Ehrlichiosis

Pathogens
- Ehrlichia chaffeensis
Vectors
- Lone star tick (Amblyomma americanum): E. chaffeensis and E. ewingii
- Deer tick (Ixodes scapularis): E. muris eauclairensis
Distribution
- Mainly east of the Rocky Mountains
- Also some cases in the Southwest
Clinical features
- Systemic: Sudden high fever, chills, severe frontal headache, myalgias, malaise.
- GI: Nausea, vomiting, diarrhea, abdominal pain.
- Rash: Uncommon in adults (<30%), more common in children (~60%). Maculopapular or petechial, usually sparing the face.
- CNS: Altered mental status, confusion, stiff neck, seizures (indicates severe infection/meningoencephalitis).
Diagnostics
- Key Labs (High-Yield Triad):
  - Leukopenia (specifically lymphopenia and neutropenia).
  - Thrombocytopenia.
  - Elevated transaminases (AST/ALT) and LDH.
- Initial/Screening:
  - Peripheral blood smear: Morulae inside monocytes (mulberry-like intracytoplasmic inclusions; low sensitivity, high specificity).
- Confirmatory:
  - Whole-blood PCR (most sensitive test in acute phase before seroconversion).
  - Serology (IFA): 4-fold rise in IgG antibody titers between acute and convalescent phases.

Tick paralysis

Definition: a rare syndrome caused by the salivary neurotoxin of certain ticks, characterized by acute ataxia, that progresses to ascending paralysis
Distribution: most commonly in the Rocky Mountains and northwestern US
Pathophysiology
- Paralysis is caused by tick neurotoxin, which is produced in the tick’s salivary gland and introduced into the person’s blood.
Clinical features
- Symptoms begin within 2–7 days of the initial tick bite.
- Typically starts with weakness in the lower extremities
- Escalates to ascending flaccid paralysis that progresses rapidly and can lead to respiratory failure due to respiratory muscle weakness
- Sensory deficits are usually absent.
- Cranial nerve palsies may occur (e.g., CN III palsy).
- No fever or rash
Treatment
- Locate and remove the tick
  - Removal of ticks usually results in improvement within 1 hour w/ recovery after several days

Epidemiology & Risk Factors
- Organism: Francisella tularensis (Gram-negative intracellular coccobacillus).
- Exposures: Rabbit skinning/hunting, tick/deer fly bites, lawn mowing over carcasses (endemic: Martha’s Vineyard, AR, MO, OK).
- Bioterrorism: Category A agent (aerosolized risk).
Clinical Presentation
- Ulceroglandular (most common): Painful punched-out skin ulcer + tender regional lymphadenopathy. c
- Pneumonic: Inhalation of aerosolized bacteria → high fever, dyspnea, hilar adenopathy (high mortality).
- Other forms: Glandular (no ulcer), Oculoglandular (conjunctivitis + preauricular LN), Oropharyngeal (ingestion).
Diagnosis
- Best Initial/Confirmatory: Serology (4-fold titer rise) or PCR.
- Contraindicated: Bacterial culture (high hazard for laboratory-acquired infection; requires BSL-3).
Differential Diagnosis
- Bartonella henselae (Cat scratch): Subacute/indolent, painless papule.
- Bacillus anthracis (Cutaneous anthrax): Painless black eschar + marked edema.
- Sporothrix schenckii: Painless ascending nodular lymphangitis (rose gardener).
Management
- Severe / Hospitalized: IV Gentamicin or Streptomycin.
- Mild / Outpatient: PO Doxycycline or Ciprofloxacin (14–21 days).
- Post-Exposure Prophylaxis: PO Doxycycline or Ciprofloxacin x 14 days.

tags	—
aliases	Tick-borne disease, Ehrlichiosis, Tick paralysis