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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Burdock pappus (Arctium spp.) bristles are common conjunctival foreign bodies in the northeastern USA that can lead to chronic, nonhealing lesions of the cornea
  • The burdock plant releases tiny, sharply pointed bristles that attach to skin and mucous membranes. They can cause dermal irritation, respiratory disease, and ocular disease in many species including horses and humans. When the bristles lodge in the conjunctiva, they contact the cornea causing irritation and corneal ulceration. The bristles may release irritating substances
  • Systems affected—ophthalmic

Genetics!!navigator!!

No breed predilections for this conjunctival foreign body.

Incidence/Prevalence!!navigator!!

Common condition in the northeastern USA.

Geographic Distribution!!navigator!!

More common in the northeastern USA; however, the plant has been found in all of the contiguous United States except Florida.

Signalment!!navigator!!

No age or sex predilection.

Signs!!navigator!!

  • History of unilateral ocular signs including photophobia, blepharospasm, lacrimation, discharge characterized as either serous or mucopurulent, and fluorescein retention on the cornea
  • Most ulcers are near the nasal limbus, near the nictitans
  • The corneal erosions or ulcerations persist despite topical medical therapy

Causes!!navigator!!

Burdock pappus bristles are a common source of small conjunctival foreign bodies. The bristles may release irritating substances.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Lid abnormalities such as distichiasis, trichiasis, and entropion; neuroparalytic and neurotrophic keratitis
  • Corneal dystrophies; indolent corneal ulcers, eosinophilic keratitis, and corneal foreign bodies
  • Inappropriate topical corticosteroid therapy causing delayed corneal healing

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

Rule out infectious causes (bacterial or fungal) with corneal scrapings for cytology, aerobic bacterial, and fungal culture of the wound bed.

Imaging!!navigator!!

N/A

Other Diagnostic Procedures!!navigator!!

N/A

Pathologic Findings!!navigator!!

N/A

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

  • Find the bristle. Apply topical anesthetic. Retropulse the eye using gentle, transpalpebral pressure on the globe. Delicately evert the third eyelid and investigate the posterior face using a focal light source
  • Conjunctivectomy of the bristle foreign body and surrounding tissue under sedation, topical anesthesia, and auriculopalpebral nerve block
  • Debridement of the conjunctiva behind the nictitans is often necessary

Nursing Care!!navigator!!

Topical antibiotic therapy 4–6 times a day until resolution of the corneal ulcer is recommended.

Activity!!navigator!!

The patient's activity should be restricted to stall rest or small paddock turnout until resolution of the keratitis.

Diet!!navigator!!

N/A

Client Education!!navigator!!

  • Patients should become progressively more comfortable after removal of the foreign body. If worsening is noted, reexamination is warranted
  • If there is evidence of self-trauma when ocular disease is present, a protective hood covering the affected eye should be placed on the horse

Surgical Considerations!!navigator!!

N/A

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

After conjunctivectomy—follow-up therapy with topical antibiotics 4–6 times daily (e.g. neomycin–polymyxin B–bacitracin ointment, erythromycin ointment), topical 1% atropine SID to TID, and 1–2 g phenylbutazone BID PO.

Contraindications, Possible Interactions!!navigator!!

  • Horses receiving topical atropine should be monitored for colic
  • Secondary infection can result in a rapidly worsening condition. See chapter Corneal ulceration for further information

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

Recheck in 5–7 days to monitor epithelialization of the ulcer, improvement in patient comfort, and decrease in keratitis/conjunctivitis.

Prevention/Avoidance!!navigator!!

Ubiquitous in the environment due to airborne dispersion, contact with the bristles may be difficult to avoid in certain areas. However, they should be removed if identified in pasture.

Possible Complications!!navigator!!

Secondary bacterial infection.

Expected Course and Prognosis!!navigator!!

After removal of the bristle, healing of the corneal defect occurs within 3–14 days.

Miscellaneous ⬆ ⬇

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MISCELLANEOUS

Associated Conditions!!navigator!!

Secondary bacterial infection.

Age-Related Factors!!navigator!!

  • N/A

Zoonotic Potential!!navigator!!

  • None

Pregnancy/Fertility/Breeding!!navigator!!

  • N/A

Suggested Reading ⬆ ⬇

Brooks DE.Ophthalmology for the Equine Practitioner, 2e. Jackson, WY: Teton NewMedia, 2009.

Gilger BC. Equine ophthalmology. In: Gelatt KN, ed. Veterinary Ophthalmology, 5e. Ames, IA: Wiley, 2013:1560–1609.

Gilger BC.Equine Ophthalmology, 3e. Ames, IA: Wiley, 2017.

Author(s) ⬆

Author: Caroline Monk

Consulting Editor: Caryn E. Plummer

Acknowledgment: The author and editor acknowledge the prior contribution of Andras M. Komaromy and Dennis E. Brooks.