Rhabdoviridae

Question 1

Describe the morphology of Rhabdoviruses

Answer 1

Enveloped
Bullet shaped
Large spikes on the envelope
Helically coiled, cylindrical nucleocapsid

Question 2

How many proteins are encoded by rhabdovirus RNA?

Answer 2

5!
Large Giraffes Need More Protein
L: large, RNA dependent RNA polymerase
G: glycoprotein for envelope spikes
N: nucleoprotein to form nucleocapsid
P: phosphoprotein mediates binding of L protein to nucleocapsid
M: matrix associates with viral nucleocapsid and lipid envelope

Question 3

Describe the genome of rhabdoviridae

Answer 3

ssRNA, negative-sense, one molecule

Question 4

Where does rhabdovirus replicate and what characterizes its maturation?

Answer 4

Cytoplasm

Budding from plasma membrane characterizes maturation

Question 5

Which virus ‘mutant’ is formed during rhabdovirus replication?

Answer 5

Defective interfering virus particles that interfere with the normal replication process

Question 6

What is the most important member of genus Lyssavirus?

Answer 6

Rabies virus, genotype-1 lyssavirus

Question 7

What animals are highly susceptible to rabies?

Answer 7

Cats and cattle

Question 8

What animals are moderately susceptible to rabies?

Answer 8

Dogs, sheep, goats, horses, primates, humans

Question 9

How is rabies transmitted?

Answer 9

Between mammals mainly via bite/scratch with the virus in its saliva, not transmitted through intact skin

• Aerosol transmission has been documented in labs or bat caves
• Human vases via organ transplant?

Question 10

Describe the two cycles by which rabies is maintained:

Answer 10

Urban: dogs are main reservoir, predominates in Africa, Asia, Central/South America
Sylvatic: Europe and N. America, usually multiple wildlife species are responsible for perpetuating a particular strain i.e. bats!
Dead end hosts: humans and most herbivores

Question 11

T or F: A bat that has rabies is less likely to interact with humans than a bat that is infected with rabies

Answer 11

False! If a bat has rabies, it is more likely to interact with humans!
Oftentimes, asymptomatic but sometimes can be aggressive*

Question 12

Which type of bat plays a major role in human and animal rabies in Mexico, Central America, and S. america?

Answer 12

Vampire bats

Question 13

Which type of bat is capable of transmission of rabies in Australia?

Answer 13

Fruit bats!

Question 14

Which type of bat is more likely to transmit rabies in North America?

Answer 14

Insectivorous bats!

Question 15

Which animal is the MOST important in perpetuation of wildlife rabies in central USA?

Answer 15

The skunk

Question 16

Which animal is the most frequently reported rabid species in the USA?

Answer 16

The raccoon

Question 17

Describe the pathogenesis of rabies

Answer 17

May enter peripheral nerves directly or multiply in non-nervous tissue until there’s enough of them to reach motor/sensory nerve endings
Shed from monocytes into extracellular spaces
G protein binds to axon terminals through lipoprotein receptors
Gets into nerves
Greater degree of innervation at site of bite, shorter incubation period

Question 18

T or F: Bites to the face have the greatest risk

Answer 18

True

Question 19

If intranasal exposure occurs, how does the virus get to the CNS?

Answer 19

Through the trigeminal nerves and ganglia

Question 20

What form of rabies happens when the virus reaches the limbic system?

Answer 20

Furious form

Think-emotions

Question 21

What form of rabies happens when the virus reaches the neuro-cortex?

Answer 21

Dumb or paralytic form

Question 22

T or F: first, rabies heads centrifugaly from the CNS to the peripheral nerves and then moves centripetally from the peripheral nerves to other organs

Answer 22

False! Opposite–first is centripetally from periphery to CNS and THEN centrifugally out bak to the peripheral nerves (salivary glands via cranial nerves–hypersalivation)

Question 23

Identify pathological findings of the rabies virus, specifically in the brain

Answer 23

There tend not to be any! Variable inflammation and very modest histological evidence of neuronal injury
Indicates primary neuronal lesion is functional, not structural

Question 24

T or F: If the bite is closer to the site of the brain, there will be a shorter incubation period

Answer 24

True!

