Pink eye in cattle
Pink eye is a highly contagious disease which causes clouding of the eye, squinting, and excessive eye discharge that often contains pus.
The condition may affect one or both eyes and is very painful, particularly in bright light, causing affected animals to seek shade and avoid direct sunlight. These animals have reduced weight gain, and may even lose weight.
Clouding of the eye surface (cornea) often progresses to corneal ulceration, which causes the eye to be red and inflamed, and pus may accumulate inside the eye. The ulcer usually heals leaving a white scar on the cornea, which may disappear with time or cause a permanent partial blindness. Occasionally, the eye will rupture through the corneal ulcer leaving the animal permanently blind in that eye, and requiring either surgery or euthanasia on welfare grounds.
Pink eye in cattle is caused primarily by the bacterium Moroxella bovis, however the severity of each case will vary depending on what other micro-organisms may also be present. This is an important difference from pink eye in sheep, which is caused by Clamydia or Mycoplasma species.
Flies act as vectors, spreading pink eye infection between animals, and carrier animals are the reservoir of infection. Factors which may predispose pink eye include dust and pollen, UV light, and trauma from grazing in wooded areas. Consequently infection is most common in the summer months, but can occur all year around.
Treatment of pink eye requires the use of antibiotic creams or sub-conjunctival injection. In more severe cases the eyelids may be temporarily sewn together by your vet, to help the cornea heal. Application of an antibiotic spray around the eyes and face may aid in control during outbreak situations, but generally control is based around reducing predisposing factors (such as controlling flies, mustering during the cool of morning/evening to minimise dust etc). Vaccination may be useful in the face of an outbreak, or when a property has significant problems from one year to the next.
Talk to your vet if you are concerned about pink eye in your herd.