Failure of immunisation against sporidesmin or a structurally related compound to protect ewes against facial eczema.

Sixty ewes, divided randomly into four groups of 15, were immunised subcutaneously against sporidesmin (sdm) -bovine thyroglobulin (BTG) or 2-amino-5-chloro-3,4-dimethoxy benzyl alcohol (ACDMBA) coupled to heat killed staphylococci or to bovine gamma globulin. Fifteen ewes served as untreated controls. Approximately 10 weeks after inoculation ewes were dosed orally with sdm at a rate of 0.1 mg/kg body weight/day for three consecutive days. Sdm antibody binding values.in plasma collected before dosing were higher in ewes immunised with sdm-BTG than ewes given the ACDMBA-complexes. Levels in the 15 untreated ewes were all very low. However, despite the presence of antibodies, the immunised ewes were not protected against sdm challenge; and cholesterol and bilirubin levels in serum and liver and urinary bladder damage scores, at slaughter, were all significantly higher (P<0.05) in the immunised compared to the control ewes six weeks after dosing. It is concluded from these results that subcutaneous immunisation against sdm or the structurally related substance used did not protect sheep against sdm dosing.

Mycotoxic tremorgens of Claviceps paspali and Penicillium cyclopium: a comparative study of effects on sheep and cattle in relation to natural staggers syndromes.

Claviceps paspali sclerotia were dosed orally at various levels to sheep and cattle and the neurotoxic effects are described. Evidence is presented which indicates that the tremors are produced by a neutral tremorgen fraction. The ergot alkaloids, principally D-lysergic acid alpha-hydroxyethylamide and its isolysergic acid isomer, are not involved. The mixture of C paspali tremorgens has not been separated and characterised but its components are chemically related to other known tremorgens, such as penitrem A, produced by saprophytic moulds, notably Penicillium cyclopium. P cyclopium mycelium and C paspali sclerotia were dosed to produce comparable effects in sheep and in cattle. Similarly, effects of penitrem A and tremorgen concentrate of C paspali were compared after intravenous dosage to sheep. Observed enurotoxic effects of both moulds were identical in most respects. A low level of tremorgenic activity was detected at the honeydew stage of C paspali. These findings are discussed in relation to staggers syndromes occurring in grazing livestock.