Influence of dexamethasone on the recrudescence of Anaplasma marginale in splenectomized calves.

Dexamethasone was administered at the dose rate of 0.2 mg/kg of body weight to 11 splenectomized Anaplasma-carrier calves (groups 1 and 3) on Monday, Wednesday, and Friday for 3 weeks. Observations were made on these calves and on 7 nontreated, comparable calves (group 2) to determine the influence of treatment on carrier infections. Dexamethasone treatment was associated in every instance with an exacerbation of the Anaplasma parasitemia and a decrease in packed red cell volume. The episode of acute anaplasmosis was of short duration, resembling the primary response, except that complement-fixation response did not increase accordingly. Serum protein electrophoresis of serums from 4 calves (group 3) undergoing the drug-induced response failed to show any significant change during the 3-week treatment period, but did show a significant increase in gamma-globulin immediately after treatment.