L26: Reoviridae (Romero) Flashcards
Reoviridae general characteristics
- dsRNA
- comprise “REO” (Respiratory Enteric Organs) viruses
- most complex of virology families
- infect wide variety of hosts
- most not assoc. with dz (exceptions: rotaviruses and orbiviruses**)
2 genera of reoviridae that DO cause disease?**
Rotaviruses
Orbiviruses
Orbivirus genus general chars.
- genus of reoviridae
- transmitted via arthropod vectors
- seasonal dz
- climate change may widen their geographical activity (esp. African horse sickness, Blue Tongue viru, and Peruvian horse sickness)**
Bluetongue virus general chars.
- an orbivirus
- acute dz in sheep
- effects cattle less severely
- genome composed on 10 dsRNA segments
CS/path. of Bluetongue virus**
- vascular endothelial damage –> edema, necrosis esp. of tongue, nose, face, etc.
- coronary bands –> lameness
- nasal d/c
- “sore muzzle” due to congestion of nasal cavity**
- serotype BTV can cross placenta –> abortion
- pericardial/pleural effusion
- virulence vaires depending on serotype**
where does most Bluetongue virus persist after viremia? **
platelets and RBCs (may remain infected long-term)
Which serotype of bluetongue virus invaded Europe from Africa? Virulence?**
Serotype 8; highly virulent for many ungulates
mortality of Bluetongue virus is highest in which species?
sheep
morbidity of Bluetongue virus
~100% in sheep, cattle, goats, deer, antelopes
Dx of Bluetongue virus
- CS
- Virus isolation
- RT-PCR
- Serology: ELISA, AGP, or Virus Neutralization**
3 methods of serology for Bluetongue virus**
ELISA
AGP
Virus Neutralization
Prevent/Control of Bluetongue Virus
- Vaccine (inactivated or live-attenuated; live-attenuated can cause abortion in ewes or undergo reassortment in vectors)
- can’t eliminate vectors
- only introduce Ab-negative animals to BTV-free area
Immunity to Bluetongue virus determined by:
virus neutralizing antibodies (serotype-specific)
epizootic hemorrhagic disease virus in what genus of reoviridae?
orbivirus
epizootic hemorrhagic disease virus general chars.
- transmitted by Culicoides insects
- infection in ruminants usually subclinical
- dz seen after drought periods
- not contagious
CS of epizootic hemorrhagic disease virus
- excessive salivation, foaming around nose and mouth
- fever, extreme thirst, mouth ulcers
- swelling of head, neck, tongue
- deer usually found dead near water sources
African Horse Sickness belongs to what genus of Reoviridae?
Orbivirus
African Horse Sickness chars.
- high mortality in horses
- not in Americas (yet)
CS of PULMONARY form of African Horse Sickness
- severe resp. distress, death
- stands w/ forelegs apart, neck extended, nostrils dilated
- profuse frothy nasal d/c
- seen in susceptible horses infected with highly virulent strains
- pleural effusion
CS of CARDIAC form of African Horse Sickness
- fever
- edema in eyelids, lips, tongue, larynx, neck, chest
- congestion and hemorrhage of conjunctiva
- pericardial effusion, hemorrhage
- death 4-8 days later
CS of Horse sickness fever caused by African horse sickness
transient fever
lack of appetite
high RR
very LOW mortality rate
Trans./Path. of African Horse Sickness
- vector-borne by midges
- seasonal
- virus replicates in local lymph nodes
- vascular injury –> inflammation, mac release
- pulmonary edema when virulent virus involved
- less virulent viruses –> gelatinous yellow fluid in subcutis
Dx of African Horse Sickness
- CS
- virus isolation
- virus neutralization
- RT-PCR (test of choice)
Immunity to African Horse Sickness
- recovered horses immune for life against that serotype and have partial immunity to other serotypes
- passive immunity via colostrum
- vaccines available
zoonotic potential of African Horse Sickness
- NOT zoonotic in wild
- zoonotic potential in labs and while making vax –> encephalitis, chorioretinitis, DIC
