Difference between revisions of "Rhabdoviridae"

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#REDIRECT[[:Category:Rhabdoviridae]]
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{{unfinished}}
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{{toplink
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|linkpage =Viruses
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|linktext =VIRUSES
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|pagetype=Bugs
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}}
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<br>
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=Introduction=
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Rabies is a neurological killer that has evolved a fool-proof technique of transmission, and it cleverly evades the species barrier to present a potent threat to mammalian life.  While the simplicity of the virus insures its transmission, it also contributes to its weakness: its monoclonal antigenicity means that a single vaccination covers all strains of the disease.  Though rabies is considered endemic in parts of the developed and undeveloped world, vaccination schemes have rendered the disease controllable to a satisfactory degree.  Nonetheless, infection is still largely fatal and the disease should not be taken lightly.
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=Morphology=
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*Large, enveloped, negative-sense RNA virus
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*'''Bullet-shaped''' with short glycoprotein spikes
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=Virulence and Pathogenesis=
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*Rabies is moderately resistant: it can survive well in dark places at low temperatures for several days
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*Infection occurs through a '''penetrating bite''' in which virus is transmitted via '''saliva'''
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*'''Incubation''' period is variable but can be long (10 days to 12 months), and increases with distance of the bite to the CNS
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**80% show signs within 4 months
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*Primary replication of the virus occurs in the '''muscle'''
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*The virus gains access to nervous tissue and travels toward the '''brain''', where it continues to replicate
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*It then migrates down cranial nerves to infect salivary glands and the cornea
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*Virus is shed in '''saliva''' and '''tears''' and can be shed BEFORE the onset of classical signs
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*The onset of clinical signs in dogs and cats includes:
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**Behavioral changes
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**Pyrexia
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**Salivation
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**Dilation of pupils
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*Two forms of the virus exist:
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**'''Furious''' form:
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***Common to cats and dogs
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***Abnormal aggression, salivation, and attack without provocation
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***Disordered wandering
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***Incoordination, convulsions, coma and death within 3-10 days
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**'''Dumb''' form
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***May or may not follow Furious form
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***Common to ruminants and horses
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***Ruminal tympany, tenesmus, diarrhoea
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***Paralysis of lower jaw, drooling saliva, tremors and progressive paralysis
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*Human infection is characterized by '''hydrophobia'''
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***In dogs, a change in voice may be observed (bellowing)
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=Epidemiology=
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*Rabies is found worldwide, though currently considered exotic to the UK
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*The current position of DEFRA holds bat lyssaviruses to be present in the UK
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*Rabies is a '''NOTIFIABLE''' zoonosis
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*Human infection and death an occur after infection with bat rabies
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=Types and Subtypes=
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Two Genera:
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#Lyssaviruses: 7 genotypes
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##'''Genotype 1''' is '''classical rabies'''
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##Genotypes 2-7 more limited in distribution
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##Genotype 4 infects '''insectivorous bats'''
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#Vesiculoviruses are all '''exotic''' to the UK:
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##Vesicular Stomatitis Virus
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##Ephemeral Fever
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##Fish Rhabdoviruses, such as viral hemorrhagic syndrome and infectious haematopoetic necrosis virus
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=Rhabdoviridae by Species=
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Host Range:
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*All mammals are susceptible
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**Very susceptible: foxes, jackals, wolves
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**Susceptible (10,000x virus necessary to infect): cats, rodents, bats, skunks, cattle, mongooses
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**Moderately susceptible (100,000x virus necessary to infect): dogs, sheep, goats, horses, primates
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*Isolates can show to some species specificity in their reservoir host
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=Rabies Control=
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*Antigenicity allows a single antigenic type to vaccinate

Revision as of 21:13, 13 October 2008


 This article is still under construction.


Infectious agents and parasitesWikiBugs Banner.png
VIRUSES



Introduction

Rabies is a neurological killer that has evolved a fool-proof technique of transmission, and it cleverly evades the species barrier to present a potent threat to mammalian life. While the simplicity of the virus insures its transmission, it also contributes to its weakness: its monoclonal antigenicity means that a single vaccination covers all strains of the disease. Though rabies is considered endemic in parts of the developed and undeveloped world, vaccination schemes have rendered the disease controllable to a satisfactory degree. Nonetheless, infection is still largely fatal and the disease should not be taken lightly.

Morphology

  • Large, enveloped, negative-sense RNA virus
  • Bullet-shaped with short glycoprotein spikes

Virulence and Pathogenesis

  • Rabies is moderately resistant: it can survive well in dark places at low temperatures for several days
  • Infection occurs through a penetrating bite in which virus is transmitted via saliva
  • Incubation period is variable but can be long (10 days to 12 months), and increases with distance of the bite to the CNS
    • 80% show signs within 4 months
  • Primary replication of the virus occurs in the muscle
  • The virus gains access to nervous tissue and travels toward the brain, where it continues to replicate
  • It then migrates down cranial nerves to infect salivary glands and the cornea
  • Virus is shed in saliva and tears and can be shed BEFORE the onset of classical signs
  • The onset of clinical signs in dogs and cats includes:
    • Behavioral changes
    • Pyrexia
    • Salivation
    • Dilation of pupils
  • Two forms of the virus exist:
    • Furious form:
      • Common to cats and dogs
      • Abnormal aggression, salivation, and attack without provocation
      • Disordered wandering
      • Incoordination, convulsions, coma and death within 3-10 days
    • Dumb form
      • May or may not follow Furious form
      • Common to ruminants and horses
      • Ruminal tympany, tenesmus, diarrhoea
      • Paralysis of lower jaw, drooling saliva, tremors and progressive paralysis
  • Human infection is characterized by hydrophobia
      • In dogs, a change in voice may be observed (bellowing)

Epidemiology

  • Rabies is found worldwide, though currently considered exotic to the UK
  • The current position of DEFRA holds bat lyssaviruses to be present in the UK
  • Rabies is a NOTIFIABLE zoonosis
  • Human infection and death an occur after infection with bat rabies

Types and Subtypes

Two Genera:

  1. Lyssaviruses: 7 genotypes
    1. Genotype 1 is classical rabies
    2. Genotypes 2-7 more limited in distribution
    3. Genotype 4 infects insectivorous bats
  2. Vesiculoviruses are all exotic to the UK:
    1. Vesicular Stomatitis Virus
    2. Ephemeral Fever
    3. Fish Rhabdoviruses, such as viral hemorrhagic syndrome and infectious haematopoetic necrosis virus

Rhabdoviridae by Species

Host Range:

  • All mammals are susceptible
    • Very susceptible: foxes, jackals, wolves
    • Susceptible (10,000x virus necessary to infect): cats, rodents, bats, skunks, cattle, mongooses
    • Moderately susceptible (100,000x virus necessary to infect): dogs, sheep, goats, horses, primates
  • Isolates can show to some species specificity in their reservoir host

Rabies Control

  • Antigenicity allows a single antigenic type to vaccinate
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