Prevalence study of in guanaco () from the Chilean Patagonia unexpectedly reveals the southernmost limit of .

This study presents the first detection of metacestodes in guanaco () within the Chilean Patagonia, marking the southernmost record of natural infection in an intermediate host on the continent. was found in the continental part of the Magallanes region where the top predators are pumas (). Conversely, all metacestodes found in guanacos collected from Tierra del Fuego Island, where no pumas exist, were identified solely as . Additionally, this research highlights a tissue preference of for liver, contrasting with , which predominantly affects the lungs in guanacos. We also report the infection of . in 1 guanaco. Our findings emphasize the need for accurate identification of metacestodes during meat inspection in an area where and overlap. This research also contributes to increase the knowledge of parasite–host dynamics in wildlife and underscores the importance of considering broader spectrum intermediate hosts in the epidemiology of parasitic infections.