This is a malignant growth on the surface of the eye ball, eye lid or 3rd eye lid. It mainly affects Hereford and Friesian breeds in areas with prolonged exposure to sunlight.
Cattle at greater risk are older (>3 years), have protruding eyes, unpigmented eyeballs or lids, and are resident in higher latitudes (more sunlight hours), or areas with long dry seasons. Cancer eye is rare in the live export process because cattle are generally young.
Lesions always start on unpigmented areas of the eye ball or eye lids. Early lesions appear as discrete raised whitish areas on the 3rd eye lid or corneoscleral junctions of the eye, or dark, crusty wart-like lesions on the margins of upper and lower eye lids. If they progress, lesions will grow, ulcerate, bleed, become friable and may smell foul from necrosis or infection. Without intervention there can be progressive invasion of the eye and face, lymph nodes of head and neck, and eventual spread to distant organs such as the liver and lungs. Affected animals will ultimately die from this condition if untreated.
Early lesions are easily missed because cattle tend to face observers side-on displaying the best functioning eye. Eye lesions in Herefords and Friesians should always be subject to close examination.
Differential diagnoses include warts, foreign bodies and pinkeye.
Options for treatment include surgical removal of lesions or the entire eye, possibly associated with cryotherapy (freezing) and irradiation. Choice of treatment will be influenced by extent of the lesion(s), time available for recovery, skill, resources and stage of the live export process. Early stage lesions are more amenable to treatment. Larger and more chronic lesions have a higher risk of recurrence and consideration should be given to exclusion of affected animals from the export process, and organising salvage slaughter without delay. It may be an offence under relevant welfare acts to allow cancer eye to develop to advanced stages and animals may not be allowed to be processed for human consumption if the eye is discharging or if lymph nodes are involved.
At sea, removal of a cancerous 3rd eye lid, using local anaesthesia and scissors, offers a quick, simple and permanent cure if adequate restraint is achievable.
Both eyes should be systematically checked during selection for the live export process and animals with suspicious lesions excluded.