Lyme Borreliosis Flashcards
What microorganism is responsible for lyme borreliosis?
borrelia burgdorferi
What are the main vectors for B. burgdorferi?
THe Ixodes tick
either I. pacificus on west coast
or I. scapularis on the east coast and here
in layman’s terms this is the deer tick or black legged tick
How long does an Ixodes tick need to be attached to ensure transmission of the bacteria?
WHy?
36 hours or longer
because when the tick isn’t feeding on something, the bacteria resides in the gut and it needs time to transfer to the salivary glands for transmission
Where do Ixodes ticks reside in their environment?
on grass and low brush, NOT trees
What are the three life stages of the deer tick? When will it pick up the bacteria? WHen will it transmit the bacteria to humans?
- larval stage
- nymphal stage
- adult stage
They will pick up the bacteria during their first blood meal which makes the into a nymph.
When the infected nymph bites us, that’s when we get the disease
So, you CAN”T get infected by being fed on by alarval tick - it’s transtatial passage
What are the two reservoir hosts for B. burgdorferi in the US? Do they get sick?
mice and deer
they don’t get sick
How can you tell a deer tick from a wood tick?
a deer tick is much smaller and they have black legs and a black dorsal shield
wood ticks (dermcentor variabilis) are bigger, have brown legs, and a colored dorsal shield (only the adult forms will feed on humans)
When is the peak month for Lyme Disease infections?
Summer - especially July
this coincides with the nymphal tick stage - it’s most active in July. THe adult form is more prevalent in the fall - but these usually aren’t attached to us as long as the nymph because we can see the adults better
What are some of the bacterial characteristics of B. burgdorferi?
- spirochete
- micro-aerophilic
- have 7 to 11 flagellae
- grow at 32 degrees celsium on a BSK medium
What trend has been seen in the number of reported cases of yme idsease per year?
It’s increasing - there may be more people being infected or we might just be better at recognizing it and reporting it.
Is there any support for a “chronic lyme disease”?
Not really
if you’re treated, you will not have a chronic lyme disease, but if you are NOT treated, you might
Is there any support for prescribing prolonged antibiotic therapy for persistent “symptoms”
no
What are the 3 stages of lyme disease and when do they occur?
early localized —– 1-2 weeks
early disseminated ——- Weeks to months
Late (persistent) ——– Month-Years
Describe what happens in early localized LB infection.
- gradual onset of symptoms - usually starting with lowgrade constitutional symptoms
- develop erythema migrans (60-80% of patient)
the rash will be erythematous, circular, at least 2 inches in diameter, painless, non-palpable, not itchy, no weeping (won’t necessarily be a bullseye rash)
What are some lab results associated with early localized LB?
CBC? LFT? ESR? CRP?
CBC and LFT may have nonspecific changes
ESR and CRP may be elevated
What symptoms can arrise in early disseminated LB?
multiple EM lesions
lymphadenopathy
arthralgias
migratory arthritis
bell’s palsy
radicular pain
polyneuritis
AV block
What are some symptoms associated with late (persistent) LB?
chronic arthritis
acrodermatitis chronicum atrophicans (mostly in Europe)
neurological impairments
What laboratory steps should you take to diagnose lyme disease?
serum screening with IFA, ELISA or EIA
Confirmatory serums with a western blott
You can also do PCR or culture
In the antibody screening test with a western blot, what is the requirement for a lyme disease diagnosis?
for IgM, you have to have at least 2 bands out of 3 possible
FOr IgG you need to have at least 5 bands out of 10
What are the issues with serologic testing for lyme disease?
- poorly standardized
- falst positive IgM results occur commonly
- IgM and IgG antibodies may persist for years after initial infection, so it can be hard to tell whether it’s a new or old infection
- early treatment may blunt of abrogat teh antibody response so you get a fals enegative
Which persists longer, IgM or IgG?
IgG
Does absolute antiboy titer correspond with severity of infection or new infection in someone who had a previous infection?
No
What acute and chronic illnesses should be considered in a differential diagnosis for lymes disease?
acute: anaplasmosis, babesiosis, RMSF, enterovirus infection
chornic: chornic fatigue syndrome, fibromyalgia, depression
A diagnosis of lyme disease is primarily a ____ diagnosis confirmed by ____.
a clinical diagnosis confirmed by lab studies
What is the primary treatment for early localized LB?
doxycycline for 2 weeks
you can also use amozycillin or cefuroxime
How does treatment differ for early localized LB and early disseminated LB?
you just use the same drugs for longer in early disseminated - a month instead of 2 weeks
Doxycyclin and amoxicillin are also used when there is arthritic and CNS involvement, but wha tis considered best with cardiac involvement?
IV ceftriaxone
Is prophylactic treatment after a tick bite useful?
Depends
it was helpful in a study that was done, but the n was pretty small and more people experienced harmful side effects from the dyxy than those that benefitted
What are some methods that protect against tick bites?
- DEET repellant on skin
Permethrin on clothin
light colored clothes so you can see them
socks outside pants
daily inspection of skin
