Final: Rhabdoviruses Flashcards
When was rhabdovirus first recognized? Who first described it?
Recognized in Egypt around 2300 BC
Aristotle in Ancient Greece
What are the 4 genera of human and animal pathogens of the Family Rhabdoviridae?
Lyssavirus
Vesiculovirus
Ephemerovirus
Novirhabdovirus
What are the 2 genera that infect plants?
Cytorhabdovirus
Nucleorhabdovirus
What is the geographic distribution of rabies virus?
Worldwide except Australasia, Antarctica, and certain islands.
Recently eradicated from portions of Europe and Scandinavia
What do all Lyssaviruses cause and who are the reservoirs?
Can cause rabies-like disease in animals and humans.
Bats are reservoirs
What are the virion properties of Rhabdoviruses?
RNA viruses
Genome is ss, linear, negative sense RNA
Enveloped
Rod- or cone-shaped
What is covering the virion surface?
G protein spikes.
N proteins make up the viral nucleocapsid
P protein is a co-factor of the viral polymerase
M proteins is an inner protein that facilitates virion budding
L protein is an RNA-dependent RNA polymerase
*some rhabdoviruses have additional genes
Virions are stable/unstable in the environment
Stable
Can with stand alkaline pH
Sensitive to UV radiation from the sun
Detergent-based disinfectants and iodine-containing solutions are effective disinfectants
Oxidizing agents, acids, aldehydes
Where does replication of rhabdoviruses occur within the cells?
In the cytoplasm
What are the steps of rhabdovirus replication?
Virion binds to cell surface receptors and enters the cell by endocytosis -> the envelope fuses with endosomal membrane and viral nucleocapsid is released into the cytoplasm -> the (-) strand RNA is transcribed into 5 subgenomic mRNAs by L and P proteins.
What are the diseases caused by rhabdoviruses?
Genus Lyssavirus - Rabies virus
T/F: Rabies can infect lol mammals and can result in death
True
What causes the spread of most rabies viruses in Africa and Asia?
Rabid-dog bites
Who are the rabies reservoirs in North America
Skunks
Raccoons
Foxes
Wolves
What species is the main reservoir in other parts of the world?
Bats
What species of bats transmits rabies virus to cattle in Central and South America?
Vampire bats
Is rabies virus zoonotic?
Clearly
Carnivores/herbivores act as a reservoir for rabies with occasional transmission to humans
Carnivores
What are the two epidemiological cycles of rabies virus?
Urban: dogs are the main reservoir (predominates in areas of Africa, Asia, and Central and South America)
Sylvatic: predominant cycle in the northern hemisphere. It can also present simultaneously with the urban cycle in some parts of the world.
What are the clinical features?
Bites of animals
Incubation period is 14-90 days
What are the clinical phases of rabies?
Prodromal phase
Excitative (fury) phase
Paralytic (dumb) phase
What is the prodromal phase of rabies infection?
Lasts about 1-3 days with behavioral changes. Aggressiveness in tame animals Daytime activities in nocturnal animals No fear of humans in wild animals Abnormalities in appetite
What is the excitative (fury) phase of rabies infection?
Severe agitation and aggressiveness
The animal often bites any material
Rabid dogs may develop a typical high barking sound during furious rabies
What is the paralytic (dumb) phase of rabies infection?
Inability to swallow-hydrophobia in dogs
Leads to excessive salivation
Some may develop paralysis beginning at the hind extremities
Complete paralysis is followed by death
What is the pathogenesis of rabies?
Virus replicates in the muscle tissue -> accesses the peripheral nerves through the sensory or motor nerves -> virus binds to receptor for acetylcholine at neuromuscular junctions -> virus moves to infect the CNS which leads to neuronal dysfunction -> virus reaches lambic system and replicates rapidly -> late in the course the virus will reach other organs (mostly salivary glands)
At which stage is the virus spread and what is the vehicle?
In the fury stage
Saliva
What is the only typical finding during histopathology?
Presence of eosinophilic intracytoplasmic inclusion bodies (Negri bodies) in neurons
How do we diagnose rabies?
Tissue from at least 2 locations in the brain, preferably the brain stem and cerebellum (look for Negri bodies)
Lab demonstration of rabies viral antigen, nucleic acid, or viable virus will be necessary for positive diagnosis
Diagnosis of rabies is preformed only in _____ ________
Reference laboratories
What lab tests can be done to diagnose rabies?
Immunochemical ID: Fluorescent antibody test Gold standard*, immunohistochemistry, ELISA
Cell culture inoculation: cell culture test, mouse inoculation
Molecular tests: RT-PCR
How do we control rabies?
