Tim Page, LSU AgCenter
INTRODUCTION
There are many cattle diseases to be concerned about as a producer but pinkeye is one of the more highly contagious diseases. It is an infectious bacterial disease of the eye of cattle caused by Moraxella bovis. It has been documented around the world. Even though pinkeye is a non-fatal disease, it does have an economic impact on the cattle industry. Pinkeye commonly occurs in the summer and fall and younger cattle are more susceptible to the disease because older animals have most likely developed acquired immunity as a result of previous exposure. The prevalence and severity of pinkeye on a particular farm may vary from year to year and is dependent on multiple factors. Infection rates may range from a few cases and up to 80 percent of the herd at the peak of infection.
CAUSES OF PINKEYE
The bacteria Moraxella bovis is the primary infectious agent initiating pinkeye. Other organisms that can initiate pinkeye include Chlamydia, Mycoplasma, and Acholeplasma, or viruses such as the Infectious Bovine Rhinotracheitis (IBR) virus, which can either add to the severity of the disease process or may serve as predisposing factors permitting a secondary infection with Moraxella bovis. Other factors that are instrumental in causing eye irritation are excessive sunlight, flies, plant material and dust and they can lead to allowing invasion of the bacteria and subsequent disease. Excessive sunlight is a problem for cattle lacking pigmentation around the eye. Lack of pigmentation allows increased ultraviolet radiation to sensitize the eye, resulting in inflammation and infection. Flies serve as irritants and they feed on secretions from the eye. They also serve as a means of transmitting the disease from infected to non-infected cattle. Some grasses, weeds and brush produce air-borne irritants, pollen, and serve as mechanical irritants.
TRANSMISSION OF PINKEYE
Transmission of pinkeye occurs through direct contact, flies and inanimate objects. The organism is located in the eyes and nasal cavities of infected cattle. Infected secretions from these areas are a source of infection for other cattle. Some cattle may show no symptoms of the disease but may be carriers and will harbor the disease for over a year. These carrier cattle are real problems because they allow for the persistence of pinkeye at a farm from year to year.
PINKEYE SYMPTOMS
Swelling and redness of the conjunctiva, excessive tearing, and squinting are the initial signs of the disease. Cattle will usually have a depressed appetite due to the excessive pain and some high body temperature. A small opaque area appears in the center of the cornea in about two days and usually within a week the entire cornea will have a gray-white to yellow color with deep central ulceration of the cornea. Severe ulceration, bulging of the eye and blindness usually does not occur. More times than not, complete recovery occurs in three to five weeks with only a few affected cattle having a persistent white scar on the cornea.
PINKEYE TREATMENT
Pinkeye is usually susceptible to oxytetracycline such as LA-200, Bio-Mycin 200 and AnchorOxy 200, ceftiofur, penicillin and sulfonamides. Sensitivity patterns can and do change which makes it necessary to sample a representative number of infected cattle in the herd to determine the most effective drug. Long acting oxytetracycline has been shown to be an effective treatment in calves when used early in the disease process. It sometimes will clear pinkeye from the infected eye in 24 hours of the first injection. When severe corneal ulceration exists, you should protect the eye from sunlight, flies and other irritants through the use of eye patches or suturing the eyelids.
PINKEYE PREVENTION
Management is usually the most effective and economical method of disease control. Properly managed environmental conditions, nutrition and herd immunity increases animal health and decreases disease frequency. A decline in disease frequency results in a decrease in concentration of infective organisms on the farm. Fly control through the use of fly tags, sprays, charged backrubbers or dusts is necessary. Manure, weeds, and brush control are required for total fly control. Proper immunization against viral diseases, isolating infected animals and decreasing environmental and nutritional distress are all important in disease management. Commercial pinkeye vaccines are available. The results reported from producers that use the vaccines are mixed. You should check with your veterinarian to determine the best method(s) for preventing pinkeye and other diseases.