Thelazia callipaeda (Spirurida, Thelaziidae): First record of an imported ocular parasite in dogs from the Canary Islands, Spain

Abstract

The ocular parasite Thelazia callipaeda is a nematode transmitted by dipterans of the genus Phortica that affects various species of domestic and wild carnivores and, sporadically, humans. Although the presence of this parasite has been widely documented on the Iberian Peninsula, no cases have been reported in the Canary Islands (Spain). In the present study, ocular parasitosis in dogs from Tenerife and Gran Canaria are reported. The affected animals, a nine-year-old Border Collie, a five-year-old Labrador Retriever and a three-year-old crossbreed dog, presented clinical signs compatible with ocular thelaziosis, including epiphora, conjunctivitis, uveitis and blepharospasm. Additionally, the three dogs had a history of travel to parasite-endemic regions. During ophthalmologic examination, nematodes were observed in the conjunctiva, and were extracted and analyzed by morphometric keys and molecular techniques. The results confirmed that the ocular infection of all dogs was caused by T. callipaeda, representing the first documented cases of this parasitosis in the Canary Islands. Given the geographical isolation of this archipelago and the absence of previous records of this parasite, these findings suggest that the introduction of T. callipaeda into the Canary Islands may be related to the movement of the infected animals. It is essential to enhance epidemiological surveillance to assess the risk of establishment of the parasite and its vector, as well as its possible autochthonous transmission.