Swine Influenza - One Health in the Caribbean

Swine Influenza

Ian Brown
Director of International Reference Laboratory for
Avian and Swine Influenza & Newcastle Disease
Animal Health and Veterinary Laboratories Agency-
Weybridge
Training for Caribbean Veterinary Services on Disease
Recognition and Response
24th - 26th March 2015, Port of Spain, Trinidad.

ian.brown@apha.gsi.gov.uk

Influenza in pigs

• Acute respiratory disease
   – Greater proportion of adult population of a national herd will have
     been exposed to influenza
• Economic impact
   – Cost of lost production in fatteners $10/pig (c£65m pa -UK)
   – Welfare issues
• Potential implications for public health HOWEVER
Reverse Zoonoses frequency > Zoonoses
• Complex aetiology

                                                      2

AETIOLOGY

INFLUENZA A VIRUSES
            (Orthomyxoviruses; Type A)
                       Haemagglutinin (HA, 1-18)
                        Neuraminidase (NA, 1-11)

                            Matrix (M1 and M2)
                            Nucleoprotein (NP)

                           Polymerase proteins
                         (PA, PB1 [PB1-F2], PB2)
                         Nonstructural proteins
2/25/2016
                              (NS1,4NEP)

Type A Influenza Surface Antigens
Surface antigen subtypes established in different hosts
                          H17N10, H18N11 New world bats
      Haemagglutinin:
              1 2 3      4 5 6 7 8 9 10 11 12 13 14 15 16
      Human   
      Equine                      
      Swine         
      Avian                       
      Neuraminidase:
              1 2 3      4 5 6 7 8 9
      Human  
      Equine                        
      Swine  
      Avian                
H17

INFLUENZA A SUBTYPES
          INFECTING PIGS

• H1N1      swine, avian and human
• H3N2      human and avian
• H1N2      swine from human

also H1N3, H1N7, H2N3, H3N1, H3N3,
  H4N6, H5N1(hp) H7N7(hp), H9N2.

EPIDEMIOLOGY

TRANSMISSION OF INFLUENZA
               A VIRUS TO/FROM PIGS

• Avian viruses require 2-3
  binding to terminal sialic acid
• Human viruses require 2-6
  binding to terminal sialic acid
• Pigs have receptors for both
  viruses and 2-3 viruses
  adapted to pigs show 2-6
  binding –REPLICATION IN
  URT

Interspecies transmission of pandemic viruses

                                    H1N1 (1918, 2009)
                                      H3N2 (1968)
                                      H1N1 (1977)

                        2.3

Origin of pandemic H1N1 2009 – mixing of North American and European swine viruses
                                 -a unique event

SWINE INFLUENZA
Pathogenesis/identification of disease

Clinical symptoms

•   All age groups can be affected
•   Pyrexia
•   Anorexia
•   Sneezing/coughing/dyspnoea
•   High morbidity
•   Low mortality
•   Reduced reproductive performance
•   Rapid recovery

2/25/2016                              13

SI pathogenesis
                          Replication in respiratory tract
                          Nasal shedding
IFN-α and other
early cytokines                           HI/VN antibodies
in lungs                                  and specific
                                          immunity
              0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 DPI

              clinical signs

  2/25/2016                                           14

2/25/2016   15

EPIDEMIOLOGY

GEOGRAPHIC DISTRIBUTION

SIV circulation in South and Central America (Data courtesy of
                 A.Pereda & J.Zanella via OFFLU

Figure 1

2/25/2016          18

2/25/2016   19

LABORATORY DIAGNOSIS

Diagnostic methods for influenza in pigs

• OIE Manual of Diagnostic Tests for Terrestrial
  Animals

• Clinical Cases: sampling
  – Carcases freshly dead or moribund/sacrificed
  – Nasal swabs in sick animals swabs
  – Clotted bloods

• Slaughterhouse survey:
  • Bloods for country/region status

Schematic overview of diagnostic steps for confirmation of SI

                   Step 1                   Classical pathway       Molecular
                                                                    pathway

                Detection of
             influenza A virus                Virus isolation   M-gene PCR
                                            (embryonated fowl
                                              eggs or cells)
  Negative                       Positive

                    Step                                          HA-gene PCR
                     2                                              (H1, H3)

             Specific identification of        Serological
             influenza virus subtype         Characterisation
                                                  HI/NI           Genotyping
                                                                Sequencing of full
                                                                    genome

Serology

• Antibody duration up to c6 months from single exposure
• Influenza A screening by ELISA (NP)
• H subtype specific in HI test
• Use contemporary virus strains relevant to region or
  country
• Panel of viruses
• Careful interpretation of all results
    – Take into account known cross reactivity between strains
    – Multiple exposures to more than one strain can affected sero-
      profiles
    – Examine at herd level; single reactors certainty – false positives

PREVENTION, CONTROL &
    ERADICATION

What options are practical?
• Prevention
   – Endemic infection of pigs
   – Good husbandry practices
   – On farm quarantine
   – Surveillance
   – Country level import controls

• Control
   – Isolating farms within production pyramid
   – Vaccination
       • Which strains?

• Eradication
   – Not applicable/feasible

Thank you for your attention
ANY QUESTIONS?