Impact of PMWS on pork production and options for control

Dr. med. vet. Barbara Wieland, PhD

Chengdu, China, October 2011

Livestock production – where are we heading to?

- Growing world population

- Increased demand for meat

- Intensification of livestock production over the last

decades, in particular monogastric animals (poultry

and pig sectors)

- Effective use of input an important requirement to

ensure sustainability

objective of this talk: discuss role of ‘production

diseases’ and how they affect output using PMWS

as an example

Pigs in China

• China is the biggest pork producing country in the

world

• 50% of the world pig population

• Domestic consumption mainly

• 33.8kg per capita consumption for China

• Increased 20% from 2002-2006 and since then has

been increasing by about 5% per year

• Trend from small scale (70% in 2005) to large scale

production

Source: the pigsite, Boal et al.

Pigs in China

Pig pathogens resulting in reduced performance

Influenza viruses

Mycoplasma hyopneumoniae (Enzootic Pneumonia)

Actinobacillus Pleuropneumoniae

Porcine Reproductive & Respiratory Syndrome virus

Porcine circovirus 2

Lawsonia intracellularis

...

Vaccines available, however often not fully protective

Impact also depends on adequate nutrition, housing

systems, and stress (social or environmental)

Post-weaning Multi-systemic Wasting Syndrome (PMWS)

• Multi-factorial disease with Porcine Circovirus

type-2 (PCV-2) as necessary agent (also in

PDNS)

• Affects pigs between 8 to 15 weeks old

• Clinical signs: wasting and growth retardation,

pallor of the skin, respiratory signs,

occasionally jaundice and intermittent

diarrhoea

• Post mortem: interstitial pneumonia,

secondary bacterial infection, enlarged lymph

nodes, oedema and intra cytoplasmic

inclusions

PMWS in China

• Ongoing outbreaks since 2001

• Up to 20-30% mortality in

affected herds

• Example of PCV-2 prevalence

studies

• Zhejiang province 47.5% (Zhang et

al)

• Gansu and Qinghai provinces

58.5% (Song et al)

Clinical picture of PMWS has changed

• ~10 years ago: high mortality in affected farms

• Decrease in mortality over time, more farms affected

• Importance of sub-clinical cases unknown

Source: GB Surveillance Quarterly report VLA (VIDA)

Severity of PMWS observed in different age groups from 2001 to 2008

0

10

20

30

40

50

60

01 02 03 04 05 06 07 08

% o

f p

rod

ucers

Not affected Slightly affected Moderately affected Severely affected

Aims and Objectives

Identify the most effective, profitable and acceptable options to

control PMWS at the farm level

• Understand severity of PMWS observed in infected farms

• Identify risk factors for PMWS severity options for control

• Assess economic impact at farm and national level

Cross-sectional study:

149 farm visits carried out

3182 pigs sampled before PCV2 vaccination

Representing 65’000 sows (17% of pig herd)

Locations of all farms included in the study, overlaid on a map of total pig numbers throughout England, aggregated into 10km squares (pig density data taken from the 2004 UK agricultural census).

Questionnaire

Farm

assessment

Data Collection General information

Productivity over time

Environment

Management

Reproduction PMWS over time

Health status

Animal Welfare

Environment

PMWS present

(incl. post mortem)

Blood

samples

Age groups: Sows

Weaners

Growers

Finishers

PCV-2 Elisa

PCV-2 PCR

PPV

PRRS

EP

APP

SI

20 samples

Results of cross-sectional study

• PCV2 present on all farms

• 88.4% PCR positive

• 98.6% antibody postive

• Severity of PMWS seen on farms very variable

Combine morbidity, production and serological variables

6 serological

variables

3 production

performance variables

Principal component analysis

PCA

Morbidity in weaners,

growers and finishers (quantitative and qualitative)

Morbidity

factor 1 & 2

factor analysis

PMWS severity score

PMWS severity score

Non/Slightly affected farms PMWS scores<4

Moderately affected farms PMWS scores 4 - 6.5

Highly affected farms PMWS scores >6.5

Alarcon, P., et al., Assessment and quantification of post-weaning multi-systemic

wasting syndrome severity at farm level. PVM 2010

PMWS severity calculator available online www.bpex.org

PMWS on a farm

Risk factors associated with PMWS severity Multivariable ordinal logistic regression

Multi-factorial characteristic of the syndrome confirmed

Variables OR 95% CI

Rearing growers indoor only 23.66 4.09-136.84 Risk

Low stocking density 0.07 0.02-0.30 Protective

>2 diet adjustment up to the age of 14 weeks 0.12 0.02-0.72 Protective

Sick pen drains to other areas 6.40 2.30-17.82 Risk

Visitors must be pig free 0.14 0.04-0.49 Protective

Buying in boars 4.81 1.70-13.61 Risk

M. hyo positive 4.29 1.37-13.49 Risk

>3 vet visits/year required 9.60 1.57-58.62 Risk

Farm level risk factors associated with severity of Post-weaning multi-systemic wasting syndrome.

