Respiratory diseases*

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 Disease and etiologic agent Clinical signs  Lesions 
gross - micro
Diagnostic aids/

Mycoplasmal pneumonia

Mycoplasma hyopneumoniae

Persistent, dry cough, retarded growth, high morbidity/low mortality. Endemic in many herds. Pneumonia and atelectasis in cranioventral lobules (gray-purple). Marked lymphoid hyperplasia around airways. History and lesions are suggestive of diagnosis. FAT and IHC applied to lung tissue or PCR of airway swabs. Serology useful on a herd basis.

Atrophic rhinitis

Bordetella bronchisepticaand/or toxigenicPasteurella multocida

Sneezing, snorting, nasal discharge, epistaxis. Tear staining at medial canthi. Usually a deviation of snouts in a few pigs. Variable turbinate atrophy. Perhaps deviation of snout. Tear staining. Secondary pneumonia often present. Based on signs, history of reduced performance, typical lesions at necropsy or at slaughter. Culture and identify the agent(s) from turbinates or nasal swabs. Confirm toxigenicity.

Pneumonic pasteurellosis

Pasteurella multocida

Coughing, dyspnea, fever, prostration. Firm, fibrinous pneumonia cranioventrally and extending into diaphragmatic lobes. Variable pleuritis, perhaps adhesions/abscesses. Culture Pasteurella multocida from lung lesions, possibly also from parenchymatous organs. Gray, firm, and subacute nature of lung lesions are suggestive of pasteurellosis. Organism a frequent, secondary, respiratory pathogen.

Inclusion body rhinitis


Sneezing, nasal discharge in young piglets with variable mortality. Possibly dead, mummified or weak piglets at farrowing. In young pigs: rhinitis with edema, petechial hemorrhages and a mucopurulent nasal exudate. Large, almost pathognomonic, intranuclear inclusions in enlarged epithelial type cells (turbinates, Harderian and lachrymal glands, kidney, choroid plexus, other sites). Signs and lesion strongly suggest the diagnosis.

Pleuropneumonia (APP)

Actinobacillus pleuropneumoniae

Acute: High temperatures, prostration, dyspnea, mouth breathing, perhaps bloody foam from nose. Short course, high morbidity and mortality.
Chronic: chronic cough, unthriftiness
Pneumonia is firm, necrotic and bloody with fibrinous pleuritis. Chronic cases have pleural adhesions often with necrotic masses in lungs. Common in diaphragmatic lobes. Signs and lesions are highly suggestive. Isolate agent from lung lesions and identify serotype. Serologically identify carrier herds by ELISA or CF tests.

Swine influenza (SIV)

Influenza type A
Subtypes H1N1 and H3N2 most common; diversity recognized.

Sudden onset, rapid spread of fever, serous nasal discharge, dyspnea, prostration. This is followed by loud coughing, and usually rapid recovery in seven days. Multifocal to diffuse red firmness. Usually has lobular anteroventral distribution. Secondary bacterial pneumonia is common. History and signs are very suggestive. Morbidity high, mortality low. Confirm presence of SIV by PCR or ELISA on nasal swabs or by PCR, IHC, FAT or VI from lung tissue. Serology by IHA or ELISA. Subtype determined by PCR.

Porcine reproductive and respiratory syndrome virus (PRRSV)


Respiratory disease and poor reproductive performance. High pre-weaning mortality. Respiratory dyspnea, fever and prolonged course, usually with abundant secondary agents. In young pigs, focal or diffuse interstitial pneumonia in any or all lobes. Generally swollen lymph nodes. Perhaps secondary bronchopneumonia. Chronic respiratory disease in growing swine. Identify virus in lung by IHC, FAT, or PCR. Isolate virus and identify. Demonstrate rising antibody titers in herd. Bronchoalveolar lavage is good specimen for PCR and isolation. Sequencing commonly performed by PCR.

Pseudorabies (PRV)


Central nervous system (CNS) signs predominate in neonates and the very young. (Sudden death common in very young) Swine >3 weeks old: sneezing, coughing, nasal discharge, dyspnea Gross: often no lesions. Perhaps rhinitis, tonsillitis, tracheitis, keratoconjunctivitis.
Histology: Nonsuppurative meningoencephalitis. Necrotic bronchitis, bronchiolitis, alveolitis.
Isolate and identify virus. Histopath with IHC. FAT on tonsil, spleen, brain. Serologic tests reveal herd infection. PRV was eradicated from US commercial swine in 2004. PRV should now be thought of as a foreign disease and all suspicious cases reported and investigated.

*  Parasitisms with respiratory signs include ascariasis (roundworm migration) and lungworm infection.

CF-complement fixation
ELISA-enzyme-linked immunosorbent assay
FAT-fluorescent antibody test
HI-hemagglutination inhibition
IHA-indirect hemagglutination
PCR-polymerase chain reaction
VI-virus isolation