07 qjegales

4TH MERIAL FORUM

HAVE WE GOT PCVD &

SWINE INFLUENZA UNDER

CONTROL?

PCVD session 3

Moderator: Dr Thaïs Vila

• PCVD in 2012: a special focus on sub clinical forms, Pr. J. Segalés

• CIRCOVAC piglet vaccination: successful field experience in Spain, Dr A. Finestra

• PCVD control in 2012: how to design the best PCV2 vaccination programme? Drs F. Smeets & G. Perreul

Barcelona

PCVDs in 2012:

a special focus on

subclinical forms

J. Segalés

• Might be not so much…

What’s new on PCVDs in 2012?

“What means subclinical? …not seen by the naked eye!”

• Subclinical infection: infection that does not produce evident clinical signs

Diccionario Ilustrado de Términos Médicos

(www.iqb.es/diccio/i/infeccion.htm)

• Subclinical infection: infection that does not produce clinical signs but it is detectable by laboratory tests or clinical investigations

Web Infogripe - diccionario

(www.infogripe.com/infogripe/gridic.htm)

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PCV2 is an ubiquitous virus…

PMWS affected farms Non-PMWS affected farms

PCV2 PCR in serum PCV2 antibodies

Sibila et al., 2004

*

Moreover… even in a PMWS affected farm, the highest percentage of pigs are those

which are subclinically infected!

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

Lo

g 1

0 I

PM

A P

CV

2 a

ntib

od

ies

.

1 3 7 11 Necropsy

Wasting-non-PMWS

PMWS

Healthy

Maternal antibody

waning

PCV2 serosonversion

after natural infection

Weeks of age

a

b

b

a

b

c a

b

b

Grau-Roma et al. 2009

PMWS outbreak

(6 groups; Mt. Average

nursery-fattening:

9.9-25.1%)

There is no doubt that the

PCV2 subclinical infection

is, in percentage, much

more frequent than

clinical forms associated

to the virus

Do we know how to diagnose a subclinical infection with PCV2?

• Yes… presumably it is easier than to diagnose clinical infections!!

• PCV2 subclinical infection diagnostic criteria: 1. Lack of clinical signs attributable to PCV2

2. Evidence por PCV2 infection

• Retrospectively: positive serology against PCV2 at slaughter age or beyond the age in which MDA are still present (vaccination!!!)

• In real time: detection of the virus (PCR, IHC, ISH, VI, etc.)

In practical terms, point No. 2 is not really needed:

“if they are pigs… they will get infection!!”

• A more formal case definition has been proposed (Segalés, 2012):

Do we know how to diagnose a subclinical infection with PCV2?

How significant is the

subclinical infection by PCV2?

Should I worry about it?

1. Which is the PCV2 subclinical impact? Can it be measured? How?

2. Is such impact economically significant? Are vaccines useful from a cost-benefit point of view?

Measuring the PCV2 subclinical impact…

1. experimental infections

CReSA – UAB:

We have performed a number of

experimental infections

• Balasch et al. 1999 – 8 inoculated / 2 controls

• Rovira et al. 2002 – 14 inoculated / 10 controls

• Resendes et al. 2004 – 30 inoculated / 12 controls

• Roca et al. 2004 – 18 inoculated

• Fernandes et al. 2007 – 12 inoculated / 8 controls

• Fernandes et al. 2008 – 2 inoculated / 2 controls

• Fort et al. 2008 – 56 inoculated / 16 controls


• Pérez-Martín et al. 2010 – 22 inoculated


• Díaz et al. 2012 – 13 inoculated / 8 controls

• Diverse studies (non-published) – 30 inoculated

261 PCV2

subclinically

infected pigs

1 pig with PMWS

Fernandes et al. 2007

Significant differences in ADG only in two experiments!!!