P Alarcon, M Velasova, A Mastin, A Nevel, K Stärk, B Wieland, (2011), Prev Vet Med,101(3-4)

Options for control

• Improve husbandry and animal welfare

• Raising growers outdoor and low stocking density were found

protective, avoid stress

• Potential importance of diet (age adjusted)

• Improve biosecurity

• Avoid infection with other diseases

• Vaccine

Outline cohort-study

1st visit (2008-2009)

Questionnaire: general

farm information,

management practices,

production parameters,

genetics, health status

Samples – 20 per farm

Pathogens tested

PCV2 Ab, PCV2 PCR, EP,

APP, PPV, PRRS

2nd visit (2009-2010)

min 6 months later

Questionnaire: general

farm information,

management practices,

production parameters,

genetics, health status

Samples – 32 per farm

Pathogens tested

PCV2 Ab, PCV2 PCR, EP,

APP, PPV, PRRS

PMWS severity: calculated difference between 1st

and 2nd visit

Preliminary results

What are the changes in PMWS severity? Before and after PCV2 vaccination

Vaccinated vs. unvaccinated farms

Vs.

Vaccinated (n=34) Before After

Mean Mean Difference (95%CI)

P-value

PMWS severity score

5.63 2.79 -2.84 (-3.60; -2.07) <0.01

Non vaccinated (n=10)

Before After

Mean Mean Difference (95%CI)

P-value

PMWS severity score 3.01 3.67 0.66 (-0.37; 1.69) 0.181

Changes in PMWS severity

Unpublished data, contact author for more information

Summary vaccination study

PCV2 vaccination successful in reducing PMWS

severity- moderately and highly affected farms

Piglet vaccine seems to be more effective

Reduction in mortality in PCV2 vaccinated farms

PCV2 still present in vaccinated farms

Take home message:

Vaccination is effective but not enough to

eliminate impact of PCV2

Vaccination is not substitute for good animal

husbandry

Economics

Economic model

(farm and

national level)

PMWS severity

measure

Morbidity details

(subclinical pigs) Risk factors for

severity

Efficacy of vaccines

to reduce severity

Clinical and post-mortem data

collected during a trial in

2000/2001 during a PMWS

outbreak

ADG for normal, PCV2 infected

and PMWS pigs

Various sources to

estimate costs

PMWS on a farm

PMWS disease model

Unpublished data, contact author for more information

Partial Budget analysis Figure 7. Illustration of how costs have been calculated to disease pig

Healthy pig Disease pig

DISEASE

Benchmarking data

used as reference

Data from longitudinal study:

↓ADG, Appetite loss, extra

days in feed, etc.

PMWS-D, PMWS-S,

PCV2-S & PCV2-D

Figu

re 7. Illustration of how costs have been calculated to disease pig

Health

y pig

D

isease pig

DISEA

SE

Benchmarking data

used as reference Data from

longitudinal study:

↓AD

G, Appetite loss, extra

days in feed, etc.

PMW

S-D, PM

WS-S,

PCV2-S & PCV2-D

Diseased pig

Partial Budget Analysis

Value (£) Value (£)

New costs:

Extra veterinary cost

Cost of carcass disposal

-

Cost saved:

Pig Feed saved

Electricity saved

Water saved

Straw & bedding saved

Transport saved

Revenue forgone

Total DWt1 sold

New revenue:

None

Total costs Total benefits

Cost of PMWS-D =

Example: PMWS-D

PMWS Economic model

Unpublished data, contact author for more information

Outlook: Economic Decision tree model

Slightly

affected

Moderately

affected

Highly

affected

Best

control

options

Best

control

options

Best

control

options

Input parameters

based on:

Risk factors identified

Vaccination efficacy

Other strategies?

(literature review)

Pilot study – 50 farmers When you

suspect a

disease

problem

To decide if

you need to

control

To decide

what control

measure to

use

To decide how to

implement the

chosen control

measure

Decide on the efficacy

of the control measure

and if to continuing

with it or not

Stockmen 33.33 (16) 16.67 (8) 19.15 (9) 44.68 (21) 42.55 (20)

Family 12.5 (6) 10.42 (5) 6.38 (3) 10.64 (5) 14.89 (7)

Veterinarian 97.92 (47) 93.75 (45) 97.87 (46) 85.11 (40) 76.60 (36)

Defra 12.50 (6) 6.25 (3) 4.26 (2) 6.38 (3) 10.64 (5)

Nutritionist 43.75 (21) 22.92 (11) 27.66 (13) 29.79 (14) 8 (17.02)

Pig consultant 12.50 (6) 8.33 (4) 17.02 (8) 12.77 (6) 10.64 (5)

Breeding

companies

14.58 (7) 10.42 (5) 2.13 (1) 4.26 (2) 4.26 (2)

Other farmers 29.17 (14) 10.42 (5) 17.08 (8) 21.28 (10) 6.38 (3)

Others:...... 2.08 (1) 4.17 (2) 4.26 (2) 2.13 (1) 8.51 (4)

Survey to 50 pig farmers in collaboration with Animal Health and

Veterinary Laboratories Agency (AHVLA)

Conclusions

Production diseases:

• Impact on food security, and therewith on society

• Result in inefficient use of resources

• Are often trying to be controlled with vaccines,

however that is most of the time not enough

If we want to improve productivity, producers need to

be involved in the discussion

Pablo Alarcon

Martina Velasova

Mandy Nevel

Dirk Pfeiffer

Katharina Staerk

Christopher Wathes

Dirk Werling