Serological and biochemical factors in bovine ephemeral fever.

Clinical signs of ephemeral fever, which were observed in individual cattle during two successive epidemics in 1973 and 1976, were related to biochemical, cellular and serological changes in the blood. The rise in peripheral blood neutrophil counts in samples collected from 12 sentinel cattle on a daily basis before, during and after natural disease in the two epidemics to mean peaks of 9.6-12.5 X 10(9) per litre, and fall in counts of lymphocytes to a trough of 5-7 X 10(9) per litre was found to occur on the same day as the fever peak. A fall in serum calcium levels from a normal mean of 2.55 mmol/l to 2.0 mmol/l occurred on the day clinical signs were most pronounced. Serum magnesium levels were affected to only a minor degree. Plasma fibrinogen rose from a normal mean of 5.0 milligrams to a peak of 18 milligrams on the second day of disease and fell towards normal in the week after recovery. Neutralizing antibodies to bovine ephemeral fever virus were detected up to 63 days prior to clinical disease, and the rise of antibody after recovery was secondary in pattern. Serological evidence of a prior infection with an antigenically related virus, Kimberley virus, was found in these animals. In more severe clinical cases of ephemeral fever serum calcium levels were as low as 1.95 mmol/l. Treatment of cattle showing clinical signs of the disease with phenylbutazone and calcium borogluconate was favourable.