In vitro cultivation of Trypanoplasma borreli (Protozoa : Kinetoplastida),a parasite from the blood of common carp Cyprinus carpio

An in vitro culture system was developed for Trypanoplasma borreli, a patho genic flagellate from the blood of European cyprinids. Trypanoplasms multip lied rapidly in a mixture of Hanks' balanced salt solution (HBSS, 45 %), L1 5 (22.5 %), Earle's minimum essential medium (MEM, 22.5 %) and 10 % distill ed water, which was supplemented with 5 to 10% heat-inactivated pooled carp serum. In medium supplemented with fetal bovine serum, multiplication of T . borreli seemed to be inhibited, Cultures initiated with less than 100 000 T. borreli per mi culture medium did not survive, and a substantial multip lication of trypanoplasms was found at inocula beginning with 630 000 flage llates ml(-1). Trypanoplasms multiplied at 15, 20 and 25 degrees C. In cult ures incubated at 4 degrees C the trypanoplasms remained viable but the num ber of flagellates did not increase. Trypanoplasms from in vitro cultures r etained their infectivity for carp for at least 90 d (5 passages). The tryp anoplasms survived in culture over a period of up to 5 mo (10 passages). Th e established culture system allows the propagation of high numbers of fish -infective trypanoplasms, which are required to study parasite-host relatio nships in carp.