Emergence of Thelazia callipaeda Infection in Dogs and Cats from East-Central Portugal

The eyeworm Thelazia callipaeda (Spirurida, Thelaziidae) infects domestic animals, wildlife and human beings, and is considered an emerging pathogen in Europe. This study aimed at investigating the prevalence and risk factors of T. callipaeda infection in dogs and cats from east-central Portugal, a region where the parasite was previously detected in two red foxes (Vulpes vulpes). Thelazia callipaeda was found in 22 (3.8%) of 586 dogs and in four (23.5%) of 17 cats. A total of 178 adult worms (71.9% of females and 28.1% of males) were collected from the conjunctiva of the infected dogs. The number of worms collected per dog ranged from 1 to 35 (average ± standard deviation: 8.08 ± 9.49), with four dogs (18.2%) harbouring only a single parasite. Worms were gathered from dogs throughout all months of the year. A total of 17 adult worms (64.7% of females and 35.3% of males) were obtained from cats. The number of worms per cat ranged from 1 to 14 (4.3 ± 6.5), with three cats (75.0%) having a single parasite. Eyeworm infection was statistically more prevalent in pastoral and farm dogs, in those dogs with contact with other animals and in dogs with ocular manifestations. T. callipaeda is endemic in the east-central part of Portugal, reportedly infecting domestic (dogs and cats) and wild carnivores (red foxes) and evidencing a southerly dissemination. Future investigations should be focused on determining the local distribution and density of the insect vector (Phortica variegata) in this geographical area. This emergent zoonosis should be included by veterinarians, physicians and ophthalmologists in the differential diagnosis of ocular manifestations in their patients, particularly in areas where T. callipaeda is endemic.