Veterinary Viewpoints: Keep an eye on the eyes

Veterinary Viewpoints: Keep an eye on the eyes

Monday, December 9, 2024

Media Contact: Kinsey Reed | Communications Specialist | 405-744-6740 | [email protected]

Common eye problems in cattle include irritation from plant awns, pinkeye and cancer eye - squamous cell carcinoma. This article outlines the predisposing factors and clinical signs associated with these conditions to aid in early detection within your herd.

Plant Awns

Eye irritation caused by plant awns can occur while cattle graze or feed on haylage. This irritation can predispose cattle to pinkeye or cause ocular foreign bodies, leading to clinical signs that mimic pinkeye. Both young and adult cattle are susceptible. Clinical signs include excessive tearing in one or both eyes, frequent blinking, and the animal holding the eye partially closed due to pain. If the foreign body is not removed, it may cause an ulcer on the cornea - the clear surface of the eye - or penetrate deeper into the eye. Over time, the affected eye may become cloudy white and later take on a reddish appearance.

Pinkeye

Pinkeye, caused by the bacteria Moraxella bovis, is most common in the summer but can occur year-round. It affects all breeds and often results in herd-wide outbreaks. Younger cattle, especially those under 2 years old, are more commonly affected. Pinkeye is spread through direct or indirect contact with infected cattle, with face flies playing a significant role in its transmission. These flies feed on eye secretions from infected animals and transfer the bacteria between cattle. Factors like sunlight, wind, dust, pollen and tall grass can irritate the eye and make cattle more susceptible to pinkeye.

The first signs of pinkeye include excessive tearing in one or both eyes, followed by redness of the conjunctiva - the inner surface of the eyelids and outer surface of the eye - and frequent blinking. As the infection progresses, the cornea may become inflamed and take on a cloudy white or blue appearance. An ulcer typically develops in the center of the cornea, and affected cattle may begin holding the eye partially or completely closed due to discomfort. As healing starts, blood vessels grow across the cornea toward the ulcer, giving the eye a red appearance. In severe cases, a white scar may remain on the cornea, and without treatment, the eye may rupture, leading to blindness.

Cancer Eye (Squamous Cell Carcinoma)

Squamous cell carcinoma (SCC) of the eye and surrounding tissues is a common condition in cattle, affecting areas like the eyelids, third eyelid, conjunctiva and cornea. Although the exact cause of ocular squamous cell carcinoma (OSCC) is not fully understood, cattle with white or unpigmented skin around their eyes - such as Herefords - and those exposed to high levels of ultraviolet (UV) sunlight are at higher risk.

The development of OSCC occurs in four stages. The first stage is the appearance of plaques, which are small, raised, white areas on the cornea. The second stage involves keratomas, which are skin growths, often occurring on the lower eyelid. The third stage, papillomas, may appear wart-like, and the fourth stage is characterized by carcinomas, which are more cauliflower-like. While the first three stages - plaques, keratomas and papillomas - are benign, they are considered precursor lesions that can progress to carcinomas - malignant - if left untreated. In advanced cases, OSCC can spread to nearby lymph nodes. This type of eye cancer is a leading cause of carcass condemnation at slaughter.

If you observe any clinical signs of plant awn irritation, pinkeye, or cancer eye in your cattle, it is important to consult your veterinarian promptly for diagnosis and treatment.

Dr. Melanie Boileau is a professor, food animal medicine and surgery large animal clinical educatorat the Oklahoma State University Veterinary Medical Teaching Hospital. Certified by the American Animal Hospital Association, the hospital is open to the public providing routine and specialized care for all species, as well as emergency care. Call 405-744-7000 for an appointment or see more information at vetmed.okstate.edu.

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