The effects of dexamethasone on the response of bronchus-associated lymphoid tissue to intranasal administration of formalin-killed Pasteurella haemolytica A2 in goats

A trial was conducted to observe the immediate and chronic effects in goats of dexamethasone administration on the bronchus-associated lymphoid tissue (BALT) response to intranasal administration of formalin-killed Pasteurell a haemolytica A2. Twenty-four goats were divided into four groups. Those in group 1 were injected intramuscularly with 1 mg/kg dexamethasone on three consecutive days, followed by intranasal exposure to formalin-killed P. hae molytica A2 one day after the last dexamethasone treatment. The goats in gr oup 2 were similarly injected with dexamethasone followed by intranasal exp osure to formalin-killed P. haemolytica A2 21 days after the last dexametha sone treatment. The animals in group 3 were exposed intranasally to formali n-killed P. haemolytica A2 without prior dexamethasone treatment. The anima ls in group 4 were untreated controls. The intranasal exposures to formalin -killed P. haemolytica A2 were repeated 2 weeks later. Intranasal exposure to formalin-killed P. haemolytica 1 day after dexamethasone treatment furth er reduced the number and size of BALT compared to the untreated control. S ignificantly (p < 0.01) more reduction of BALT occurred in goats exposed to formalin-killed P. haemolytica A2 21 days after dexamethasone treatment. O n the other hand, intranasal exposure of goats without prior dexamethasone treatment stimulated the BALT compared to the untreated controls.