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 USno M hyo vaccineno M hyo targeted abc programsrare to see clinical disease outbreaks

SPF herds

role as App facilitator

M. hyo history

Late 1980’s - 1990’sdramatic “paradigm shift” in hog-

raising management introduction of PRRSv and

subsequent epidemicsemergence of PRDC

M hyo central role

Presentation Overview

Swine Industry Changes

PRRSv Impact on Disease

Antibiotic Therapy Challenges

Swine Industry Changes

Continuous Pig-Flow Rearingmultiple age groups

building or site

never cleaned / disinfectedendemic disease model

Day Care / School-kid model

Swine Industry Changes

All In - All Out (AIAO) Pig-flow Rearingsingle age group

room / building / site

placed at same timeemptied completelycleaned and disinfected

Swine Industry Changes

AIAO Pig-flow RearingEnd 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 control1 site production

“farrow to finish”

(Farrowing)(Nursery)(grow-Finish)

Swine Industry Changes

Site level disease control3 site production

further decrease old to young transmission risk

Farrowing (Breeding Herd)

Nursery

grow-Finish

Swine Industry Changes

3 site production intentionsEliminate 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 adaptationunmedicated before weaningweaned at standard 3 weeksseparation to different siteVERY LARGE group sizes

low rate vertical transmission important???

Swine Industry Changes

3 site production adaptationUNSUCCESSFUL in preventing

disease transmission and lossesSuccessful in decreasing disease

losses of the pastMay have facilitated emergence new

(delayed) disease syndromes

Swine Industry Changes

3 site production adaptationSINGLE SITE source of pigs

ESSENTIAL for disease controlPRV, TGE, pneumoniaPRRSv

multiple “strains”, different status virus circulation between herds

PRRSv Impact on Disease

PRRS Clinical signsabortion, stillbirths, mummieshigh preweaning mortalityhigh nursery disease and mortaliltylater 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 immunosupressivein utero infection

thymic atrophy lymph node enlargement interstitial pneumonia secondary bacterial lesions

PRRSv Impact on Disease

PRRSv immunosupressivePeripheral Blood Mononuclear

Lymphocyte CD4 / CD8 ratio reversal

IU infected pig PBMC Cytokines

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7IF

Nga

mm

a :c

yclo

phil

in

0 14 67

Days of age

PRRSV Control

IU infected pig PBMC Cytokines

00.050.1

0.150.2

0.250.3

0.350.4

0.45IL

6 :

cycl

ophi

lin

0 14 67

Days of age

PRRSV Control

IU infected pig PBMC Cytokines

0

0.1

0.2

0.3

0.4

0.5

0.6IL

10:c

yclo

phil

in

0 14 67

Days of age

PRRSV Control

IU infected pig PBMC Cytokines

0

0.2

0.4

0.6

0.8

1

1.2IL

12 :

IL

10

0 14 67

Days of age

PRRSV Control

PRRSv Impact on Disease

In utero PRRSv infection impactimmunosuppressed

VERY susceptible 2o bacterial infection

long-term viremicTyphoid Marys MUST CONTROL SOW PRRSv

infection to control finisher PRRS

PRRSv Impact on Disease

I = pc y/NI = incidencep = transfer probabilityc = contacty = quantity of infectious pigsN = group size

PRRSv Impact on Disease

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16 18 20 22 24

Weeks of Age

PR

RS

v P

revale

nce

High Prev Low Prev

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 swinePRRSvM hyoSIVPCR 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