Studies on the pathogenesis of bovine ephemeral fever in sentinel cattle. II. Haematological and biochemical data.

Twenty-two non-lactating dairy cattle from a sentinel herd previously described (St. George, 1985) were monitored daily during an outbreak of ephemeral fever. Nine developed clinical ephemeral fever between 25 December 1981 and 30 January 1982. There were no subclinical infections with bovine ephemeral fever virus in the group. There were, however, subclinical infections with CSIRO Village, Akabane, Aino, Tinaroo and Kimberley viruses as described by St. George et al. (1984). Six of the nine affected cattle showed a neutrophilia with a concurrent lymphopaenia on the day of pyrexia; however, the differential white cell profile had begun to change up to 24 h prior to leucocytosis. Serum carboxypeptidase values fell by 24 h following the febrile response. Plasma fibrinogen rose rapidly in all six cows. The peak concentration (15.6 +/- 2.70 g l-1) occurred 3 days after pyrexia with the highest individual increase being from 6.05 to 19.6 g l-1. Plasma fibrinogen levels remained elevated for at least 7 days. Serum calcium fell significantly during Day 1 of the disease, the mean decline being 0.22 +/- 0.08 mmol l-1. The greatest individual fall was from 2.33 to 1.92 mmol l-1. None of the affected cattle showed any compensatory change in serum magnesium. There was no change in the normal values of creatinine, urea, gamma-GT, AST and alkaline phosphatase. Bovine ephemeral fever virus was isolated from only four of the six cases, whereas specific antibody was detected in all cattle 3-4 days after recovery.