Feline thelaziosis (Thelazia callipaeda) in Spain: state-of-the-art and first prophylactic trial in cats

Objectives Thelaziosis caused by the nematode Thelazia callipaeda (Spirurida, Thelaziidae) affects the eyes of domestic and wild carnivores, lagomorphs and even humans. The role of cats in spreading thelaziosis remains unclear. The present study assesses the current status of feline T callipaeda infection in Spain and presents the results of the first prophylactic trial conducted in this species. Methods We retrospectively analysed the occurrence of feline thelaziosis (study 1), examined its prevalence based on cross-sectional sampling of endemic areas (study 2), and assessed the therapeutic/prophylactic benefits of a spot-on (moxidectin) and therapeutic efficacy of an eye drop (ivermectin) formulation (study 3). Results In study 1, 69 Thelazia-infected cats were examined. Autochthonous cases were detected in 18/26 municipalities surveyed in Spain, which corresponds to 88.4% (n = 61/69) of the total number of cases. In study 2, 74 cats (20 from La Vera region and 54 from Orense province) were examined from 2011 to 2013. Ten of these cats (13.5%) were infected with T callipaeda. The infection prevalence was 40% (n = 8/20) in La Vera and 3.7% (n = 2/54) in Orense. The therapeutic efficacy of ivermectin was assessed over a summer (2011) in 12 cats, while that of moxidectin was examined over a 17-month period in seven cats. Four of these seven cats were subsequently included in an all-year-round prophylaxis trial. Treatment efficacy ranged from 91.7% (ivermectin) on day 28 after treatment to 100% (moxidectin) on day 14. Moxidectin prevented reinfections in cats. Conclusions and relevance Our data confirm the endemic status of T callipaeda infection in Spain, revealing its high prevalence in cats living in known endemic areas. Moxidectin was effective in treating and preventing infection. We strongly recommend the inclusion of thelaziosis in the differential diagnosis of pets and humans presenting with ocular manifestations, along with adequate preventive measures.