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.

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
  - Cough, fever
  - Secondary infections
    - Streptococcus suis
    - Glaeserella parasuis
    - Mycoplasma spp.
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

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

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

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

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

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

All images courtesy of Meghann Pierdon, VMD, DACAW.

Porcine