Feline ocular onchocercosis by Onchocerca lupi: Phylogenetic insights and implication for veterinary health

Onchocerca lupi is a vector-borne filaroid which affects wild (i.e., wolves, coyotes) and domestic carnivores (i.e., dogs, cats), and occasionally humans. This nematode causes ocular damage due to the location of adult worms embedded in the eye connective tissues. Several human cases of onchocercosis by O. lupi have been reported in Europe, Asia, north Africa, and the USA where the infection thrives in dogs and less frequently in cats. In this study, we review clinical aspects of feline infestation by O. lupi, and report the first case of this onchocercid in a cat from Romania, showing a subconjunctival mass located at the medial canthus of the right eye; worms were surgically removed from the ocular nodule and morphologically and molecularly identified. Lesions were examined and characterized using histological procedures. Nematodes were identified as O. lupi based on their morphology at the direct observation as well as at the histological examination. Molecular and phylogenetic analysis confirmed the identification of this onchocercid, with the cox 1 sequence obtained clustering with those available in public repositories, including isolates from dogs and cats from Europe and USA. Despite the few reports available on the occurrence of this parasite on domestic cats, these felines are regarded as potential hosts of O. lupi in Portugal and USA. Moreover, the spread of feline ocular onchocercosis in Eastern Europe countries draw attention on the need of additional studies to confirm the potential vectors involved in its transmission cycle.