Total Cases of PMWS and PCV2-Associated Disease at ISU-VDL

1. 1993 1994 1995 1996 1997 1998 1999 Total Cases of PMWS and PCV2-Associated Disease at ISU-VDL 11 14 15 18 37 130 449* * First full year using PCV IHC as routine diagnostic tool.

2. 1999 Dz. 1993 1994 1995 1996 1997 1998 Trend PRRS 120 367 708 714 869 859 1168 10X Mhyo 218 357 417 624 731 894 867 4X Pmult 360 376 563 638 653 715 815 2X SIV 117 175 291 384 447 350 694 6X PCV2 — — 0 1 20 111 290 290X APP 262 235 220 298 271 230 178 Flat Cases of pneumonia submitted to the ISU-VDL from 1993-1999

3. Postweaning Multisystemic Wasting Syndrome (PMWS) • primarily in 10-20 week old pigs in the U.S. • pneumonia • wasting • anemia, paleness, +/- icteric • +/- diarrhea • 2-50% morbidity (usually < 10%) • mortality of affected pigs may approach 100%

5. 35 30 25 20 Cases 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 -5 AgeinWeeks Age of Onset of PMWS

6. Gross Lesions of PMWS • Lungs • diffusely red-tan, noncollapsed, rubbery, with variable amounts of cranioventral consolidation • Lymph nodes • diffusely enlarged and tan • Other less common lesions • Icterus, gastric ulcers, skin lesions (PDNS), enlarged kidneys, swollen or atrophied liver • Gross lesions are rarely diagnostic - very similar to PRRS

7. Microscopic Lesions of PMWS • Lung Lesions • Bronchial and bronchiolar epithelial attenuation, hyperplasia, erosion, luminal obliteration & epithelial sequestration • Lymphohistiocytic, proliferative interstitial pneumonia • Peribronchiolar and septal fibroplasia • Lymphoid Lesions: Lymphoid depletion and replacement of follicles with macrophages, intracytoplasmic inclusions • Liver: Hepatocellular necrosis and lymphoplasmacytic inflammation • Kidney: Lymphoplasmacytic interstitial nephritis

8. SIV and PRCV epithelial necrosis epithelial attenuation epithelial hyperplasia mononuclear cuffing PCV2 epithelial necrosis epithelial attenuation epithelial hyperplasia mononuclear cuffing peribronchiolar fibrosis luminal obliteration epithelial sequestration Differential Diagnosis of Necrotizing Bronchitis and Bronchiolitis in Swine

9. Porcine Circovirus: Diagnosis • Clinical signs and gross lesions very similar to PRRS • unique microscopic lesions and inclusion bodies • immunohistochemistry (IHC), in situ hybridization (ISH) to confirm association of virus with lesion • virus isolation and serology available in some labs • offered at ISU VDL • ubiquitous virus so value and interpretation of serologic information is difficult • attempt virus isolation in recurrent cases to have virus available for potential autogenous vaccine production

10. PMWS Case Observations • PMWS concurrent infections • confirm PRRSV in 60% of the cases, • suspect PRRSV is involved in 80% of the cases • other common concurrent infections • SIV, HPS/S. suis, M. hyo. • Mortality much higher in concurrent infection cases • acute SIV + circovirus + M. hyo. pneumonia cases • 2-10% mortality in finishers • chronic PRDC due to PRRSV + M hyo + PMWS • 10-15% mortality in finishers

11. PMWS Case Observations • Duration of disease in a system varies • often a single batch problem in smaller, single-site herds that use internal gilt replacements • increasing number of cases where PMWS has become endemic in multiple building finishing sites

12. Porcine Circovirus: Pathogenesis • PMWS strains (Type 2) differ from PK/15 cell culture strains (Type 1) • genetically types 1 and 2 are quite different • multiplex PCR can differentiate • PCV1 is nonpathogenic in growing pigs (Allan et al.) • evidence that “shaker pig disease” may be caused by PCV1 or PCV2 • High seroprevalence of PCV2 but limited cases • tested 27 high health herds with no clinical evidence of PMWS • 100% or herds seropositive for PCV2 • high percent of animals within a herd positive • passive antibody decay by 10-20 weeks

