Current trends in presentation of disease associated with m hyopneumoniae
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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 no M hyo vaccine no M hyo targeted abc programs

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Current trends in presentation of disease associated with m hyopneumoniae l.jpg

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 l.jpg
M. hyo history hyopneumoniae

  • 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


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M. hyo history hyopneumoniae

  • 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


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Presentation Overview hyopneumoniae

  • Swine Industry Changes

  • PRRSv Impact on Disease

  • Antibiotic Therapy Challenges


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Swine Industry Changes hyopneumoniae

  • Continuous Pig-Flow Rearing

    • multiple age groups

      • building or site

    • never cleaned / disinfected

    • endemic disease model

      • Day Care / School-kid model


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Swine Industry Changes hyopneumoniae

  • All In - All Out (AIAO) Pig-flow Rearing

    • single age group

      • room / building / site

    • placed at same time

    • emptied completely

    • cleaned and disinfected


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Swine Industry Changes hyopneumoniae

  • 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???


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Swine Industry Changes hyopneumoniae

  • Site level disease control

    • 1 site production

      • “farrow to finish”

  • (Farrowing)(Nursery)(grow-Finish)


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Swine Industry Changes hyopneumoniae

  • Site level disease control

    • 3 site production

      • further decrease old to young transmission risk

  • Farrowing (Breeding Herd)

  • Nursery

  • grow-Finish


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Swine Industry Changes hyopneumoniae

  • 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


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Swine Industry Changes hyopneumoniae

  • 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???


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Swine Industry Changes hyopneumoniae

  • 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


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Swine Industry Changes hyopneumoniae

  • 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


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PRRSv Impact on Disease hyopneumoniae

  • PRRS Clinical signs

    • abortion, stillbirths, mummies

    • high preweaning mortality

    • high nursery disease and mortalilty

    • later see finisher pig pneumonia

      • M hyo central role

      • PRDC


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PRRSv Impact on Disease hyopneumoniae

  • PRRS disease and mortality often from secondary bacterial diseases


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PRRSv Impact on Disease hyopneumoniae

  • PRRSv infections are immunosupressive

    • in utero infection

      • thymic atrophy

      • lymph node enlargement

      • interstitial pneumonia

      • secondary bacterial lesions


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PRRSv Impact on Disease hyopneumoniae

  • PRRSv immunosupressive

    • Peripheral Blood Mononuclear Lymphocyte CD4 / CD8 ratio reversal






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PRRSv Impact on Disease hyopneumoniae

  • 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


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PRRSv Impact on Disease hyopneumoniae

  • I = pc y/N

    • I = incidence

    • p = transfer probability

    • c = contact

    • y = quantity of infectious pigs

    • N = group size



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PRRSv Impact on Disease hyopneumoniae

  • 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


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PRRSv Impact on Disease hyopneumoniae

  • 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


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Antibiotic Therapy Challenges hyopneumoniae

  • PRRS (nursery / finisher)

    • Increased amount of finisher disease???

    • Appears increased use of antibiotics


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Antibiotic Therapy Challenges hyopneumoniae

  • PRRS (nursery / finisher)

    • complaint antibiotics “aren’t working”

      • must use much longer duration

      • withdraw antibiotics in frustration


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Antibiotic Therapy Challenges hyopneumoniae

  • PRRS-associated antibiotic “failure”

    • PRRSv infects macrophages

      • PAM, PIM

      • decreased phagocytic activity

      • decreased killing ability

    • Impaired bacterial clearance mechanisms!!


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Antibiotic Therapy Challenges hyopneumoniae

  • PRRS-associated antibiotic “failure”

    • Uncertian effects upon PMN recruitment and bacterial killing in vivo


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Antibiotic Therapy Challenges hyopneumoniae

  • 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


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Summary modern antibiotic use challenges in swine hyopneumoniae

  • Dramatically changed animal “flow” patterns that create nearly naive populations and epidemic disease conditions


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Summary modern antibiotic use challenges in swine hyopneumoniae

  • Immunocompromising viral infections common in nursery and finishing swine

    • PRRSv

    • M hyo

    • SIV

    • PCR 2


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Summary modern antibiotic use challenges in swine hyopneumoniae

  • Antibiotics appear less effective against bacterial diseases such as M hyopneumoniae during coinfections involving immunosupressive viruses like PRRSv and possibly PCV2


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