In each of the last two years, we have had an early winter “outbreak” of what looks like pinkeye in our bred heifers. They are housed indoors, and there are no flies around at that time of year in southern Wisconsin. We have given them antibiotics and it seems to help, but some have been affected quite badly. Is this really pinkeye? – WISCONSIN B.G.

Simon Peek
As many readers will have experienced, pinkeye can be a nuisance for producers and extremely painful for cattle. In nonlactating heifers, there are more and better treatment options compared to lactating adults because some of the preferred, established treatments identified by research studies utilize long acting intramuscular or subcutaneous antibiotics are either not permitted in lactating animals or have excessive residues.

The term “pinkeye” tends to be used quite loosely to describe any case of inflamed, painful ocular disease in cattle where several animals in a group are often affected. The technical name is infectious bovine keratoconjunctivitis, but for obvious reasons, no one prefers to say that term quickly or several times in a conversation.

For decades, the cause has been considered to originate from the bacterial species Moraxella bovis. Flies, UV radiation, and trauma to the eye’s surface from plants, grass awns, and so forth enable the bacterium to colonize the surface of the eye and elaborate its specific toxins that damage the surface of the eye.

Pinkeye has often been thought to be pasture-associated, and therefore a summertime condition, partly because of the role insects and sunlight play in the disease. However, many farmers and veterinarians have encountered individual cases and outbreaks of pinkeye in the winter months, and this raises the possibility that there are other infectious agents involved. Irritation from dust and new bedding, particularly when new material is added with animals in the pen, can also play a role during winter months. Bedding down pens with animals present may be a significant contributor to outbreaks in younger animals that are closer to the ground due to their stature.

Mycoplasma, infectious bovine rhinotracheitis (IBR, a herpes virus), Listeria, and other bacterial species (including another Moraxella species known as Moraxella bovoculi) can also be associated with pinkeye in cattle. Without samples from affected eyes submitted to a diagnostic laboratory, it would be hard to know which of these potential agents might be involved in a seasonally unusual outbreak of the problem.

Some pointers can come from the appearance of the eyes upon close veterinary examination. The presence or absence of other forms of disease that are associated with these additional agents can also help narrow down the cause. Listeria, for example, can also cause neurologic disease in cattle of the age you describe. Mycoplasma and IBR might be associated with pneumonia, whereas Moraxella spp are purely a cause of ocular disease.

No conversation about pinkeye would be complete without mentioning vaccines. There are commercial vaccines against both Moraxella bovis and Moraxella bovioculi available, and many people have used autogenous vaccines, which are made by a commercial laboratory “to order” for a veterinarian or farm using an isolate obtained from cases over the years, with variable success. If any vaccine is going to be used, it is likely to be most effective if administered in advance of any seasonal incidence of disease, rather than in the midst, or worse still, immediately following an outbreak.

Sample submission from acutely affected eyes is recommended, especially in the presence of an unusual outbreak. This will help guide both treatment decisions as well as whether or not specific vaccines should be entertained and the timing of when they should be utilized in the future.