Comparing Diagnostic Coding and Laboratory Results

Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 7, July 2005 1151 species. However, the new spirochete is distinct from all other known Borrelia spp. with an available 16S rDNA sequence in the GenBank database. Its partial 16S rDNA sequence differed by 3.3% to 4.2% from 9 LB group species and 2.4% to 3.4% from 15 relapsing fever group species. For comparison, intragroup sequence differences were <1.9%. On this basis, as well as the finding of partial IGS sequences (GenBank accession nos. AY668955 and AY668956) that were unique among all Borrelia spp. studied to date (3,5), we propose that this is a new species of Borrelia, provisionally named Borrelia davisii in honor of Gordon E. Davis for his contributions to Borrelia research and taxonomy. While the new species was detected in 8 of 131 P. leucopus blood samples by using PCR for the IGS, the assays for this organism in the DNA extracts of 282 I. scapularis nymphs (4) from the same geographic site were uniformly negative (p = 0.0003, 2-sided Fisher exact test). This finding suggests that the new spirochete has another vector. The only other documented tick species that has been found feeding in small numbers on P. leucopus in Connecticut is Dermacentor variabilis (7). Holden et al. reported the presence of Borrelia in D. variabilis ticks in California by using PCR with genus-specific primers, but the species in these ticks was not identified by sequencing (8). Although how B. miyamotoi and B. davisii affect the health of humans and other animals remain to be determined, our finding of 3 Borrelia species with overlapping life cycles in the same host in the same area shows that the ecology of Borrelia is more complex than was imagined. The presence of species other than B. burgdorferi in a major reservoir will have to be considered in future surveys and interventions. Acknowledgments We thank Hany Mattaous and Lili Sheibani for technical assistance and Jean Tsao, Klara Hanincova, and Durland Fish for discussions and ongoing collaborative studies.