| Etiology: |
| Parainfluenza-3 virus (PI-3) is an RNA virus classified in the paramyxovirus family. Infections caused by PI-3 are common in cattle. Although PI-3 is capable of causing disease, it is usually associated with mild to subclinical infections. The most important role of PI-3 is to serve as an initiator that can lead to the development of secondary bacterial pneumonia. |
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| Clinical Findings and Lesions: |
| Clinical signs include pyrexia, cough, serous nasal and lacrimal discharge, increased respiratory rate, and increased breath sounds. The severity of signs worsens with the onset of bacterial pneumonia. Fatalities from uncomplicated PI-3 pneumonia are rare. Lesions include cranioventral lung consolidation, bronchiolitis, and alveolitis with marked congestion and hemorrhage. Inclusion bodies may be identified. Most fatal cases have a concurrent bacterial bronchopneumonia. |
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| Diagnosis: |
| Diagnostic procedures for PI-3 are similar to those for bovine respiratory syncytial virus (
Bovine Respiratory Syncytial Virus). |
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| Treatment and Prevention: |
| Treatment focuses on the antimicrobial therapy directed toward bacterial pneumonia (
Bacterial Pneumonia: Overview). NSAID are also a therapeutic consideration. |
| PI-3 vaccines are available and are almost always combined with bovine herpesvirus 1 (infectious bovine rhinotracheitis). Modified live and inactivated vaccines are available for IM administration. Vaccines containing temperature-sensitive mutants for intranasal administration are also available. |
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