Vector-spirochete relationships in louse-borne and tick-borne borrelioses with emphasis on Lyme disease

Salient findings on the development and transmission of Borrelia burgdorferi in and through its Ixodes vectors are compared and contrasted with these aspects of B. recurrentis, B. duttonii and B. theileri (among other borreliae) in their respective louse (Pediculus humanus) and tick (Ornithodoros moubata, Rhipicephalus spp., Boophilus spp.) vectors. After a brief historical introduction, a table summarizes the characteristics and geographical distribution of all arthropod-borne borreliae. Three sections then follow on the behaviour of louse-borne and tick-borne spirochaetes, of B. theileri, and of B. burgdorferi in their vectors, then a section on the relationship of B. burgdorferi to non-specific tick vectors (notably Dermacentor variabilis, Amblyomma americanum, and ticks of the jack rabbit Lepus californicus californicus) and other haematophagous arthropods (Chrysops callidus, Aedes spp.), and finally a section identified "B. burgdorferi: subject to a complex development cycle? ". In conclusion, the main points and areas for further research in this fast-moving subject are highlighted, including the apparent relative unimportance of transovarial transmission for B. burgdorferi, the likelihood that Haemaphysalis leporipalustris and I. dentatis play a role in maintaining B. burgdorferi in lagomorph populations, the possibility of mechanical transmission by Chrysops, Tabanus and mosquitoes, and certain complexities of spirochaete development in their arthropod and vertebrate hosts.