Porcine respiratory disease complex

Question 1

Clinical signs

Answer 1

• Coughing – low level common without pneumonia / requiring treatment
• Anorexia
• Lethargy
• Losing body weight – can be sudden or may manifest as increasing variation over a period of time
• Increased hair growth
• Increased respiratory effort
• Increased mortality
  ◦ Can be sudden acute deaths without clinical signs
  ◦ Can be due to increased number euthanized due to excessive body condition loss

Question 2

What pathogens can cause PRDC?

Answer 2

• Viral
  ◦ PRRS (SV, YV)
  ◦ SIV (SV)
  ◦ PCV-2 (SV, YV)
• Bacterial
  ◦ Glasserella parasuis (SV, YV)
  ◦ Mycoplasma hyopneumoniae (YV)
  ◦ Mycoplasma hyorhinis
  ◦ Streptococcus suis (SV, YV)
  ◦ Pasturella multiocida
  ◦ Actinobacillus pleuropneumoniae (YV)

Question 3

What are causes of stress in nursery and finisher pigs?

Answer 3

Causes of stress - Nursery
* chilling
* weaning/mixing
* feed access
* water reg
* immunosuppresion

Causes of stress - Finisher
* chilling
* transport/mixing
* feed demand
* water reg
* competition / sexual maturation
* immunosuppression

Question 4

What concurrent diseases can complicate PRDC?

Answer 4

• Complicated by the immunosuppressive nature of some pathogens
  ◦ PRRS – also a primary / secondary cause of pneumonia
  ◦ SIV – also a primary / secondary cause of pneumonia
  ◦ PCV-2 – also a primary / secondary cause of pneumonia
  ◦ Mycoplasma hyopneumoniae – also a primary / secondary cause of pneumonia

Question 5

How can we diagnose which pathogen is causing PRDC?

Answer 5

• Elisa - blood or oral fluids
  ◦ Beware endemic disease – we expect antibodies
  ◦ Beware vaccination regimes – we expect antibodies
  ◦ Not all strains maybe pathogenic - APP
  ◦ Paired serology
  ◦ Strain differentiation and comparison
  ◦ Compare different groups
  ◦ Compare to previous samples
  ◦ Antibodies take time to develop
• PCR - blood or oral fluid or nasal & tonsillar swabs
  ◦ Colonisation not equal to disease with some pathogens
  ◦ Live vaccines – PRRS

Question 6

What can we do on post mortem to diagnose PRDC?

Answer 6

• Histopathology
  ◦ In my opinion vital part of all PME’s
  ◦ Presence of pathogen not always = disease
  ◦ Presence of pathogen + typical histo-pathology = diagnosis
  ◦ IHC
• PCR - tissue/blood/BAL/swab
  ◦ Colonisation not equal to disease with some pathogens
  ◦ Live vaccines – PRRS
• Culture - tissue/swab
  ◦ Some pathogens very difficult to culture – GPS, APP, PMO
  ◦ Allows sensitivity

Question 7

If mycoplasma is found to be the pathogen causing PRDC, what antibiotic would you use?

Answer 7

NOT beta lactams
Use macrolides or tetracycline