Difference between revisions of "Rhabdoviridae"
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*Large, enveloped, negative-sense RNA virus | *Large, enveloped, negative-sense RNA virus | ||
*'''Bullet-shaped''' with short glycoprotein spikes | *'''Bullet-shaped''' with short glycoprotein spikes | ||
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+ | =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= | =Virulence and Pathogenesis= | ||
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*Rabies is a '''NOTIFIABLE''' zoonosis | *Rabies is a '''NOTIFIABLE''' zoonosis | ||
*Rabies is found worldwide, though currently considered exotic to the UK and Australia | *Rabies is found worldwide, though currently considered exotic to the UK and Australia | ||
+ | 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 | ||
*Reservoir species by region: | *Reservoir species by region: | ||
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*Immune recovered animals are rare, but are not shown to be infections | *Immune recovered animals are rare, but are not shown to be infections | ||
− | = | + | =Diagnosis= |
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=Rabies Control= | =Rabies Control= | ||
*Antigenicity allows a single antigenic type to vaccinate | *Antigenicity allows a single antigenic type to vaccinate |
Revision as of 21:28, 13 October 2008
This article is still under construction. |
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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 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
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
- 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)
- Furious form:
- Human infection is characterized by hydrophobia
Epidemiology
- Rabies is a NOTIFIABLE zoonosis
- Rabies is found worldwide, though currently considered exotic to the UK and Australia
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
- Reservoir species by region:
Region | Reservoir Species |
---|---|
Europe | Red fox |
Russia, Turkey, Middle East | Dog, Raccoon |
USA | Raccoon, Fox, Skunk |
Africa | Dog, Jackal, Mongoose |
Asia | Dog, Mongoose |
South America | Dog, Vampire bat |
Worldwide | Insectivorous Bats |
- The current position of DEFRA holds bat lyssaviruses to be present in the UK
- Human infection and death an occur after infection with bat rabies
- Nocturnal bat bites account for 50% of human cases in the USA
- Humans develop disease but excrete little virus
- Immune recovered animals are rare, but are not shown to be infections
Diagnosis
Rabies Control
- Antigenicity allows a single antigenic type to vaccinate