13. Experimental Reproduction of PMWS • Ellis et al., 1999 • reproduced PMWS lesions in CDCD pigs inoculated with tissue filtrates; both PCV2 and PPV detected • Allan et al. 1999; and Kennedy et al. 2000 • inoculated colostrum-deprived pigs with PCV2 alone, PPV alone, and PCV2+PPV; reproduced severe disease and lesions typical of PMWS in dually-inoculated group whereas only mild lesions and subclinical disease was reproduced in the PCV2 only group • Krakowka et al. 2000 • reproduced disease and PMWS lesions in gnotobiotic pigs co-infected with PCV2 and PPV

14. Experimental PCV2/PRRSV Co-Infection • Field cases suggested interaction • Objective: • Reproduce disease seen in field cases • Develop model to study the interaction • Develop model for evaluating intervention strategies

15. Experimental Design • 4 groups of 3 week old CD/CD pigs • Control 9 pigs • PCV2 19 pigs • PRRSV 13 pigs • PRRSV/PCV2 17 pigs • Intranasal inoculation of PRRSV and PCV2 • Scheduled necropsies at 7,10,14,21,35,49 days post-inoculation

16. Clinical Respiratory Scores 6 5 Control 4 PCV 3 PRRSV 2 PCV/PRRSV 1 0 7 10 11-14 15-21 Days

17. Mean Gross Lung Scores 100 90 80 70 Control 60 PCV 50 % Lung Affected PRRSV 40 30 PCV/PRRSV 20 10 0 7-10 11-14 15-21 Days

18. Summary of Findings: PCV2-PRRSV Co-infection • PCV2 Group • Minimal respiratory disease • Mortality of 40% between 10-30 DPI • Mild necrotizing bronchiolitis, minimal pneumonia • Lymphoid depletion, necrotizing hepatitis • PRRSV group • Moderate respiratory disease • Mortality = 0% • Interstitial pneumonia, no airway lesions

19. Summary of Findings: PCV2-PRRSV Co-infection • PCV2/PRRSV group • Severe respiratory disease • Mortality >90% between 10-21 DPI • Necrotizing and ulcerative bronchiolitis • Severe interstitial pneumonia • Lymphoid depletion, necrotizing hepatitis

20. Experimental Evidence for PRRSV-Induced Potentiation of PMWS • Harms et al, 2000 • Reproduction of severe disease and lesions typical of PMWS in CDCD pigs co-infected with PCV2 and PRRSV • Less severe disease, mortality, and lesions in PCV2 only group • No evidence of PPV infection • Allan et al., 2000 • Experimental infection of CD piglets with PCV2 and PRRSV potentiates PCV2 replication

21. Activation of the Immune System May Lead to Increased Susceptibility to PCV2-induced PMWS? • Allan et al., 2000 Vet Rec; Krakowka et al., Vet Path, IN PRESS. Activation of macrophages in lymphoid tissues of colostrum fed pigs may lead to potentiation of PCV2 replication and development of clinical disease and lesions typical of PMWS • 7/7 colostrum fed pigs inoculated with PCV2 and then immunized with keyhole limpet haemocyanin (in Freund’s incomplete adjuvant) developed clinical disease and lesions typical of PMWS whereas subclinical disease and minimal lesions were reproduced in PCV2-inoculated pigs without immunization • 3/14 pigs vaccinated with M. hyo (2 dose) and APP (1 dose) developed PMWS whereas 0/14 unvaccinated pigs developed PMWS

22. Control of PMWS • Confirm PMWS/circovirus by necropsy, histopath, IHC, ISH • Identify farm, site, or system specific concurrent infections • eliminate PRRSV from the mix if possible • work to avoid simultaneous coinfection • focus on breeding herd stabilization and pig flow • eliminate/control SIV with vaccination • further explore role of PPV and use of PPV vaccine • minimize effects of M. hyo. with vaccination and medication • treat bacterial coinfections • anti-inflammatories (aspirin, ketoprofen) useful

23. PMWS Summary and Conclusions • PMWS has become a major disease in the U.S. • Field and experimental evidence supports a major role for PCV2 in PMWS • Field evidence also supports a role for PCV2 in porcine respiratory disease complex