Bovine Respiratory Respiratory Syncytial Bovine SyncytialVirus Virusin inCattle Cattle By: Jose By: JoseValles, Valles,MS MSand andLisa LisaTaylor, Taylor,MS, MS, Production Production Animal Consultation Animal Consultation Bovinerespiratory respiratory syncytial syncytial virus Bovine virus (BRSV) (BRSV)is is prevalentinincattle cattlepopulations populations worldwide. ItIt was prevalent wasfirst first recognizedasasa apathogen pathogen in in 1970 recognized 1970 in inSwitzerland, Switzerland,and andthe first case of BRSV in the United States was recorded four the first case of BRSV in the United States was recorded years later. BRSV shares similarities with human four years later. BRSV shares similarities with human respiratorysyncytial syncytial virus virus (HRSV), is no respiratory (HRSV),but butthere there is no evidence of cross-species infection. Similar respiratory evidence of cross-species infection. Similar respiratory syncytial viruses also affect sheep and goats. syncytial viruses also affect sheep and goats. BRSV a viral component the bovine BRSV is aisviral component of theofbovine respiratory respiratory disease (BRD) complex and one of the disease (BRD) complex and is one of theisprimary BRD primary BRD pathogens. This ribonucleic acid virus pathogens. This ribonucleic acid virus is categorized asisa categorizedand as abelongs pneumovirus and belongs to the pneumovirus to the Paramyxovirus family. Paramyxovirus family. The virus has a cytopathic effect, creating syncytial The virus has a cytopathic effect, creating cells in the mucosal lining of the respiratory tract. BRSV syncytial cells in the mucosal lining of the respiratory tends to affect the lower respiratory tract, and infection tract. BRSV tends to affect the lower respiratory tract, with BRSV increases susceptibility to viral and secondary and infection with BRSV increases susceptibility to viral bacterial infections. and secondary bacterial infections. The virus can be transmitted by direct contact with The virus can be transmitted by direct contact respiratory secretions of infected animals or by inhalation with respiratory secretions of infected animals or by of aerosolized respiratory secretions. inhalation of aerosolized respiratory secretions. cases ofof BRSV arearemost Severe clinical Severe clinical cases BRSV mostcommon common in in beef and dairy animals up to 6 months of age. Typically, beef and dairy animals up to 6 months of age. beef cattle between 6 weeks and 13 months old13and dairyold Typically, beef cattle between 6 weeks and months cattle 2 weeks and29weeks months old are mostold prone and between dairy cattle between and 9 months are to most infection. Experts believe that passive immunity from prone to infection. Experts believe that passive maternal antibodies and active immunity from previous immunity from maternal antibodies and active immunity exposure help decrease the severity of respiratory disease from previous exposure help decrease the severity of associated with BRSV but do not prevent infection. respiratory disease associated with BRSV but do not Reinfection prevent infection. with the virus is possible. While the first Reinfection exposure towith BRSV usually results While in acute the virus is possible. the disease, subsequent exposure is often associated with first exposure to BRSV usually results in acute disease, or exposure mild respiratory disease. Outbreaks most subclinical subsequent is often associated with subclinical often occurrespiratory during thedisease. fall andOutbreaks winter andmost are often commonly or mild occur caused by stress-inducing factors such as diet changes, during the fall and winter and are commonly caused by transportation, and weather stress-inducingovercrowding, factors such asweaning, diet changes, changes. Case fatality rates in BRSV outbreaks can be as transportation, overcrowding, weaning, and weather changes. Case fatality rates in BRSV outbreaks can be as high as 20 percent. high as 20 percent. suspected of BRSV infection must be Animals suspected of Examination BRSV infection musttake be examined Animals in a timely manner. should examined a timely manner.lung Examination should take into account in rectal temperature, score, visual clinical into account rectal temperature, lung score, visual clinical signs, movement, and feed and water consumption. signs, movement, and feed and water consumption. Evaluation should be performed without compromising should be performed without compromising theEvaluation health of the animal. the health of the animal.
signs ofofBRSV BRSV in severity Clinical Clinical signs cancan varyvary in severity and and may include cough, depression, decreased appetite, may include cough, depression, decreased appetite, decreased milkproduction, production, dehydration, difficulty decreased milk dehydration, difficulty frothy mouth, grunting, increased breathing, fever,frothy breathing, fever, mouth, grunting, increased respiration lowered head head and andextended extendedneck, neck,nasal nasal respiration rate, rate, lowered discharge, oculardischarge, discharge, open-mouth breathing, discharge, ocular open-mouth breathing, reluctance to movement, and subcutaneous emphysema reluctance to movement, and subcutaneous emphysema (Figure (Figure 1). 1).
Figure 1: Animal with BRSV
Animals typically typically begin begin expressing expressing clinical clinical signs signs Animals BRSV exposure and and may may continue 33 to to 55days daysafter after BRSV exposure continue showing clinical signs for 1 to 2 weeks thereafter. showing clinical signs for 1 to 2 weeks thereafter. Necropsy ofofsuspected BRSV mortalities is BRSV mortalities is Necropsy suspected encouraged. Because infection is commonly encouraged. BecauseBRSV BRSV infection is commonly followed by by secondary followed secondary bacterial bacterial infection, infection,gross grosslesions lesions may vary. Common visible lesions in BRSV-infected may vary. Common visible lesions in BRSV-infected animals may diffuse interstitial pneumonia; animals mayinclude include diffuse interstitial pneumonia; interstitial edema (usually in the caudal lobes),interstitial interstitial interstitial edema (usually in the caudal lobes), and sub-pleural sub-pleuralemphysema, emphysema,alveolitis, alveolitis,and andadenomatosis adenomatosis and (Figures 2, 2, 3). 3). (Figures
Figure 2: Subpleural and bullous emphysema due to BRSV 10
