Unraveling parasite identification in invasive and endangered squirrel species: potential for parasite spillover

Invasive species can impact ecosystem health by introducing parasites during their establishment in new areas. However, the dynamics of parasite loads between invasive and native species remain poorly understood. In the 1940s, Abert’s squirrels ( Sciurus aberti ) were introduced to the Pinaleño Mountains in southeastern Arizona where they now co-occur with endemic endangered Mt. Graham red squirrels ( Tamiasciurus fremonti grahamensis ). The study aimed to identify and quantify parasites in both Abert's and Mt. Graham red squirrels, with a focus on investigating possible parasite spillover between these two species and examining how host-related factors affect parasite presence. PCR amplification and morphological analyses revealed two endoparasite species: Citellinema sp. and Trypanoxyuris ( Rodentoxyuris ) sp. In Abert's squirrels, ectoparasites such as Opisodasys robustus , Anomiopsyllus sp., and Neohaematoinnus sciurinus were encountered, while Mt. Graham red squirrels carried Orchopeas caeden and a mite from the Glycyphagidae family. Our findings suggest new host and geographic record for the Glycphagidae mite in Mt. Graham red squirrels of Arizona and indicate possible spillover of Trypanoxyuris ( Rodentoxyuris ) sp. from Abert’s squirrels to Mt. Graham red squirrels. Additionally, sex influenced presence of ectoparasites in Abert’s squirrels. We can offer a better understanding of factors that place species at risk of extinction with enhanced insights into probable parasite transmission routes and the role that parasites play in biological invasion.