Detection of Borrelia duttonii, a tick-borne relapsing fever agent in central Tanzania, within ticks by flagellin gene-based nested polymerase chain reaction.

Argasid ticks collected in the site near Mvumi Hospital, Dodoma, Tanzania, were subjected to flagellin gene-based nested polymerase chain reaction (PCR) amplification for examination of borrelial infections. Eight of 13 ticks gave a strong 350-bp signal; three had a weak signal at the same size, and the rest were negative. Sequence determination of eight of the positive samples resulted in three types of flagellin gene sequences. The first type of sequence (shown by three individuals) was identical to that of Borrelia duttonii strain Ly. The second type of sequence from PCR products from four individual ticks had only one base substitution without amino acid alteration in deduced protein sequence. The third type of sequence was different from that of any other Old World relapsing fever borreliae, and the tick was thought to be infected with an unknown Borrelia species. Ticks were also examined to determine the nucleotide sequence of the mitochondrial 16S rRNA gene. The partial sequence of approximately 470 bases was aligned for comparison with previously published sequences to identify the species. The sequences of 13 individual ticks were all identical, and the sequence similarity analysis revealed the ticks should be classified as members of the Ornithodoros porcinus species. The PCR method described in this report appears to be a reliable tool for the detection of borreliae and epidemiological study of tick-borne relapsing fever.