Genetic diversity in Ixodes scapularis (Acari: Ixodidae) from six established populations in Canada.

Although Ixodes scapularis is the most important vector of Borrelia burgdorferi sensu stricto, the causative agent of Lyme disease in North America, little is known of the genetic diversity in this tick species within the recently established populations in Canada. In the present study, 153 I. scapularis adults collected from southern Canada were compared genetically using single-strand conformation polymorphism (SSCP) analyses in combination with DNA sequencing of the mitochondrial 16S rRNA gene. Nineteen haplotypes were detected, 8 of which have not been reported in the U.S.A. One 'new' haplotype was only detected at Lunenburg, Nova Scotia, and comprised 38% of the ticks examined for that population. The population in the southeast corner of Manitoba contained 3 'new' haplotypes. Although the most common haplotype (Is-1) was present in all 6 populations of I. scapularis in Canada, there were significant differences in the genetic structure among population. This suggests different geographical origins for the tick populations in Canada, which may be related to the transportation of larval and nymphal ticks by migratory passerines using different flyways. Determination of the origins of the endemic populations of I. scapularis in Canada, as well as those predicted to establish in the near future, has important implications with respect to understanding the risk of exposure to pathogenic bacteria infecting these ticks.