Arenaviruses, Rhabdoviruses, Reoviruses, Birnaviruses

Question 1

Arenaviruses

• structure
• genome
• specific type

Answer 1

• Enveloped; host cell ribosomes packaged (arena = sand)
• ssRNA, ambisense (2 genome segments)
• Lymphocytic choriomeningitis virus

Question 2

Lymphocytic choriomeningitis virus***

• family of virus
• host
• clinical signs if infected in utero or <48hrs old vs older animals
• lesions

Answer 2

• Arenavirus
• Mice and hamsters
• infected in utero or <48 hr old: tolerant infection largely asymptomatic -> runting, lower reproduction
• older animals: acute infection, clear virus and recover, may be runted.
  lesions: vasculitis, glomerulonephritis, choriomeningo-encephalitis; lymphocytic infiltration in visceral organs

Question 3

Rhabdoviruses

• structure
• genome

Answer 3

• Enveloped, distinctive ‘bullet’ shape
• (-)ve sense RNA
• Broad host range

Question 4

Rabies virus***

• family
• transmission
• pathogenesis
• clinical signs

Answer 4

• Rhabdovirus
• Transmission: Bites
• Pathogenesis: Inoculation from bite of a rabid animal -> local replication -> attach and infect peripheral nerves at motor end plates -> retrograde spread within peripheral nerves -> SC and brain -> centrifugal spread from brain to salivary gl’s and other tissues -> secretion into saliva

Signs:
- prodromal phase: change in temperament

Two forms: 
Furious Rabies 
- restless/nervous
- aggressive
- loss of fear of humans
- hypersalivation
- hypersensitive to sound and light
- hyperesthesia
- dumb

Paralytic Rabies

• depression
• paralysis
• seizures
• coma
• respiratory arrest
• death

Question 5

Vesicular stomatitis virus***

• Family
• Indistinguishable from which disease?
• Clinical signs

Answer 5

• Rhabdovirus
• Indistinguishable from foot-and-mouth disease
• Transient fever
• Lameness
• Vesicles and erosions typically in mouth
• Lesions on tongue, oral mucosa, teats, coronary bands are painful causing salivation and anorexia
• Horses are often severely affected - oral lesions, coronary band lesions

Question 6

Reoviruses

• Structure
• Genome

Answer 6

• Nonenveloped

- segmented dsRNA

Question 7

Bluetongue virus

• Family
• Transmission and hosts affected
• Pathogenesis
• Clinical signs
• Lifelong immunity?
• Reportable?

Answer 7

• Reovirus - Orbiviridae

Transmission:

• Biting midges
• mechanical vectors (ticks, sheep keds)
• veneral (found in semen, unlikely route of transmission)
• transplacental

Hosts:
Ruminants
- clinical disease most severe in sheep (and deer, antelope, and Pronghorn); cattle are a reservoir

• saliva of biting midge -> replication in regional ln’s -> viremia -> replication in hematopoietic cells and endothelial cells -> prolonged viremia
• Transplacental transmission in late fall to a late-term developing fetus can lead to birth of a viremic calf; endothelial damage -> vascular occlusion -> tissue edema and epi sloughing due to loss of microvasculature
• hemorrhage
• 3 F’s = Fever, face, and feet
• depression
• anorexia
• rapid wt loss
• hyperemia of muzzle, face, or neck
• salivation
• heavy breathing or panting
• sores on tongue, mouth, or nostrils
• lameness (coronitis)
• abortions and congenital abnormalities
• Systemic antibody response gives lifelong immunity
• Reportable

Question 8

African horse sickness virus

• Family
• Transmission
• Hosts affected (severity in each)
• Clinical signs

Answer 8

• Reovirus - Orbiviridae
• Culicoides species (Biting midges)
• Very high mortality; zebras are natural reservoir (asymptomatic); sp’s affected: donkeys, mules, and horses (most)

Subacute edematous form

• fever 3-6d
• edema (supraorbital fossa and eyelids, cheeks, lips, tongue, laryngeal region, and neck)
• depression
• anorexia
• colic
• petechiae under tongue and on conjunctivae

Peracute disease

• acute fever
• sudden onset of severe resp distress
• inc resp rate w forced expirations
• profuse sweating
• terminally spasmodic coughing and frothy nasal exudate
• rapid death

Question 9

Rotavirus

• Family
• Transmission
• Hosts affected
• Clinical disease caused
• Pathogenesis

Answer 9

• Reovirus (Rotavirus is the family name)
• Oro-fecal transmission
• All domestic animals
• Diarrhea (in intensively reared young animals)

(Very stable in environment)

• Infects mature enterocytes in proximal ileum -> kills apical enterocytes
• produces a viral enterotoxin (induces Cl- secretion)
• causes villus ischemia
• activates enteric nervous system (infected cells release vasoactive intestinal peptide - inc’s intestinal motility, dec’ing absorption)

Question 10

Birnaviruses

• Structure
• Genome

Answer 10

• Non-enveloped

- dsRNA (2 RNA segments)

Question 11

Infectious bursal disease virus

• Family
• Another name for disease caused
• Transmission
• What does it primarily infect?
• Where is it shed?
• Clinical signs
• Vaccination challenges

Answer 11

• Birnavirus - Avibirnavirus
• Gumboro disease in chickens
• Oro-fecal
• Primarily infects the bursa of Fabricius
• virus excreted in feces - very stable and highly contagious
• Can lead to permanent immunosuppression
• Feather ruffling
• depression
• anorexia
• trembling
• dehydration
• watery diarrhea
• inc’ed susceptibility to other viral inf’s

Oral live attenuated vax - not fully effective, virus constantly changing making vax development challenging