THELAZIOSIS IN DOGS: CLINICAL, EPIDEMIOLOGICAL ASPECTS AND ZOONOTIC IMPLICATIONS – A LITERATURE REVIEW

Abstract

Thelaziasis is an ocular parasitosis caused by nematodes of the genus Thelazia, affecting dogs, cats, and occasionally humans. The genus was described in the 17th century, and since then several species have been identified, notably Thelazia callipaeda, which is of zoonotic importance. Transmission occurs through lacrimophagous flies of the genus Phortica, which ingest larvae present in the ocular secretions of infected animals and subsequently deposit them in new hosts, completing the biological cycle. Although widely reported in Europe and Asia, the disease is poorly documented in Brazil, despite the favorable climatic and environmental conditions for the presence of the vectors. The main clinical signs include conjunctivitis, excessive tearing, photophobia, and ocular discharge, which can progress to corneal ulcers and secondary infections. Diagnosis is made by direct observation of the parasites in the ocular structures and microscopic analysis of the secretions. Treatment is based on the mechanical removal of the worms associated with the use of antiparasitics such as ivermectin and moxidectin. Control involves environmental measures and prevention of exposure to vector flies, as well as owner awareness. The scarcity of national records reinforces the need for epidemiological studies and veterinary surveillance to assess the actual occurrence of the disease in the country. Thus, understanding the transmission dynamics and risk factors is essential for early diagnosis and effective control of thelaziasis in dogs, also preventing possible zoonotic implications.