Flashcards in Porcine Reproductive and Respiratory Syndrome (PRRS) Deck (30)
What causes PRRS?
What are the clinical properties of arteriveridae?
1. can cause asymptomatic persistent infections
2. can cause severe fatal dz
3. replicate in macrophages
What are PRRS virus preferred macrophages to infect?
those in the lung and maternal fetal interface
What are the features of PRRSV?ble
2. strain variation
3. variation in virulence
What are the major subtypes of PRRSV?
High path PRRSV
What is the epidemiology of PRRS?
1. highly infectious
2. not highly contagious
3. persistent (>100d carrier state)
4. not fully cross-protective across stains
5. subclinical endemic infection common (low virluence in w. canada)
How is environmental survival of PRRSV?
1. poor off host
2. susceptible to drying, disinfection etc
How is PRRSV transmitted?
1. vertical (semen, transplacental)
2. horizontal (pig to pig, dam to piglet)
4. aerosol--prevalent in hog dense regions
What is the pathogenesis of PRRS?
1. replication in lymphoid tissues
2. prolonged viremia--->persistent infection
3. predelication for pulmonary alveolar macrophages and pulmonary intravascular macrophages
4. intersitial pneumoniae
5. cross placenta in late gestation (>d 70). fetal death
What are the clinical reproductive signs of PRRS
1. In the pregnant sows can have anorexia, fever, mortality if virulent but more often SUBCLINICAL early farrowing
What are the features of the piglets that are born in premature farrowings due to PRRS?
1. weak, liveborn
2. persistently viremic
3. neonatal scours (nonresponsive to antimicobials)
4. elevated preweaning portality
What are the respiratory clinical signs of PRRS?
1. dypsnea (thumping)
2. cyanosis of extremities
3. minimal coughing if pure PRRS
What are the clinical signs of high fever disease (high path PRRS)
1. high fever
2. blotchy congestion skin
4. high case fatality rate
What is the pathology of high fever disease (high path PRRS)
wide spread hemorrhages and edema, diffuse petechiation, splenic infarcts mixed infections
What is the etiology of high fever disease?
high path PRRSV
What is the pathology of PRRS?
1. non-suppurative interstitial pneumonia
2. systemic vasculitis
How is PRRS diagnosed?
What is the timeline of antibody response to PRRS?
1. IgM positive 5-14d (recent infection)
2. IgG positive 10-14d (exposure last 1-2 mo)
3. SN serum neutralization--positive within 28d (correlated with clearance
What does serum neutralization detect?
correlated with viral clearance but not required for protection
How can you monitor for PRRS?
1. oral fluids
2. Studs: ELISA serology, PRRS PCR on semen or blood
How is PRRS treated and controlled?
1. treat affected individuals (anti-inflam, secondary infection)
What vaccines should be used for PRRS?
1. attenuated live
prior to breeding/during lactation, in progeny 3-6wk
Who are the PRRS vaccinations NOT licenced for?
boars or pregnant sow
How is herd elimination of PRRS performed?
1. mass immunization or mass eposure--sterilizing immunity and cessation of ongoing vertical transmission
=breeding herd stablization
*using homologous strain to that present on farm
What is serum innoculation (PRRSV)
it is a high risk procedure that involves inoculating the breeding herd with live VIRULENT PRRS
What are the steps of serum inoculation (herd elimination of PRRSV)
1. remove NGF population
2. load and close herd
3. expose animals
4. impliment McRebel
5. test pigs at weaning (PCR)
5. restock NGF when consistently negative
6. sentinel gilts
7. open herd
What is McRebel?
good managemnet procedures:
max passive immunity
euthanize fall behinds
don't move piglets between rooms
euthanaize pigs that are very sick
dn;t feed back repro tissue to sows before farrowing
all in all out
What is the issue with regonal control of PRRSV?
it is not easily kept out of non-infected farms
How do you prevent PRRSV entry onto naive farms?
1. live animal quarantine and test
2. test semen
3. transport and wash protocols
4. wash fomites
5. no use of MLV vaccine
6. farm location
8. air filtration! (esp hog dense area)