08.04.2019: In recent decades, the oriental eye worm has been increasingly found in pets and humans in Europe. Until now, however, this causative agent of eye infections had not been endemic in Austria. A recently published study by Vetmeduni Vienna now confirms the suspicion that this has changed. The Vetmeduni Vienna research team therefore recommends that doctors and veterinarians consider the possibility of oriental eye worm infection when diagnosing ocular diseases.

Over the last 30 years, the oriental eye worm (Thelazia callipaeda) has increasingly been reported as an agent of ocular infections in animals and humans throughout Europe. The nematode, which is transmitted by a specific species of fruit fly, infects the conjunctival sac and associated ocular tissue of domestic and wild carnivores, rabbits and hares, and humans. An ocular infection caused by T. callipaeda can exhibit a variety of clinical signs ranging from mild to severe.

First case of an infected cat in Austria

Following the first cases of ocular thelaziosis in dogs recorded recently in Austria, the researchers describe in the present paper the first case of a T. callipaeda infection in an Austrian cat with no history of travelling abroad. The finding represents clear proof for the parasite’s autochthonous transmission cycle in the country.

Proper diagnosis led to full recovery

The infested cat from Deutschlandsberg in the southern state of Styria showed serous ocular discharge, conjunctival hyperaemia and mild conjunctival oedema in the right eye. Mechanical removal of the parasite from the cat’s eye, in combination with milbemycin oxime/praziquantel oral treatment and topical use of tobramycin/dexamethasone eye drops, led to a complete resolution of the symptoms within two weeks.

Increased infestations among humans and animals

The results presented in the current study are of great importance, as the zoonotic parasites responsible for the infection are largely unknown in Austria. As co-author Georg Duscher, vice director of the Institute of Parasitology at Vetmeduni Vienna, points out: “In view of the present data, increased awareness of medical and veterinary communities is imperative for preventing further infections in both animals and humans. As recently demonstrated in a study conducted in Spain, it is reasonable to expect more cases of ocular thelaziosis in the following years and its further expansion to new areas in Austria.”

Oriental pathogens invasive in Europe

Because the nematode originally occurred in the Far East, it has often been referred to as “oriental eye worm”. However, the first European case of ocular thelaziosis was described in Italy already in 1989. Since the turn of the millennium, T. callipaeda has increasingly been reported in animals from France (2007), Switzerland (2008), Germany (2010), Spain (2011), Portugal (2012), Bosnia and Herzegovina (2014), Croatia (2014), Serbia (2014), Romania (2015), Bulgaria (2016), Hungary (2016), Slovakia (2017) and Greece (2015).

Exact route of transmission still unknown

The exact way in which the parasite was introduced to Austria remains unknown. One of the possible explanations is that T. callipaeda arrived via pet travelling, the illegal pet trade or the import of stray dogs from Eastern Europe. Another explanation links the spread of the parasite to the migration of infected wild carnivores, in particular foxes or the golden jackal. Adnan Hodžić from the Institute of Parasitology at Vetmeduni Vienna: “The transmission by wild animals is a plausible scenario which could explain the introduction of the eye worm to Austria. Future studies should therefore focus on wild animals in order to assess the role they play in the ecoepidemiology of this zoonotic parasite.”

The article “The first autochthonous case of feline ocular thelaziosis in Austria” by Adnan Hodžić, Albert Payer and Georg G. Duscher was published in Parasitology Research.