Focus - Companion animal - July 2019
Case study: Ocular the laziosis in a travelled dog
Theo de Waal PhD MRCVS, associate professor, School of Veterinary Medicine, UCD; Amanda Lawlor BAgrSc, senior technical officer, School of Veterinary Medicine, UCD; and Susan Roulston MVB MRCVS, present a case study on the discovery of eyeworm in a three-year-old dog, and subsequent treatment of thelaziosis
Thelaziosis is an infection of the eye caused by the nematode Thelazia callipaeda in a wide range of host species, including humans. Autochthonous transmission has been reported in an increasing number of European countries but, to our knowledge, it has not been reported in Ireland.1
A three-year-old male Labrador X Poodle had travelled to southern Spain for a month in October 2018. The dog wore a deltamethrin collar during the stay in Spain and received routine anthelmintic treatment before re-entry into Ireland. In April 2019, the dog started to show signs of itchy eyes and was presented to a private veterinarian on May 14, 2019. On ophthalmic examination, a thread-like worm was seen wriggling across the cornea of the left eye. The dog was sedated on the same day and on examination, the conjunctiva of the left eye was inflamed, especially the nictitating membrane. There were multiple small nodules on the conjunctiva. On flushing with sterile water, a worm emerged from under the upper lid (Figure 1) and was retrieved with fine forceps. The right eye showed similar inflammation of conjunctiva with multiple nodules and another worm identified on flushing.
The dog was treated with eye drops – one drop, twice daily for five to seven days and 10% imidacloprid and 2.5% moxidectin spot-on was applied. Three days later, the owner reported that the eyes seemed normal with no more itchiness observed.
One of the worms was submitted to the UCD veterinary parasitology laboratory for identification. It was identified as a female T callipaeda nematode (Figure 2), approximately 12mm in length, using the morphological criteria as described by Otranto et al.2
T. callipaeda is also known as the oriental eyeworm, and has increasingly been being reported in recent years from many European countries including Spain.3 It is a vector-borne, zoonotic helminth transmitted by male drosphilid fruit flies, Phortica variegata, in Europe.4
Both moxidectin and milbemycin oxime is effective against T. callipaeda but slow-release insecticide collars do not seem to protect animals against thelaziosis.5 Monthly treatments with moxidectin spot-on or milbemycin oxime per os, when animals are travelling to endemic areas, is advised to reduce the infection risk.5,6
Under the pet travel scheme pet owners are required to fulfil specific health requirements when travelling with their dogs in Europe (https://www.agriculture.gov.ie/pets/); however, the required tapeworm treatment will have no effect on this parasite and, therefore, pet owners need to be aware of the potential danger of importing parasites into non-endemic areas.
The vector fly, P. variegate, has not been recorded in Ireland and recent ecological niche models have shown that although large areas of mainland Europe are suitable for the development of P. variegate, its habitat in the United Kingdom and Ireland would be limited to the southern and eastern parts of England.1,7
This case highlights how easy it is to introduce foreign diseases into Ireland from mainland Europe and that veterinarians should always be vigilant when examining pets who have travelled.
Palfreyman J, Graham-Brown J, Caminade C, Gilmore P, Otranto D, Williams DJL. Predicting the distribution of Phortica variegata and potential for Thelazia callipaeda transmission in Europe and the United Kingdom. Parasites & Vectors 2018; 11(1): 272.
2. Otranto D, Lia RP, Traversa D, Giannetto S. Thelazia callipaeda (Spirurida, Thelaziidae) of carnivores and humans: morphological study by light and scanning electron microscopy. Parassitologia 2003; 45(3-4): 125-133.
3. Miró G, Montoya A, Hernández L, Dado D, Vázquez MV, Benito M, et al. Thelazia callipaeda infection in dogs: a new parasite for Spain. Parasites & Vectors 2011; 4(1): 148.
4. Otranto D, Cantacessi C, Testini G, Lia RP. Phortica variegata as an intermediate host of Thelazia callipaeda under natural conditions: Evidence for pathogen transmission by a male arthropod vector. International Journal for Parasitology 2006; 36(10): 1167-1173.
5. Lechat C, Siméon N, Pennant O, Desquilbet L, Chahory S, Le Sueur C, et al. Comparative evaluation of the prophylactic activity of a slow-release insecticide collar and a moxidectin spot-on formulation against Thelazia callipaeda infection in naturally exposed dogs in France. Parasites & Vectors 2015; 8(1): 93.
6. Ferroglio E, Rossi L, Tomio E, Schenker R, Bianciardi P. Therapeutic and prophylactic efficacy of milbemycin oxime (interceptor) against Thelazia callipaeda in naturally exposed dogs. Veterinary Parasitolohy 2008; 154(3): 351-353.
7. Otranto D, Brianti E, Cantacessi C, Lia RP, Maca J. The zoophilic fruitfly Phortica variegata: morphology, ecology and biological niche. Medical and Veterinary Entomology 2006; 20(4): 358-364.