Top Pig Diseases to Know for Boards Success Part 1:
Respiratory conditions

For my own personal use only:
Sick pigs with PRRS may huddle together for warmth
  • Porcine reproductive & respiratory syndrome (PRRS) is the most costly pig disease worldwide.
  • Only 15 (6%) NAVLE® test questions cover pigs.

1. Porcine reproductive and respiratory syndrome (PRRS)

  • Classic case
    • Can be subclinical: i.e., infected pigs w/ NO signs
    • Breeding herd: Varies from mild to severe
      • Abortions
      • Early farrowing
      • Anorexia
      • Up to 100% neonatal mortality
    • Growing pigs: Transient disease w/ up to 20% mortality
  • Etiology
    • RNA Arterivirus: Different strains
    • Invades pulmonary alveolar macrophages
  • Dx
    • Necropsy: Lungs fail to collapse w/ multifocal consolidation, enlarged lymph nodes
    • Histopath: Necrotizing interstitial pneumonia, lymphoid hyperplasia, and focal follicular necrosis
    • Oral fluids or serum on sows and newly weaned piglets
      • ELISA
      • PCR
    • PCR on lungs
  • Tx: None
    • Supportive: Prevent secondary infections
    • Very common: If low level and not causing significant economic losses, may do nothing but monitor
  • Pearls
    • Most economically costly disease in pig production
    • Highly infectious and contagious
    • Biosecurity is key! 
      • Must test new animals before entry
Sows with PRRS that farrow early will have small pigs with a weak immune system
Lungs that fail to collapse with diffuse, multifocal consolidation from a pig with PRRS

2. Influenza A virus (IAV)

  • Classic case: Affects all ages!
    • Acute: Transient disease, worse in younger pigs, better in vaccinated pigs
      • Sudden onset of fever and cough 
      • 100% morbidity
      • Nasal discharge
    • Endemic IAV in sow farms and nursery pigs
      • Poor reproductive performance 
      • Piglets coughing in farrowing crates
      • Cough and poor performance in nursery
  • Etiology
    • Influenza A viruses
    • Major surface antigen types in swine: H1N1, H3N2
  • Dx
    • Gross lesions:
      • Sharply demarcated multifocal areas of consolidation
    • Microscopic lesions:
      • Degeneration and necrosis of the epithelium in the bronchi and bronchioli
      • Hyperemia and dilatation of the capillaries
      • Infiltration of alveolar septae with lymphocytes etc.
    • Oral fluids: PCR (or, less commonly, virus isolation)
    • Nasal swabs on febrile pigs for PCR
    • PCR on lung tissue 
  • Tx
    • Outbreak
      • Supportive care such as aspirin, NSAIDs like flunixin meglumine
      • Need to get fevers down so pigs eat and drink
      • Treat secondary bacterial infections with antimicrobials
    • Prevent via vaccination: sows and piglets
      • Homologous protection is best
  • Pearls
    • Zoonotic: Humans and other animals can get IAV from pigs so we DON'T call it "swine flu" anymore
      • Conversely, pigs are good incubators of different flu viruses they get from birds and humans
      • In 2009, an H1N1 IAV strain of swine origin spread globally, infecting people, poultry, dogs, cats, and other animals
    • One of the most common respiratory pathogens of growing pigs
Febrile, coughing pigs with nasal discharge are indicative of influenza infection
Lungs from a pig with influenza that fail to collapse with diffuse multifocal consolidation

3. Actinobacillus suis

  • Classic case
    • Acute death
      • Affects all ages from sows and neonates to finishing pigs
      • May be accompanied by cough, lethargy, epistaxis, and sometimes discoloration of ears 
    • Respiratory disease in finishing pigs
      • Dyspnea
      • Acute death
  • Etiology: Ubiquitous small gram-negative rod
  • Dx: Culture visible lesions
    • Gross lesions
      • Petechial to ecchymotic hemorrhages in multiple organs
      • Serous to serofibrinous exudates in the thoracic and abdominal cavities
      • Pleuritis, pericarditis, arthritis, and miliary abscesses in a variety of organs 
    • Microscopic lesions
      • Foci of necrosis in multiple organs associated with bacterial thromboemboli
  • Tx
    • Antimicrobials
    • Spreads nose to nose so inject antimicrobials into those pigs that have nose-to-nose contact with the pigs that died 
    • Follow up with antimicrobials via the water if needed
    • Good prognosis with Tx
  • Pearls
    • Can be primary pathogen, but also associated with viral diseases
    • Sporadic and difficult to prevent
A. suis is spread via nose-to-nose contact
Lungs are hard and deep red to black in color with A. suis pneumonia