Vaccines
Quarantine animals in rabies-free countries
Control programs for enzootic countries
T/F: Raccoons, skunks, foxes and most other wild carnivores, including bats are all regarded as rabid unless the animal is proven negative
True
Poor babies just want some love
What do you do if you think you dog, cat or ferret has rabies?
10 day observation
Postexposure prophylaxis recommendations: persons should not begin vaccination unless animal develops clinical signs
What species of animals will Vesiculovirus infect?
Horses Cattle Swine Humans Carp Salmonids
What does vesiculovirus, or vesicular stomatitis virus (VSV) cause and in what species? Is it a reportable disease?
Causes vesicular stomatitis
Cattle, swine, and horses
YES! REPORT!!!
What are the clinical features of vesiculovirus?
Incubation of 1-5 days
Excessive salivation and fever, first signs in cattle and horses
Lameness first sign in swine
Vesicles on tongue, oral mucosa, teats, coronary bands in cattle and swine
In horses, tongue lesions are most pronounced!
What is the pathogenesis of vesiculovirus?
Enters the body through mucosal or skin abrasions (bites by arthropods or bruises from rough forage)
Viremia does not occur in many animals apart from swine
Virus replicates in intraepithelium of mucosa and skin leading to edema, hence vesicles filled with fluid
What is the epidemiology of vesiculovirus?
Biting insects transmit - black flies, houseflies and mosquitoes
Sand flies in the tropics and subtropics
Virus is stable for many days in the environment
Epizootics appear every 2-3 years in tropical and subtropical countries
How do we diagnose vesiculovirus?
Clinically, indistinguishable from other vesicular diseases of swine and cattle
Vesicular lesions in horses are only characteristic of VSV infection
Virus can be recovered from vesicular fluid or tissue scrapings from lesions
Isolation and RT-PCR
What does VSV cause in cattle?
Vesicles in oral cavity, mammary glands, coronary bands, interdigital space
What does VSV cause in pigs?
Vesicles in oral cavity, mammary glands, coronary bands, interdigital space
What are signs of VSV in sheep and goats?
Rarely show signs
What does VSV cause in horses, donkeys, and mules?
Most severe with oral and coronary band vesicles, drooling, rub mouths on objects, lameness
How do we prevent and control VSV? Is it zoonotic?
Control flies
Inactivated or attenuated virus vaccines have been tested but not yet available commercially
YES
What are the rhabdoviruses of fish (wild and cultured)?
Novirhabdovirus
Vesiculovirus
What does viral haemorrhagic septicemia virus cause in fish?
Systemic infection in salmon is.
Fish of all ages are susceptible
Causes high mortality rate (up to 100%)
A big problem in farmed salmon in Europe, North America and Japan
Infection occurs at water temps of 4-14 degrees Celsius but disappears at anything over 15
Exposure to viral hemorrhagic septicemia virus is characterized by what?
Lethargy Spiral swimming pattern Darkened body color Pale gills Exophthalmia Hemorrhage at base of fins
What are the internal lesions seen with viral hemorrhagic septicemia virus?
Hemorrhage in several organs
Liver is mottled and variably congested
Multifocal necrosis in several organs
How do we diagnose viral hemorrhagic septicemia viruses?
Typical signs
Isolation of virus in fish cell lines
ID by RT-PCR, ELISA or IF
There is no commercial vaccine available
What does infectious hematopoietic necrosis virus cause?
Hematopoietic necrosis in salmonid fish (both sean and fresh water)
Enzootic in wild and hatchery fish populations in North America and Europe
Disease involves juvenile fish at water temperature of 8-15 C
Mortality is high (50-90%)
What are the clinical features of infectious hematopoietic necrosis virus?
Darkened body color Lethargy Pale gills indicating anemia Bilateral exophthalmia Distention of abdomen due to ascites Hemorrhage at base of fins
What is the important virus of Ephemerovirus and what does it cause?
Bovine ephemeral fever virus
3 day stiff sickness
Arthropod transmitted disease of cattle and water buffaloes
Occurs in tropics and subtropics of Africa, Middle East, Asia and Australia
NOT reported in North and South America
What are the clinical features of Bovine ephemeral fever virus?
Immediate drop in milk production
Occasionally nasal and ocular discharges
How do we diagnose bovine ephemeral fever virus?
Virus isolation in mosquito cell culture or suckling mouse brain GOLD STANDARD
RT-PCR
Neutralization test
Immunofluorescence or gel diffusion
Prevention of bovine ephemeral fever virus
Infection gives long-lasting immunity
Following an outbreak, only animals born after the outbreak are susceptible to infection
In Japan, Australia and South Africa an inactivated and attenuated virus vaccine is used
A recombinant baculoviruses vaccine is available
