Updated: 7/9/2018

Rabies Virus and Infection

Topic
Review Topic
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Questions
3
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Evidence
3
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Snapshot
  • A 10-year-old boy presents to the emergency room after being bit by an animal in a cave. His parents report that they live near some caves that the boy frequently explores. While they are not sure if it was a bat, they are concerned about rabies. On physical exam, there is a small excoriation on his left leg. Otherwise, physical exam is within normal limits. The boy is given the rabies vaccine and immunoglobulin.
Introduction
  • Classification
    • rabies virus
      • linear negative single-stranded RNA virus
      • rhabdovirus
      • helical capsid and bullet-shaped
    • transmission
      • via bites from infected animals
        • developed countries
          • bats > raccoons and skunks > dogs
        • developing countries
          • dogs > others
      • via aerosol transmission (rare)
        • bats
  • Epidemiology
    • demographics
      • more common in children
      • majority of cases are in Asia and Africa
    • risk factors
      • interaction with non-domestic animals
  • Pathogenesis
    • long incubation period (weeks to months)
    • replicates in muscle and binds to the nicotinic acetylcholine receptor
      • retrograde migration to central nervous system via dynein motors
  • Associated conditions
    • encephalitic rabies (more common)
    • paralytic rabies
  • Prevention
    • whole virus inactivated vaccine
      • active immunization
    • rabies immunoglobulin
      • passive immunization
  • Prognosis
    • most cases, without early intervention, lead to coma and death within weeks
Presentation
  • Symptoms
    • nonspecific prodrome
      • malaise
      • fever
      • headache
  • Physical exam
    • fever
    • encephalitic rabies
      • hydrophobia
        • muscle spasms when offered water
        • leads to “foaming at the mouth”
      • photophobia
      • autonomic dysfunction
        • excess sweating
        • piloerection
        • hypersalivation
      • agitation
      • seizures
    • paralytic rabies
      • quadriparesis
      • bilateral facial weakness
    • late-stage disease
      • paralysis
      • coma
      • death
Studies
  • Labs
    • viral studies
      • reverse transcription polymerase chain reaction (RT-PCR)
      • isolation of virus
  • Histology
    • brain biopsy
      • performed post-mortem
      • Negri bodies
        • eosinophilic inclusion bodies in cerebellar Purkinje cells and hippocampal neurons
        • pathognomonic
  • Making the diagnosis
    • based on clinical presentation
Differential
  • Botulism
    • distinguishing factor
      • flaccid paralysis without other signs of encephalopathy
  • Temporal lobe (herpes simplex virus-1) encephalitis
    • distinguishing factor
      • disinhibited behaviors such as hyperphagia, hypersexuality, and hyperorality
Treatment
  • Management approach
    • give post-exposure prophylaxis immediately
      • when bitten by rabid animal
      • when bite cannot be ruled out
    • once patients are symptomatic, there is no treatment and patients should receive supportive care
      • pain management
      • sedation
  • Conservative
    • wound cleaning
      • indication
        • post-exposure
  • Medical
    • rabies immunoglobulin
      • indication
        • post-exposure prophylaxis
Complications
  • Respiratory failure leading to death
 

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Questions (3)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

(M1.MC.4752) A 35-year-old spelunker presents to the emergency room complaining of one week of worsening malaise. His last solo spelunking trip was two months ago. While in the examination room, he asks to turn down the lights because they are too bright. His temperature is 101°F (38.3°C), blood pressure is 130/80 mmHg, pulse is 100/min, and respirations are 18/min. On examination he appears tremulous and agitated. He is oriented to person and place but not time. Which of the following pathogens is most likely responsible for this patient’s condition? Review Topic

QID: 108810
1

(-) single-strand RNA virus

36%

(46/129)

2

(+) single-strand RNA virus

24%

(31/129)

3

Double-strand RNA virus

12%

(16/129)

4

Non-enveloped DNA virus

5%

(7/129)

5

Enveloped DNA virus

12%

(15/129)

M1

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