First report of eyeworm infection by Thelazia callipaeda in gray wolf (Canis lupus) from Serbia

Thelazia callipaeda, originally known as an "Oriental eyeworm," is a small nematode parasitizing the conjunctival sacs of domestic and wild animals and humans. Previous studies conducted in Serbia have reported the eyeworm infections in dogs, cats, and foxes, as well as in a human patient. As the data regarding thelaziosis from wildlife is still scarce, the aim of this study was to investigate the presence of T. callipaeda in gray wolf (Canis lupus) from Serbia. All collected nematodes were morphologically identified as T. callipaeda males (n = 64) or females (n = 225). Molecular characterization, conducted by PCR amplification followed by sequence analysis of partial cytochrome c oxidase subunit 1 gene (cox1), revealed only haplotype 1 of T. callipaeda. The overall prevalence of thelaziosis was 38.1% (8/21). In all positive animals, both eyes were affected, with a total parasitic load ranging from four to 132 worms per animal. Our results indicate the important epidemiological role of wolves as wildlife reservoirs of T. callipaeda, expanding geographic range of infection, as well as intra- and interspecies contact rates, although the role of other wild carnivore species (i.e., foxes and jackals) should be investigated in future studies.