Spotted Fever Group Rickettsia spp. Molecular and Serological Evidence among Colombian Vectors and Animal Hosts: A Historical Review

In 2012, a study provided evidence of a novel species Candidatus R. colombianensi, which is a species found in A. dissimile ticks from northern Colombia [24]. First described in ticks collected from iguanas in the Córdoba department, this emerging species has been described across north and central Colombia (Figure 1) [24,27,30,55,56,57]. In its first description, 24.7% of A. dissimile pools showed the presence of Rickettsia sp. Authors then isolated Candidatus R. colombianensi from four of the positive pools [24]. Candidatus R. colombianensi pathogenicity has not been described, and high infection rates are noted among A. dissimile, where more than half of the adult, nymph and larvae pools are positive for at least one Rickettsia sp., including Candidatus R. colombianensi, which could imply humans might be highly exposed to this species [55,58]. Amblyomma dissimile infection with Candidatus R. colombianensi is described in several studies across the country, which is likely associated with the host ticks’ bloodmeal preference for amphibians and reptiles [23,30,31,36,59,60]. Candidatus R. colombianensi has only been identified from sampling areas with humid or semi-humid climates; thus, increased surveillance in other climates is warranted to understand the ecology of this species. While the presence of A. dissimile in Colombia is primarily associated with reptiles and birds [24,56], it might occasionally play a role in domestic transmission: for example, horses with attached A. dissimile ticks have been reported positive for anti-SFGR antibodies, and some of the collected ticks showed the presence of Candidatus R. colombianensi [38]. This species gained relevance when it was found among anthropophilic ticks within the A. cajennense s.l. complex, which are relevant for human SFGR epidemiology in Colombia [40]. One study collected host-attached A. cajennense s.l. among capybaras and found that 2.6% were positive for Candidatus R. colombianensi [27]. Among the A. cajennense complex, Candidatus R. colombianensi has also been found in A. mixtum, which is a known human-biting tick; thus, implications of this species in SFGR epidemiology should be further evaluated [23].