Eye discharges are the result of irritation to the cornea or conjunctiva, or both. They are commonly encountered in the live export process, are usually very noticeable, and may raise concerns at health inspections.
Eye discharges are often initially serous and may then become purulent over time due to chronic inflammation and bacterial involvement. Unilateral discharge may be due to local inflammation, while bilateral discharge may be due to systemic disease. Eye discharge associated with closed, partly closed or excessive movement of eyelids, indicates pain in the eye from ulceration, foreign body or both. Conjunctival inflammation may result in prominent blood vessels, vascularisation, and reddening of the eye. Corneal inflammation (keratitis) may result in increased vascularization, ulceration and scarring, with more severe and chronic changes potentially interfering with normal eyesight.
Animals with eye discharges should be examined if possible to determine the cause and particularly to look for foreign bodies. Examination may require physical restraint, sedation, topical anaesthesia, and a light source.
Clues to diagnosis are whether single or multiple animals are infected and whether discharges are unilateral or bilateral, watery or purulent, and whether they are accompanied by other localised or systemic signs. Watery (serous) discharges are usually from dust, ammonia vapour and upper respiratory tract viruses. The hair on the face becomes wet and stained. Yellow, thick discharges are usually from foreign material such as grass seeds, chaff and sawdust. Severe inflammation and discharge on one side may be from listeriosis or middle ear infection.
Common causes of eye discharges in export livestock are foreign bodies or trauma, pinkeye, and in cattle infectious bovine rhinotracheitis (IBR) and malignant catarrhal fever. Excessive lacrimation may accompany many other systemic diseases including heat stress, bovine virus diarrhoeal virus infection, bovine ephemeral fever and malignant catarrhal fever. These conditions should be associated with other characteristic signs or histories.
If there is recent history suggesting grass seeds, chaff or other foreign bodies having entered the eye, each affected animal should be restrained and undergo examination of the eyes, especially of the conjunctival sacs. Removal of foreign bodies is made easier by use of topical anaesthesia and forceps.
Antibiotics (procaine penicillin, oxytetracycline, or trimethoprim sulpha) and non-steroidal anti-inflammatory drugs (flunixin meglumine, or ketoprofen) are commonly used to treat inflammatory eye conditions. Parenteral administration usually achieves therapeutic concentrations in the eye and tears. Topical treatments may be more problematic because of the effort required to restrain each animal to administer treatment and the need to repeat intra-ocular treatments frequently because they are rapidly washed away by tears.
Powdered formulations for topical use are contraindicated because they can scratch the eye and worsen the problem. Subconjunctival antibiotic injection (under the eyelid) may also offer an alternative approach to treatment.
Controlling the factors contributing to corneal irritation such as flies and dust and preventing aerial dispersion of sawdust and chaff should lower incidence of eye discharges.