Trojan hosts: the menace of invasive vertebrates as vectors of pathogens in the southern cone of South America.
Invasive alien species (IAS) can act as vectors for the introduction of pathogens in ecosystems and their transmission to threatened native species (TNS), leading to biodiversity loss, population reductions and extinctions. We assessed pathogens potentially occurring in a set of IAS in the Southern Cone of South America and identified TNS potentially vulnerable to their effects. Also, we assessed how risk analysis systems proposed or adopted by national authorities in the study region value the importance of pathogens. We identified 324 pathogens in the selected IAS, which could potentially affect 202 TNS. Wild boar (Sus scrofa) was the IAS with the largest number of pathogens (91), followed by domestic dog (Canis familiaris) (62), red deer (Cervus elaphus) (58), rock dove (Columba livia) (37), American vison (Neovison vison) (18), European hare (Lepus europaeus) (17), common starling (Sturnus vulgaris) (12), common slider (Trachemys scripta) (6), and American bullfrog (Lithobates catesbeianus) (2). Most TNS were in the "vulnerable" IUCN category, followed by "endangered" and "critically endangered" species. Bacteria were the most frequently represented pathogens (112), followed by ectoparasites (78), viruses (69), protozoa and other (65). The direct effects of IAS on native wildlife are beginning to be addressed in South America, and their potential impact as pathogen spreaders to native wildlife has remained largely unexplored. Risk analysis systems associated with the introduction of IAS are scarce in this region. Although the existing systems contemplate hazard analyses for the co-introduction of pathogens, they underestimate the potential impact of diseases on TNS. Conservation efforts in the region would benefit from systems which give pathogen risk a relevant place, and from government agencies promoting targeted disease surveillance in IAS and wildlife.