PCV3, who cares?

B Arruda1Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary

Medicine, Iowa State University, Ames, Iowa

The Story of a Great Masquerader

https://top10bestpro.com/best-masquerade-masks-for-men/

Sporadic disease 1985

Devastating epidemicsLate 1990s

Present at least by 1962

EM of PCV21994

‘Unusual’ disease1990s

Effective vaccinesLate 2000s

The Story of a Great Masquerader

Schwartz

Madson

https://slideplayer.com/slide/4456534/

MadsonMadson

Madson

SchwartzSchwartz

StevensonSchwartz

Majority of infections are SUBCLINICAL

A New Circo

PCV3 vs PCV2

PCV2

• PCV3 strains are very similar

• PCV3 is very different from PCV2

• PCV2 vaccination does not appear to protect against PCV3 infection

Is It Important?

E F E F E F E F

Consistent detection by PCR Accurate case

definition Absence or

inconsistent detection of other known pathogens

High viral load (low CT) Repeat diagnosis Multiple sites

Absence of unknown viruses

Agent in diseased tissue

Reproductive Failure

• January and November of 2018• 22 cases

• 36 fetuses/fetal groups• Multiple groups per case

• 20 different sites• IA, IN, NE, KS, SD, MI, NC, OH

Reproductive Failure

• Clinical history• Uptick in mummies and stillborns

• 5%

• Gilts and/or low parity sows

Reproductive Failure

IF YOU ARE LOOKING AT AVERAGES YOU MISS THINGS.Example

0.7 mummified fetus/litterSows: 0+1+0+0+0+0+0+0+0+0 = 0.1 mummified fetus/litterGilts: 0+1+3+0+3+0+0+4+0+5 = 1.6 mummified fetuses/litter

Look at the individual litter/sow level diagnosis

What is a ‘normal’ number of mummified fetuses in a litter?

What is an ‘acceptable’ number of mummified fetuses in a herd?

= 0+0+0+3+4+0+0+0+0+0

Reproductive Failure

• Samples• Mummies from the same or different litters and

stillborns• CRL varied from 7 cm to 30 cm

• 7 cm to 17 cm 45 and 70 days of gestation

Reproductive Failure

• PCV3 PCR• Commonly detected in multiple litters/groups

• PCV3 Ct values• 9.4 – 34.4• 10-20

1.3 trillion/mL1.7 billion/mL

Reproductive Failure

• PRRSV, PCV2, PPV, Leptospira• Negative

• Bacterial culture• No significant growth

• Next generation sequencing sequences ‘all’ of the genetic material in a sample• PCV3 (n=14 fetal pools)

Inflammation in the heart PCV3

0

5

10

15

20

25

30

PRRSV PPV PCV2 PCV3

No. of

Case

s

Reproductive Failure Cases by VirusJan 1, 2018 – Oct 1, 2018

5%

11%

13%

Is It Important? Reproductive Failure

Lesion + PCV3 in situ

E F E F E F E F

Strongly associated with mummies and stillborns

PCV3 high viral load

Repeated detection Litters Submissions Multiple sites

No other common/known cause of reproductive failure

No other novel agent detected by NGS

No evidence PCV3 is a cause of abortion

Perinatal Infection

• Three cases• Two sites from two different production systems

• Newly populated herd• Genetic multiplier

• Weak-born and/or abnormal piglets• PCV3 Ct values

• Cerebrum• 7.5-13.3

Billions to trillions of copies / mL

Most UNCOMMON clinical presentation based on VDL case submissions

Inflammation surrounding blood vessels Foci of inflammation PCV3

* ** *

Perinatal Infection

Viral infection

Inflammation surrounding vessels and in the heart PCV3

* *

*

*

**

Perinatal Infection

Inflammation in the brain

Inflammation in the heart

PCV3

*

PCV3

**

**

Growing Pig• February and October 2018• Twelve cases

• Ten different sites• Five from the same sow source

• Age range• 3- to 10-weeks-old• Commonly 4- to 6-weeks-old

• Clinic signs vary• Dermatopathy, acute death, lameness,

enteric, respiratory, small sickly looking pigs, loss of condition

• Lesions at the cell level Distinctive• No notable gross lesions

• PCV3 PCR Ct • Low 20s (lung)

No good clinical case definition

We don’t know the number/percent of pigs affected on affected farms probably low

Periarteritis Periarteritis & arteritis

Multisystemic Inflammation

* **

**

Point/Counterpoint

It has been around for decades

It is endemic

Our herd infectious/immunity status has and continues to change

Numerous cases of PDNS & innumerable cases of reproductive failure without detection of known causes over the past decades

We do not know at what prevalence

Yup, as is rotavirus, SIV, PCV2, S. suis…endemic agents cause disease in a subset of individuals due to various factors

Evidence is the currency by which one fulfills the burden of proof.

Detection of PCV3

• Detected by PCR in multiple sample types• Processing fluids, serum, colostrum, tissues,

feces, nasal swabs, oral fluids• Detection ≠ Disease (causation)• Its there…now what? Implications?

Detection of PCV3

• Case definition/clinical signs? • Sample type? • Viral load? • Diseased tissue?

Detection of PCV3

• Processing or oral fluids • You have it• Probably isn’t helping• Don’t know how much it is hurting

• Productivity/economic impact undetermined• Additional info/data needed

Detection of PCV3

Mummified/stillborn fetuses

Ct < 25 Probable

Ct <20 Highly probable

Prevention

• Gilt acclimation?• How?• When

• Leave plenty of time between exposure and breeding

• Viremia appears to be greater than a month• Vaccine?

• A few companies are working on it• One currently available

• Efficacy as demonstrated with vaccinates and non-vaccinates is not known

Submission?

• Reproductive workup You see mummies• 3 affected litters

• 2-3 mummies and stillborns• 4-6 fetuses from each affected litter

Importance of PCV3?

• It’s a pathogen of pigs• It causes clinical disease in a subset of pigs

it infects• It does not appear to cause enteric disease,

primary respiratory disease or loss of condition like PCV2 (PMWS)

• Impact? No great answer fetal wastage• NOT PRRSV or IAV

Next Steps

• Serologic assay development• Infection dynamics• Monitor interventions (gilt exposure)

• Reproduction of disease• Model of disease

• Vaccine efficacy trials

Meat and Potatoes• What is it?

• Virus• Causes mummified fetuses

• How do I know if I got it?• Submit as previously outlined

• How do I treat it?• Probably can’t

• How do I prevent it?• Most likely gilt acclimation

Questions/Comments/Insights?