Detection of Candidatus Rickettsia andeanae in ticks from sympatric canids in northeastern Argentina.

In northeastern Argentina, wild canids such as the pampas fox (Lycalopex gymnocercus) and the crab-eating fox (Cerdocyon thous) coexist with domestic dogs (Canis lupus familiaris) across rural and peri-urban landscapes, creating opportunities for tick and pathogen exchange. Characterizing tick assemblages and associated pathogens in these hosts is essential to assess potential public health risks at the wildlife-domestic interface. Ticks were collected opportunistically from domestic dogs and road-killed foxes near two protected areas in Corrientes Province. Specimens were identified using morphological and molecular approaches and screened for Rickettsia spp. by PCR. A total of 30 adult ticks were obtained from 12 dogs and 8 foxes, representing four species: Amblyomma tigrinum, A. ovale, A. dubitatum and Rhipicephalus sanguineus. Amblyomma tigrinum was the most frequent species (50%). Seven individual ticks were confirmed as Candidatus Rickettsia andeanae in A. tigrinum, while one pooled sample was positive by screening only and was not confirmed. These findings expand the known geographic distribution of Ca. R. andeanae and provide molecular evidence of its circulation in ticks collected from both wild and domestic canids in northeastern Argentina. Our results highlight the importance of these hosts as sentinels for tick-borne pathogens and underscore the need for integrated One Health surveillance to better anticipate emerging potential risks in interface areas.