Lyme Disease and Tick-borne Illnesses - Key Concepts Flashcards

A comprehensive set of vocabulary-style flashcards covering Lyme disease, RMSF, Anaplasmosis, Ehrlichiosis, Bartonella, Varicella zoster, and cellulitis with common presentations, diagnostics, and treatments as provided in the notes.

Lyme disease causative agent

Borrelia burgdorferi, a spirochete transmitted by ticks (primarily Ixodes species).

Lyme disease reservoir hosts

Deer, cattle, and white-footed mouse.

Lyme disease major vector in the US

Ticks (primarily Ixodes scapularis); peaks in early summer.

Erythema migrans (EM)

Bull’s-eye rash at the tick bite site, 3–32 days after bite; may be absent in about 20% of patients; expands to a large annular lesion with bright red outer border and central clearing.

Stage 1 Lyme disease

Localized infection with flu-like symptoms and EM.

Stage 2 Lyme disease

Disseminated infection with migratory arthralgias, meningitis/encephalitis, facial nerve palsy, peripheral neuropathy, carditis/heart block, and disseminated EM lesions.

Stage 3 Lyme disease

Persistent infection with large-joint arthritis; possible postinfectious Lyme arthritis and subtle encephalopathy.

Post-Lyme syndrome (chronic Lyme disease)

Persistent symptoms after treatment (pain, fatigue, cognitive issues) with normal inflammatory/neurologic findings; antibiotics have not shown clear benefit.

Lyme serology testing strategy

Two-step approach: screen with ELISA; reflex to Western blot if positive/equivocal; confirm with band criteria.

Lyme ELISA

Initial screening test; may be negative early in infection.

Lyme Western blot IgM criteria

Positive if two of three IgM bands are present.

Lyme Western blot IgG criteria

Positive if five of ten IgG bands are present.

Doxycycline for erythema migrans (adults)

100 mg PO twice daily for 10–14 days.

Alternative antibiotics for EM in Lyme

Amoxicillin 500 mg PO three times daily for 14 days; Cefuroxime 500 mg PO twice daily for 14 days; Azithromycin if intolerant.

Lyme facial palsy treatment (adults)

Doxycycline 100 mg PO twice daily for 14–21 days.

Lyme arthritis treatment duration

Doxycycline 100 mg PO twice daily for 28 days; alternatives include amoxicillin or cefuroxime for 28 days.

Lone Star tick allergy connection

Lone Star tick bite associated with alpha-gal (red meat) allergy in some individuals.

RMSF organism

Rickettsia rickettsii.

RMSF vector

Dog tick and wood tick.

RMSF incubation period

4–10 days.

RMSF rash progression

Maculopapular rash starting on wrists/ankles, blanchable, spreading to trunk and extremities; may involve palms/soles and become petechial.

RMSF diagnosis

Indirect immunofluorescence assay (gold standard); PCR from rash biopsy; titers may not be detectable until 7–10 days.

RMSF treatment

Doxycycline 100 mg PO twice daily for 5–7 days and until 72 hours after fever subsides; applicable to children and adults; desensitize if allergic.

Anaplasma phagocytophilum

Bacterium causing Anaplasmosis; transmitted by ticks; NE and upper Midwest; peaks in summer.

Anaplasmosis signs

Fever, malaise, myalgias, headache, nausea/vomiting; can progress to respiratory distress, septic shock, multiorgan failure, rhabdomyolysis, meningoencephalitis.

Anaplasmosis diagnosis

CBC with leukopenia and thrombocytopenia; PCR most sensitive in first week; IFA IgG often negative early; morulae on peripheral smear; check for Lyme co-infection.

Anaplasmosis treatment

Doxycycline 100 mg every 12 hours for 10–14 days; rifampin if pregnant or doxy intolerance.

Ehrlichiosis agent

Ehrlichia species.

Ehrlichiosis diagnosis

CBC with leukopenia and thrombocytopenia; elevated LFTs; PCR most sensitive in first week; IFA; morulae on smear; IgG negative early.

Ehrlichiosis treatment

Doxycycline 100 mg every 12 hours for 5–7 days and until 72 hours after fever resolution with clinical improvement.

Bartonella henselae

Cat scratch disease; self-limiting; transmitted via cat scratch, bite, or lick (flea-feces origin).

Typical Bartonella presentation

Papule or pustule at inoculation and regional lymphadenopathy near inoculation site; fever and malaise common.

Atypical Bartonella disease

Parinaud’s oculoglandular syndrome; hepatosplenic disease; neuroretinitis; arthralgias; neurologic symptoms; fever of unknown origin.

Bartonella diagnosis

Serology (IgM/IgG); PCR from lymph node aspirate.

Bartonella treatment mild-moderate

Azithromycin 500 mg on day 1, then 250 mg on days 2–5.

Bartonella treatment severe

Doxycycline 100 mg twice daily + rifampin 300 mg twice daily for 4–6 weeks.

Varicella zoster spectrum

Varicella (chickenpox) and herpes zoster (shingles).

VZV transmission

Respiratory droplets or contact with infected vesicular fluid.

Varicella zoster rash

Unilateral dermatomal vesicles on an erythematous base; “dew drops on a rose petal”; pain/itching may precede rash.

VZV ophthalmic involvement

Herpes zoster ophthalmicus; trigeminal nerve involvement; Hutchinson sign; ophthalmologic emergency.

Ramsay Hunt syndrome

Herpes zoster involving the facial nerve; ear pain and facial weakness.

VZV complications

Postherpetic neuralgia; keratitis; uveitis; meningitis/encephalitis; pneumonia; hearing loss; disseminated disease.

VZV diagnosis

Usually clinical; PCR from vesicular fluid, CSF, or blood; Tzanck test has low sensitivity; shows multinucleated giant cells.

VZV treatment

Antivirals if rash onset <72 hours or new vesicles appear after 72 hours: acyclovir, valacyclovir, or famciclovir; pain control and wound care; hospitalization for severe/immunocompromised.

Shingrix vaccine

Recombinant zoster vaccine indicated for adults >50; two-dose schedule (dose 1 at 0 months; dose 2 2–6 months after dose 1).

Postherpetic neuralgia management

Amitriptyline; gabapentinoids (pregabalin, gabapentin); lidocaine patch; opioids as needed.

Cellulitis overview

Bacterial infection of the skin involving deeper subcutaneous layers; commonly due to Staphylococcus aureus and Streptococcus species.

Purulent vs nonpurulent cellulitis

Purulent involves abscess/drainage; nonpurulent lacks purulence and may show lymphangitis.

Cellulitis diagnosis

Usually clinical; CBC may show leukocytosis; soft-tissue ultrasound can detect abscess or foreign body.

Cellulitis outpatient treatment options

Empiric antibiotics: TMP-SMX, doxycycline, clindamycin, penicillin VK, cephalexin, or dicloxacillin; I&D for abscess; topical mupirocin.

Cat/dog bite antibiotics

Amoxicillin-clavulanate preferred; alternatives include cefuroxime + clindamycin/metronidazole, TMP-SMX + clindamycin/metronidazole, or doxycycline + metronidazole.

Human bite pathogens

Eikenella corrodens, Staphylococcus aureus, Haemophilus influenzae, viridans streptococci, and anaerobes.

Tetanus prophylaxis in wounds

Tetanus prophylaxis as indicated for wounds.

Indications for hospitalization in cellulitis

Worsening fever, increased pain, spreading/streaking erythema, immunocompromised status, outpatient treatment failure.