4. Porcine circovirus diseases (PCV2)

  • Classic case
    • Ages affected: Pigs early in grower (>10 weeks of age) have two syndromes
      • Post-weaning wasting multisystemic wasting syndrome (PMWS) 
        • Diarrhea
      • Porcine dermatitis and nephropathy syndrome (PDNS)
        • Pale to icteric skin with coalescing raised red to purple lesions covering the rump
    • Ages affected: Gilts in sow herd
      • Increased mummified fetuses
      • Late term abortions
  • Etiology: Small, nonenveloped DNA virus 
  • Dx
    • Gross lesions:
      • Enlarged lymph nodes
      • Lungs do not collapse, with interlobular edema
      • Kidneys are enlarged and pale and subcapsular surface may have spotted white foci
    • Microscopic lesions:
      • Lymphocytic histiocytic infiltration of lymphoid tissues
      • Sloughing of lung epithelium with fibroplasia
    • Oral fluids: PCR
    • IHC and PCR (low cycle time [CT]) on lung tissue and lymph nodes

AND

  • Histopathologic lesions of lymphocytic histiocytic infiltration of lymphoid tissue
  • Tx
    • No Tx
    • Prevent via vaccination
    • Prognosis poor in unvaccinated pigs
  • Pearls
    • UNcommon now due to vaccines, but can occur in unvaccinated or under-vaccinated pigs
    • Ubiquitous in pigs world-wide
    • There are other types of PCV that are not pathogenic, or their pathogenicity is unknown
Cross section of a lung with marked interlobular edema consistent with PCV2

5. Mycoplasma hyopneumoniae a.k.a. enzootic pneumonia

  • Classic case
    • Ages affected: Late finishing (>15 weeks of age)
      • Deep, barking and/or non-productive cough
      • Pigs stop growing
    • May occur in sow farms if positive animals are introduced to a negative farm
  • Etiology: slow-growing bacterium
  • Dx
    • Gross lesions:
      • Cranioventral consolidation (apical, cardiac, and accessory lobes)
    • Microscopic lesions:
      • Lymphocytes in perivascular, peribronchial, and peribronchiolar tissues
      • Cuffing and lymphoid hyperplasia around the airways
    • Not a good candidate for culture
    • PCR: Lung, oral fluids, tonsil scrapings
    • ELISA in negative herds
  • Tx
    • Prevent using vaccination
      • In piglets (twice)
      • In replacement gilts depending on status of sow herd they are entering
    • Antimicrobials during outbreaks in late finishing pigs
    • Hard to eliminate cough in pigs
  • Pearls
    • May be seen in conjunction with PRRS or other pathogens 
    • Many farms have eliminated the pathogen
    • Poor growth may persist after infection
Cranioventral consolidation in the lung consistent with M. hyopneumoniae

Bonus! - Atrophic rhinitis

  • Classic case: Ages affected: three- to six-week-old pigs
    • Sneezing
    • Nasal discharge
    • Tear staining
    • Decreased growth rate
  • Etiology: Cause is combination of Bordetella bronchiseptica ± toxigenic Pasteurella multocida + management factors (e.g., poor air quality)
  • Dx
    • Gross lesions
      • Mild to moderate turbinate atrophy
      • ± Deviation of the nasal septum
    • Microscopic lesions
      • Disruption of normal bone formation in the turbinates
    • Gross lesions
      • Mild to moderate turbinate atrophy
      • ± Deviation of the nasal septum
    • Microscopic lesions
      • Disruption of normal bone formation in the turbinates
  • TX
    • Vaccination
      • Sow twice @ pre-farrowing
      • Piglets twice
    • Antimicrobials to the sow at parturition
  • Pearls
    • No longer a major health concern in the US - RARE
    • Still found at slaughter surveillance
    • Usually mild Dz and turbinate damage may be reversible
Snout at post-mortem with extensive turbinate damage and deviated septum due to atrophic rhinitis

All images courtesy of Meghann Pierdon, VMD, DACAW.

Top Topic Category
Porcine