THE POSSIBLE ROLE OF STRESS IN THE INDUCTION OF PNEUMONIC PASTEURELLOSIS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 48  (3) , 268-274
Abstract
Five groups of range bred calves (4 calves/group) were used to investigate the effect of stress on susceptibility to aerosol exposures with bovine herpesvirus-1 or Pasteurella haemolytica. Twelve calves were weaned, transported, processed at a commercial feedlot and transported to isolation facilities 3 days later. An aerosol challenge of either 1010 colony forming units of P. haemolytica or 107.5 plaque forming units of bovine herpesvirus-1 virus was given to 2 groups of calves, and the 3rd group was not challenged. The 4th group was transported directly to the isolation facilities after weaning, and aerosol challenged with P. haemolytica. The 5th group remained at the farm after weaning, and was not challenged. All transported animals had elevated plasma cortisol levels, which remained above normal for at least 3 days postchallenge. The blastogenic response of all calves was depressed after leaving the farm, and it remained depressed throughout the experiment. The suppression correlated well with elevated serum cortisol levels. Calves processed through the feedlot encountered bovine herpesvirus-1, because 8 of 12 animals seroconverted to this antigen. Most calves seroconverted to P. haemolytica whether they were experimentally challenged or not. Where the unchallenged calves encountered P. haemolytica is unknown. Calves challenged with bovine herpesvirus-1, but not with P. haemolytica, had significant clinical signs of pneumonia, and 2 animals died due to bovine herpesvirus-1 infection. Transportation and handling under the present circumstances was not sufficient to make calves susceptible to P. haemolytica, but they did make calves more susceptible to bovine herpesvirus-1 virus.