Current Trends in Presentation of Disease Associated with M. hyopneumoniae

1. Current Trends in Presentation of Disease Associated with M. hyopneumoniae Monte B. McCaw DVM PhD Farm Animal Health and Resource Management Dept. NCSU College of Vet. Med.

2. M. hyo history • Pre 1990 “insignificant” in US • no M hyo vaccine • no M hyo targeted abc programs • rare to see clinical disease outbreaks • SPF herds • role as App facilitator

3. M. hyo history • Late 1980’s - 1990’s • dramatic “paradigm shift” in hog-raising management • introduction of PRRSv and subsequent epidemics • emergence of PRDC • M hyo central role

4. Presentation Overview • Swine Industry Changes • PRRSv Impact on Disease • Antibiotic Therapy Challenges

5. Swine Industry Changes • Continuous Pig-Flow Rearing • multiple age groups • building or site • never cleaned / disinfected • endemic disease model • Day Care / School-kid model

11. Swine Industry Changes • All In - All Out (AIAO) Pig-flow Rearing • single age group • room / building / site • placed at same time • emptied completely • cleaned and disinfected

17. Swine Industry Changes • AIAO Pig-flow Rearing • End old-to-young transmission • decreasing contact / exposure • Must be perfect to be successful!!?? • Naïve population if successful • Epidemic Disease Model???

18. Swine Industry Changes • Site level disease control • 1 site production • “farrow to finish” • (Farrowing)(Nursery)(grow-Finish)

20. Swine Industry Changes • Site level disease control • 3 site production • further decrease old to young transmission risk • Farrowing (Breeding Herd) • Nursery • grow-Finish

21. Swine Industry Changes • 3 site production intentions • Eliminate bacteria vertical transmission • antibiotic medication at birth • early weaning (3 to 7 days) • separation to different site • small group sizes

22. Swine Industry Changes • 3 site production adaptation • unmedicated before weaning • weaned at standard 3 weeks • separation to different site • VERY LARGE group sizes • low rate vertical transmission important???

23. Swine Industry Changes • 3 site production adaptation • UNSUCCESSFUL in preventing disease transmission and losses • Successful in decreasing disease losses of the past • May have facilitated emergence new (delayed) disease syndromes

26. Swine Industry Changes • 3 site production adaptation • SINGLE SITE source of pigs ESSENTIAL for disease control • PRV, TGE, pneumonia • PRRSv • multiple “strains”, different status virus circulation between herds

27. PRRSv Impact on Disease • PRRS Clinical signs • abortion, stillbirths, mummies • high preweaning mortality • high nursery disease and mortalilty • later see finisher pig pneumonia • M hyo central role • PRDC

28. PRRSv Impact on Disease • PRRS disease and mortality often from secondary bacterial diseases

29. PRRSv Impact on Disease • PRRSv infections are immunosupressive • in utero infection • thymic atrophy • lymph node enlargement • interstitial pneumonia • secondary bacterial lesions

32. PRRSv Impact on Disease • PRRSv immunosupressive • Peripheral Blood Mononuclear Lymphocyte CD4 / CD8 ratio reversal

33. IU infected pig PBMC Cytokines

34. IU infected pig PBMC Cytokines

35. IU infected pig PBMC Cytokines

36. IU infected pig PBMC Cytokines

37. PRRSv Impact on Disease • In utero PRRSv infection impact • immunosuppressed • VERY susceptible 2o bacterial infection • long-term viremic • Typhoid Marys • MUST CONTROL SOW PRRSv infection to control finisher PRRS

39. PRRSv Impact on Disease • I = pc y/N • I = incidence • p = transfer probability • c = contact • y = quantity of infectious pigs • N = group size

40. PRRSv Impact on Disease

41. PRRSv Impact on Disease • Horizontal nursery / finisher spread • critical finisher disease M hyo • PRDC (SIV, PRCV, PCV2 / PMWS) • difficult to recreate experimentally • severe PRRSv strain Halbur / Thacker • dexamethazone enhanced Zimmerman

42. PRRSv Impact on Disease • Horizontal nursery / finisher spread • possible field contributing factors • large populations • social interaction factors • poorer ventilation control • persistent bacterial / virus exposure • compromised / stressed pigs on entry

43. Antibiotic Therapy Challenges • PRRS (nursery / finisher) • Increased amount of finisher disease??? • Appears increased use of antibiotics

44. Antibiotic Therapy Challenges • PRRS (nursery / finisher) • complaint antibiotics “aren’t working” • must use much longer duration • withdraw antibiotics in frustration

45. Antibiotic Therapy Challenges • PRRS-associated antibiotic “failure” • PRRSv infects macrophages • PAM, PIM • decreased phagocytic activity • decreased killing ability • Impaired bacterial clearance mechanisms!!

46. Antibiotic Therapy Challenges • PRRS-associated antibiotic “failure” • Uncertian effects upon PMN recruitment and bacterial killing in vivo

47. Antibiotic Therapy Challenges • PRRS-associated antibiotic “failure” • Antibiotic efficacy reduced by inability of pig’s immune system to effectively clear bacteria • antibiotics alone not kill all bacteria in vivo

48. Summary modern antibiotic use challenges in swine • Dramatically changed animal “flow” patterns that create nearly naive populations and epidemic disease conditions

49. Summary modern antibiotic use challenges in swine • Immunocompromising viral infections common in nursery and finishing swine • PRRSv • M hyo • SIV • PCR 2

50. Summary modern antibiotic use challenges in swine • Antibiotics appear less effective against bacterial diseases such as M hyopneumoniae during coinfections involving immunosupressive viruses like PRRSv and possibly PCV2