Ethiopian strains of Trypanosoma brucei subspecies.

SINCE 1967 we have isolated 6 strains of Trypanosoma (Trypanozoon) brucei subspecies from various hosts in Illubabor Province, Ethiopia, where human trypanosomiasis was first recognised in 1967 and where it became epidemic in 1968-1970 (McConnell Hutchinson & Baker, 1970; Hutchinson, 1971). Some but not all of these isolations have been reported previously; all of those from mammals were made from circulating blood. This note collates information concerning these strains which are maintained as frozen stabilates at the Molten0 Institute, Cambridge. All the strains produced high, though fluctuating, parasitaemias in laboratory rats and mice, in which they were pleomorphic and resistant to tryparsamide at a maximum single dose of 160 mg/kg body wt. (McConnell & Baker, 1971); they were therefore identified as T. bvucei rhodesiense if isolated from man, and as that subspecies or T. b. brucei if isolated from non-human hosts. Further identification of the latter isolates was made on the basis of their response to the Blood Incubation Infectivity Test (B.I.I.T.) of Rickman & Robson (1970) and, for one strain, inoculation to a human volunteer by the method of Onyango, van Hoeve & de Raadt (1966); we thank Dr. Onyango for doing this (see Table 1). The buoyant density in caesium chloride of deoxyribonucleic acid (DNA) isolated from these strains was determined as described by Newton & Burnett (1972); we are grateful to Mrs. L. Hislop and Mr. J. Boulter for these determinations. Table I shows that all the buoyant densities were closely similar to those reported for T. 6. brucei and T. b. rhodesiense. All our strains possessed satellite component “B”, apparently characteristic of the subgenus Trypanozoon, but lacked satellite “C” which has been recorded from T. b. pmbiense (Newton & Burnett, 1972). DNA was isolated from two clones of strain Gambela 5, one derived from a stabilate prepared before the strain had been subjected to the B.I.I.T. (“pre-B.I.I.T.” of Baker & McConnell, 1973) and the other from the line which infected rats after the B.I.I.T. (“postB.I.I.T.“). There was no significant difference between the buoyant densities of these two preparations. Possible reasons for the failure of this strain to infect a human volunteer, in spite of its positive reaction to the B.I.I.T., have already been discussed (Baker & McConnell, 1973); although it is probably T. b. brucei, its exact identification cannot be regarded as certain and strain Gambela 5 should therefore be treated as possibly infective to man and handled with due caution. Of the other strains, Gambela 1, 2 and 3 are, by virtue of their isolation from human hosts, considered to be T. 6. rhodesiense; Gambela 4 and 6 are identified as T. b. brucei.