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Summary

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 Phi 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 Phi. 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 Phi. These goats were studied for 35 days, then challenge exposed transthoracically by injection of Phi in saline solution (1.2 × 10⁷ 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 Phi 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 Phi antibody response, which was attributed to the bronchial method of depositing the Phi. The corresponding response of the control group remained negative. The Phi agar beads (1 × 10⁶ 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. Also, live Phi were isolated on day 32 during necropsy of respiratory tracts of 3 principals. At necropsy, no Phi isolates were found in the controls. Bacteriolytic activity was not induced against Phi in either control or principal groups in this trial.

In trial 2, the indirect hemagglutination Phi antibody response of the controls remained unchanged throughout the study, but antibody titers of the principals increased to a geometric mean of 1:250 seven days after lung injection (1 × 10⁵ cfu in 0.5 ml). Serum bacteriolytic titers on day 0 indicated that both principals and controls could be subgrouped to high or low subgroups on the basis of their bacteriolytic activity. The bacteriolytic activities of the controls remained unchanged during the experiment, and neither control subgroup was protected from Phi challenge exposure. Bacteriolytic activities of the high and low principal subgroups responded differently to Phi agar bead lung injection, but both principal subgroups were protected from lung challenge exposure. The low principal subgroup generated high titers of indirect hemagglutination Phi antibody, whereas, the high principal subgroup generated lower antibody titers. Total complement, serum bacteriolytic, and blood bactericidal profiles were similar in the principal group with high bacteriolytic activity. The immune factors that protected 2 principal subgroups did not appear to be associated with Phi serum bacteriolysis.

SUMMARY

A method of inducing Pasteurella haemolytica serotype 1 (Ph1) lung infection in goats, using low numbers of bacteria and without impairing host immunity, was developed. Two trials were conducted. Results of trial 1, using 10 principals (Ph1 agar beads) and 6 controls (agar beads alone), indicated that Ph1 organisms imbedded in agar beads could survive host lung defenses for 32 days. Results of trial 2 indicated that lung immunity in the inoculated goats (principals) was high and they were more protected than controls against a transthoracic challenge of Ph1 (1.18 × 10⁷ colony-forming units) injected into a lung of each goat on posttreatment day 35. When comparing challenge-exposed principals with controls, the controls developed rectal temperatures above normal for a longer time, duration of anorexia was longer, and signs of depression were seen. The controls developed large areas of consolidated lung tissue, more Ph1 isolates were recovered from nasal turbinates and lung tissue, and higher Ph1 concentrations were found in the lungs. The serum Ph1 indirect hemagglutination antibody titers in the principals of both trials increased, compared with titers in controls. Principal goats in ferial 2 had higher Ph1 indirect hemagglutination antibody titers after injection of Phi-impregnated agar beads and less severe lung lesions after challenge exposure than did controls. The small pneumonic consolidated lesions in the principals, compared with extensive lesions in controls after Ph1 challenge exposure, indicated a high degree of immunity after exposure to Ph1 organisms imbedded in agar beads.

SUMMARY

Classical hemolytic complement (C) of calves was analyzed during a protocol designed to imitate the usual market handling of feeder calves from the southeastern United States. Serum C concentrations of the calves (n = 100 × 4 years) were evaluated on their farm of origin, on arrival at an auction market, on arrival at a feedyard, and during their first 4 weeks in the feedyard. Complement concentrations (measured in ch ₅₀ units) were typically lowest at the farm of origin and highest when the calves entered the auction market 28 to 133 days later. Serum C concentrations decreased after the calves encountered the severe stresses of being in the auction market for 7 days, 24-hour truck transport (1,932 km) to the feedyard, and the first 7 days in the feedyard. The C concentrations recovered after 21 to 28 days in the feedyard. Steers had significantly (P ≤ 0.05) lower C concentrations than did heifers in 3 of 4 years at the farm of origin, and in 2 of 4 years at the auction market. Morbid calves had significantly (P ≤ 0.05) lower C values than did healthy calves on day 7 in the feedyard in 3 of 4 years. There were significant differences in C concentrations of calves from different farms of origin in each of the 4 years. There was no significant difference in C concentrations of calves that were vaccinated vs those not vaccinated with Pasteurella haemolytica.