Pink eye can be a real problem over summer.
Pink eye is caused by a number of viral and bacterial factors but the cause is a bug called Moraxella bovis. Moraxella bovis is carried in the nose and eye fluid from infected and carrier cattle. If the factors are favourable, pink eye can spread quickly and cause pain, eye damage and production losses, particularly in young stock.
Factors that increase the risk of pink eye:
- Flies – responsible for spread of the bacteria between animals.
- Ultraviolet light – sensitises and can damage the cornea.
- Long grass – causes physical damage and can cause mechanical transmission.
- Dust – irritates eyes, increases tear production and assists spread of bacteria.
- Pigmentation – pinkeye is generally more common in non-pigmented eyes.
- Breed - more common in Bos taurus than Bos indicus cattle.
- Overcrowding (e.g. cattle congregating for drought feeding, yard weaning).
- Immune status - cattle in poor body condition tend to be less able to mount a protective immune response against the bacteria.
- Prior exposure leads to immunity, hence disease is more common in young stock. Adult stock are still susceptible if they have not been previously infected. Herd outbreaks were observed in Tasmania when the disease was first introduced.
Clinical Signs of Pink Eye
- Increased tear production is often the first sign seen.
- The cornea then becomes cloudy and a white spot can appear in the centre.
- Some cases clear at this stage but others progress to corneal ulceration and the cloudiness covers the whole cornea.
- The eye changes from a white to a pink to a yellow colour.
Some of these eyes will return to normal following treatment, some will resolve with no treatment, some develop a small white scar and others are left permanently blind.
How does the vaccine work?
Pili are hair like structures on the surface of many bacteria – they aid attachment of bacteria to the surface of the cornea. Vaccination with Piliguard, which contains pilus antigen, blocks the attachment of bacteria to the cornea and prevents establishment of infection.
Vaccination has a number of advantages over current treatment methods for pinkeye:
- Vaccination reduces the incidence and severity of the disease,reducing individual animal suffering and production losses.
- Pinkeye is often well advanced before animals are treated and as such animals often don’t respond well to treatment.
- Vaccination reduces the need for antibiotics and therefore reduces the risk of bacterial resistance or residues.
To be effective, the vaccine needs to be given 3 to 6 weeks before the “pink eye season”. The vaccine is a single, 2 ml injection under the skin Annual revaccination is recommended. Calves as young as 1 week can be vaccinated. There is no milk or meat withhold.
Is it worth vaccinating?
The vaccine only claims to AID in the control of pink eye – it will not totally prevent it. There are different strains of the bacteria which causes pink eye and the vaccine contains 3 of the strains. Research in Australia showed that in over 77% of pink eye outbreaks examined, the causative bacteria found in the cattle cross-reacted with the strains in the vaccine. What this means is that in three quarters of the outbreaks examined, the vaccine would have helped make the outbreak less severe.
To decide whether the vaccine would be a worthwhile addition to your pink eye risk management, you will need to weigh up:
- How much your herd is typically affected by pink eye
- The weather forecast for the season ahead – dryer spring/ summer tends to exacerbate the risk of pink eye
- The cost of vaccinating
- The cost of production losses and treatment in dealing with pink eye
BUT, remember, the vaccine must be given 3 to 6 weeks BEFORE the peak pink eye season. Late September/early October is the time to be administering this vaccine.
You can help prevent pink eye by limiting fly numbers with products such as Easy-Dose, Solfac Duo and QuickBayt, trying to choose paddocks which are not dusty or have long, dry grass. If animals do get pink eye, prompt treatment with the correct ointment will prevent the severe damage to the cornea. If animals get severe Pink Eye, we can help limit the damage and animal suffering. Sometimes we will give injections into the tissue around the eye and sometimes we will sew the eyelids together for a short time to protect the eye and aid healing.