Rabies

Introduction

Rabies is an acute disease of the CNS caused by a bullet-shaped rhabdovirus that affects all mammals.
The virus is a single-stranded RNA virus found in animals, in all regions as urban rabies or sylvatic rabies.
It is transmitted by infected secretions, usually saliva.
Most exposures are through bites of an
infected animal; occasionally contact with a virus-containing aerosol or the ingestion or transplant of infected tissues may initiate the disease process.
Human infection is through contact with unimmunized domestic animals.
Dogs are the most important vectors
worldwide

Clinical features

There are four stages:
1. A non-specific prodrome of 1 – 4 days consisting of

  • Fever
  • Headache
  • Malaise
  • Myalgia
  • Anorexia
  • Nausea
  • Vomiting
  • Sore throat
  • Cough
  • Paraesthesia

2 . An acute encephalitic stage

  • Excitement
  • Agitation
  • Confusion
  • Hallucinations
  • Combativeness
  • Bizarre aberrations of thought
  • Muscle spasms
  • Meningismus
  • Seizures
  • Focal paralysis
  • Hydrophobia
  1. Brainstem dysfunction
  • Diplopia
  • Facial paralysis
  • Optic neuritis.
  • Difficulty with deglutition
  • Priapism
  • Spontaneous ejaculation
  • Coma
  1. Death or recovery

Differential diagnoses

  • Gullain-Barre syndrome
  • Other causes of viral encephalitis
  • Poliomyelitis
  • Allergic encephalomyelitis

Complications

  • Inappropriate secretion of ADH
  • Diabetes insipidus
  • Cardiac arrythmias
  • Adult Respiratory Distress Syndrome (ARDS)
  • Gastro Intestinal (GI) bleeding
  • Thrombocytopenia
  • Paralytic ileus

Investigations

  • Full Blood Count and differentials
  • Urea and Electrolytes
  • Culture of secretions
  • Cerebro Spinal Fluid (CSF) analysis
  • Serology
  • Polymerase Chain Reaction (PCR)

Treatment objectives

  • Disinfect wound; avoid early suturing
  • Provide passive immunization with
    antirabies antiserum
  • Provide active immunization with the vaccine

Non-drug treatment

Wound care
The wound or site of exposure should be:

  • Cleansed under running water
  • Washed for several minutes with soapy water
  • Disinfected and dressed simply
  • It should not be sutured immediately

Drug treatment

Unimmunized persons or those whose prophylaxis is probably incomplete

Rabies (cell mediated) vaccine

  • Adult: 1 ml by deep subcutaneous or intramuscular injection in the deltoid region on days 0, 3, 7, 14 and 30

Plus:

Rabies immunoglobulin given on day 0

  • Child:  same as for adult

 For fully immunized persons:

Rabies (cell mediated) vaccine

  • Adult: 1 ml by deep subcutaneous or intramuscular injection in the deltoid region on days 1 and 3
  • Child: same as for adult

Post-exposure prophylaxis (PEP)

  • Should be initiated as soon as possible after exposure
  • The decision to initiate PEP should include:
  • Whether the individual came into physical contact with saliva or another substance likely to contain rabies virus
  • Whether rabies is known or suspected in the species and area associated with the exposure
  • The circumstances surrounding the
    exposure e.g. whether the bite was provoked or unprovoked
  • Consider the use of rabies vaccine
    whenever a patient has been attacked by an animal in an environment where rabies is enzootic, even if there is no direct
    evidence of rabies in the attacking animal
  • Pregnancy not a contraindication

Supportive measures

  • Allay anxiety: reassure
  • Other measures as appropriate for clinical situation.

Notable adverse drug reactions, caution

  • Concomitant chloroquine administration interferes with antibody response to rabies
    vaccine
  • There are no specific contraindications

Prevention

Pre-exposure prophylaxis

  • Should be offered to persons at high risk of exposure and/or contact with rabies virus:
    • Veterinnarians
    • Cave explorers
    • Laboratory workers who handle the rabies virus.
    • Animal handlers
    • Workers in quarantine stations
    • Field workers who are likely to be bitten by
    • infected wild animals
    • Certain port officials Bat handlers
    • Persons living in (or travelling to) areas where rabies is enzootic and/or where there is limited access to prompt medical care
    • Those caring for patients caring for patients with rabies
      • Although there is no proven evidence of human transmission
  • Pregnancy is not a contraindication: if there is substantial risk of exposure, and rapid access to post-exposure prophylaxis is
    limited, give pre-exposure prophylaxis

Rabies vaccine:

  • 1 ml by deep subcutaneous or intramuscular injection in the deltoid region on days 0, 7 and 28
  • Booster doses every 2-3 years for those at continued risk