Pink eye

Dairy cow with pink eye

What to look for

  • Affected eyes are painful and develop a discharge
  • Animals go off their feed and try to avoid bright light
  • Ulcers may appear in the front part of the eye (the cornea)
  • Ruptured ulcers may cause permanent blindness

Cause - a bacterial infection (Moraxella bovis)

The organism is found in the environment and can remain in the eyes for long periods. Infection is aided by damage to the eye caused by dust, UV light, tall plants, pollens so pinkeye is most often seen in the summer.

Animals likely to be affected

Most common in younger animals. Under bad conditions a large number of animals may be infected. Most animals recover over a few weeks but scarring of the cornea may persist.

Confirming the diagnosis

Pinkeye is usually diagnosed by clinical examination and the history of the animals concerned. If only one or two animals are affected, other causes of eye damage must be considered e.g. grass seeds, foreign bodies. In older animals cancer eye (squamous cell carcinoma) must be ruled out. Laboratory test may be of value if the eye condition is not typical of pinkeye.

Spread of the disease

The pinkeye organism persists in the farm environment and some animals can carry the infection without showing any symptoms. Flies help spread the organism between animals.


Antibiotic eye ointments can be effective in limiting damage to the eye if applied early and repeated several days later. Injectible antibiotics may be needed in severe cases. It is helpful to apply a patch over the eye to protect the eye and assist healing.

Risk factors

  •  Yarding of animals
  • Supplementary feeding of young animals with dusty feeds
  • Feeding roughage with stalks and seed heads
  • Eye damage due to dust, strong ultraviolet light, tall plants, pollens
  • High fly populations


Minimise the effect of predisposing factors and attempt to control flies with insecticides. Separate infected animals from uninfected animals and avoid yarding of animals because this can accelerate the rate of spread. A vaccine is available and should be administered about a month before the anticipated pinkeye season and maintained by an annual booster.

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