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.

M. hyo history Pre 1990 “insignificant” in US äno M hyo vaccine äno M hyo targeted abc programs ärare to see clinical disease outbreaks  SPF herds ärole as App facilitator

M. hyo history Late 1980’s ’s ädramatic “paradigm shift” in hog- raising management äintroduction of PRRSv and subsequent epidemics äemergence of PRDC  M hyo central role

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

Swine Industry Changes Continuous Pig-Flow Rearing ämultiple age groups  building or site änever cleaned / disinfected äendemic disease model  Day Care / School-kid model

Swine Industry Changes All In - All Out (AIAO) Pig-flow Rearing äsingle age group  room / building / site äplaced at same time äemptied completely äcleaned and disinfected

Swine Industry Changes AIAO Pig-flow Rearing äEnd old-to-young transmission  decreasing contact / exposure äMust be perfect to be successful!!??  Naïve population if successful äEpidemic Disease Model???

Swine Industry Changes Site level disease control ä1 site production  “farrow to finish” (Farrowing)(Nursery)(grow-Finish)

Swine Industry Changes Site level disease control ä3 site production  further decrease old to young transmission risk Farrowing (Breeding Herd) Nursery grow-Finish

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

Swine Industry Changes 3 site production adaptation äunmedicated before weaning äweaned at standard 3 weeks äseparation to different site äVERY LARGE group sizes  low rate vertical transmission important???

Swine Industry Changes 3 site production adaptation äUNSUCCESSFUL in preventing disease transmission and losses äSuccessful in decreasing disease losses of the past äMay have facilitated emergence new (delayed) disease syndromes

Swine Industry Changes 3 site production adaptation äSINGLE SITE source of pigs ESSENTIAL for disease control äPRV, TGE, pneumonia äPRRSv  multiple “strains”, different status virus circulation between herds

PRRSv Impact on Disease PRRS Clinical signs äabortion, stillbirths, mummies ähigh preweaning mortality ähigh nursery disease and mortalilty älater see finisher pig pneumonia  M hyo central role  PRDC

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

PRRSv Impact on Disease PRRSv infections are immunosupressive äin utero infection  thymic atrophy  lymph node enlargement  interstitial pneumonia  secondary bacterial lesions

PRRSv Impact on Disease PRRSv immunosupressive äPeripheral Blood Mononuclear Lymphocyte CD4 / CD8 ratio reversal

IU infected pig PBMC Cytokines

PRRSv Impact on Disease In utero PRRSv infection impact äimmunosuppressed  VERY susceptible 2 o bacterial infection älong-term viremic äTyphoid Marys äMUST CONTROL SOW PRRSv infection to control finisher PRRS

PRRSv Impact on Disease I = pc y/N äI = incidence äp = transfer probability äc = contact äy = quantity of infectious pigs äN = group size

PRRSv Impact on Disease

Horizontal nursery / finisher spread äcritical finisher disease M hyo  PRDC (SIV, PRCV, PCV2 / PMWS) ädifficult to recreate experimentally  severe PRRSv strain Halbur / Thacker  dexamethazone enhanced Zimmerman

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

Antibiotic Therapy Challenges PRRS (nursery / finisher) äIncreased amount of finisher disease??? äAppears increased use of antibiotics

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

Antibiotic Therapy Challenges PRRS-associated antibiotic “failure” äPRRSv infects macrophages  PAM, PIM  decreased phagocytic activity  decreased killing ability äImpaired bacterial clearance mechanisms!!

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

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

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

Summary modern antibiotic use challenges in swine Immunocompromising viral infections common in nursery and finishing swine äPRRSv äM hyo äSIV äPCR 2

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