L 77 Lyme Disease Flashcards
Name the 3 genera of pathogenic spirochetes
Treponema
Borrelia
Leptospira
What is the causative agent in North America for Lyme disease?
Borrelia burgdorferi
It is a spirochete bacteria
What is the reservoir and vector for Borrelia that causes Lyme disease?
Small mammals and birds are the reservoir–White footed mouse most important
Larger mammals like white-tailed deer are reservoirs for the ticks to mature but not for the bacteria
Ticks (Ixodes) are the vector
How do the ticks get infected with Borrelia burgdorferi?
Ticks get infected the first time they feed on an infected host. The disease is not passed on from generation to generation (transovarial passage)
How long does it take for the disease to transfer to a human after a bite?
Takes 24-48 hours for the disease to transfer to the human so it the tick is removed in a timely manner you should be ok.
How long do ticks live and when is the highest risk of human infection during the year?
Ticks live about 2 years
Spring and into Summer is the highest chance of infection when the Nymph stage is most prominent
Characteristics of Borrelia burgdorferi
Gram (-) spirochete Microaerophile Linear chromosome Internal flagella makes it motile Obligate parasites Like BSK medium for growth
Borrelia burgdorferi virulence factors
OSP: (outer surface proteins) differentially expressed based on the different hosts and environment
OSPA: binds bacteria to tick gut, disabled when ready to move to salivary gland before transfer to next host
OSPC: invasion of the bacteria into skin to establish mammalian host infection
What causes the problems and symptoms from the Borrelia infection?
There are no endotoxins or proteases or other destructive molecules. The OSP’s bind to macrophages and cause release of cytokines that make a reaction like that to endotoxins. So, it is our own immune system that causes the problems.
What are the stages of infection for Borrelia?
1) Early and localized infection
2) Disseminated infection
3) Persistent infection
Describe the early stage of infection by Borrelia
Localized infection at the site of the bite
Incubation of 2-3 weeks
Multiplication of the bacteria in the skin
Readily treated by antibiotics
Erythema Migrans: Bull’s eye rash in 80% of cases
Non-specific constitutional symptoms that are flu-like (fatigue, fever, chills, headache, myalgia, arthralgia, LAD, but no respiratory or GI symptoms)
Describe the Early disseminated stage of Lyme disease
Weeks to months after infection
Lymphohematogenous spread
Bacteria move to other sites like joints, CSF, spleen, liver, heart, muscles
Causes: arthralgia, arthritis, erythema migrans in more areas, Bell’s palsy, radiculopathy, cardiac arrhythmias
Describe the late stage of lyme disease
months to years later
Lyme arthritis: persistent or intermittent in a few large joints
Lyme neuropathy: cognitive disturbances, radicular pain
How is Lyme disease diagnosed?
Early: erythema migrans, exposure in endemic area, no isolation of microbes required, treat with antibiotics
Serology if: travel to area, risk of exposure, symptoms of late or disseminated disease
2-Step test: 1) ELISA for anti-borrelia antibodies, 2) Western Blot looking for specific borrelia proteins
Both are highly specific and have no false positives
Treatment of Lyme Disease
Early and disseminated stages including only facial palsy: oral doxycycline unless
