prrs co-infections in asia - prrspective.com.cn€¢prdc - thailand - korea - china - philippines...

PRRS co-infections in Asia

Dr. Marika Genzow

Dr. Paiboon Sungnak

Bojong Cho

Yanhua Guo

Dr. Carlo Maala

PRRS co-infections

Table of contents

• Introduction

• PRDC

- Thailand

- Korea

- China

- Philippines

• PNP

• PRRSV and other pathogens

• Conclusion

PRRS co-infections

Introduction

• Intensification of pig production globally

• Epidemiology becomes more and more important as pigs are often mingled (different sources, sometimes also different ages)

• Emerging of new pathogens (e.g. PCV2)

• Naïve populations are still an exception

PRRS co-infections

PRRS seroprevalences in Asia (individual animal basis)

Country seroprevalence Source

China 80% Yan et al (2003)

Philippines 90% Cruz et al, (2006)

Malaysia 94% Jasbir et al (1994)

Taiwan 94.7-96.4% Chung et al (1997)

Thailand 97% (Ratanavanichrojn, 2000)

Korea 67.4-73.1% Park,personal communication, 2006

PRRS co-infections

PRRSV replicates in alveolar macrophages and thus impairs lung function

• Additional bacterial/viral lesions

- Mycoplasma hyopneumoniae

- PCV2

- SIV

• Clinical expression of co-infectious agents varies with production system (Dorr et al, 2007)

PRRS co-infectionsIntroduction

PRRSV co-infections and their associations with management system variables (Dorr et al, 2007)

• Study in 791 pigs from 41 production flows in the US

• Necropsy of 5 pigs/production flow of the following age groups:

- 3 wk old pigs (early nursery)

- 9 wk old pigs (late nursery)

- 16 wk old pigs (early to mid finishing)

- 24 wk old pigs (late finishing)

• Serology, PCR, IHC, histology for the main pathogens

PRRS co-infections

Results• Confirmation for age-related and management system related

pathogen associations of PRRSV co-infections

- Most common co-infections in PRRS positive pigs: SIV (H1N1), Mycoplasma hyopneumoniae

- Strong association between PRRSV S/P ratios and co-infection with SIV in the 9 week and 16 week old group; suggesting that SIV is a significant PRRSV co-infection in late nursery and early-to mid finishing ages

- In one site systems significantly higher PRRSV S/P ratios and higher lung lesions

PRRS co-infections

Conclusions• PRRSV positive status was associated with more lung damage,

SIV co-infection, higher SIV H1N1 titers and higher prevalence of Mycoplasma hyopneumoniae

PRRS co-infectionsPRDC

Porcine respiratory disease complex (PRDC)

Mhyo

PRRSV

Coughing persists for 4-6 weeks

SIV

Pm

Strep. suis

PRDC

EP/CP

Non-productive cough

Pneumonia

Low ADG

High FCR

Mortalities

Morbidities

High Cull ratesPCV2


• PRRSV and PCV2 weaken the innate immune system, which facilitate secondary bacterial infections

• Factors that impact risk of PRRSV infection and transmission anddisease:

- Animal age (younger pigs [6-8 weeks vs 6 months old] are more susceptible to infection, have higher levels of viremia and excrete virus at higher concentrations) (Van der Linden et al., 2003)

- Co-infections with Mycoplasma hyopneumoniae seem to increase duration and severity of PRRS clinical disease (Thacker, 1999)


PRRSV and Mycoplasma hyopneumoniae (M.hyo)• M.hyo often found concurrently with PRRSV infection in growing

pigs (Moreau, 2004)

• Both pathogens separately capable of causing pneumonia in pigs

• Experimental evidence that these pathogens potentiate the effects of the other is equivocal

• PPRSV infection does not impair vaccination response to M.hyo (Moreau et al, 2004)

Thailand (Ratanavanichrojn, Sungnak et al., 2000)

• Survey of farrow-to-finish farms with mortality

and cull rates of 8-21 %

• Study evaluation included 4 stratified groups:

1. 13-14 week old pigs




PRRS co-infectionsPRDC in Asia (Thailand)


Results (Ratanavanichrojn, Sungnak et al., 2000)

• PRRS sero-prevalence: 97%

• Post mortem findings: interstitial pneumonia

42.519- 20 weeks

3517- 18 weeks

2815- 16 weeks

3113- 14 weeks

Mycoplasma lesions (%)Age group


Conclusions (Ratanavanichrojn, Sungnak et al.)

• Losses in commercial Thai pig production systems is not a singlecause phenomenon, but a multifactorial disease

• PRRS prevalence: 97%

• Mycoplasma prevalence in groups 1-4: 31%, 28%, 35% and 42.5%

• Microbiology: Strep suis, Pasteurella spp and Haemophilus spp

The results are confirmed by Pirarat (2002) who showed that the majority of viral pneumonia in pigs that were submitted to the Thai diagnostic lab was PRRSV.

