Porcine viral diseases 2 - Steph Flashcards
What are 2 important viruses within the family circoviridae
circovirus and gyrovirus
Circovirus gives rise to what virus
procine circovirus type 2 (type 1-4)
gyrovirus gives rise to what virus
chicken anaemia virus
what are some distinguishing characteristics of circovirus
- smallest virus
- only produces 2 proteins (capsid and helps with replication)
- causes circovirus 1-4
what does PCV stand for
porcine circovirus virus
out of the 4 types of PCV virus, which ones are global
PCV 1-3
out of the 4 types of PCV virus, which ones have the highest prevalence
2 + 3, 1 is low, PCV4 is only recently described in china
out of the 4 PCV viruses, which has the largest genome
PCV 3 (1999-2001 nucleotides)
out of the 4 PCV viruses, which has the smallest genome
PCV 1
describe the distribution and prevalence of PCV 1
Global distribution, low prevalence
describe the distribution and prevalence of PCV 2
Global distribution, high prevalence
describe the distribution and prevalence of PCV 3
Global distribution, high prevalence
Describe the distribution and prevalence of PCV 4
China, prevalence is not known
***what is important to know about the different genotypes of PCV 2
there are 8 different genotypes, only 3 of those 8 are prevalent in north america. all the genotypes have different prevalence
describe the distribution of PCV3 in domestic and wildboar populations
widespread
what is PDNS
porcine dermatitis and nephropathy syndrome
What is the most prevalent PCV type in canada
PCV2
what are the clinical syndromes that PCV2 presents with
reproductive, respiratory, enteric, systemic, PDNS (questionable CNS manifestation)
what are the clinical syndromes reported for PCV3
Reproductive, respiratory, systemic, PDNS, CNS. (enteric manifestation lacking)
2 outcomes of PCV2
subclinical and clinical
how can PCV2 result in a clinical outcome
high viremia, lymphoid depletion –> 80% mortality
what is the % mortality for the clinical manifestation of PCV2
70-80% mortality
what are the important implication of PCV2 subclinical infections**
leads to immunosuppression. When there is immunosuppression, there can be co-infections which together leads to growth retardation
in other words…
It can lead to immunosuppression that is manifested in vaccine efficacy, secondary bacterial infections and retardation of growth
what are the major clinical signs of the subclinical infection of PCV2 (i know, not very intuitive)
even though the animals are considered subclinical for PCV2 infections, can still see a decreased average daily gain (approx. 10-40g/day) without any evident clinical signs.
what are 3 individual diagnostic criterion for PCV2 subclinical infections
- lack of overt clinical signs
- no or minimal histopathological lesions in tissues (mainly lymphoid)
- no amount of PCV-2 in few (lymphoid) tissues, usually in follicular areas
what does PMWS stand for**
post-weaning multi systemic wasting syndrome
Individual diagnostic criterion for PMWS***
- weight loss and paleness of skin (respiratory and/or digestive clinical signs may be present as well)
- moderate to severe lymphocyte depletion with granulomatous inflammation of lymphoid tissues (plus granulomatous inflammation in other tissues)
- moderate to high amount of PCV-2 in lymphoid tissued
what is the major clinical manifestation of PCV-2 systemic disease***
PMWS (post weaning multisystemic wasting syndrome)
when looking at a herd, how will you know that there is a potential PCV2 infection
uneven herd animals, some are smaller, some are larger
which cells does PCV2 replicate in
macrophages
what are the histological signs that an animal has been infected with PCV2
lymphoid depletion, hystiocytic replacement and inclusions (can demonstrate viral replication in cytoplasm)
what are the major clinical signs for PCV2 reproductive disease***
abortions and mummifications (still births)
what is the individual diagnostic criterion for PCV2 reproductive disease***
- reproductive failure at late gestation or SMEDI-like condition
- fibrous to necrotizing myocarditis of fetuses
- moderate to high amount of PCV-2 in heart
PDNS ***
porcine dermatitis and nephropathy syndrome
what are the major clinical signs of PDNS
dark red papules and macules on skin, mainly in hind limbs and perineal area
what are the individual diagnostic criteria for PDNS**
- hemorrhagic and necrotizing skin lesions and/or swollen and pale kidneys with generalized cortical petechia
- systemic necrotizing vasculitis, and necrotising and fibrinous glomerulonephritis (seen in kidney as well)
what cells does PCV2 target during fetal life versus post natally?
