Borrelia

Mendoza-Roldan, Jairo Alfonso, Mendoza-Roldan, Miguel Angel & Otranto, Domenico, 2021, Reptile vector-borne diseases of zoonotic concern, International Journal for Parasitology: Parasites and Wildlife 15, pp. 132-142 : 137

3.1.3. Borrelia

Borrelia are spirochete bacteria divided in the relapsing fever, the reptilian Borrelia , monotreme associated Borrelia , and the Lyme borreliosis groups. This latter group englobes around 20 species within the B. burgdorferi sensu lato complex, nine of which can be pathogenic to animals and humans (Majl´athova´et al., 2008; Mendoza-Roldan et al., 2019). Lyme disease and other borrelioses include species such as Borrelia lusitaniae , a species pathogenic to humans, that has reptiles as natural reservoirs. Ticks of the genus Ixodes (e.g., I. ricinus , I. pacificus ,

Ixodes persulcatus and Ixodes scapularis ) are vectors of these bacteria ( Kuo et al., 2000; Szekeres et al., 2016; MacDonald et al., 2017; Mendoza-Roldan et al., 2019). Moreover, Lyme disease species are likely associated to lacertid lizards, being natural reservoirs (Majl´athova´et al., 2006, 2008; Mendoza-Roldan et al., 2019), or refractory to the infection (e.g., species of lizards in the United States) by means of complement-mediated killing effect ( Kuo et al., 2000). Similarly, some species of lacertid lizards seem to be incompetent hosts for many pathogenic Borrelia spp. in Europe (i.e., Lacerta spp. ), due to borrelicidal effect of blood components that can reduce the bacterial load in infected ticks. Thus, some species of lizards, in specific epidemiological contexts, might reduce the prevalence of borrelial bacteria resulting in a zooprophylactic effect or reducing the vectors that can feed on competent hosts (Tijsse-Klasen et al., 2010). Additionally, a separate clade of reptile-associated Borrelia , with no demonstrated pathogenicity, has been detected in Turkey, Mexico, Japan, and Australia from reptiles (i. e., varanid lizards, snakes and tortoises) and ticks (i.e., Amblyomma spp. , Bothriocroton spp. , H. aegyptium ) ( Güner et al., 2003; Takano et al., 2010; Panetta et al., 2017; Morales-Diaz et al., 2020; Colunga-Salas et al., 2020). This group of borrelial agents, and also those from the relapsing fever group, have been detected in imported reptiles to non-endemic areas together with their ticks, highlighting the need of quarantine and control measures (Takano et al., 2010; Colunga-Salas et al., 2020). The origin of these distinct groups of Borrelia is still not clear, though phylogenetic analyses showed that the reptilian Borrelia spp. diverged from a common ancestor of relapsing fever Borrelia (Takano et al., 2010) . Conversely, main clades of Borrelia (i.e., Lyme disease and relapsing fever) are thought to have co-evolved when Ixodidae and Argasidae ticks diverged. Given that reptile- Borrelia group is associated with ixodid ticks, current hypothesis suggest that a switching event could have occurred, either by host or vector switching ( Charleston and Perkins, 2003). In addition, since ticks from both families may occur in sympatry on the same species of reptile host, it is likely that co-feeding and vector-switching events could have happened in the past, thus originating this reptile-associated monophyletic group.