Surgical extraction of eye worm in equine

Introduction

India, Seteria digitata, Setaria equina and Thelazia lacrymalis are commonly responsible for equine corneal opacity (Sellon and Long, 2013) [9] . Setaria digitata is primarily prevalent in Asia and parasitizes cattle and other hoofed animals. Worldwide, Horses and other equids are infected with Setaria equine. Adult Setaria worms typically prefer the peritoneal cavity. They can occasionally enter the eyes or the central nervous system (Yadav et al., 2006) [15] . The blood contains microfilariae which are young larvae. Anopheles peditaneniatus and Culex nilgiricus mosquitoes spread the parasite through blood stream. Microfilariae are released by adult female worms into their host's abdominal cavities. The microfilariae enter the bloodstream and travel to the skin's capillaries. When mosquitoes consumes the blood of infected hosts, they can contract microfilariae. Within 2 to 3 weeks, these microfilariae transform into infectious larvae inside the mosquitoes. The infected mosquitoes then transmit these infective larvae to other susceptible hosts during their blood meals. The ocular seteriasis spreads mostly in summer and autumn when the mosquito vectors are most prevalent (Al-Azawi et al., 2012) [1] . The parasite can be detected in a variety of organs, including the heart, lung, spleen, kidney, uterus, oviduct, ovary, and bladder, and it can migrate in odd hosts including horses, donkeys, or humans. In general, ocular worms are more common in all horses (Jayakumar et al., 2012) [4] . Additionally, the immature worm might enter the eye (Tuntivanich et al., 2011) [12] through the vascular system (Townsend, 2013) [11] . When worms are localized in the anterior chamber of an equine's eye, it causes ongoing irritation and excruciating pain (Kumar et al., 2011) [5] . Typically, the infected animals exhibit lacrimation and photophobia (Basak et al., 2007) [2] . The worm's serrated cuticle and its lashing motions inside the anterior chamber of the eye severely damaged and inflamed the cornea, causing corneal opacity and ultimately blindness. Corneal oedema caused by dead filarial worm adhering to the endothelium in the anterior chamber.

The dead worm may release toxins into the anterior chamber, which could cause corneal oedema and be fatal to the endothelium. Devastating consequences like retinal detachment, cataracts, and synechia could result from it (Paglia et al., 2004) [6] . Although eye involvement is typically unilateral, reports of bilateral occurrences have sometimes been made (Buchoo et al., 2005) [3] .

Materials and Methods

A 7-year-old Marwari Stallion was presented at Department of Veterinary Surgery and Radiology, Kamdhenu University, Anand with a history of thread-like floating worm in the left eye along with corneal opacity. Complete ophthalmic examination was performed using hand held slit lamp. The anterior chamber was thoroughly examined by both lateral and retro-illumination to detect the presence of worm in the anterior chamber and lacrimation, conjunctivitis with partial loss of vision was observed clinically. Tetanus toxoid (5 ml, IM), topical (0.3% flurbiprofen), systemic (flunixin meglumine @ 0.5 mg/kg of body weight, IV) non-steroidal anti-inflammatory agents and antibiotic (strepto-penicillin 5g) were administered pre-operatively. Sedation was carried out by Xylazine HCl 1.1 mg/kg, IV in combination with supraorbital nerve block and auriculopalpebral nerve block using 2% lignocaine HCl. Topical local anesthetics 0.5% proparacaine was instilled to control the movement of eye ball. Paracentesis of worm was carried out in standing position with 16 G needle at the corneo-scleral junction at 6 'o'clock position (Fig. 1). Auto blood therapy was carried out by sub-conjunctival injection of blood (Fig. 2). Afterward topical antibiotic moxifloxacin and NSAID (flurbiprofen) were instilled in the eye. Temporary tarsorrhaphy was done by using non-absorbable suture material. Post-operatively topical antibiotics and antiinflammatory were given for 5 days.

Results and Discussion

On 7 th post-operative day, progressive reduction in lacrimation and conjunctivitis was seen. There was reduction in corneal opacity at 15 th post-operative day. Similar findings also reported by Patil et al. (2016) [7] ; in eye worm infestation in horses. Surgical interventions include incision at 3 O'clock (Vadalia, 2013) [13] or at 6-8 O'clock (Verma et al., 2019) [14] and at 12 O'clock position (Buchoo et al., 2005) [3] . Similar to present study, Verma et al. 2019 [14] carried out needle aspiration of the worm by inserting 18 gauze needle successfully. Complete corneal opacity reduced after 28 th post-operative days and recovered uneventfully with clear vision.

References

1. Al-Azawi AK, Fadhl AR, Fadhl SR. Epidemiological study of Setaria equina infection in donkeys. Iraq Veterinary Journal. 2012;36:93-97.
2. Basak SK, Hazra TK, Bhattacharya D. Persistent corneal edema secondary to presumed dead adult filarial worm in the anterior chamber. Indian Journal of Ophthalmology. 2007;55:67-69.
3. Buchoo BA, Pandit BA, Shahardar RA, Parrah JD, Darzi MM. Surgical management and prevalence of ocular filariasis in equines. Indian Vet J. 2005;82:8182.
4. Jayakumar K, Dharmaceelan S, Rajendran N, Senthilkumar S, Kathirvel S, Nagarajan L, Kumaresan A. Ocular setariasis in a pony. Indian Veterinary Journal. 2012;89:64-66.
5. Kumar M, Monsang SW, Pawde AM, Singh SK, Madhu DN, Zama MMS. Post-surgical healing effects of placentrex in equine (Equus caballus) ocular setariosis: A review of 22 cases. Indian Journal of Field Veterinarians. 2011;6(4):240-245.
6. Paglia DT, Miller P, Dubielzig RR. James Wardrop and equine recurrent uveitis. Archives of Ophthalmology. 2004;122:1218-1223.
7. Patil DB, Kelawala DN, Parikh PV, Sheth MJ, Sini KR, et al. Surgical management of ocular setariasis in horses. Indian J Vet Surg. 2016;41:13-17.
8. Rafee MA, Amanpal A. Equine ocular setariasis and its management. J Expt Biol Agric Sci. 2016;75:33-34. doi: 10.18006/2016.4(Spl-4-EHIDZ).S139.S143
9. Sellon CD, Long M. Equine Infectious Diseases. 2nd ed. Science Direct Publication; 2013.
10. Sreedavi C, Sudhakar K, Murthy PR, Prasad V. Clinical microfilariasis in a horse: A case report. Indian Vet J. 2002;79(5):487-488.
11. Townsend WM. Food and fiber-producing animal ophthalmology. In: Gelatt KN, editor. Essentials of Veterinary Ophthalmology. 2nd ed. Wiley-Blackwell Publication; 2013. p. 532.
12. Tuntivanich N, Tiawsirisup S, Tuntivanich P. Success of anterior chamber paracentesis as a treatment for ocular setariasis in equine eye: A case report. Journal of Equine Veterinary Science. 2011;31:8-12.
13. Vadalia JV. Surgical treatment of ocular setariosis in a stallion. The Indian Journal of Vet Sci. 2013;13:11.
14. Verma NK, Reetu, Raghuvanshi PDS, Gautam D, Saxena A. Surgical management of equine ocular setariosis: A review of 10 cases. Indian J Vet Surg. 2019;40(1):62-63.
15. Yadav A, Kumar A, Bhadwal MS, Khajuria JK, Gupta A. Ocular setariosis in horses: A case study. Journal of Veterinary Parasitology. 2006;20:1-10.