Global warming and displacement of vectors and wild and domestic hosts by humans greatly change host-parasite interactions
and parasite transmission rates. Thelazia callipaeda Railliet and Henry, 1910 (Spirurida: Thelaziidae) is a zoonotic
parasite rapidly colonizing Europe from its Asian native range. This nematode is vectored by Phortica flies and may cause
ocular disorders, such as keratitis and corneal ulcers, in wild mammals, dogs, cats and humans. With the aim of detecting
possible threats for the European wildcat (Felis silvestris) in one of its last Mediterranean strongholds, we initiated in 2017
a long-term monitoring program in Sierra Arana (southeastern Spain), which includes exploring its epidemiological and
spatial relationships with domestic cats (Felis catus). During routine medical check-ups, we detected ocular nematodes
in 3 of 17 (17.6%) wildcats and 1 of 23 (4.3%) domestic cats tested, confirmed to be T. callipaeda by microscopic and
molecular analyses. This nematode species was first detected in the study area in 2021. To our knowledge, this is the first
case of infection in wildcats in Spain. Through telemetry, we detected little spatial overlap between the home ranges of
wildcats and domestic cats, which seems to be sufficient to facilitate the inter-specific transmission of T. callipaeda. Our
findings suggest that this pathogen could be a new threat to the wildcat, a locally endangered wild felid. Further ecoepidemiological
monitoring and sanitary control of domestic cats will be strongly needed, especially given the ongoing
global warming scenario
