Summer weather often signals the onset of pinkeye in cattle. Meat and Livestock Australia (MLA) estimates this familiar but challenging disease costs Australian beef farmers over $23 million annually in lost production and treatment costs.
Pink eye – infectious bovine kerato-conjunctivitis – is painful and debilitating. Left untreated it can lead to permanent blindness. The potential impact on the mob – up to 80% infected – makes effective and early treatment of the disease essential.
The causative organism, the bacterium Moraxella bovis, produces a toxin that causes severe inflammation on the surface of the eye and in the surrounding tissues. It is highly infectious and can spread rapidly through a herd.
Producers usually first notice increased tears running down the face of an affected animal. The eye is red and inflamed, and increased sensitivity to light causes the animal to blink and close its eye frequently. One or both eyes can be affected.
The classic pink eye white spot (an ulcer) forms in the centre of the eye. In an attempt to heal the ulcer, the cornea responds by growing blood vessels into the centre of the eye, making it appear pink. If the eye heals at this stage, it turns cloudy blue then, after 4 to 5 weeks, it returns to normal or may retain a white scar. If large enough, the scarring can impair vision.
Without early treatment, the initial white spot often progresses to affect the entire eye. It turns yellow (indicating an eye chamber full of pus), may rupture, and ultimately becomes a shrunken, sightless eye. Cattle with both eyes affected can die from starvation, thirst or misadventure.
Environmental and other predisposing factors
Summer conditions – flies, dusty yards and paddocks, harsh ultraviolet light and damage to the eyes from foreign bodies such as thistles and grass seeds – all predispose cattle to pink eye infection. The potential for outbreaks increases if cattle are confined in dusty yards for any length of time.
Younger animals are more vulnerable to infection and genetics also play a role. British and European breeds are more susceptible than Bos indicus cattle, and the white faces of Herefords increase susceptibility.
One of the key factors in the disease’s persistence and spread in a herd is the carrier status of individual cattle. These carrier animals show no signs of pink eye but if predisposing conditions create excess tear production, flies are attracted which feed on the infected secretions and spread the bacteria from animal to animal. Moraxella can also be carried in discharges from the nose and vagina.
Prevention with vaccination
A single dose pink eye vaccine is now available from CVH and for best results, should be given 3 to 6 weeks before the pink eye season – that is, in early spring. The vaccine is much less effective once the infection becomes established in a herd during the warmer months. This means timing is critical for producers – especially those with a history of pink eye in their herds – to take preventative action by vaccinating in September.
Minimising infection and spread
Aim to avoid:
- Confining cattle in dusty yards for any length of time
- Grazing paddocks with heavy infestations of thistles and sharp, dry stubble
- If mustering a mob to treat pink eye, water down dusty yards, or isolate and treat individual animals to avoid spread.
- Consider fly control strategies. Applying an animal fly repellant to the head of cattle deters flies for several weeks.
Early treatment is essential and results in faster healing with less scarring. Most importantly, it limits spread by decreasing the infective bacteria in a mob.
- The most effective treatment to date is a long-acting (48 hours) penicillin eye ointment such as Opticlox or Orbenin. If treated early enough, one dose may be sufficient.
- Powders and sprays are not as effective and can be painful when applied.
- Long acting antibiotics (such as oxytetracycline) can be useful, if more expensive.
- Eye patches give excellent protection from UV light, flies and dust and are cheap and easy to use.
Talk to our vets about pink eye – it’s important to work out a management strategy quickly to minimise spread and deliver the most effective prevention and/or treatment for your particular situation.
Acknowledgement: NSW Department of Primary Industries