Studies on the Occurrence and Significance of Bovine Respiratory Syncytial Virus in Saskatchewan M. Moteone, L. A. Babiuk and B. Schiefer* ABSTRACT
Seventy-six percent of 49 blood samples from Saskatchewan cattle had serum antibodies against bovine respiratory syncytial virus. Experimental infection of one week and seven month old calves with bovine respiratory syncytial virus (Iowa strain) caused transient fever, mucopurulent nasal discharge and coughing but no macroscopic or microscopic lesions attributable to bovine respiratory syncytial virus.
RISUMA La recherche d'anticorps a l'endroit du virus syncytial respiratoire bovin, dans 49 echantillons de serum de bovins de la Saskatchewan, a revele que 76% de ces echantillons en contenaient. L'infection experimentale de veaux ages d'une semaine et de sept mois, avec la souche Iowa de ce virus, provoqua une hyperthermie transitoire, un ecoulement nasal muco-purulent et de la toux, mais aucune lesion macroscopique ou microscopique.
*Departments of Veterinary Pathology and Veterinary Microbiology, Western Coliege of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan W7N OWO. Submitted July 4, 1977.
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A virus designated bovine respiratory syncytial virus (BRSV) has been isolated from the respiratory tract of cattle in Switzerland, Japan, Belgium, England and the U.S.A. (5, 8, 9, 10, 11). The virus is antigenically closely related to, but distinct from a human respiratory syncytial virus associated with allergic reactions in the lung of infants and children (4). In order to determine what role, if any, BRSV might play in respiratory disease syndromes in Western Canada, a limited serological survey and two experiments, one with newborn calves, the other with seven month old calves was carried out. Bovine respiratory syncytial virus (Iowa strain) was obtained from Dr. M. H. Smith, Iowa State University, Ames, Iowa. Virus stocks were prepared by infecting confluent 100 mm Petri plate cultures of Georgia bovine kidney cells at a multiplicity of infection of 0.5. Following a one hour adsorption period the unadsorbed virus was removed and replaced with Eagle's minimal essential medium (MEM) and 5% fetal bovine serum (FBS). When the cells showed extensive cytopathic degeneration, four to five days postinfection, they were removed with a rubber policeman, subjected to one freeze-thaw cycle, centrifuged to remove cellular debris and the cell free virus was stored frozen at -70°C until required. This cell free virus stock usually gave a titre of 105 plaque forming units/ml (PFU) when assayed by the microtitre plate method.
Can. J. comp. Med.
Five one week old and six seven month old calves purchased locally and found to have no detectable neutralizing antibodies against BRSV were used for the infection studies. Calves were infected intranasally with 2 x 10' plaque forming units of BRSV by aerosolizing 2 ml of virus directly into the nasal passage with the aid of a DeVilbis No. 40 nebulizer.1 The calves received a thorough clinical examination including temperature, respiration rate, assessment of lung sounds as well as observation of the external nares once daily and were checked visually twice daily for any outward signs of illness. Blood samples were taken daily in 2 ml EDTA test tubes' for total and differential cell counts. Nasal swabs3 were taken daily from each calf for virus isolation. One week old calves were each killed at three day intervals, beginning with the day of infection. Slight to harsh lung sounds, coughing, ocular discharge, mucopurulent nasal discharge and slight elevation of temperature (103-103.5°F vs 102-102.50F preinoculation) were noticed in four of the one week old calves and four of the seven month old calves at days 2, 3, and 4. No significant changes in the haematocrit, white cell count, differential leukocyte count, plasma fibrinogen and total protein concentration were observed. The virus was reisolated from the nasal cavity of three one week old and four seven month old calves on five different days (0-8) of the observation period. No macroscopic or microscopic (histological) changes which could be associated with BRSV infection were seen in the lungs. Blood samples from 49 animals from herds in the surrounding area of Saskatoon were obtained for serum neutralization tests. The serum was heat inactivated at 56°C for 30 minutes and stored frozen. To measure neutralizing ability 100 PFU of BRSV were incubated for one hour at 370C with twofold dilutions of sera. Following the preincubation period the virus and sera were added in quadruplicate to microtitre plates, the virus allowed to adsorb for one hour, removed and replaced with MEM plus 5% FBS. Cultures were incubated for six days in a humidified CO2 IDeVilbis Co., Somerset, Pennsylvania. 2Kimble-Terumo Inc., Ellcton, Maryland. 3Kimble-Terumo Inc., Elkston, Maryland.
