ABSTRACT
The presence of Borrelia theileri in Argentina is confirmed after recording the spirochete from a bovine in northern Argentina. The analysis of sequences of the flagellin gene (fla) and length of Borrelia spp. specimens on thick blood films shows that the local isolate clusters within a well-supported clade with B. theileri isolates from different geographical origins, confirming the presence of B. theileri in Argentina. The mean length of 30 specimens of B. theileri was 12.89⯵m (standard deviation 2.88⯵m, range 9.35-20.16⯵m). The only known vector of Borrelia theileri in northern Argentina is the cattle tick Rhipicephalus microplus, therefore Borrelia infection should be regarded as a potential complication of other cattle tick-borne diseases such as babesiosis, especially on cattle introduced from areas free of R. microplus. The possibility of serologic cross-reaction with B. theileri must not be minimized in studies of other spirochaetes in the R. microplus infested region of Argentina.
