At the request of Dr Robert Churchill of Crookwell Veterinary Hospital I have done a brief evaluation of the subconjunctival injection of antibiotic and steroid as a treatment for pink eye in cattle caused by Morexella bovis.
Some decades ago we had a troublesome pinkeye outbreak when we farmed at Picton. Pinkeye has not been a serious problem to us since moving to Binda in 2001. We have probably had more cases of grass seed in the eye than pink eye and the need for prompt and effective treatment is equally important. However, over the past six months we have had a severe outbreak of pink eye in our young stock. December 2013 and January 2014 were very hot and dry and then consistent rain from February to June ensured a wonderful autumn but seems to have created condition ideal for pinkeye. Cases continued into June when 2 calves, only 4 and 8 weeks old, were found to be affected.
Our conclusion about the outbreak was that flies transferred the infection onto the farm and then contact between animals caused spread within the herd. Animals that recover from the infection can carry the organism and spread infection after they apparently recover.
Animals affected initially were predominantly young bulls (6 months) which were obviously transferring infection between themselves by their preoccupation with head butting each other. A number of animals had infection in both eyes. The calves had not been vaccinated with Piligard.
The photo is of a very early case with slight central ulceration and cloudiness of the cornea. Treatment at this early stage with Opticlox Eye Ointment ®
(https://www.norbrook.com/australia/products/opticlox-eye-ointment-aus/) will usually produces a complete cure with a single treatment. If the infection is not detected early a severe corneal ulceration may lead to a prolapse of the eye and residual blindness.
This photo shows a more advanced case prior to treatment with Opticlox eye ointment and a sub-conjunctival injection of antibiotic and steroid. A patch was glued over the eye.
The same eye some weeks later demonstrating a residual corneal opacity but the active inflammation has subsided. The glue that held the patch remains on the hair around the eye. Two months later there is no evidence of corneal opacity and there is no impairment of vision.
If treatment is delayed the body defence mechanisms start to increase blood supply around the eye and a reaction occurs at the junction between the cornea and the conjunctiva as shown in the above photograph. There is little corneal ulceration here and I suspect that the antibody response would probably heal the eye.
I have no doubt that putting a patch on the eye reduces the risk of corneal scarring and blindness problems. Patches have become quite a fashion item in the Cadfor herd.
I am not sure from my cases whether the injection is more effective than ointment alone but the research overseas suggests that the injection gives longer lasting antibiotic coverage and a better response. The research indicates that the injection needs to be given under the conjunctiva over the eyeball itself rather than under the eyelid. This requires the animal to be very still and is best done by someone with experience in the technique. The average farmer may not be brave or confident enough to do it.