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| − | {{unfinished}}
| + | #REDIRECT[[:Category:Rhabdoviridae]] |
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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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| − | | |
| − | =Types and Subtypes=
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| − | Two Genera:
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| − | #Lyssaviruses: 7 genotypes | |
| − | ##'''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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| − | =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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| − | ***In dogs, a change in voice may be observed (bellowing)
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| − | *Human infection is characterized by '''hydrophobia'''
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| − | | |
| − | =Epidemiology=
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| − | *Rabies is a '''NOTIFIABLE''' zoonosis
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| − | *Rabies is found worldwide, though currently considered exotic to the UK and Australia
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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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| − | Reservoir species by region:
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| − | {| style="width:60%; height:200px" border="1" align=center
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| − | !'''Region'''
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| − | !'''Reservoir Species'''
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| − | |-
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| − | |Europe
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| − | |Red fox
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| − | |-
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| − | |Russia, Turkey, Middle East
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| − | |Dog, Raccoon
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| − | |-
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| − | |USA
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| − | |Raccoon, Fox, Skunk
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| − | |-
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| − | |Africa
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| − | |Dog, Jackal, Mongoose
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| − | |-
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| − | |Asia
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| − | |Dog, Mongoose
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| − | |-
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| − | |South America
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| − | |Dog, Vampire bat
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| − | |-
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| − | |Worldwide
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| − | |Insectivorous Bats
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| − | |}
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| − | *The current position of DEFRA holds bat lyssaviruses to be present in the UK
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| − | *Human infection and death an occur after infection with bat rabies
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| − | **Nocturnal bat bites account for 50% of human cases in the USA
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| − | *Humans develop disease but excrete little virus
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| − | *Immune recovered animals are rare, but are not shown to be infections
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| − | =Diagnosis=
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| − | *'''Isolate''' and monitor for clinical signs
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| − | *In the field:
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| − | **Remove brain core sample via straw through occipital foramen in the direction of an eye
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| − | **Place contents in a 50% glyerol/PBS for FAT or virus isolation, or in 10% formaldehyde for histology
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| − | **Whole head can also be removed and sent to lab
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| − | *In the lab:
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| − | **'''Fluorescent Antibody Test (FAT)''' on smears or frozen sections of hippocampus or cerebellum should show presence of Negri bodies
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| − | ***Being replaced by testing for monoclonal antibodies to nucleoprotein
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| − | **Histological detection of Negri bodies using Mann's or silver stains
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| − | **Intracerebral inoculation of mice followed by FAT testing of brain smears of affected mice
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| − | **RT-PCR on brain or saliva can be performed to determine genotype
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| − | =Rabies Control=
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| − | For countries where rabies is considered exotic:
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| − | *6 month quarantine of carnivores and ruminants (Norway, Sweden, Portugal, Australia, New Zealand)
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| − | *In the UK, this has been replaced by the '''Pet Travel Scheme''' ([http://www.defra.gov.uk/animalh/quarantine/index.htm PETS])
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| − | For virus-endemic countries:
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| − | #Control in pets:
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| − | #*Annual Vaccination:
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| − | #**Antigenicity allows a single antigenic type to vaccinate
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| − | #**'''Inactivated virus''' or '''canarypox''' recombinant viruses
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| − | #*Control of stray population
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| − | #*Muzzling in public
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| − | #Control of wildlife reservoir hosts:
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| − | #*Feeding vaccinated bait
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| − | #*Secondary consequence of increasing reservoir host population (eg European foxes)
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| − | #Control in humans
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| − | ##Prevention by vaccination with a single booster if bitten
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| − | ##*The current vaccine is grown in human diploid cells (HDCV) and is BPL-inactivated, and therefore costly
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| − | ##*Developing countries utilize older vaccines passaged from a 1939 case ("Flury" vaccines)
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| − | ##If Bitten and unvaccinated:
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| − | ##*Clean and disinfect wound
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| − | ##*Human '''anti-rabies immunoglobulin''' administered around bite
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| − | ##*Intramuscular vaccination program: 2 dose-1 dose-1 dose at 0, 7, and 14 days post-bite
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| − | For more on Rabies control in Europe, see [http://www.who-rabies-bulletin.org/About_Rabies/Control.aspx here]
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