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EYEWORMS ~ THELAZIASIS: Life Cycle & Treatment


Eyeworms (Thelaziasis):

                      
    Thelazia callipaeda In A Dog                                                         Thelazia callipaeda Female 

Thelaziasis (occasionally spelled "Thelaziosis") is the term for infestation with parasitic nematodes of the genus Thelazia.

Thelazia worms parasitize the eyes & associated tissues of various bird & mammal host, including humans.  They are often called "eyeworms". 

Adults are usually found in the eyelids, tear glands, tear ducts, or the so-called "third eyelid" (nictitating membrane). Occasionally, they are found in the eyeball itself, either under the conjunctiva (the membrane that covers the white part of the eye) or in the vitreous cavity of the eyeball. 

All species of Thelazia for which the life cycle has been studied are transmitted by species of Diptera (flies) which do not bite, but which feed on tears.

General Life Cycle:

In the uterus of the adult female, the embryos develop into first-stage larvae, which remain in the eggshell (sheath).  The female deposits these sheathed larvae in the tears of the mammal or bird definitive host, & the larvae are ingested by tear-feeding flies. 

In the fly, the larvae "hatch" (exsheath), penetrate the gut wall, & migrate to either the fat body, testes, or egg follicles (depending on the species).

There they develop into third-stage larvae (L3), which migrates to the head of the fly.  The infective L3 larvae wiggle out of the straw-like feeding apparatus of the fly when it feeds on the tears of another mammal or bird host.  The L3 larvae develop into adults in the eye or surrounding tissues of the host, where they may live for over one year.

In the definitive host, Thelazia have been found in various tissues of the orbit (or socket) of the eye, including within the eyelids, in the tear glands, tear ducts, or the so-called "third eyelid" (nictitating membrane) or in the eyeball itself.

Hosts & Geographic Range Of Thelaziasis:

While a few dozen species of Thelazia have been described in the literature, only 2 have been reported to infest humans, and only 7 are commonly reported in veterinary contexts. The remaining species are occasionally found in birds or wild mammals.

In humans, dogs and cats, thelaziasis cases due to Thelasia callipaeda (Asia, Europe) & T. californiensis (western North America) have been reported.

Horses are infested by T. lacrymalis (worldwide) & less frequently by T. rhodesii (Africa, Asia, Europe).

In catle, T. gulosa (Asia, Europe, North America), T. rhodesii (Africa, Asia, Europe) & T. skrjabini (Europe, North America) are the primary species of concern.

In camels, T. leesei infestations have been reported from the post-Soviet states & India.

The intermediate hosts of several Thelazia species are tear-feeding flies of the genera Musca (family Muscidae), Phortica (family Drosophilidae), or Fannia (family Fannidae).

Symptoms & Diagnosis:

In animal and human hosts, infestation by Thelazia may be asymptomatic, though it frequently causes watery eyes (epiphora), conjunctivitis, corneal opacity, or corneal ulcers (ulcerative keratitis).   Infested humans have also reported "foreign body sensation" – the feeling that something is in the eye.

Diagnosis involves simply examining the eyes and nearby tissues for the worms.  Adult Thelazia are very active, one author described T. californiensis as a "short lively piece of nylon fishing line about 10 mm long."

Prevalence:

By one author's count, 257 human cases of  Thelazia callipaeda had been reported worldwide by the year 2000, though thelaziasis is still considered to be a rare disease.

Various livestock & wildlife surveys suggest that thelaziasis is quite common among animals.

  • A slaughterhouse survey in Canada found that about one-third (32%) of cattle over an 8-month period were infested with eyeworms.
  • A survey of horses in Kentucky revealed a 42% rate of infestation with Thelazia lacrymalis.
  • In Wyoming and Utah, a survey of hunter-harvested  mule deer found 15% to be infested by Thelazia californiensis.
  • A survey of various sites in Italy found 23-60% of dogs, 5% of foxes, & 4 out of 4 cats to be infested with Thelazia callipaeda.

Treatment & Control:

Because they live so close to the outside of the body, Thelazia is one of the few nematode infections which can be treated topically.

Topical treatment of livestock, dogs, & cats with organophosphates (such as ecothiopate iodide or isofluorophate) & systemic treatment with antihelmintics (such as ivermectin, levamisole, & doramectin) are recommended by the Merck Veterinary Manual.  Other sources have reported positive results treating dogs with moxidectin, imidacloprid, or milbemycin oxime.

For the treatment of human cases, removal of the worm is suggested. Topical treatment with cocaine or thiabendazole have have also been reported to kill the worms in human cases.

Because most, if not all, species of Thelazia are spread by flies, sanitary practices which reduce the presence of flies will also reduce the spread of Thelaziasis.  (http://en.wikipedia.org/wiki/Thelaziasis & http://en.wikipedia.org/wiki/Eyeworm)

Treatment Meds

In a recent post, forum member Getout found that Dectomax treats this type of parasite & can be ordered from jefferslivestock.com (http://curezone.com/forums/fm.asp?i=1757157),

Other US online vet suppliers:

E-Bay:  http://shop.ebay.com/i.html?_nkw=dectomax&_fln=1&_sc=1&_sop=15&am...

Ordering info for Ivermectin (tablets, pour-on suspension, & paste) is covered in the Albendazole & Ivermectin Protocol:  http://curezone.com/forums/fm.asp?i=1586882#i 

Other topical treatments for parasites in skin, soft tissue, & scalp:  http://curezone.com/forums/fm.asp?i=1750708#i.

Cheers ~~ ICU

   

Parasite Drug Protocols:  Roundworms, Tapeworms, Flukes, Strongyloides, Filariasis, Morgellons, & Protozoa:  http://curezone.com/forums/fm.asp?i=1574645#i 

 

 
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