Lec10_Lyme_Disease_and_Rabies - Lyme Disease Lyme Disease...

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Lyme Disease
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Lyme Disease Lyme borreliosis (Lyme disease) first came to prominence about 30 years ago, following its emergence in the area of Lyme, Connecticut. It is the most common vector-borne bacterial infection in temperate regions of the northern hemisphere, caused by several genospecies of Borrelia burgdorferi , a spirochaete transmitted by ticks of the Ixodes ricinus complex. Over 35 000 confirmed or probable cases were notified in the United States in 2008. Most occur in 10 north-eastern and north-central states.
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First Recognition of Lyme Arthritis in Connecticut, 1976
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Characteristics of the First 52 Cases Identified
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Borrelia burgdorferi Borrelia are motile, helical, Gram-negative spirochetal bacteria that are maintained in zoonotic cycles. The genome is small and consists of an unusual linear chromosome and 21 linear and circular plasmids. The structure includes an inner membrane, and periplasmic flagella. The primary outer surface lipoproteins (Osps) vary antigenically between strains and can undergo phase shifts as an important means of organisms adaptation to growth in vertebrate and invertebrate hosts.
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Lyme Disease: Early Disease B. burgdorferi is introduced into the skin of a susceptible host by the saliva of an infected tick. The earliest manifestation is often a slowly expanding skin lesion that appears within days to weeks at the site of the bite. The lesion starts as a red macule or papule. The later appearance of the lesion, which may become very large, is characteristic of an EM lesion with an erythematous border and a clearing center. The lesion is usually warm but not painful or itchy.
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Typical Skin Lesion: Erythema Migrans (EM) Source: CDC
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Typical Skin Lesion: Erythema Migrans (EM) Source: CDC
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Lyme Disease: Early Disease This stage of the disease is often accompanied by flu-like symptoms including fever, chills, malaise, stiff-neck, and headache. At this point, the spirochaete can be isolated from the blood. Even in the absence of treatment, symptoms will typically resolve in 3-4 weeks.
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Lyme Disease: Secondary Disease The secondary disseminated phase of the disease usually occurs within 1-6 months after exposure and may manifest in more generalized EM lesions, myocarditis or neurological disease. There are typically more intense systemic manifestations with severe lethargy, encephalopathy, myalgias, generalized lymphadenopathy and splenomegaly.
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Lyme Disease: Secondary Disease Carditis occurs in approximately 5% of untreated infected individuals and presents with palpitations associated with atrioventricular conduction abnormalities and occasionally S-T segment and T-wave changes on the electrocardiogram. These signs and symptoms generally resolve within 6 weeks.
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Lyme Disease: Secondary Disease The bacteria frequently invades the central nervous system and neurological complications occur in 15% of untreated patients.
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