PCV2 targets cardiomyocytes, hepatocytes and macrophages during fetal life
only macrophages postnatally
what are some ways to diagnose PCV2
- clinical history of herd (respiratory and/or gastrointestinal disease of animals especially but not exclusively after weaning, wasting, immunosuppression [secondary infections, vaccine failures])
- post mortem findings
- immunohistochemistry for virus on lymphoid tissue
- PCR (swab [rope sample], serum): lab results will only provide information on infected/non infected. Persistent infection does not necessarily lead to clinical problems)
- qPCR: PCV2-associated disease correlates with high viral load in serum and tissues
what are the two main syndromes in PCV2?***
PMWS, PDNS
name the several clinical manifestations of PCV2
subclinical
PMWS
Systemic disease
reproductive disease
PDNS
(also GI manifestation?)
for diagnosis of PCV2, what do you need?
both PCR and immunohistochemistry
what are 3 important things to remember about PVC2 vaccines**
- vaccines has PCV2 genotype (PCV-2a isolates) but can cross protect against other things PCV-2b and PCV 2d)
- vaccines are able to generate both cellular and humoral responses
- vaccine does not prevent infection of PCV2 but does decrease the diseases associated with
what is PRRSV
porcine respiratory and reproductive syndrome virus
what does PRRSV cause
PEARS (procine epidemic abortion and respiratory syndrome)
mystery diease
blue ear disease
SAMS (sow abortion and mortality syndrome)
SIRS (swine infertility respiratory syndrome) \
How many different strains of PRRSV are there?
2 different strains/genotypes, PRRSV-1 is a european strain and PRRSV-2 is american
where is PEARS endemic to?*
North america
how does PRRSV gain genetic variability
point mutations and recombination
describe the pathogenesis of PRRSV
virus targets macrophages (alveolar macrophages and tissue macrophages)
what are the primary sites of infection for PRRSV in the acute disease
- lung
- lymphoid tissue:lyphymphoadenopathy common
- many other possible sites: kidney, spleen, heart, thymus, skin, reproductive tract, nervous system
where is the virus found in PRRSV chronic phase
peripheral lymph nodes and tonsils
what is important to remember for PRRSV subclinical infection
one of the viruses that produces PERSISTENT infection for as long as 5 months
what are the mechanisms PRRSV persistence
weak immune response because of glycan sheilding, immune decoy epitopes and genetic variation
why does it take the immune system 5 months to get an ideal response when responding to PRRSV
the virus targets immune cells –> interferes with their function and causes immunosuppression
what are the clinical signs associated with PRRSV
reproductive problems:
- late gestation is common, litters with normal, weak, stillborn, mummies, anorexia and agalactia in sows
- early gestation losses possible: abortions, return to service
Respiratory disease:
- dyspnea, tachypnea, ill-thrift, poor growth
- interstitial pneumonia
- rarely, severe fatal disease
Cutaneous signs also possible
neurologic signs in sows are rare
high fever and shivers in neonates and adults
on necropsy, what would the lungs and kidney look like for a pig infected with PRRSV
kidney showing numerous red blood spots
severe lesions and haemorrhage of lungs
out of all the clinical manifestations of PRRSV, what are the two main ones
respiratory and reproductive manifestations
(note: repro manifestations look like SMEDI)
what are some diagnostic tests we can use to detect PRRSV/ confirm PRRSV
PCR, ELISA (oral and serum), immunohistochemisty (i think we need all of these)
What are ways that we can control PRRSV if we are going to live with it
- maintain herd wide immunity using vaccination!
- prevent introduction of new strains (live animals, semen, fomites, mosquitos, aerosol transmission
what ways can we control PRRSV if we want to be PRRSV free
- have to depopulate the infected herd an repopulate with clean herd
- surveillance with serological and virological testing
- prevent introduction
