Evolutionary Aspects of Emerging Lyme Disease in Canada

Abstract

fIn North America, Lyme disease (LD) is a tick-borne zoonosis caused by the spirochete bacterium Borrelia burgdorferi sensu stricto, which is maintained by wildlife. Tick vectors and bacteria are currently spreading into Canada and causing increasing numbers of cases of LD in humans and raising a pressing need for public health responses. There is no vaccine, and LD prevention depends on knowing who is at risk and informing them how to protect themselves from infection. Recently, it was found in the United States that some strains of B. burgdorferi sensu stricto cause severe disease, whereas others cause mild, self-limiting disease. While many strains occurring in the United States also occur in Canada, strains in some parts of Canada are different from those in the United States. We therefore recognize a need to identify which strains specific to Canada can cause severe disease and to characterize their geographic distribution to determine which Canadians are particularly at risk. In this review, we summarize the history of emergence of LD in North America, our current knowledge of B. burgdorferi sensu stricto diversity, its intriguing origins in the ecology and evolution of the bacterium, and its importance for the epidemiology and clinical and laboratory diagnosis of LD. We propose methods for investigating associations between B. burgdorferi sensu stricto diversity, ecology, and pathogenicity and for developing predictive tools to guide public health interventions. We also highlight the emergence of B. burgdorferi sensu stricto in Canada as a unique opportunity for exploring the evolutionary aspects of tick-borne pathogen emergence.

Haemoplasmas in wild rodents: Routes of transmission and infection dynamics

“…. Revealing the mechanisms of these bacteria's transmission and persistence will shed light on the evolutionary strategies underlying host-parasite/pathogen coexistence and will have an applied aspect considering that some of these bacteria are pathogenic to wild animals and humans (Atif, 2015;Breitschwerdt & Kordick, 2000;Eisen & Eisen, 2011;Hoelzle, Zeder, Felder, & Hoelzle, 2014;Liang, Nelson, & Fikrig, 2002;Messick, 2004;Ogden et al, 2015).…”

“…However, recent evidence points to more permanent blood bacterial residents such as Bartonella and haemoplasma (haemotropic Mycoplasma ) species, which may use red blood cells as their primary microhabitat (Cohen, Einav, & Hawlena, ; Cohen, Toh, Munro, Dong, & Hawlena, ; Gavish et al., ; Gutiérrez, Morick, Cohen, Hawlena, & Harrus, ; Gutiérrez, Nachum‐Biala, & Harrus, ). Revealing the mechanisms of these bacteria's transmission and persistence will shed light on the evolutionary strategies underlying host–parasite/pathogen coexistence and will have an applied aspect considering that some of these bacteria are pathogenic to wild animals and humans (Atif, ; Breitschwerdt & Kordick, ; Eisen & Eisen, ; Hoelzle, Zeder, Felder, & Hoelzle, ; Liang, Nelson, & Fikrig, ; Messick, ; Ogden et al., ).…”

Evidence for Host-Genotype Associations of Borrelia burgdorferi Sensu Stricto

“…burgdorferi genotypes in samples collected in the field from different sources [ 24 – 26 ], and differential infection and transmission efficiency among different host-genotype pairings [ 25 , 27 ]. Such associations are of public health interest as they may be linked to the capacity of the different genotypes to show different pathogenicity in humans and varying capacity to stimulate antibodies detectable in current serological tests, while the existence of host associations may allow prediction of regions and habitats where different genotypes are more likely to occur [ 28 ].…”

“…burgdorferi phylogenetic tree obtained using concatenated housekeeping genes of a multilocus sequence typing (MLST) method does not seem to be based on geographic isolation of genotypes [ 29 , 30 ]. It has been hypothesized that the clades were associated with introductions and/or population expansions after bottlenecks possibly associated with glacial-interglacial periods [ 31 ], although ecological isolation driven by host species associations may also explain the origin and maintenance of discrete clusters [ 28 ]. Small and medium-sized vertebrates, particularly rodents, are key requirements for B .…”

Unexpected Risks for Campers and Hikers: Tick-Borne Infections

“…Lyme disease is a frequently seen tick-borne infection in the Northern Hemisphere. [16][17][18][19][20] Borrelia burgdorferi sensu lato is a group of spirochete bacteria that has been identified in at least 19,21,22 Ixodes ricinus has a four-stage life cycle: egg, larva, nymph, and adult. Only female ticks feed on blood from a vertebrate host at every active stage, and B. burgdorferi transmission occurs through saliva during the bite.…”