GENOMIC AND PHENOTYPIC DIVERSITY OF TUNISIAN THEILERIA-ANNULATA ISOLATES

This study describes polymorphism in Theileria annulata, an intracellu lar protozoan parasite of bovine leucocytes and red blood cells. Fifty -three different stocks of T. annulata, isolated from 17 sites (distri cts) in Tunisia, have been characterized by anti-parasite monoclonal. antibody (MAb) reactivity, glucose phosphate isomerase (GPI) isoenzyme electrophoresis, and Southern blotting with two genomic DNA probes. T here appears to be considerable diversity amongst T. annulata stocks f rom Tunisia, no two isolates being identical, even those from animals on the same farm. Two distinct antigenic populations were detected by MAb 7E7. They were defined by negative and positive cells in the indir ect fluorescent antibody test. The percentage of positive cells in dif ferent isolates ranged between 0 and 100%. The population variation se en by GPI analysis and DNA probes was greater; 7 different GPI phenoty pes were identified amongst the stocks studied, while DNA probes T. an nulata Tunis (TaT) 17 and 21 detected up to 5 different variants. The majority of isolates were shown to contain more than one parasite popu lation, the number of variants per isolate ranging from 1 to 4. No cor relation between particular parasite phenotypes or genotypes and their geographical site of isolation was observed. Selection of parasite po pulations in vivo and in vitro is also discussed.