Continuation of experiments for inoculation against equine piroplasmosis (biliary fever)

Abstract

Conclusions: (1) The inoculation of animals with horse foal blood of 1st, 2nd and 3rd generations caused a mortality of 7 out of 186, or 4 per cent. (2) The inoculation of animals with horse foal blood of 4th, 5th, 6th, 7th and 8th generations caused a mortality of 1 in 16, or 6 per cent. (3) The inoculation of animals with donkey foal blood of 2nd to 6th generation caused no mortality amongst 25 animals. (4) The reactions caused by injection of horse foal blood were more severe than those given by injection of donkey foal blood. (5) No cases of relapses after discharge have occurred, proving that the immunity given by the injection of donkey foal blood is as good as that afforded by horse foal blood. (6) For further immunisation purposes, therefore, I recommend the passing of blood originating from a natural infection of a donkey with piroplasma equi through donkey foals, and to use 1 c.c. blood of that obtained from the 4th generation and upwards, bearing in mind the precautionary measures mentioned above. (7) Finally, all foals kept for tapping purposes, and used in connection with the inoculation, must be kept free from ticks. This precaution has been carried out at this Laboratory with all foals used in the experiments, and it stands to reason that a reinfection bv means of ticks would increase the virulency of the blood which is to be used as vaccine.