This season has been particularly bad for pink eye with outbreaks involving large numbers of calves and even adult dairy cows. It can be frustrating as it can involve a lot of time and cost.
Three calves in a mob of 103 were noticed to have weepy eyes. On closer inspection a few days later 35 were isolated for a vet visit. Symptoms were consistent with pink eye, ranging from slight weeping of the eye to severely affected eyes with large corneal ulcers.
Most cases were treated with eye ointment while nine severely affected eyes required eye surgery to create a third eyelid flap (essentially acting as a bandage). Two cases were swabbed to identify if vaccinating would be beneficial. Severe cases were also given antibiotic and anti-inflammatory treatment. Affected calves were managed in their own mob to limit the spread of infection.
At the follow up a week later most cases were significantly better. Swab results interestingly were negative for the bacteria which the vaccination targets, so the decision was made not to vaccinate. The farmer continues to isolate and treat new cases (18 more over two weeks). Many have recovered well. Overall around 50% of the mob has been affected.
Pink eye peaks in summer
UV radiation from sunlight can damage the surface of the eye so it is no wonder we commonly see this disease in New Zealand’s hot dry summer. To make matters worse, the dust, pollen and plant debris (like grass awns and PKE dust) can exacerbate or even initiate a pink eye outbreak.
Face flies, another summer nuisance, are known to carry pinkeye organisms between animals or even from one eye to another on the same cow. Spread can be rapid but animals affected in one eye may recover then present with the other eye affected some weeks later.
How do we identify pink eye?
Typically, we make a presumptive diagnosis based on clinical signs such as:
- Sudden onset of discharge from the eye (e.g. tears)
- Redness and swelling of the tissue around the eye
- Cloudiness of the cornea (the surface of the eye)
- Holding the eye closed or partially closed
- Sensitivity to light
- Inflammation in the front chamber of the eye
- Animals may appear to be blind and some advanced cases can go totally blind
- Pain – ulcers on the surface of the cornea are very painful although some animals may hide their pain.
There are several different causes of pink eye so we recommend getting your vet to swab a few newly affected eyes to identify which organism is the cause. The results of the swab will help us determine if you should vaccinate your stock (only certain bacteria are covered by the vaccine) and can help us choose and appropriate and effective antibiotic for treatment.
What to do in an outbreak?
Unfortunately, there are some things we just cannot control, like the dry, dusty wind. However, there are some steps you can take if you are experiencing an outbreak:
- CATCH IT EARLY; CALL YOUR VETERINARIAN TO TAKE SWABS OF THE EYE!
- Use the vaccine. It can be used in an outbreak but it takes weeks to work and it does not protect against all causes of pink eye.
- Use the eye antibiotics prescribed by your vet and follow their directions.
- Manage the flies by covering food and use fly repellent products like Blaze or Ripcord.
- Limit yarding of stock to reduce the spread of infection to healthy animals.
- Consider set stocking calves, 2 or 3 to a paddock, to reduce infection pressure.
- Wet the race before the cows come in and add molasses to PK to dampen dust.
- Avoid contact with neighbouring or new cows and consider quarantining new animals including calves and breeding bulls.
- Isolate suspicious animals and start treatment immediately.
- If possible, offer shaded areas for all animals during peak sunlight hours.