BOVINE RESPIRATORY DISEASE

Bovine Respiratory Disease Complex: PI3

Bovine Parainfluenza-3 Virus

Introduction
Bovine parainfluenza-3 is a respiratory disease present in cattle population.  It is considered to be associated with the bovine respiratory disease (BRD) complex.  It causes only mild disease and is only of real significance when it results in secondary bacterial infection causing pneumonia.

Etiology/History
Parainfluenza-3 is classified as a RNA virus of the paramyxovirus family (previously classified myxovirus).  Infection is common in cattle and usually only causes mid to subclinical disease. More importantly it can predispose an animal to secondary bacterial pneumonia.


Distribution/Prevalence and Transmission
Parainfluenza-3 is common throughout the in many countries including Canada and the usa. It is highly contagious and prevalent. Previous survey has shown that in Nebraska 86% of cattle have antibodies but this is variable as the same paper stated that prevalence of antibodies in New York was around 48%. The high number of animals with antibodies suggest that it is the most prevalent and widespread respiratory disease.  Evidence points to a higher incidence of new cases in the fall. Transmission takes place from animal to animal through the inhalation of aerosolized virus.

Clinical Findings & Lesions
The clinical signs of parainfluenza-3 include pyrexia (fever), cough, serous (watery) nasal and lacrimal discharge as well as increased rate of respiration and an increase breathing sounds.  Infection can increase morbidity of other viral diseases such as bovine viral diarrhea and infectious bovine rhinotracheitis. The impact of infection is more significant when coupled with secondary bacterial pneumonia. These cases are where most of the mortalities are presented from.  Without uncomplicated pneumonia, there is little chance that infection will result in death.  Lesions are more confined to the cranial (head) end of the lungs. The alveoli of the lungs show congestion and hemorrhage.



Diagnosis
Parainfluenza-3 is detection is often difficult.  Isolation is much more likely if samples are taken from animals that are either in the incubation or acute phase of infection.  Detection is usually based on an antibody detection enzyme immunoassay used to detect if there are antibodies in the animal to the virus.  Two samples, one taken acutely (acute) and the other a week later (convalescent), can be used to make a diagnosis. It may not be helpful because the antibody response is rapid and antibody levels may be reduced by the time the convalescent sample is taken.  What may be useful in diagnosis is high antibodies for parainfluenza-3 in many individuals during a respiratory disease outbreak coupled with clinical signs.


Treatment and Prevention (Vaccination)
Prevention through vaccination is the best way to prevent any large impact of parainfluenza-3.  Most vaccines are combined with other respiratory viruses, and is almost always combined with bovine herpesvirus 1 (bovine rhinotracheitis).  The vaccine is available in modified live or inactivated through intramuscular (IM) administration or temperature sensitive mutant strains for intranasal vaccination.

References
Carrière, P.D., Maxie, M.G.,  Wilkie, B.N., Savan, M.,  Valli, V.E., and Johnson, J.A. 1983. Exposure of calves to aerosols of parainfluenza-3 virus and Pasteurella haemolytica. Can J Comp Med.; 47(4): 422–432.

Gale, C. 1970. Role of Parainfluenza-3 in Cattle. Journal of Dairy Science; 53(5): 621-624

The Merck Veterinary Manual. Acessed on-line at http://www.merckvetmanual.com/mvm/index.jsp

Image obtained from: wyethah.ca

Produced by Chase Wendorff, Tim Ritson-Bennett, Adam Schierman, Troy Gowan, Justin Rosing for WCVM class project