Current Trends in Presentation of Disease Associated with M. hyopneumoniae Monte B. McCaw DVM PhD...
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Transcript of Current Trends in Presentation of Disease Associated with M. hyopneumoniae Monte B. McCaw DVM PhD...
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