Trace Element and Macro Electrolyte Behaviour during Inflammatory Diseases in Cattle and Sheep

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Ephemeral fever is a disease of cattle caused by bovine ephemeral fever (BEF) virus, a rhabdovirus. It occurs in a wide band of tropical and sub-tropical Asia, Africa and Australia and is spread by insect vectors (St. George et al., 1984). In susceptible cattle, BEF causes high morbidity and variable mortality. Effects are worst in prime, fat cattle and high producing cows. St. George et al. (1986) have argued that the viraemia should be considered as an inflammatory/toxic response as shown by the marked neutrophilia and elevated fibrinogen levels. We (Murphy et al., 1986) have provided physiological support for this hypothesis by measuring changes in circulating levels of Fe, Zn and Cu during the viraemia. As well, we have confirmed an earlier report (St. George et al., 1984) that in affected animals (a) uncompensated hypocalcaemia (plasma Ca < 2.0 mM L−1) is commonplace; and (b) the cardinal signs (tachycardia, tachypnea, ruminal stasis and sternal recumbency) are consistent with the gross disturbance of calcium homeostasis. More importantly, phenylbutazone treatment of BEF affected cattle has shown that the trace element changes and hypocalcaemia are independent of fever per se (Murphy et al., 1986). Overall, this physiological expression of BEF is consistent with an Interleukin-1 initiated sequence.