A relapsing fever group spirochete transmitted by Ixodes scapularis ticks

Area of Science:

• * Microbiology
• * Vector-borne diseases
• * Genomics

Background:

• * Ixodes scapularis ticks are known vectors for Lyme disease spirochetes.
• * A previously unidentified Borrelia species has been detected in North American I. scapularis.
• * This novel spirochete is phylogenetically distinct from Lyme disease-associated Borrelia burgdorferi.

Purpose of the Study:

• * To identify and characterize a novel Borrelia species found in North American ticks.
• * To determine the prevalence and transmission dynamics of this new spirochete.
• * To assess its potential public health implications.

Main Methods:

• * Polymerase chain reaction (PCR) and DNA sequencing (16S rDNA, flagellin gene) for species identification.
• * Phylogenetic analysis to determine evolutionary relationships.
• * Surveys of field-collected ticks and experimental transmission studies (transovarial, transstadial).
• * Vertebrate infection models using Peromyscus leucopus mice.

Main Results:

• * A novel Borrelia species, closely related to Borrelia miyamotoi, was identified in I. scapularis ticks.
• * The spirochete was detected in 1.9–2.5% of nymphs from four northeastern states.
• * Evidence of transovarial and transstadial transmission was confirmed.
• * Vertebrate infection was demonstrated in mice.

Conclusions:

• * A new Borrelia species, distinct from B. burgdorferi, circulates in North American I. scapularis populations.
• * This spirochete is capable of efficient transmission through tick generations and to vertebrate hosts.
• * Further research is required to ascertain the public health significance of this novel zoonotic agent.