Question 25

Identify and describe the three general phases of the clinical course of rabies

Answer 25

Prodromal: virus shedding and change in temperament before obvious clinical signs are observed Furious (acute): nervous, irritable, dilated pupils, loss of caution and fear, hydrophobia, excessive salivation, exaggerated responses to light and sound Paralytic (dumb): fury gives way to paralysis, ataxia, muscle weakness, seizures, coma, respiratory arrest and death 2-14 days after clinical signs *Ruminants don't tend to exhibit fury

Question 26

How do you diagnose rabies?

Answer 26

FAT (recommended by WHO and OIE) to look for rabies antigen Negri bodies in the brain (not all positive brains will have these) RT-PCR for viral RNA Intercerebral inoculation of weanling mice for virus isolation Mice develop encephalitis in 14 days

Question 27

How do you control rabies in a rabies free country?

Answer 27

Quarantine involving segregation of dogs and cats in licensed premises for 6 months

Question 28

What are the preexposure and post-exposure recommendations for dogs and cats?

Answer 28

Pre: Vaccinate at 3 months of age, revaccinate every 1 or 3 years after Post: Unvaccinated animals are euthanized immediately, non-current vaccinated animals are evaluated on a case by case basis, and current vaccinated animals have to be revaccinated immediately and kept under owner's control for 45 days

Question 29

What are the two serotypes of the vesiculovirus?

Answer 29

Indiana: Fort Lupton, Alagos, Coccal | New Jersey: more virulent with the widest distribution!

Question 30

T or F: the vesiculovirus can remain stable for days or weeks in cool water, soil, and on vegetation

Answer 30

True

Question 31

What animals does vesiculovirus mostly infect?

Answer 31

Cattle, pigs, horses in the Americas, sometimes sheep and goats Influenza-like disease in humans

Question 32

Describe the transmission of the vesiculovirus?

Answer 32

Probably enters through breaks in mucosa/skin, contamination of milking machines, chewing or ingestion of contaminated fomites, arthropods via mechanical transmission! Like houseflies

Question 33

Describe the pathogenesis of vesicular stomatitis

Answer 33

Localized infection on the epiehtlium leads to intraepithelial edema and vesicles that quickly ulcerate, common on the tongue! Not typically a substantial systemic phase of infection

Question 34

What are the clinical signs of vesicular stomatitis?

Answer 34

Generally self limiting with lesions that develop 1-5 days after incubation, excess salivation and fever in cattle/horses, lameness in swine, vesicles on tongue, oral mucosa, teats to ulcers Lesions may cause salivation/anorexia, lameness, rejection of suckling calve In horses, tongue lesions most pronounced In swine, vesicular lesions most common on snout and coronary bands Humans: influenza like disease

Question 35

How do you diagnose vesicular stomatitis?

Answer 35

Vesicular lesions in horses are characteristic of only vesicular stomatitis!! V.S. is clinically indistinguishable from other vesicular diseases of swine and cattle Virus isolation RT-PCR

Question 36

How do you prevent V.S.?

Answer 36

``` Quarantine of affected premises Reportable in the USA! Control insect population Keep infected animals away from surface water in pastures Vaccines aren't widely used ```

Question 37

How is bovine ephermeral fever transmitted and who are the hosts?

Answer 37

Transmitted via arthropods and the hosts are water buffalo and cattle Arthropod probs Culicoides and maybe mosquitoes

Question 38

T or F: bovine ephemeral fever has never been reported in the USA

Answer 38

True!

Question 39

Describe the pathogenesis of bovine ephemeral fever

Answer 39

It is poorly understood, site of replication is unknown There is an early neutrophilia with an abnormal level of immature neutrophils in the circulation Increase in plasma fibrinogen and decrease in plasma calcium

Question 40

What are the most common lesions in bovine ephemeral fever?

Answer 40

Polyserositis affecting the joints, pleural and peritoneal surfaces Increase in neutrophils increases permeability!

Question 41

What are the clinical features of bovine ephemeral fever?

Answer 41

Begins with fever followed by inappetence, excessive salivation, drooling, increased HR, stiffness, lameness, sudden decrease in milk yield Recovery is dramatic and usually in 3 days! Some animals are recumbent/paralyzed for 8 hours to 1 week though

Question 42

How do you diagnose bovine epheremal fever?

Answer 42

Isolation is difficult but can be attempted by inoculation of infected buffy coat cells into cell cultures or IC inoculation of suckling mice FA staining of blood smears Paired serum samples

Question 43

How is bovine ephemeral fever controlled?

Answer 43

Attenuated virus vaccines are effective BUT should only be used in endemic areas! Vector control, duh