurological symptoms:bilateral Bell’s palsy
