Quantitative Character of Coccidian Infection in Recipients of Blood from Immunized Animals. ∗

Abstract

The writers have shown 1 that rats may be immunized to the coccidium Eimeria miyairii by feeding each day for 5 days or less standard doses of sporulated oocysts. Other workers have demonstrated the development of a specific immunity in coccidiosis of certain other hosts. The nature of the immunity, however, still remains problematic. In the present experiment injections of blood from hyperimmunized animals were employed in the attempt to reduce the number of oocysts eliminated by the recipients to below the normal.

Nineteen Wistar A rats and 9 rats from a random strain were each given in all from 6 to 9 cc. of citrated or defibrinated blood (not including∗ the citrate solution), some intravenously, some in-traperitoneally. The blood injections for each rat were made on either 2 or 3 occasions, and in most cases were planned so that one injection would come from 1 to 9 days previous to the date of the first infective dose, and the others on the day of the first infective dose and several days later. Each rat was infected with 1500 oocysts daily for a period of 5 days, and all the oocysts passed during the period of elimination were conserved and counted by a dilution method. For each recipient of immune blood a litter mate of about the same weight was kept as a control. The controls received the same immunizing doses of parasites and other treatment as the rats receiving blood, except that they were not injected.

The mean number of oocysts eliminated by the Wistar A series receiving immune blood was 176.2± 14.73 × 10⁶ oocysts, while the controls eliminated 161.5 ± 8.063 × 10⁶ oocysts. The ratio of the difference of the means to the probable error of the difference is 0.8, an insignificant number.