Pinkeye is caused by infection of the eye by the bacteria Moraxella bovis.  It occurs worldwide and is most common during summer and autumn.


Prevalence of Pinkeye varies within a herd from year to year.  Only cattle are affected and younger stock are the most susceptible.  Up to 80% of a herd can be affected in an outbreak.


Risk Factors

  • Eyes with complete pigmentation are less often affected.
  • Exposure of the eye to high levels of UV light increases susceptibility.
  • Flies, dust and long grass increase infection rates.  This is due to contamination with ocular and nasal discharge from infected cattle being transferred to other individuals.
  • The bacteria can be carried in the nose of cattle for longer than a year which enables the disease to persist from year to year.
  • Although infection is most common in summer and autumn severe outbreaks can occur during winter when cattle are kept in confined spaces such as barns and feed lots.


Clinical Signs

Swelling around the eye, watery discharge and shutting of the eyes are usually the first signs noticed.  After 1-2 days a white area often develops in the centre of the eye and may spread to cover the entire surface.  Recovery usually occurs after 3-5 weeks.