First report of canine ocular thelaziosis by Thelazia callipaeda in Portugal

Background: Thelazia callipaeda eyeworms are transmitted by the non-biting insect vector Phortica variegata in Europe and infest the conjunctiva(s) of several mammalians, including dogs and humans. Infested hosts might remain asymptomatic or display clinical manifestations characterized by variable degrees of severity. Methods: From July to November 2011, nine dogs were detected with eyeworms at two veterinary clinics in Chaves and Braganca (North of Portugal). Nematodes collected from dogs were morphologically and molecularly characterized at species level. Results: Nematodes were identified as T. callipaeda. The number of worms collected from each dog ranged from three to 76 (average = 17.9 +/- 26.8) and was not associated with the severity of clinical signs. Ocular discharge and conjunctivitis were observed in all dogs and ocular pruritus occurred in six of them. Polymerase chain reaction and sequencing of a portion of target cytochrome c oxidase subunit 1 gene further identified all nematodes as haplotype 1. Conclusions: This is the first report of T. callipaeda and associated ocular disease in dogs from Portugal, suggesting that thelaziosis should be included in the differential diagnosis of canine ocular affections. The risk of the infestation spreading from Spain and France to Portugal, through domestic dogs or wild mammals, is realistic.