Eye cancers – blink and you’ll miss them
Eye cancers in cattle are invasive and can spread rapidly, leading to significant economic losses if the animal is condemned. Figures from NSW indicate that 33 per cent of total condemnations in mature cattle are due to cancer eye, while 58 per cent of all cancers that result in condemnation of mature cattle slaughtered in NSW involve the eye. (Australian Quarantine Inspection Service, NSW, 2010–2014).
Eye cancers are more common in cattle with little or no pigmentation around their eyes, such as Herefords or Holstein-Friesians. As in humans, this unpigmented skin is higher risk for sun damage predisposing to cancers, but they are possible in any animals of any colour.
Older cattle are also more susceptible, with cancers being uncommon in cattle under the age of five. Other risk factors are not fully understood, but it is suggested that viruses and infections causing inflammation of the soft tissues in and around the eye may also predispose animals to eventually developing eye cancers. Risk factors leading to eye cancers are moderately heritable.
Tumours may be found on the third eyelid, along the the edges of the upper and lower eyelids, and on the eyeball itself.
There are four common types of growth involving the eye region:
- Plaque (benign) — small circular, white elevation on the surface of the eyeball. Minimal to no discharge.
- Keratoma (benign) — hard, raised growth on the eyelids, often with discharge and debris.
- Papilloma (benign) — a wart-like growth.
- Carcinoma (malignant) —nodular and cauliflower-like. Commonly bloody, ulcerated, and discharge is foul smelling. These tumours can be quite painful, and are a welfare concern. Benign growths can also transform into carcinomas over time. Malignancy means carcinomas are able to spread and invade surrounding tissues including the soft tissue and bone of the eye and eyelids, and lymph nodes (lumps felt under the ear or jaw).
Veterinary attention to cancer eyes should be prompt. Treatment is usually aggressive.
The success of treatment is highly dependent on the location of the tumour and invasion of surrounding tissues. Your veterinarian should check the lymph nodes of the head and neck prior to any treatment to help give a prognosis. If there is evidence of spread, the animal should be humanely euthanased as it will be condemned at an abbatoir and is not fit for sale.
Cryotherapy (freezing the tumour off with a cryogen such as liquid nitrogen) works well on small tumours (<2 cm diameter) on the eyeball itself. Ionising radiation such as strontium-90 may also be applied to the tumour.
Surgical treatment of eye cancers is common and warranted, particularly in the early stages, but must be performed by a veterinarian. Cancers can be removed, either in isolation or by removal of the entire eyeball.
In some cases, removal of very early cancers will result in a permanent cure, however despite treatment 50-60 per cent of cases recur — particularly where the cancer is more advanced and achieving good surgical margins is unlikely. Where possible it is not advisable to continue to breed from treated cattle.
Prevention and control
To avoid financial loss and maintain a high standard of welfare in your herd, early detection and appropriate treatment are essential. Maintaining easy identification of cow numbers and performing regular inspections of both eyes is advisable. Personally, nothing makes me more disappointed in a client than spotting an eye cancer during a herd health visit that has been left far too long and is causing the animal pain. You can expect a stern conversation with your veterinarian if you knew about it but haven’t acted - failing to obtain veterinary attention or provide appropriate treatment for a cow with an advanced eye cancer is a notifiable offence.
Cattle with moderate to severe cancers (large, ulcerated or foul-smelling tumours) are not fit for transportation. If transported, they may be judged unfit for sale and condemned, and farmers risk penalties. Animals with small (less than a 2cm diameter or 5¢ coin size) and mild lesions where treatment is not pursued should be sent directly to the abattoir rather than to public saleyards. If there is any evidence of spread of the cancer to nearby lymph nodes, the animal will be condemned at abbatoir inspection. Occasionally, a seemingly small cancer may have already spread internally, in which case the carcass will also be condemned.
Lucy is completing her Dairy Residency with The University of Melbourne. She works as an on-farm veterinarian for Apiam Animal Health, and alongside her partner on his family’s dairy farm in South West Victoria. She is a 2021 Nuffield Scholar supported by Gardiner Dairy Foundation.