Pinkeye is properly called infectious bovine keratoconjunctivitis (IBK) in cattle, which translates to an infection that causes inflammation of the surface of the eye and the tissues surrounding the eye. Pinkeye can affect cattle at any age, but it is much more of a problem in young cattle because they have not yet had the opportunity to develop immunity to it. Although cases can occur any time of year, it is more prevalent in the summer because that is the time of greatest irritation and the time for the presence of vectors. Although pinkeye is not fatal, it results in very significant economic losses due to costs of treatment, poor performance, and in the case of blindness, the value of the animal is decreased.

The infection is primarily due to the bacteria Morexella bovis, but other bacteria such as Morexella bovoculi and Mycoplasma spp. have been implicated. Respiratory virus infections, particularly Infectious Bovine Rhinotracheitis (IBR), can be part of the picture by either causing an inflammatory eye condition that predisposes the animal to the more severe bacterial infection, or by acting as secondary invaders that make bacterial damage even worse.

Although an organism acts as the causative agent, several conditions contribute to the syndrome. Animals with compromised immune systems due to either poor nutrition or chronic debilitating disease are more susceptible. Physical irritation contributes to an environment in the eye for the organism to thrive. Sources of irritation include UV light, dust, plant or hay materials, and flies. Flies are a two-edged sword because they not only contribute to the irritation of the eye but also serve as vectors to carry bacteria from one animal to another. Flies may carry the organism for up to 3 days. Animals that overcome the syndrome without treatment can remain as carriers for up to one year, thereby carrying the problem forward from one year to the next spreading the organism to susceptible animals.

The course of the disease is fairly rapid. Within 2 or 3 days from onset, an opaque area can be seen on the surface of the eye and the tissues around the eye may become reddened and swollen. The eye weeps or tears excessively, and the animal usually stands with the eye closed due to pain. This discomfort seriously reduces grazing time and weight loss may follow. In time the surface of the eye will become entirely opaque, causing blindness, and on close examination deep ulcers can be seen on the cornea. If untreated, the condition can last for 4 to 8 weeks. Eventually resolution comes in one of three forms. With proper treatment, most animals eventually heal with no permanent damage but experience severe economic loss. Some animals heal but develop varying degrees of white scarring on the cornea. In some cases, the cornea ruptures resulting in a cone shaped bulging of the eye structure and permanent blindness.

Early diagnosis is the key to successful treatment. Treatment should begin by removing the animal from the herd and placing it in isolation. Although long acting oxytetracycline is labeled for treatment of pinkeye, a producer may wish to consult with their veterinarian on antibiotic selection since some antibiotics may work better in certain situations. Also, a veterinarian may prescribe non-steroidal anti-inflammatory drugs for pain relief. If it is treated early, there is less tissue damage and faster healing. However, if allowed to progress until ulcers are formed, pain and damaged tissues persist much longer. Healing is facilitated by using a patch over the eye to keep out irritants such as flies, light, and dust. Another option is to suture the eyelids together for a few weeks which not only keeps irritants out of the eye but also provides structural support that may help prevent the eye from rupturing. A veterinarian can help with this procedure.

 

In all cases, producers should control flies for the comfort of the sick animal and for the prevention of the spread of the disease.

With pinkeye, as with many other syndromes, an ounce of prevention is worth a pound of cure. Fly control is perhaps the most important preventative measure. Shade should be provided so that animals can find relief from UV light during the brightest part of the day. When shade is limited, it can cause the animals to group tightly which allows for increased spread of the organisms from animal to animal by flies or by direct contact of eye secretions. It is helpful to reduce eye irritations by clipping seed heads off tall grass. Do not feed hay overhead where grass and seed heads can fall into the eyes. Vaccinating for virus respiratory diseases may help reduce the incidence and the intensity of pinkeye outbreaks. Although several pinkeye vaccines are available, they may or may not be helpful since there are many different strains of M. bovis and the many other factors involved in the disease process. Being selective with replacement heifers is also good practice since choosing animals with pigment around their eyes reduces the risk. When possible, select heifers that come from cows that have no history of pinkeye infections. Heredity for this trait is low but over time immunity should improve in the herd.

 

There is no silver bullet for pinkeye. No single management practice will eliminate the disease. Control depends on understanding factors involved, such as bacteria, vectors, irritants, and immunity. By incorporating consideration of these factors into the overall management of cattle, one can minimize the impact of pinkeye on animals and on profitability. An excellent fact sheet VTMD-9128 on pinkeye is available from Oklahoma State University County Extension Office. For additional information, producers should consult with their veterinarian or Oklahoma State University County Extension Ag Educator.

 

Reference

Angelos JA. Infectious bovine keratoconjunctivitis (pinkeye). Vet Clin North Am Food Anim Pract. 2015 Mar;31(1):61-79, v-vi. doi: 10.1016/j.cvfa.2014.11.006. Epub 2015 Jan 6. PMID: 25576389.