Rabies

Original article by Lily Stanley | Last updated on 2/6/2014
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Organism

  • Viral zoonosis
  • RNA rhabdovirus
  • Incubation: 9-90 days

 

Transmission

Spread by bites from infected mammals (saliva)
Risk of transmission when bitten by rabid animal is <50%

Epidemiology

  • Dogs (+wolves and jackals) are main transmitters worldwide
  • Bats transmit in North America, parts of south America, parts of Europe and recently Australia
  • Kills approximately 50,000 people per year

 

Pathogenesis

Virus multiplies in muscle and then is transmitted along nerve axons. On reaching the brain of the infected person, virus spreads along peripheral nerves to reach skin and lacrimal and salivary glands.
 

Clinical features

General

  • Myalgia
  • Headache
  • Pain parasthesia or pruritus in bitten area
  • Anxiety and agitation
  • Fever

 
Paralytic form
Ascending sensorimotor neuropathy with ocular, cranial and laryngeal palsies and sphincter disturbances.
 
Encephalytic (furious) form

  • Intermittent episodes of confusion, agitation and aggression(mania) intervened with periods of lucitidy.
  • Hydrophobia
  • Froth at mouth
  • Painful spasms of throat
  • +/- seizures

 

Complications

Death usually occurs within one week with respiratory and bulbar paralysis.
 

Diagnosis

  • Generally on characteristic clinical picture (lymphocytes in CSF, history for dog bite, absent muscle rigidity between spasms)
  • Diagnostic antibody tests do not become positive until day 8 (and difficult to interpret in vaccinated patients)
  • Brain biopsy might show negri bodies.

 

Treatment

  • Wash wound (soap and water 10-15 mins)
  • If previously immunized, give vaccine on day 0 & 3
  • If not unimmunized, give vaccine on days 0,3,7,14 & 28 + human rabies IgG (half given IM and half infiltrated around wound)

 
The Milwaukee protocol – induced coma in patients with unvaccinated rabies infections has shown some success in survival and functional outcome
 

Prevention

Avoid contact with animals in high risk areas.
Vaccination - Human diploid cell rabies vaccine
 

Prognosis

Post-exposure prophylaxis is very successful in prevention of rabies if given within ten days of infection (and is almost 100% effective if given immediately)
Unvaccinated - usually fatal once neurological symptoms have appeared