Vector-Borne Diseases

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3 most important arthropod vectors in U.S. :

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Ticks, mosquitoes, fleas

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Where do we see Lyme?

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NE, MW, CA/WA/OR

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Borrelia burgdorferi

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Borrelia burgdorferi

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Life cycle of Lyme disease:

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*blood meal from mouse/other animal
*mild winter, tick nymph takes blood meal and passes disease.

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LYME DISEASE: NYMPH STAGE

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Lyme Disease: Erythema Migrans
*also present with fever, chills, stiff neck

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LYME DISEASE
*Nymph stage on right, adult on left
*Nymph most likely to pass disease

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LYME DISEASE: ENGORGED TICK
*EEEEEEEWWWWWWWW
*Must be attached for 24-36 hours.

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LYME DISEASE: ENGORGED TICK
-engorged tick, deeply embedded in the skin

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Comparison of Ticks:

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*A. americanum is "lone star tick"
*I. scapularis is in the NE
*D. variabilis transmits RMSF

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LYME DISEASE: ERYTHEMA MIGRANS
*also present with fever, chills, stiff neck

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LYME DISEASE: ERYTHEMA MIGRANS
*rash is fading; size is variable
*also present with fever, chills, stiff neck

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LYME DISEASE: ERYTHEMA MIGRANS
*also present with fever, chills, stiff neck

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LYME DISEASE: ERYTHEMA MIGRANS
*also present with fever, chills, stiff neck
*rash has faded here

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LYME DISEASE: ERYTHEMA MIGRANS
*also present with fever, chills, stiff neck

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LYME DISEASE: MULTIPLE EM
*doesn't mean more than one bite!
-rash pops up as bacteria move through the blood.

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Lyme Disease: Unusual Presentation of a rash

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LYME DISEASE: BELL’S PALSY/ARTHRITIS
SECOND STAGE OF LYME DISEASE
*follows ~2-3 months after the bite.
*NS involved (aseptic meningitis-lymphocytic LP; neuritis; III, IV nerve palsies)
*Cardiac: heart block (or AV block)
*Eye: conjunctivitis, optic neuropathy (uncommon)

*These will likely go away on their own

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What's the third stage of Lyme Disease?

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*Frank Arthritis (MS, tendons, bone, mm, migratory, intermittent/relapsing for years) occurs in 60% of pts who weren't treated in stage I.
*Primarily LARGE joints (knee, elbow, shoulder; asymmetric)
*10% develop chronic arthritis and permanent damage to joints.

*Neuropsych symptoms (mostly in kids/young adults)--problems concentrating, mood swings, irritability
*Focal CNS lesions; encephalitis, transverse myelitis
*Chronic fatigue

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% of clinical syndromes in Lyme:

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How do you diagnose Lyme disease?

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*ELISA (not great at catching stage I disease)
*followed by Western blot (distinguishes acute and chronic)
*PCR testing only works for synovial fluid
*C6 Peptide test is a follow-up test to confirm disease is gone.

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How do you treat Lyme disease in stage I?

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Stage 1: Doxycycline/Amoxicillin/Cefuroxime Axetil/Ceftriaxone/IV penicillin (cures 97-98% of cases)

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How do you remove a tick?

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-Use forceps, pull perpendicularly
-Get the head out

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Where does Erhlichiosis occur?

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AKA anaplasmosis.

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Lone Star Tick -- Ehrlichiosis

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What kind of ehrlichiosis do we get in the NE?

What kind of ehrlichiosis do they get in TX?

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Human Granulocytic Ehrlichiosis

Human Monocytic Ehrlichiosis

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Ehrlichiosis: Morulae
*looks like a cluster of berries (the bacteria inside a monocyte
*HME

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Ehrlichiosis: Morulae
*the bacteria inside a PMN.
*HGE

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Ehrlichiosis: Morulae

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Ehrlichiosis
Morulae on EM

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Rupture of Morula
*it then spreads!

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Treatment of Ehrlichiosis:

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Doxycycline
Chloramphenicol or Rifampin for kids

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what is this and what's it carried by?

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Babesiosis
-inside RBCs
-Carried by ixodes tick; reservoir is white-footed mouse
-RBCs rupture, but not all at once
*Splenectomized pts can die.
*Can be carried by blood transfusion

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How do you diagnose babesiosis

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*Thick and thin smear. It's a parasite in the RBC.
*Look for the ring form and the cross form

*serology- PCR or ELISA

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Where does RMSF occur?

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Treatment for babesiosis:

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-IV clindamycin or po quinine
-might need an exchange transfusion if it's really far advanced

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Tularemia:

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*Francisella tularensis
*Tx by dog ticks
*handling of infected rabbits, rodents, animal bites
*10 to 15% mortality
*usually ulceroglandular--> axillary lump
*Aminoglycoside treatment

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RMSF:

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*Rickettsia rickettsiae
*andersoni tick (west coast) and dog tick (east coast)
*8% mortality
*Not all pts present with usual symptoms
*Rash preceded with HA, pains, high fever

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RMSF: Petechial Rash

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RMSF: Late Stage

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RMSF: Petechial Rash

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RMSF: Skin Biopsy
*this is one way to diagnose it

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Rickettsia within Endothelial cells
*RMSF