PRRS SeroprevalenceKoreaJan 2005 – Aug 2006 (Prof. Park, personal communication)

73.1%

48.7%60.6%

83.0% 86.1%93.9%

0

20

40

60

80

100

sow (n=1078)

0- 30 (n=798)

31- 60 (n=695)

61- 90 (n=638)

91- 120 (n=339)

121- 180 (n=99)

day

sero

posi

tive

%

• 162 farms, total of 3692 samples tested

PRRS co-infectionsPRDC in Asia (Korea)

Korea (Lee et al., 2007)

• 481 cases with respiratory problems investigated at the Korean National Veterinary Research and Quarantine Service in 2005 and 2006

• Results:

- 348 cases (72.3%) co-infections defined as PRDC

- PRRSV and PCV2 most commonly isolated pathogens

- Followed by PCV2 and HPS

• Conclusion: PRDC with PRRSV as the most frequent pathogen is widely distributed in Korea


Association of PCV2 with PRDC (Kim et al, 2003, Korea)

• Retrospective study of PRDC cases (n=105) in Korea

- Diagnosis of viral/ bacterial pathogens: in-situ hybridization of lung tissue

• Results

- 85/105 positive for PCV2

- 66/105 positive for PRRS

- 61/105 positive for Parvovirus (PPV)


• Results (continued)

- 85/105 PCV2 positive

- 17 PCV2 single infection

- 15 PCV2 + PRRSV

- 10 PCV2 + PPV

- 43 PCV2 + PRRSV + PPV

PRRS co-infectionsPRDC in Asia (China)

China

Results of 582 samples tested Ministry of Agriculture, China

8.080.171.032.9222.3428.6945.19% positive

471617130167263No. of positive samples

APPPast. Mult.Streptococcus suisPRVPCV2CSFPRRS

Report to OIE, Sept. 12, 2006*all samples from “HFD” infected pigs

PRRS co-infectionsPRDC in Asia (China)

China

Co-infections of PRRSV, PRV and PCV2 (LiHua et al, 2004)

• Investigation of 77 clinical samples from 5 provinces (Shanghai,Jiangsu, Zhejiang, Fujian and Shangdong)

• Results

- PRRSV + PCV2 24/77 (31.2%)

- PRRSV + PRV 17/77 (22.1%)

- PRV + PCV2 9/77 (11.7%)

- PRRSV + PRV + PCV2 8/77 (10.4%)

Philippines (Bruguera and Torres,2005)

• N=39 farms

PRRS co-infectionsPRDC in Asia (Philippines)

82%

31%

41%

74%

18%

64%

3% 3%0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

PRRSV HPS SIV M Hyo ADV APP PCV-2 HCV

PRRSV: Porcine Reproductive and Respiratory Syndrome virus; Hps:Haemophilusparasuis, SIV: Swine Influenza virus, M.hyo: Mycoplasma hyopneumoniae, ADV:Aujeszky’s virus, App: Actinobacillus pleuropneumoniae, PCV-2 Porcine Circovirus type 2, HCV: Hog Cholera virus


Philippines (continued)

• The three top pathogens of PRDC are PRRS, Mhyo and App

• Most co-infections involve a viral pathogen (PRRS, Aujeszky’s, SIV)

• In 19/39 cases, more than one pathogen was involved

PRRS co-infectionsPNP

Porcine Proliferative and Necrotizing Pneumonia (PNP)

• Severe form of interstitial pneumonia

• First described in 1990 in Quebec (Canada), subsequently in Spain

• Initially thought to be caused by a novel strain of swine influenza virus type A

• Then it was hypothesized that PRRSV and PCV2 were the primary agents of PNP

• Other researchers suggest also Aujeszky virus as a potential co-factor

• Or just different strains of PRRS responsible?


PRRSV, PCV2 and SIV in porcine PNP (Drolet at al, 2003)

• Investigation of 60 cases with PNP in North America (Canada) by means of ISH for PRRSV

Results

74None

21SIV only

00PCV2 only

4225PRRSV + PCV2

5030PRRSV only

% positiveNo positiveVirus

Total 60 cases


Conclusion (Drolet et al)

• In the present study PRRSV virus most consistently present

• PCV2 only detected in post weaned pigs

• PCV2 always found in combination with PRRSV

• PRRSV seems to be the principal ethiological agent in PNP


PRRSV, PCV2, SIV, ADV in PNP (Grau-Roma and Segalés, 2007)

Investigation of 74 PNP cases from Europe (Spain) by IHC for PRRSV

74Total

10.88None

1.41PCV2 + ADV

4.13PCV2 + SIV

40.530PCV2 + PRRSV

00ADV

00SIV only

4.13PRRSV only

39.129PCV2 only

% positivesNo positivesPathogen


PRRSV, PCV2, SIV, ADV in PNP (Grau-Roma and Segalés, 2007)

Conclusion

• PCV2 most frequently isolated pathogen

• PRRS virus not „essential“ for PNP

- (contradiction to Drolet)

• Rare involvement of SIV

• PCV2 the most important agent in Europe while PRRSV is the most important agent in PNP in North America??

• What about Asia??

- “Heavy wet lungs”???

PRRS co-infectionsPRRSV and other pathogens

PRRSV and other pathogens

1. PRRSV + H. parasuis- Strong association between PRRSV PCR positives from

lymphnodes and H. parasuis PCR from pericardium, pleura and peritoneum (Gucht et al (2003) and Palzer et al (2007))

2. PRRSV + Strep suis- PRRSV predisposed pigs to Strep suis (Galina, 1994)- In utero PRRSV infection increases the susceptibility of

neonates to Strep suis (Feng et al, 2001)

PRRS co-infectionsPRRSV and other pathogens

PRRSV and other pathogens

3. PRRSV + Classical Swine Fever (CSF)- Reduced antibody response against CSF vaccine in PRRSV

infected animals (Li and Yang, 2001, Suradhat et al, 2006)

- Higher prevalence of CSF in PRRSV prevalent farms (Li and Yang, 2006)

PRRS co-infectionsConclusion

Conclusion

• PRRSV is highly prevalent in almost all countries

• PRRSV is involved in various multi-factorial diseases

• PRRSV control is essential to combat economical impact

- Develop action plan to manage PRRSV infection/ co-infections

- Diagnostic protocols

- Biosecurity protocols

- Gilt acclimatization

- Vaccination

PRRS co-infections

Thank you!

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