Rhabdoviridae

Question 1

Which virus subfamilies are included in the family Rhabdoviridae?

Answer 1

• lyssaviruses
• vesiculoviruses
• unclassified viruses

Question 2

Name the 5 viruses in the Lyssavirus family

Answer 2

• Rabies: zoonotic, CNS
• Mokola: Nigerian shrews, CNS
• Lagos: Nigerian bats, CNS
• EBLV 1 & 2: European bats, humans, CNS
• Duvenhage: bats, CNS

Question 3

Name the 3 viruses in the Vesiculovirus family

Answer 3

• Vesicular Stomatitis Virus: vesicular stomatitis, Indiana and NJ serotypes
• Piry: vesicular disease
• Chandipura: vesicular disease

Question 4

Name the 6 viruses that fall into the Unclassified family

Answer 4

• *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

Question 5

Which virus gets into pet coy fish?

Answer 5

Spring Viremia

Question 6

Which virus is indigenous to the US?

Answer 6

Infectious Hematopoetic Necrosis Virus

- located in northwest

Question 7

Rabies viral genome

Answer 7

Linear, single stranded RNA, negative sense

- enveloped particle, RR trnascriptase is carried by the virus

Question 8

How many proteins does the rabies virus code for?

Answer 8

5!

Question 9

Where does the rabies virus replicate?

Answer 9

Cytoplasm of host neural cell

Question 10

Is the rabies virus cytocidal or persistent?

Answer 10

Persistent

- disrupts neuronal function, produces very little neural destruction

Question 11

What species does vesiculaoviruses infect?

Answer 11

Horses, cows, deer, pigs, and humans

Question 12

What are the rule outs for a pig possibly infected with vesicular stomatitis virus?

Answer 12

Swine Vesicular Disease (picornavirus) and Vesicular Exanthema (calicivirus)
- VE only occurs in swine, SVD does not occur in horses and cattle

Question 13

Even though all warm blooded animals are susceptible to rabies virus, which animals appear to be somewhat resistant?

Answer 13

Opossums, guinea pigs, rats, and birds

Question 14

Sylvatic rabies

Answer 14

“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

Question 15

Street rabies

Answer 15

Dogs and Cats

- domestic animals

Question 16

Fixed Virus

Answer 16

Cell, egg, and lab animal cultures (attenuated)

- not pathogenic, exist strictly in the lab

Question 17

Vets are most susceptible to rabies from ______, while most humans get infected with ______ rabies

Answer 17

Cattle; bat

Question 18

______, ________, and ______ have serious epidemics of rabies

Answer 18

India, Ethiopia, Philipines

Question 19

Where does attachment, penetration, and uncoating of the rabies virus occur?

Answer 19

Locally, in the myocytes

- limited replication occurs in myocytes (why we give vaccine IM)

Question 20

Transmission to a nerve cell occurs at the __________

Answer 20

Neuromuscular junction and sensory endings of the PNS

- viral establishment in the PNS occurs

Question 21

Transport in the axon

Answer 21

Occurs via centripetal migration up the PNS to the dorsal root ganglion against axoplasmic transport

Question 22

What happens once the virus enters the spinal cord?

Answer 22

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

Question 23

What happens after the CNS is affected?

Answer 23

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)

Question 24

Transmission occurs via ____, _____, and _______

Answer 24

Bites, aerosols, and transplants

- death results from neural, respiratory, and cardiac arrest

Question 25

What are the 3 routes to the CNS?

Answer 25

Hematogenous, neural pathways, olfactory

Question 26

Hematogenous

Answer 26

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

Question 27

Which virus travels to the CNS via hematogenous route?

Answer 27

Canine distemper virus

Question 28

Olfactory

Answer 28

Cranial nerve penetrates the cribiform plate, rare for rabies but common for Herpes simplex 1 virus

Question 29

Neural pathways

Answer 29

Axons, Schwann cells, perineural lymphatics, and endoneural spaces - seen with rabies and canine distemper virus

Question 30

Collection for rabies diagnostics

Answer 30

- 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

Question 31

Why can't a rabies collection be frozen?

Answer 31

Has to be fresh, ice crystals will disrupt cells

Question 32

What are Negri bodies?

Answer 32

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

Question 33

What will histopathology show?

Answer 33

Perivascular cuffing of lymphocytes around cerebral vessels and Negri bodies

Question 34

What is the primary method of rabies diagnostics?

Answer 34

DFA (direct fluorescent antibodies) test

Question 35

Cell culture

Answer 35

Baby hamster kidney cells, chick embryo fibroblasts, murine neuroblastoma cells, human diploid cells (fibroblasts)

Question 36

Animal culture

Answer 36

Rabbit pups and pinkie mice by intra-cranial inoculation - chick and duck embryos by chorioallantoic inoculation - **only example of viral diagnostics in animals!**

Question 37

What is the most antigenic substance in the world?

Answer 37

Glycoprotein

Question 38

Which 2 processes are occurring simultaneously for rabies pathogenesis?

Answer 38

Transcription/ translation and replication

Question 39

Transcription and translation

Answer 39

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

Question 40

Replication

Answer 40

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

Question 41

Once transcription and replication occurs, _____ occurs at the plasma membrane

Answer 41

Assembly