Eye worms, the new dog parasite from continental Europe: Pete the Vet Podcast from Newstalk’s Pat Kenny Show

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Eye worms: a mildly irritating new type of parasite in dogs

Just when you thought parasites of pets could not get more “icky”, a new variation on the theme has become increasingly common, invading the UK and possibly Ireland from continental Europe. The “eye worm” can infect dogs and cats, and can even be passed on to humans. The worm causes direct irritation to the eye by its presence in the conjunctival sac, inside the eyelids. It causes an irritation in the same way as a piece of thread or a speck of hay would irritate the eye, and the immediate treatment is simple: removing the worm with a pair of tweezers.

The worm (Thelazia callipaeda) was originally a parasite that was common in East Asian countries (e.g., China, Thailand, Japan and many others), leading to its original name as the “oriental eye-worm”. However, due to its recent spread to European countries, this common name of is no longer appropriate, and “eye worm” is probably a better term to use.
Since the first diagnosis of eyeworm infection in dogs from northern Italy in 1989, the parasite has been increasingly reported in many European countries including Italy, Belgium, France, Greece, Portugal, Spain, and Switzerland, as well as eastern European countries. Three have been reported in the UK to date, but many more are suspected. It has not been seen in Ireland yet but it is likely that it is just a matter of time.
In Europe, T. callipaeda has been documented in domestic animals (dogs and cats) and wildlife (e.g., foxes, hares, rabbits) and cases of human thelaziosis have been reported in Italy, Spain,, Croatia, and, Serbia. In these countries the infection is well established in local animal populations. The increased number of eyeworm infections in both animals and humans is linked to the presence of the fruit flies that act as the intermediate host in Europe while feeding on lachrymal (tear) secretions of infected animals. These flies are seen in UK and Ireland as well as in Europe.
Both adult and larval stages of the eyeworm are responsible for symptoms ranging from mild (e.g., lacrimation, ocular discharge, epiphora) to severe (e.g., conjunctivitis, keratitis and, corneal opacity or ulcers). The degree of severity of symptoms relates to the load of parasites inhabiting the orbital cavity and the speed with which treatment is given. Worms (adult and larvae) may be removed mechanically by rinsing the conjunctival sac with saline solutions (much as you might do to remove dust and grime from a sore eye). Adults can be seen with the naked eye, and can be removed with fine forceps or swabs.
Successful treatment of eyeworm infection in animals involves the administration of anti-parasitic drugs, which can be given as tablets or spot-on medications. The products that are currently used by vets in Ireland to treat fleas and worms are highly effective against eyeworm

Incubation Period:

After being deposited in the tears of the new host, the larvae take 3-6 weeks to reach maturity.

Life Cycle/Stages:

  • The adult female worm lays her eggs in the tears of the animal.
  • Flies ingest these eggs when feeding on the ocular secretions.
  • The eggs develop into larvae in the flies’ body cavity.
  • When the fly next feeds the larvae move out of the fly and onto the conjunctiva of the animal.
  • In 3-6 weeks the larvae mature into adult worms which lay their eggs in the conjunctival sac of the animal.
  • Morphology: Adult worms are creamy-white and measure up to 0.75 X 17.00 mm, so are visible to the naked eye

Questions about pets from listeners

  • Would you ask the vet is this unusual ? My cat came up to my bed and wee’d on it during the night, l only noticed it this morning. She has never soiled the house in any way before. Should l leave her outside in future ? David in Tallaght.
  • My dog was attacked by another dog. Naturally an exuberant nature, no aggression. Unprovoked attack. since then he is slow to come out from house. Shivers, back down, tail under. I coax firmly with treats. 1. Is he likely to become vicious, when stress eases? 2 what should I do to normalise and ease stress? 3. should I neutered him to reduce chance of attacks?
  • My terrier mix recently has been vomiting yellow bile and occasionally similar colour the other end also. We have him a couple of months and we got him from the dog pound.
  • CALLER: MARK Two pups have had diarrhoea for 4 days. Could they have gotten it from eating plumbs that had fallen from trees in back garden covered with slugs. Are feeding them on chicken and rice now will that work?
  • When my dog is on the lead I allow him to lead the way but he constantly walks around behind me emerging on the other side and forcing me to change hands on the lead. Why does he do this? P.S it brought a tear to my eye last week when you said that he loves me more than his food. Peter Kill cullen
  • I have 2 ministers Yorkshire terriers ( aunt and niece ) aunt is 4 years , niece is 6 months. Pup is in heat and she has turned from a cute pup to a vicious pup when around her aunt ! I keep them separate but they used to get in great will this behaviour in my pup pass ? Help ! Many thanks
  • How do I stop my gorgeous new Great Dane puppy from nipping, have four children one who is only three, puppy is 10 weeks, and a really placid good and happy puppy -it’s just normal puppy nipping, thanks Sheila Sligo

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