1. experimental infections

Limitations of experimental infections

• The number of animals under study is usually too low to observe statistical significant differences in terms of ADG

• Can we use other criteria? – Percentage of infected animals

– Viral load

– Microscopic lesions

NO… since inoculated

are compared with

non-inoculated pigs

• Under experimental conditions, PCV2

vaccination in piglets:

– Decreases viral load in tissues, serum and excretion

routes

– Decreases lesion severity in lymphoid organs

• However, again, the number of animals under

study is usually not sufficient to show significant

differences parameters of economic interest

(ADG, mortality, etc.)


2. experimental infection and vaccination

• PCV2 vaccination in PMWS scenarios:

– Increase in ADG

– Decrease in mortality and percentage of runts

– Decrease viral load in tissues, serum and excretion

routes

– Decrease lymphoid lesion severity

• Market trends: single-dose vaccination

– Improves clinical outcome but it does not avoid

infection


3. natural infection and vaccination

PMWS scenarios: effect of

PCV2 vaccination

on viral load

• Which is the effect of PCV2 vaccination in a farm

with no PMWS?

TAKE CARE! A farm without a diagnosis of PMWS does

not preclude the lack of clinical effects linked to PCV2…

To diagnose PMWS is not that easy, especially in

more “enzootic” scenarios with the disease…

• Which is the effect of PCV2 vaccination in a farm

subclinically infected with this virus?



• Does PCV2 vaccination decrease viral load in serum, tissues and excretion routes?

Díaz et al. 2008

YES



• Does PCV2 vaccination decrease viral load in serum, tissues and excretion routes?

Fraile et al. 2012

YES

again



• Does PCV2 vaccination decrease mortality and

runts?

Díaz et

al. 2008

YES



• ¿Does PCV2

vaccination

improves

ADG? YES

Measuring the PCV2

subclinical impact… 3. natural infection

and vaccination

Young et al., 2011

Measuring the PCV2 subclinical impact… 3. natural infection and

SOW vaccination

• Does PCV2 vaccination decrease the severity of

lymphoid lesions?

Segalés et al. 2009

YES



Definitively, the PCV2 subclinical infection causes detrimental

effects which are quantifyable in terms of pig production

• Dr. Frank Aherne, Univ. Alberta (Canadá)

– “In God we trust; from all others we want data”

• FUNDAMENTAL: learn how to quantify the negative effects of the PCV2 subclinical infection

PERCEPTION REALITY (€)

The second question: ”Is such impact economically significant? Are vaccines useful from a cost-benefit point of view?”

PCV2

subclinical

Infection

effects

Vaccination

cost

PCV2

subclinical

Infection

effects

PCV2

subclinical

Infection

effects

In order to be fair, you should do such

calculations comparing vaccinated versus

non-vaccinated pigs (ideally contemporary

or comparing with previous batches)

Vaccination

cost

Vaccination

cost

• Controlled clinical essay

• Statistic process control

(SPC)


• To compare a vaccinated group against a non-vaccinated one

• Primary criterion: – ADG: Sample size

• Secondary criteria: – Mortality

– Decrease in clinical signs

– PCV2 viremia

Controlled clinical assay

Significance Level 5%

Statistical Power 80%

ADGe (gr/day) 725 725 725 725 725

ADGc (gr/day) 690 690 690 690 690

Sigma (gr/day) 140 105 87.5 70 52.5

1/(Effect Size) 4 3 2.5 2 1.5

Specimen Size

N per group 253 143 100 65 37

Statistical process control (SPC)

Grau-Roma et al., 2012

PCV2 subclinical infection… is it worthy to vaccinate?

To go from perception

to reality implies to

measure the PCV2

subclinical effects

Or… are you waiting another

to do the job for you?

The use of piglet vaccines

Estimated vaccination rates:

Europe:

>80%: Germany, UK, Ireland, Austria

<30%: Russia, Denmark, Poland

±60%: Spain

USA, Canada, Mexico, Brazil, Chile: 80-98%

Korea & Japan: 70-90%

China & Vietnam: <5%

Australia: 34%

Baekbo et al., 2011

Acknowledgements –

CReSA people

Special thanks for Lorenzo Fraile

Thank you very much for

your attention

Health & Medicine

07 qjegales