PINK Eye (Infectious Bovine Keratoconjunctivitis) is a highly infectious disease generally caused by the bacterium Moraxella bovis.

The economic cost of Pink Eye in Australia has been estimated at $23.5 million annually through loss of production, reduced weight gain, decreased fertility, increased culling and treatment costs, to name a few.

As Pink Eye causes significant pain in affected stock, it has important animal welfare implications as well.

Predisposing factors for the development of Pink Eye include flies, UV light, long grass or hay, dust, viral infections (IBR), reduced immune status and stress.

After initial infection, the bacteria attaches to the surface of the eye where it produces toxins that erode the cornea causing ulceration, severe inflammation (uveitis) and pain.

The clinical signs of Pink Eye vary with the severity and progression of the disease.

Stage 1 – cattle have excessive tearing, blinking and squinting due to increased sensitivity to light and pain. As the disease progresses, a small ulcer will appear in the centre of the cornea which appears cloudy.

Stage 2 – The ulcer becomes large and deeper and the eye becomes increasingly cloudy. Blood vessels begin to grow across the cornea which make the eye look pink.

Stage 3 – The ulcer covers the entire surface of the eye and extends into the inner structures of the eye. This leads to severe inflammation which makes the eye appear yellow.

Stage 4 – The ulcer extends completely through the cornea resulting in the eye rupturing. The iris will plug the rupture and may protrude through the ulcer. At this stage the animal will not regain sight in this eye and the eyeball may collapse or end up being permanently swollen (glaucoma).

Prevention of pink eye revolves around controlling flies, reducing competition around hay and grain feeders, minimising yarding, optimising health and nutrition, vaccination and isolating affected animals from the rest of the mob to reduce spread if possible.

Fly control often needs to be a multi–pronged approach.

Topical repellents applied to cattle regularly can be an important control method.

Baits and surface sprays are important in controlling flies in areas such as calf sheds.

An effective fly control program needs to be started early in the fly season to prevent a build–up of larvae and pupae that will continue to hatch over summer.

Vaccination can also be an important part of a Pink Eye control program.

A registered vaccine is available in Australia and covers three of the five strains of M. bovis present in Australia.

It is not 100 per cent effective in preventing Pink Eye but surveys have shown that in about 70 per cent of outbreaks of Pink Eye, at least one of the three strains present in the vaccine is involved.

The vaccine needs to be administered three to six weeks before the start of the Pink Eye season as a single vaccination.

Immunity will last for about five to six months.

Calves as young as two weeks old can be vaccinated.

The vaccine is an oil emulsion vaccine and accidental "self–inoculation" is serious – seek immediate medical advice if this occurs.

Occasionally, outbreaks of Pink Eye are caused by a different bacteria – Moraxella bovoculi.

M. bovoculi tends to cause severe Pink Eye that often affects both eyes in an animal.

An autogenous vaccine for M. bovoculi can be manufactured and used under strict veterinary supervision on individual farms.

Treatment of Pink Eye is often frustrating and time consuming.

If small numbers of animals are affected, a registered topical antibiotic eye ointment is the treatment of choice.

It only needs to be applied every second day, reducing the stock handling needed.

If a high percentage of a mob of cattle are affected, it is often more time and cost effective to treat the entire mob at once with a long acting injectable antibiotic.

An anti–inflammatory injection should be administered to any affected animals to control the pain and reduce the inflammation in the affected eye(s) and a patch applied to protect the eye from sunlight and reduce spread to other stock.

In severely affected animals (stage three and four) or valuable individual animals, your vet can inject antibiotics and cortisone under the sclera (white part of the eye) and perform a third eye lid flap to protect the eye and promote healing.

Pink Eye can be a complex disease to prevent, control and treat.

Contact your local veterinarian for advice tailored to your individual farm and situation.