BABESIA EQUI ERYTHROCYTIC STAGE CONTINUOUSLY CULTURED IN AN ENRICHED MEDIUM

Babesia equi was continuously cultured through 90 passages in an enric hed chemically defined basal medium (HL-1) supplemented with 20% fetal bovine serum and serum replacement factors, including lipid-rich bovi ne serum albumin, bovine insulin, and human transferrin. Cryopreservat ion and subsequent recovery of B. equi were easily achieved. Inoculati on of a splenectomized and an intact horse with cultured infected eryt hrocytes resulted in parasitemias and B. equi in vitro reisolation fro m both animals. In vitro forms of the parasite resembled in vivo forms . After establishment, parasitemias of 10-15% were commonly observed.