L 77 Lyme Disease Flashcards

1
Q

Name the 3 genera of pathogenic spirochetes

A

Treponema
Borrelia
Leptospira

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2
Q

What is the causative agent in North America for Lyme disease?

A

Borrelia burgdorferi

It is a spirochete bacteria

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3
Q

What is the reservoir and vector for Borrelia that causes Lyme disease?

A

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

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4
Q

How do the ticks get infected with Borrelia burgdorferi?

A

Ticks get infected the first time they feed on an infected host. The disease is not passed on from generation to generation (transovarial passage)

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5
Q

How long does it take for the disease to transfer to a human after a bite?

A

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.

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6
Q

How long do ticks live and when is the highest risk of human infection during the year?

A

Ticks live about 2 years

Spring and into Summer is the highest chance of infection when the Nymph stage is most prominent

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7
Q

Characteristics of Borrelia burgdorferi

A
Gram (-) spirochete
Microaerophile
Linear chromosome
Internal flagella makes it motile
Obligate parasites
Like BSK medium for growth
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8
Q

Borrelia burgdorferi virulence factors

A

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

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9
Q

What causes the problems and symptoms from the Borrelia infection?

A

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.

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10
Q

What are the stages of infection for Borrelia?

A

1) Early and localized infection
2) Disseminated infection
3) Persistent infection

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11
Q

Describe the early stage of infection by Borrelia

A

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)

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12
Q

Describe the Early disseminated stage of Lyme disease

A

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

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13
Q

Describe the late stage of lyme disease

A

months to years later
Lyme arthritis: persistent or intermittent in a few large joints
Lyme neuropathy: cognitive disturbances, radicular pain

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14
Q

How is Lyme disease diagnosed?

A

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

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15
Q

Treatment of Lyme Disease

A

Early and disseminated stages including only facial palsy: oral doxycycline unless

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16
Q

What is a possible and significant side-effect of treating Lyme Disease?

A

Jarisch-Herxheimer response: massive killing of the bacteria => release of cytokines causing this reaction

Symptoms: restless, aprehensive, intense rigors 30 mins, temp, resp, pulse, and BP increase, profuse sweating, decline in temp, and decrease in bp that requires close monitoring, can cause death

17
Q

What is Lyme-like disease (STARI)?

A

Vector: Amblyomma americanum
Infective agent not yet isolated
Erythema migrans smaller in diameter and more circular
Flu-ike symptoms
Recover rapidly after antibiotics (doxycycline 10 day)