Revision as of 21:00, 13 October 2008

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:

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:

Lyssaviruses: 7 genotypes
1. Genotype 1 is classical rabies
2. Genotypes 2-7 more limited in distribution
3. Genotype 4 infects insectivorous bats
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

@@ Line 8: / Line 8: @@
 <br>
-*Vesicular stomatitis in [[Viral skin infections - Pathology#Other viruses|skin lesions]]
+=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:
+=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:
+#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
+=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

Difference between revisions of "Rhabdoviridae"