NUCLEOTIDE-SEQUENCE HETEROGENEITY IN THE SMALL-SUBUNIT RIBOSOMAL-RNA GENE VARIABLE (V4) REGION AMONG AND WITHIN GEOGRAPHIC ISOLATES OF THEILERIA FROM CATTLE, ELK AND WHITE-TAILED DEER

The phylogenetic relationships among fourteen isolates of benign Theil eria spp. infecting cattle, elk and white-tailed deer were studied by nucleotide sequence comparisons of the variable (V4) region (200 nucle otides) of the small subunit ribosomal RNA gene. Included were six Kor ean bovine, one Japanese bovine, three North American bovine, and four North American cervine isolates. The SSU rRNA gene from each isolate was amplified, cloned, and the V4 region fragment sequenced. Seven dif ferent nucleotide sequence patterns were obtained and classified. Type A was identical to T. buffeli SSU rRNA gene sequence (GenBank Accessi on No. Z15106) and was found in Korean, Japanese, and North American b ovine isolates. Type B was found in bovine isolates from Korea, Japan and North America, Type C was found only in the Korean bovine isolate from Chungnam. Type D was found in a Korean and in a North American bo vine isolate. Type E was found in a bovine isolate from Cheju Island o f Korea and a North American cervine (elk) isolate. Types F and G were found only in North American cervine isolates (both white-tailed deer and elk) and appear to represent a species separate from the bovine i solates. The presence of several sequence types observed in most of th e bovine Theileria isolates may indicate mixed species (or subspecies) populations and/or multiple genotypes within a single species. (C) 19 98 Elsevier Science B.V.