Volume 42 - April, 1978
TABLE I. Results of Serum Neutralization Tests of 49 Samples from Cattle in the Saskatoon Area Titre
Seventy-six percent of 49 blood samples from Saskatchewan cattle had serum antibodies against bovine respiratory syncytial virus. Experimental infection of one week and seven month old calves with bovine respiratory syncytial virus (Iowa strain) caused transient fever, mucopurulent nasal discharge and coughing but no macroscopic or microscopic lesions attributable to bovine respiratory syncytial virus.
RISUMA La recherche d'anticorps a l'endroit du virus syncytial respiratoire bovin, dans 49 echantillons de serum de bovins de la Saskatchewan, a revele que 76% de ces echantillons en contenaient. L'infection experimentale de veaux ages d'une semaine et de sept mois, avec la souche Iowa de ce virus, provoqua une hyperthermie transitoire, un ecoulement nasal muco-purulent et de la toux, mais aucune lesion macroscopique ou microscopique.
*Departments of Veterinary Pathology and Veterinary Microbiology, Western Coliege of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan W7N OWO. Submitted July 4, 1977.
246
A virus designated bovine respiratory syncytial virus (BRSV) has been isolated from the respiratory tract of cattle in Switzerland, Japan, Belgium, England and the U.S.A. (5, 8, 9, 10, 11). The virus is antigenically closely related to, but distinct from a human respiratory syncytial virus associated with allergic reactions in the lung of infants and children (4). In order to determine what role, if any, BRSV might play in respiratory disease syndromes in Western Canada, a limited serological survey and two experiments, one with newborn calves, the other with seven month old calves was carried out. Bovine respiratory syncytial virus (Iowa strain) was obtained from Dr. M. H. Smith, Iowa State University, Ames, Iowa. Virus stocks were prepared by infecting confluent 100 mm Petri plate cultures of Georgia bovine kidney cells at a multiplicity of infection of 0.5. Following a one hour adsorption period the unadsorbed virus was removed and replaced with Eagle's minimal essential medium (MEM) and 5% fetal bovine serum (FBS). When the cells showed extensive cytopathic degeneration, four to five days postinfection, they were removed with a rubber policeman, subjected to one freeze-thaw cycle, centrifuged to remove cellular debris and the cell free virus was stored frozen at -70°C until required. This cell free virus stock usually gave a titre of 105 plaque forming units/ml (PFU) when assayed by the microtitre plate method.
Can. J. comp. Med.
Five one week old and six seven month old calves purchased locally and found to have no detectable neutralizing antibodies against BRSV were used for the infection studies. Calves were infected intranasally with 2 x 10' plaque forming units of BRSV by aerosolizing 2 ml of virus directly into the nasal passage with the aid of a DeVilbis No. 40 nebulizer.1 The calves received a thorough clinical examination including temperature, respiration rate, assessment of lung sounds as well as observation of the external nares once daily and were checked visually twice daily for any outward signs of illness. Blood samples were taken daily in 2 ml EDTA test tubes' for total and differential cell counts. Nasal swabs3 were taken daily from each calf for virus isolation. One week old calves were each killed at three day intervals, beginning with the day of infection. Slight to harsh lung sounds, coughing, ocular discharge, mucopurulent nasal discharge and slight elevation of temperature (103-103.5°F vs 102-102.50F preinoculation) were noticed in four of the one week old calves and four of the seven month old calves at days 2, 3, and 4. No significant changes in the haematocrit, white cell count, differential leukocyte count, plasma fibrinogen and total protein concentration were observed. The virus was reisolated from the nasal cavity of three one week old and four seven month old calves on five different days (0-8) of the observation period. No macroscopic or microscopic (histological) changes which could be associated with BRSV infection were seen in the lungs. Blood samples from 49 animals from herds in the surrounding area of Saskatoon were obtained for serum neutralization tests. The serum was heat inactivated at 56°C for 30 minutes and stored frozen. To measure neutralizing ability 100 PFU of BRSV were incubated for one hour at 370C with twofold dilutions of sera. Following the preincubation period the virus and sera were added in quadruplicate to microtitre plates, the virus allowed to adsorb for one hour, removed and replaced with MEM plus 5% FBS. Cultures were incubated for six days in a humidified CO2 IDeVilbis Co., Somerset, Pennsylvania. 2Kimble-Terumo Inc., Ellcton, Maryland. 3Kimble-Terumo Inc., Elkston, Maryland.
Volume 42 - April, 1978
TABLE I. Results of Serum Neutralization Tests of 49 Samples from Cattle in the Saskatoon Area Titre
