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Dinámica de infección Cadena de Infección/Cadena de
Prevención PRRS
Eduardo Fano Edgar Díaz Reid Philips
Jean Paul Cano Enrique Mondaca
Boehringer Ingelheim Vetmedica Inc
Enfoque en lechón Enfoque en el sistema
Chain of the infection in the Epidemiology field: Individual (host)approach
diciembre 4, 2013
3 Image courtesy of: http://www.cetl.org.uk/learning/img1/chain-infection.jpg
Cadena de infección entre fases de producción con enfoque poblacional
diciembre 4, 2013
4
diciembre 4, 2013
PLEASE INSERT Presentation title 5
Sow Herd
Nursery
Finishing
GDU
Multiplier
"Cadenade Produccion" "Cadenade Infeccion" "Cadenade Prevencion"
Cadena de Producción/Cadena de infección/Cadena de Prevención
Fuente de Primeriza
s
Desarrollo Reemplazo
s Hembras
Parto y lactantes
Destete a finalizado
Venta a mercado
Cadena de infección/Prevención Un enfoque sistemá:co
Enfoque sistematico
Minimizar exposición y Maximizar inmunidad
Minimizar exposición y Maximizar inmunidad
Minimizar exposición y Maximizar inmunidad
Minimizar exposición y Maximizar inmunidad
Manejo de la Transmision
Vertical
TH -------------TH---------------TH--------------TH-------------TH
TV
TH -------------TH---------------TH--------------TH---------------TH
PRRS virus “Infection Chain”
Level 1
Replacement animals
Level 2
Sow herd
Level 3
Wean to finish pigs
Horizontal transmission
Vertical transmission
Horizontal transmission
Lateral
spread
External - Gilts +Gilts
Local Replacement
Fano et al., 2007
Important to understand the PRRSv status and pattern of circulation within herds at each phase of production.
Level 1: Gilt Development
• Goal: Prepare and introduce immune and non-infectious replacement animals to recipient breeding herds
• Why important? A reason for endemic/chronic PRRSv transmission/infection within a breeding herd is introduction of naïve or actively infected replacement gilts
• How? • Appropriate pig-flow w/ AI-AO strategy • Manage immunity to PRRSv
• Role of the replacement gilt in the maintenance of the PRRS infectious process; S.A. Dee PhD, Leman Swine Conf., 1998
• The science of PRRS: What do we really know about its transmission, diagnosis and control?; S.A. Dee PhD, AASV proc., 2004
0 7 37 67 97 127 DPI
Sent 1
MN30100 MLV 1 MLV 2 MLV 3
Sent 2 Sent 3 All + All + NVC + All Vx -
Therapeutic MLV reduced PRRSV shedding to sentinels
Level 2: Sow Herd
• Goal: Attain and maintain stability to PRRSv in positive breeding herds – wean PRRSv negative pigs
• Definition of stability: No evidence of PRRSv transmission horizontally or vertically • The science of PRRS: What do we really know about transmission, diagnosis &
control; S.A. Dee PhD, AASV, 2004
• Must understand the status and pattern of PRRSv circulation within the breeding herd
• PRRSv status of incoming replacement gilts
• PRRSv status of piglets at weaning
Achieving Breeding Herd Stability for PRRS
o Ultimate Goal : Wean PRRSv Negative Pigs
o Employ protocols that minimize viral replication and transmission w/in a population of animals
§ Must eliminate subpopulations to attain and maintain uniform immunity within the population § Detecting subpopulations after PRRSv infection in large breeding herds; S.A.
Dee PhD et.al., SHAP, 1996
o Employ protocols that generate uniform population immunity – Mass Vaccination
§ Maximize Immunity & Minimize Exposure o Often employed w/ a form of herd/population closure
§ LOAD – CLOSE- EXPOSE protocol w/ Al-AO farrowing room mgmt § Quantifying the production impact in farms using load-close-expose
programs for PRRSv; D. Linhares et.al., AASV proc, 2013 § Time to produce PRRSv-negative pigs from infected breeding sites; D.
Linhares et.al., AASV, 2013 § McRebel PRRS; MB McCaw, Leman Proc., 1995
Stabilization of PRRS virus infection in breeding herds: research summary
From Daniel Linhares PhD dissertation
Daniel Linhares,1 Jean Paul Cano,2 Montse Torremorell,1 Robert Morrison1
1College of Veterinary Medicine, University of Minnesota 2Boehringer Ingelheim Vetmedica, Inc
0 10 20 30 40 50
LVI
MLV
weeks
Treatm
ent
PRRSV Load-‐Close-‐Expose program ?meline
PRRSv-‐detec:on LCH TTBP TTNP
PRRS-negative herd?
Dion et al., 2010
Level 3: PRRSv Control in Growing Pigs Wean to finish pigs
• Understand/Confirm prevalence of PRRSv at weaning
• Understand/Confirm pattern of PRRSv transmission/infection in growing pig flow and/or risk of lateral introduction of virus
• Horizontal and/or Lateral introduction
• Fundamental for targeting control interventions
Control Group
Vaccine Group
DD
DD
-29 5 0 3 8 36 70 95 118 DPI
Pig arrival Sorting
Weigh ID
1-18-2 challenge
ATP vaccinations
» Serum and Bioaerosol samples tested by RT-PCR
Slaughter Weigh
Therapeutic MLV reduced PRRSV shedding in OF & air
PRRSV in aerosol CONTROL VACCINATED Mean (RNA copies/mL) 4.3 x 108 a 4.5 x 108 a
range min 1.2x104 4.9x103
range max 1.9x109 2x109
95% conf interval 2.6 x108 - 6.1 x 108 a 2.7 x 108 - 8.1 x 108 a # pos days 31a 17b
last DPI positive 70 45
# pos days (McNemar's test p-value 0.0004)
RNAc/mL in positive days (Wilcoxon p-value 0.1243)
Different superscript represent statistical significance (α = 0.05)
Vertical transmission modulation : multiplier farm
Young Gilt immunization and horizontal transmission manipulation by proper animal flow Re- immunization, Status verification
Massive intervention: immunization
Massive intervention: immunization Status verification
Massive intervention: immunization Pre-farrowing intervention Status verification Vertical transmission modulation : sow herd, In-house processes (cross fostering, environment control, etc)
Piglet immunization Agent spread: Nursery and Finishing
Piglet colonization Exposure level, piglet immune status
Vertical Transmission Sow shedding status, sow immunity status, exposure level. etc
Sow herd infection pressure Shedding, exposure, immunity, etc
Gilts-P1 and P2+ interaction
I Horizontal transmission
Gilts Introduction Final status?, Naïve or Shedder?, Promoting Sow herd instability?
Gilts development (100 to 200 days old) Naïve?, Shedding? Recovery? , Acclimatization method
Gilts (21 to 100 days old) Onset , Severity and Duration of the infection, shedding status
“Infection Chain™ ”: Understanding Epidemiological events… then.. “Prevention Chain™”
Conclusions
• Minimizing Exposure – Gilt Management – Sow herd stability – Pig flow – Immunity
• Maximizing Immunity – Vaccination at levels or phases of production
to mitigate the biologic and economic impact of PRRSv
5-Steps PRRS Control Program: A Systematic Approach
1. Identify Desired Goals
2. Determine Current PRRS Status
3. Understand Current Constraints
4. Develop Solution Options
5. Implement and Monitor Preferred Solution
Systematic (individual) approach and Regional approach
“The perfect strategy”
diciembre 4, 2013
21
Sow Herd
Nursery
Finishing
GDU
Multiplier
Production Chain "Infection Chain" "Prevention Chain"