In DCHA Gold Standards II, production and performance guidelines for heifers from 6 months of age to freshening, one of the areas covered is "Vaccinations and Parasite Control." With the weather becoming more spring like in southern areas, it's a good time to focus on pinkeye and its prevention.
The November 2010 issue of Veterinary Clinics of North America Food Animal Practice is devoted to diseases and abnormal conditions of the eye; about half of the issue considers eye diseases of cattle.
The condition commonly identified on the farm as "pinkeye" can be:
1. "infectious bovine keratoconjuctivitis" or IBK, is due to an infection by Mycoplasma boviculi or Chlamydophila spp or other Moraxella spp. The primary agent M. bovis, is spread primarily by the face fly (Musca autumnalis). Other bacterial species also have been found to cause IBK.
2. "listerial keratoconjunctivitis and Uveitis," otherwise known as "silage eye," is due to an infection by the Listeria monocytogenes. Listeria infections are fatal in 25% of human cases, most of which arise from food contamination. Listeria causes encephalitis, abortions and septicemia in both cattle and people. In recent years, Listeria has been identified as the source of eye infections in cattle. The primary source of Listeria bacteria that infect the eyes of cattle is silage, thus the common name "silage eye."
3. Bovine Ocular Squamous Cell Carcinoma (cancer of the eye) may affect less than 1% of a herd up to over 30% of a herd consisting exclusively of Hereford cattle with white eyelids living in areas that are subject to higher than average amounts of sunlight. If detected early, many cases can be cured with a simple removal of the 3rd eyelid (which is often the first part of the eye that is affected).
4. Physical injury, which often is followed by bacterial infection.
Prevention of "pinkeye" must thus be directed at controlling each of these factors. Moraxella boviculi is present everywhere. To the extent that the bacteria is spread by flies, the frequency of the disease can be reduced by fly control. In an article entitled "Infectious Bovine Keratoconjunctivitis: A Review of Cases in Clinical Practice" in the November 2010 issue of Veterinary Clinics of North America Food Animal Practice, Dr. Dominic Alexander of the University of Cambridge notes that treatment of IBK can often be very effective if detected early.
Injecting antibiotics (not labeled for treating pinkeye) directly into the eyelid is commonly practiced, but the procedure is controversial and should not be attempted without consultation from your veterinarian. This method is more difficult and potentially more dangerous to the animal than other options, and relapse of infection often occurs if the infection is advanced. Tests have been done with other antibiotics, without clear success.
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