© Springer Nature Switzerland AG 2021
C. S. Foster et al. (eds.)Uveitishttps://doi.org/10.1007/978-3-030-52974-1_33

33. Rickettsial Diseases

Karen Wingartz Small1   and Mahmut Kaya2
(1)
Professional Eye Care, Mission of Sight, Jamaica, Chattanooga, TN, USA
(2)
Department of Ophthalmology, Dokuz Eylul University, Izmir, Turkey
 
Keywords
Rickettsial diseasesUveitis

Overview

  • Definition
    • A group of diseases transmitted by ticks (less commonly by fleas and lice) infected with rickettsias – pleomorphic, intracellular bacteria that primarily affect the vascular endothelial cells and smooth muscle cells of small and medium vessels

    • Divided into spotted fever and typhus groups

    • Classic triad with mild to severe organ dysfunctions (see “Systemic association”)
      • Fever

      • Headache and malaise

      • Rash

    • Rocky Mountain Spotted Fever (RMSF) is the most common rickettsiosis in the United States
      • Pathogen: Rickettsia rickettsii

      • Potentially lethal

      • North Carolina, South Carolina, Oklahoma, Tennessee, Arkansas

      • >90% contracted between April and September

    • Other spotted fever rickettsioses in the United States include
      • Rickettsia parkeri rickettsiosis (R. parkeri)

      • Pacific Coast tick fever (R. species 364D)

      • Rickettsialpox (R. akari)

  • Symptoms
    • Conjunctival injection

    • Decreased visual acuity

    • Paracentral scotomas

    • Floaters

  • Laterality
    • More commonly unilateral

  • Course
    • Ocular disease is acute and self-limited.

  • Age of onset
    • All age groups affected

  • Gender/race
    • No gender or racial predilection

    • Anyone living in endemic areas with exposure to rickettsial reservoirs

  • Systemic association

    While RMSF is considered the most potentially severe of all spotted fever rickettsioses, many rickettsial diseases can be complicated by
    • Acute renal failure

    • Respiratory distress syndrome

    • Meningoencephalic syndrome (especially the typhus group)

    • Myocarditis

    • Hepatic failure

    • Fulminant RMSF: in individuals with G6PD deficiency, RMSF can result in severe hemolysis and anemia, with life-threatening complications, within 5 days of disease onset

Exam: Ocular

Anterior Segment

  • Most common
    • Conjunctivitis

    • Conjunctival petechiae and hemorrhage

    • Conjunctival nodules

  • Less common
    • Mild non-granulomatous anterior chamber (AC) inflammation

    • Keratitis and marginal ulcer

    • Iris nodules

Posterior Segment

  • Most common
    • Mild vitritis

    • Retinal vascular involvement in half the patients:
      • Perivascular white retinal lesions

      • Subretinal hemorrhage

      • White-centered hemorrhage

      • Arterial plaque similar to toxoplasmic Kyrieleis

  • Less common
    • Choroidal lesions

    • Macular star

    • Branch retinal artery occlusion (BRAO)

    • Exudative retinal detachment (RD)

    • Anterior ischemic optic neuropathy

Exam: Systemic

  • Incubation period varies among different rickettsias, ranging 2–21 days

  • Characteristic rash appears 3–5 days after constitutional symptoms, though rash never develops in some cases (“spotless fever”)
    • Typical progression: wrists/ankles → palms and soles → forearms, neck, face, axilla, buttocks, and trunk

    • Small, flat pinkish spots (macules) → darker and raised (papules) → papules may develop petechia and merge to form larger hemorrhagic patches (even gangrenous in severe cases)

  • Patients with spotted fever rickettsioses other than RMSF will have an eschar (dark scab) at the site of the tick or mite bite

Imaging

  • Fluoresceine angiogram
    • Early hypofluorescence and late staining of large retinal lesions

    • Vascular leakage

    • Optic nerve staining

    • Blocked fluorescence from retinal hemorrhage

  • Indocyanine green angiography
    • Mid-phase hypofluorescent dots if choroidal lesions are present

Laboratory and Radiographic Testing

  • Anti-rickettsia immunoglobulin G & M (IgG/IgM) and rickettsia deoxyribonucleic acid (DNA) amplification via polymerase chain reaction (PCR) are offered at commercial laboratories

  • Complete blood count (CBC) is nonspecific, but may show
    • Thrombocytopenia

    • Hyponatremia

    • Elevated liver function tests (LFTs)

Differential Diagnosis

  • Ehrlichioses (Ehrlichia chaffeensis and Ehrlichia ewingii)

  • Human granulocytic anaplasmosis (Anaplasma phagocytophilum)

  • Measles

  • Dengue fever

  • Meningococcemia

  • Leptospirosis

  • Toxic shock syndrome (S. aureus)

  • Syphilis

Treatment

  • Treat suspicious cases empirically, as serologies can take 1–2 weeks

  • Doxycycline is the treatment of choice

  • Chloramphenicol 50–75 mg/kg/day in tetracycline allergy

  • Fluoroquinolones show efficacy anecdotally; penicillin, cephalosporine, and aminoglycosides are ineffective

  • Patient should be afebrile for at least 3 days before antibiotic discontinuation

  • Topical tetracycline for conjunctivitis and keratitis

  • Topical corticosteroids for anterior uveitis

Referral/Comanagement

  • Infectious disease