Comparison of four immune variables and pulmonary lesions of goats with intrapulmonary exposure and subsequent intrathoracic challenge exposure with Pasteurella haemolytica.

A comparison of immune variables following lung sensitization with live Pasteurella haemolytica serotype 1 (Ph1)-impregnated agar beads was done in 2 separate trials. The Ph1 immune variables studied were blood bactericidal activity, serum bacteriolysis, total classical complement, and indirect hemagglutination antibody. Each trial had 16 male weanling goats: 6 controls and 10 principals. In trial 1, each goat was surgically catheterized through the trachea, then the material was deposited in a bronchus. The controls received only agar beads and the principals received agar beads impregnated with live Ph1. These goats were studied for 32 days, euthanatized, and necropsied. In trial 2, the controls were each transthoracically injected with agar beads into the left lung and the principals were similarly injected with agar beads impregnated with live Ph1. These goats were studied for 35 days, then challenge exposed transthoracically by injection of Ph1 in saline solution (1.2 x 10(7) CFU/ml) into the right lung. Four days later, they were euthanatized and necropsied. The volume of lung consolidated tissue was an excellent measure of Ph1 immunity. Principal goats generated solid protective immunity to subsequent challenge exposure because minimal or no lung consolidation was observed, whereas large volumes of lung consolidation were seen in the controls. The principal goats in trial 1 gave a weak serum indirect hemagglutination Ph1 antibody response, which was attributed to the bronchial method of depositing the Ph1. The corresponding response of the control group remained negative. The Ph1 agar beads (1 x 10(6) CFU in 0.5 ml) protected the bacteria from immediate phagocytosis and lysis as indicated by the induced pneumonic deaths of 2 principals 5 days later.(ABSTRACT TRUNCATED AT 250 WORDS)