New World Relapsing Fever Borrelia Found in Ornithodoros porcinus Ticks in Central Tanzania

Abstract

Tick-borne relapsing fever (TBRF) is found in Africa, Europe, western Asia, and North America (2). The disease is caused by several species of relapsing fever borreliae and is transmitted by various species of Ornithodoros and Argas ticks (15). Specific relationships often exist between Borrelia species and vector tick species, and certain Borrelia species are reported to be transmitted by a single tick species (18). Ornithodoros moubata complex ticks, such as O. moubata and Ornithodoros porcinus, are distributed in East Africa and are known to carry Borrelia duttonii, which is responsible for Old World TBRF (22). Ticks live in close proximity with humans, and the sole reservoir host for borreliae is thought to be humans. The disease is endemic in central Tanzania, where clinical and epidemiological studies have been conducted (20). TBRF causes a significant amount of morbidity and mortality in the Dodoma region, mainly in children under five and pregnant women (12). People in Dodoma Rural District live in traditional dwellings constructed of mud with earthcovered roofs, and house infestation with O. moubata complex ticks is very high (20). Residents sleep on the floor on animal skins, and it is probable that nocturnal tick bites are frequent and pass unnoticed because tick feeding takes only about 30 min.Cutler et al. (3) have successfully cultivated B. duttonii in artificial BSKII medium from pediatric patients in Mvumi Hospital (which is 40 km southeast of the Tanzanian capital Dodoma), and five clinical isolates were characterized genetically. The sequences of 16S ribosomal RNA gene (rrs) and flagellin B gene (flaB) of B. duttonii were quite similar to those of Borrelia recurrentis, the causative agent of louse-borne relapsing fever, which is transmitted by the human louse, Pediculus humanus (4, 13). We have reported that O. moubata complex ticks collected from the houses in Dodoma Rural are highly infected with spirochetes, based on flagellin gene-based nested PCR (9). While most of the borrelia in ticks were B. duttonii, we have also found a different spirochete in O. porcinus ticks. In this study, we extended our work (8,14) to elucidate the phylogenetic position of unidentified Borrelia found in O. porcinus ticks (9) and to screen spirochete infection rates in ticks collected from tick-infested houses in Mvumi village. Materials and Methods Ticks, collection sites, and tick species identification.Adult and nymphal ticks were collected from 8 houses Mvumi Hospital, PO Box 32, Mvumi, Dodoma, Tanzania Received February 20, 2004; in revised form, March 22, 2004. Accepted April 9, 2004 Abstract: Ticks were collected from 8 houses in Mvumi Mission village, near Dodoma, Tanzania. All ticks were examined for Borrelia infestation by flagellin gene-based nested polymerase chain reaction. All houses were highly infested with ticks, and all ticks collected were of the Ornithodoros porcinus species. Fifty-one out of 120 ticks were infected with spirochetes, and a flagellin gene sequence comparison showed that most ...

Typing African Relapsing Fever Spirochetes

“…crocidurae ; and c) a further group containing unique amplicons from ticks collected in Tanzania. This last group was distinct in its IGS sequence and is likely compatible with the novel Borrelia species from this region ( 3 , 4 , 20 ). Three sequence types were identified that clustered within this novel IGS sequence clade, separate from the B .…”

“…hermsii and B . turicatae , rather than Old World tickborne relapsing fever and louseborne relapsing fever isolates ( 3 , 4 , 20 ). Insufficient material remained to allow repeat analysis for either flaB or rrs genes to confirm that Borrelia species types 1–3 were indeed the same spirochete described above.…”

“…turicatae (Figure 1), thus supporting earlier reports of a new Borrelia spp. characterized by using flagellin and 16S RNA sequences ( Borrelia species AB113315 [3], Figure 2), and reported to show greater resemblance to Nearctic isolates such as B . hermsii and B .…”

“…However, this spirochete has an established reservoir in rodent populations that also serve as hosts for the Ornithodoros erraticus ticks. Recent reports have also established additional spirochetes in tick vectors ( 3 ) and in human blood samples ( 4 ); however, their clinical relevance has yet to be defined.…”

Possibilities for Relapsing Fever Reemergence

“…in Africa that strongly resemble New World relapsing fever species suggests greater globalization of these spirochetes ( 22 – 24 ). As yet, the possible clinical importance of these spirochetes, for which the name " Candidatus Borrelia mvumii" has been proposed, remains unresolved ( 16 , 22 , 23 ). Studies are particularly hampered by the current lack of cultivatable strains.…”