SUSCEPTIBILITY TO ACTINOBACILLUS-PLEUROPNEUMONIAE INFECTION IN PIGS FROM AN ENDEMICALLY INFECTED HERD IS RELATED TO THE PRESENCE OF TOXIN-NEUTRALIZING ANTIBODIES

Our objective was to identify pigs of an endemically infected herd tha t were susceptible to pleuropneumonia due to Actinobacillus pleuropneu moniae. The presence of toxin-neutralizing antibodies was studied in s erum of 36 pigs from birth until 24 weeks of age. Titers gradually dec lined during the first twelve weeks of life and increased thereafter. Sera from one-hundred 3-weeks-old piglets and one-hundred 20-weeks-old pigs were sampled and neutralization titers were determined. From eac h group we selected 5 pigs with the lowest titers and 5 pigs with the highest titers. These selected pigs (n = 20) were inoculated endobronc hially with A. pleuropneumoniae. Pigs that survived from infection wer e necropsied after 48 h. Pigs with low neutralization titers had sever e lung lesions, whereas pigs with high titers had no or minor lung les ions. These differences were significant (P < 0.05). From this field s tudy we conclude that susceptibility to Actinobacillus pleuropneumonia e can be predicted by absence of toxin-neutralizing antibodies.