Rhabdoviridae Flashcards
Which virus subfamilies are included in the family Rhabdoviridae?
- lyssaviruses
- vesiculoviruses
- unclassified viruses
Name the 5 viruses in the Lyssavirus family
- Rabies: zoonotic, CNS
- Mokola: Nigerian shrews, CNS
- Lagos: Nigerian bats, CNS
- EBLV 1 & 2: European bats, humans, CNS
- Duvenhage: bats, CNS
Name the 3 viruses in the Vesiculovirus family
- Vesicular Stomatitis Virus: vesicular stomatitis, Indiana and NJ serotypes
- Piry: vesicular disease
- Chandipura: vesicular disease
Name the 6 viruses that fall into the Unclassified family
- *Bovine Ephemeral Fever: African, Asian, Australian ruminants, fever
- Hemorrhagic Septicemia Virus: European salmonids
- *Spring Viremia: abd dropsy of Carp
- *Infectious Hematopoetic Necrosis Virus: Salmonids
- Red Disease of Pike: hemorrhagic
- Numerous Plant and Insect Viruses: yellow necrosis of lettuce, Sigma Virus of Drosophilia
Which virus gets into pet coy fish?
Spring Viremia
Which virus is indigenous to the US?
Infectious Hematopoetic Necrosis Virus
- located in northwest
Rabies viral genome
Linear, single stranded RNA, negative sense
- enveloped particle, RR trnascriptase is carried by the virus
How many proteins does the rabies virus code for?
5!
Where does the rabies virus replicate?
Cytoplasm of host neural cell
Is the rabies virus cytocidal or persistent?
Persistent
- disrupts neuronal function, produces very little neural destruction
What species does vesiculaoviruses infect?
Horses, cows, deer, pigs, and humans
What are the rule outs for a pig possibly infected with vesicular stomatitis virus?
Swine Vesicular Disease (picornavirus) and Vesicular Exanthema (calicivirus)
- VE only occurs in swine, SVD does not occur in horses and cattle
Even though all warm blooded animals are susceptible to rabies virus, which animals appear to be somewhat resistant?
Opossums, guinea pigs, rats, and birds
Sylvatic rabies
“Of the woods”
- Foxes: North East and West Texas
- Skunks: Midwest
- Raccoons: GA and FLA, Northeast
- Bats: Pancontinental (carnivora and microchiropteran bats)
- Coyotes: Southwest Texas
Street rabies
Dogs and Cats
- domestic animals
Fixed Virus
Cell, egg, and lab animal cultures (attenuated)
- not pathogenic, exist strictly in the lab
Vets are most susceptible to rabies from ______, while most humans get infected with ______ rabies
Cattle; bat
______, ________, and ______ have serious epidemics of rabies
India, Ethiopia, Philipines
Where does attachment, penetration, and uncoating of the rabies virus occur?
Locally, in the myocytes
- limited replication occurs in myocytes (why we give vaccine IM)
Transmission to a nerve cell occurs at the __________
Neuromuscular junction and sensory endings of the PNS
- viral establishment in the PNS occurs
Transport in the axon
Occurs via centripetal migration up the PNS to the dorsal root ganglion against axoplasmic transport
What happens once the virus enters the spinal cord?
Ascent to the brain via cell to cell transmission is fast
- localizes in soma of neurons
- hippocampus, brain stem, and purkinje cells of cerebellum are most heavily affected
What happens after the CNS is affected?
Centrifugal descent down the PNS to retina, cornea, salivary glands, nasal mucosa, hair and taste buds occurs
- virus is released only at nerve endings! (reason for nuccal biopsy in humans using RT-PCR)
Transmission occurs via ____, _____, and _______
Bites, aerosols, and transplants
- death results from neural, respiratory, and cardiac arrest
What are the 3 routes to the CNS?
Hematogenous, neural pathways, olfactory
Hematogenous
Via viremia that can infect endothelium and leukocytes
- passive transport thru permeable areas can occur
- choroid plexus: passage thru and replication in the ependymal cells
Which virus travels to the CNS via hematogenous route?
Canine distemper virus
Olfactory
Cranial nerve penetrates the cribiform plate, rare for rabies but common for Herpes simplex 1 virus
Neural pathways
Axons, Schwann cells, perineural lymphatics, and endoneural spaces
- seen with rabies and canine distemper virus
Collection for rabies diagnostics
- decapitate at atlanto-occipital joint
- expose calvarium
- remove brain, brain stem, and cerebellum by detaching ventral cranial nerves
- bisect brain at longitudinal fissure
- fix one half of brain in 10% buffered formalin for histopath (Negri bodies) and the other half is placed on ice for DFA test, virus isolation, and animal inoculation
Why can’t a rabies collection be frozen?
Has to be fresh, ice crystals will disrupt cells
What are Negri bodies?
IC inclusions in neuronal soma present in ganglia of hippocampus, purkinje cells of cerebellum and medullary ganglia
- are NOT definitive! if absent, animal is still a suspect
What will histopathology show?
Perivascular cuffing of lymphocytes around cerebral vessels and Negri bodies
What is the primary method of rabies diagnostics?
DFA (direct fluorescent antibodies) test
Cell culture
Baby hamster kidney cells, chick embryo fibroblasts, murine neuroblastoma cells, human diploid cells (fibroblasts)
Animal culture
Rabbit pups and pinkie mice by intra-cranial inoculation
- chick and duck embryos by chorioallantoic inoculation
- only example of viral diagnostics in animals!
What is the most antigenic substance in the world?
Glycoprotein
Which 2 processes are occurring simultaneously for rabies pathogenesis?
Transcription/ translation and replication
Transcription and translation
Start with linear negative sense (3’ to 5’) transcriptase strand –> create monosistronic transcripts and that undergo capping and poly adenylation –> mRNA 5’ to 3’ = proteins (translation) = nucleocapsid, nonstructural, large transcriptase (RR enzyme) , glycoprotein, matrix or membrane protein
Replication
Start with negative sense, linear (3’ to 5’) transcriptase –> replicate more negative sense strands with a replicative intermediate (polysistronic!!) –> full length RNA is not capped or polyadenylated
- replication intermediate builds up, creating Negri bodies (polysistronic, positive sense strands)
- goal: to make more full length neg-sense to go back into the virus
Once transcription and replication occurs, _____ occurs at the plasma membrane
Assembly
