The concern was evident in the voice on the other end of the phone line. A purebred Angus producer was in the middle of a situation. Three days ago he found three heifers with red, weepy, painful eyes. The next day there were four new cases, and this morning he found nine new cases. Was this going to go through his whole herd?
Anyone who has raised cattle for any length of time knows about Infectious Bovine Keratoconjunctivitis-better known as pinkeye. Pinkeye is a contagious inflammation of the cornea (clear part) and the conjunctiva (white part and surrounding tissue) of the eye. While inflammation anywhere in the body is bad, in the eye it's a catastrophe. The cornea becomes cloudy and cratered, the conjunctiva becomes fire-red, and the eye is swollen, painful, and blind.
Several bacteria are implicated in infectious pinkeye cases, most notably Moraxella bovis. Another bacteria, Moraxella bovoculi (sometimes called Moraxella ovis) is also frequently implicated. These bugs aren't enough to cause damage by themselves. Eye irritation or damage must occur first. These initial damaging factors are well-known and include irritation from flies, excessive sunlight, sharp weeds or grass, and dust. The bacteria then attach to the irritated eye and secrete substances that cause the inflammation and damage.
Once established in a herd, the bacteria is readily spread between animals through face flies and direct contact. The bacteria itself does not survive very long outside the animal's body. When the environmental dynamics are right for pinkeye to affect one animal in the herd, they are present for the others, too. The result is an occurrence of disease that appears to rapidly spread through a herd.
While pinkeye is something veterinarians and producers have dealt with for generations, in recent years it seems that more peculiar manifestations of the disease are more frequent. For example, during the first ten years of my practice career I only saw pinkeye cases in the summer. Now it's not uncommon for us to see winter pinkeye cases. Whether in summer or winter, it also appears that the number of cases that fail to respond to our normal treatments is increasing.
Many in the profession are asking whether these new phenomena are due to new bacterial strains. In reality, the most common bacteria associated with pinkeye cases is still Moraxella bovis. We are finding different species of pinkeye bacteria more often, but this might reflect us getting better at identifying those bacteria rather than an increase in their incidence.
An illustration of the increasing expertise in bacterial identification is a new machine we recently installed at SDSU. Traditionally after you grow bacteria out of an animal sample like an eye swab, you put it through a battery of test tube reactions to identify the bug. These reactions take time-up to 3 days in some cases. This spring we put in a machine called the MALDI -a high-tech machine that creates a chemical fingerprint of the bacteria and compares that fingerprint to a vast database. It can identify dozens of bacterial isolates at a time and can do it quickly. A set of reactions that took days can now be done in 10 minutes! This is a great example of the way SDSU's ADRDL is reinvesting in technology to better serve our veterinarians and animal producers.
We hope that new knowledge might bring new strategies to prevent this disease, because current prevention strategies leave much to be desired. Vaccines, increasingly including farm-specific vaccines made from previous cases, have not been universally effective. Fly control and managing exposure to irritants remain important but are difficult to accomplish. Pinkeye is an animal well-being issue, and animals suffering from it should get prompt attention; timely treatment with antibiotics is important. Many techniques and home-spun remedies to treat pinkeye are out there, but in my view many of them have the potential to create further damage rather than healing. Always talk to your veterinarian before contemplating a new way of treating your animals.
It turns out there is still more to know about pinkeye and its prevention. In the meantime, we need to use our current tools to help these animals get through the summer without sore eyes.