Equine ocular setariasis and its management

Abstract

Ocular setariasis is a common vision threatening ophthalmic condition in equine resulting from ectopic parasitism by Setaria digitata, Setaria equina and Thelazia lacrymalis. The disease occurs mostly in summer and autumn seasons and it displays signs of lacrimation, photophobia, corneal opacity, conjunctivitis and loss of vision. Close inspection of the eye reveals a moving worm in the anterior chamber of the eye. B-mode (brightness mode) ultrasonography helps in the diagnosis in case of complete opacity. The best treatment is the surgical removal of the parasite under regional/ general anesthesia. Needle paracentesis at 3 O' clock and nick incision at 12 O' clock position are most commonly used surgical procedure. Both the techniques give good results. A slightly modified technique of using a 21 gauge needle attached with the syringe to aspirate the worm into the syringe also gives satisfactory results. In medicinal therapy ivermectin is the most advocated drug for ocular equine setariasis, but long term tying of medicinal should be avoided and surgery should be advocated. Corneal opacity is the most common post operative complication reported. Post surgical use of placentrex has also been advocated to enhance healing and to resolve corneal opacity. The present review is aimed at etiology, diagnosis and management of ocular setariasis in equine species.

Subconjunctival nodule due to Setaria equina erratic migration in a horse: First case report

“…Although S equina parasitosis has a large geographic distribution including Western and Eastern Europe, the North America, Middle East, India, Asia and North Africa, to the authors’ knowledge this is the first documented case of subconjunctival aberrant migration of this parasite in a horse. Based on the morphological features of the parasite cross sections, histopathological examination identified a nematode of the Onchocercidae family and ruled out Habronema spp, Thelazia lacrymalis , and Onchocerca spp parasitic infections.…”

“…Differences in infection rates are presumed to be due to differences in the duration of the seasonal activity of the mosquito vectors . Equine intraocular setariasis manifests as a unilateral, acute anterior uveitis, and on close examination of the affected eye a thread‐like, white, and motile worm can be seen within the anterior chamber . There have been no publications to date in Europe on equine intraocular infection due to S equina , while a few cases were reported in North America in 1927 and 1969, respectively.…”

“…At their normal site, S equina worms are considered to be nonpathogenic to the host, although serious complications can occur when immature forms migrate to aberrant locations, such as the pleural cavity, the bladder wall, the testicles, and the anterior chamber of the eye . Intraocular infection of horses and donkeys with S equina appears to be uncommon and has mainly been reported in India, Egypt, Pakistan, and Thailand . Here, we describe the nodular presentation of a subconjunctival infection with S equina in a filly resident in southwest France.…”

A review of investigated risk factors for developing equine recurrent uveitis

“…In particular, Onchocerca cervicalis and other Onchocerca species have been linked with uveitis in humans and horses 8,78,79 . Connections between uveitis and infection of Setaria or Halicephalobus species have also been reported in horses 46,80–84 . However, case reports indicate that infections of Setaria , Halicephalobus , and Onchocerca species are not major risk factors for recurrent uveitis in horses as inflammation often resolves after treatment ( Setaria and Onchocerca ) or affected individuals do not survive the infection ( Halicephalobus ) 46,85,86 …”

Epidemiological investigation of equine hindlimb ataxia with Setaria digitata in South Korea

“…S. digitata is a parasite of cattle and hoofed animals and is found mainly in Asia [ 2 3 ]. The intermediate hosts are mosquitoes, such as Anopheles sinensis (A. sinensis) , Armigeres subalbatus (A. subalbatus) , and Aedes togoi (A. togoi) [ 4 ].…”