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=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 ensures 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
=Types and Subtypes=
Two Genera:
#Lyssaviruses: 7 genotypes
##'''Genotype 1''' is '''classical rabies'''
##Genotypes 2-7 more limited in distribution
##Genotype 4 infects '''insectivorous bats'''
#Vesiculoviruses are all '''exotic''' to the UK:
##Vesicular Stomatitis Virus
##Ephemeral Fever
##Fish Rhabdoviruses, such as viral hemorrhagic syndrome and infectious haematopoetic necrosis virus
=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, "copulatory" movements.
***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
***In dogs, a change in voice may be observed (bellowing)
*Human infection is characterized by '''hydrophobia'''
[[Category: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 ensures 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
=Types and Subtypes=
Two Genera:
#Lyssaviruses: 7 genotypes
##'''Genotype 1''' is '''classical rabies'''
##Genotypes 2-7 more limited in distribution
##Genotype 4 infects '''insectivorous bats'''
#Vesiculoviruses are all '''exotic''' to the UK:
##Vesicular Stomatitis Virus
##Ephemeral Fever
##Fish Rhabdoviruses, such as viral hemorrhagic syndrome and infectious haematopoetic necrosis virus
=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, "copulatory" movements.
***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
***In dogs, a change in voice may be observed (bellowing)
*Human infection is characterized by '''hydrophobia'''
[[Category:Viruses]]