# Presentation: 567708

## 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
- rare to see clinical disease outbreaks
- SPF herds
- role as App facilitator

## 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

## Presentation Overview

- Swine Industry Changes
- PRRSv Impact on Disease
- Antibiotic Therapy Challenges

## Swine Industry Changes

- Continuous Pig-Flow Rearing
- multiple age groups
- building or site
- never cleaned / disinfected
- endemic disease model
- Day Care / School-kid model

## Slide 10

## 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

## Slide 16

## 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???

## Swine Industry Changes

- Site level disease control
- 1 site production
- “farrow to finish”
- (Farrowing)(Nursery)(grow-Finish)

## Slide 19

## Swine Industry Changes

- Site level disease control
- 3 site production
- further decrease old to young transmission risk
- Farrowing (Breeding Herd)
- Nursery
- grow-Finish

## 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

## 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???

## 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

## Slide 24

## Slide 25

## 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

## 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

## PRRSv Impact on Disease 

- PRRS disease and mortality often from secondary bacterial diseases

## PRRSv Impact on Disease 

- PRRSv infections are immunosupressive
- in utero infection
- thymic atrophy
- lymph node enlargement
- interstitial pneumonia
- secondary bacterial lesions

## PRRSv Impact on Disease 

- PRRSv immunosupressive
- Peripheral Blood Mononuclear Lymphocyte CD4 / CD8 ratio reversal

## IU infected pig PBMC Cytokines

## IU infected pig PBMC Cytokines

## IU infected pig PBMC Cytokines

## IU infected pig PBMC Cytokines

## 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

## Slide 38

## PRRSv Impact on Disease

- I = pc y/N
- I = incidence
- p = transfer probability
- c = contact
- y = quantity of infectious pigs
- N = group size

## PRRSv Impact on Disease

## 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

## 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

## Antibiotic Therapy Challenges

- PRRS (nursery / finisher)
- Increased amount of finisher disease???
- Appears increased use of antibiotics

## Antibiotic Therapy Challenges

- PRRS (nursery / finisher)
- complaint antibiotics “aren’t working”
- must use much longer duration
- withdraw antibiotics in frustration

## Antibiotic Therapy Challenges

- PRRS-associated antibiotic “failure”
- PRRSv infects macrophages
- PAM, PIM
- decreased phagocytic activity
- decreased killing ability
- Impaired bacterial clearance mechanisms!!

## Antibiotic Therapy Challenges

- PRRS-associated antibiotic “failure”
-  Uncertian effects upon PMN recruitment and bacterial killing *in vivo*

## 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*

## 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
- PRRSv
- M hyo
- SIV
- PCR 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