Each organism's titre was declared as positive or negative based on predetetermined cutpoints and seroconversion means that the titre changed by doubling (or halving) or more. The latter usually is taken to indicate recent infection. Titre on arrival indicates prior exposure at an unknown date.
Initial experiments depended on an interaction between viruses and P haem to repoduce the disease with consistency. Thus we would want to watch for evidence of this in our analyses.
Pasteurella haemolytica cytotoxin which is produced by a subset of P. haem organisms (now called Mannheimia haemolytica); P haem agglutinins which are surface antigens possesed by all P haem; infectious bovine rhinotracheitis virus which was the flag ship virus studied for its role in BRD; bovine respiratory syncytial virus, parainfluenza type 3 virus, bovine virus diarrhea virus largely studied for its ability to immunosuppress cattle, and Haemophilus somnus a bacterial agent that can cause BRD.
This data set was obtained by sampling a number of calves at arrival at the feedlot and then again at day 28. Each calf was observed for the occurrence of bovine respiratory disease (BRD) and was also weighed at arrival and again at day 28. The blood samples were analyzed for titre against a number of putative respiratory pathogns. These include