Effect of humoral antibodies on the course of Theileria parva infection (East Coast fever) of cattle.

A study was made of the effects of serum and gamma-globulins from vaccinated cattle (donor cattle) given to cattle (principals) exposed to Theileria parva infection (East Coast fever (ECF)). The principals were treated with normal serum, with serum containing high antibody titer against T parva (as evaluated by the indirect fluorescent antibody (IFA) technique), or with globulins prepared from normal and from immune serums. For exposure, the principals were inoculated with standardized suspension of the tick Rhipicephalus appendiculatus containing T parva infective particles. Comparison was made between treatments with normal serum and globulin and treatments with immune serum and globulin, using observations of time lapse after exposure to febrile response (39.5 C), to appearance of T parva macroschizonts, and to death. In addition, hematologic changes were determined. Neither the establishment of infection nor the clinical and hematologic changes in the principals were influenced by their treatment with immune serum or concentrated globulins; all died of ECF. Humoral antibodies did not protect cattle against fatal ECF, nor was enhancement of T parva infection observed.