PINK EYE IN CATTLE


WHAT IS PINKEYE OR BLIGHT?

Infectious bovine keratoconjunctivitis, commonly known as pinkeye or blight, is an infectious disease of cattle that occurs throughout Australia. It is a painful, debilitating condition that can severely affect animal productivity. Most cattle producers are familiar with pinkeye but may not know the best way to prevent spread or treat cases within their herd. While deaths are rare, economic losses are very important.


WHATCAUSES IT?

Pinkeye is caused by the bacteria Moraxella bovis. The bacteria infects the eye and produces a toxin that attacks the surface of the eye (cornea) and surrounding membranes. This results in corneal ulcers, and severe inflammation of the eye.


HOW IS IT SPREAD?

The pinkeye bacteria is present in a herd in the eyes of carrier cattle that do not show any signs of disease. When eyes become irritated from dust, thistles and long grasses, the eyes become irritated and have an increase in tear production. These secretions attract flies which move from animal to animal as they feed, spreading the bacteria as they go.


RISK FACTORS THAT INCREASE INFECTION RATES

There are several factors that predispose cattle to infection including:

  • Dusty conditions (yarding, weaning, drought feeding, marking etc.)
  • Flies
  • Bright sunlight
  • Physical irritation to the eye (thistles, weeds etc.)

Pinkeye is most commonly seen in Summer and Autumn when flies are more prevalent, ultraviolet radiation is high and the weather is warm and drier. Those cattle with unpigmented eyelids and protruding eyes such as British and European breeds are more susceptible to pinkeye than Bos indicus breeds.


WHAT TO LOOK FOR?

  • Copious watery eye discharge
  • Membranes of the eye are red and swollen
  • Excessive blinking and irritation/rubbing of the eyes
  • Cloudy or blue cornea with a small white spot in the centre of it
  • In more severe infections, the spot in the centre starts to enlarge and changes from a small white spot to a large mass of tissue on the eye; this often change in colour from white to yellow and then to red
  • In severe cases the eyeball may rupture

Other causes of eye irritation that need to be ruled out include grass seeds, cancers of the eye, localised trauma and other viral diseases.

 

TREATMENT

Early treatment of affected cattle reduces the risk of further complications including blindness and starvation, and allow the eye to heal much faster. Treatment options are listed below and the choice will vary depending on how many are affected and how severe their infection is.


Orbenin/Opticlox Eye Ointment
This is the treatment of choice and the ointment must be purchased from a veterinarian. It is a long acting penicillin, a single application will last for 48hrs and it has a nil withholding period. It should be applied to the space between the lower eyelid and the eye. Usually one-quarter to one-third of a tube is all that is required.

 

Antibiotic Injection
An intramuscular injection of an antibiotic such as oxytetracycline can also be effective at treating pinkeye. Two doses 3-4d apart are usually required. It should be remembered though that this method will be more expensive and there will be a meat and milk withhold period that needs to be placed onto these animals.

 

Eye Patches
Eye patches can be placed over the affected eye after Orbenin/Opticlox eye ointment has been applied. The patch offers protection from any further irritation from dust, flies and sunlight as well as reducing the spread within the herd.

 

Veterinary Treatment
In severe cases of pinkeye or in stud, pet or highly valuable animals, a veterinarian should attend to the animal as soon as possible. After examining the animal, the veterinarian may choose to inject antibiotics and corticosteroids into the conjunctiva around the eye to provide local relief. The may also suture the eyelid across the eye after administering local anaesthetic to provide localised protection to the ulcerated eye.

 

HOW TO PREVENT PINKEYE OUTBREAKS


Fly Control
Reduce the local fly population in your herd and you will significant reduce the risks of a pinkeye outbreak. Regular spraying, ear tags, bag rubs and dung beetles are all ways in which you can minimise the number of flies.


Dust Control
When yarding, try to water your yards to reduce the amount of dust pollution present. This will reduce irritation and minimise the risk of an outbreak.


Thistle/Weed Control
Heavy infestations of thorny weeds will irritate and injure the eyes of cattle when they are grazing. Weed control should be a standard part of your management program.


Vaccination
Coppers Piliguard is a vaccination that may be useful in some management systems to reduce the number and severity of cases. It involves two start up booster vaccinations with an annual vaccination then administered just prior to the expected onset of pinkeye season.

This information sheet is not intended as a substitute for a veterinary consultation. It is recommended that a consultation be arranged with a Veterinarian if you have any concerns with your herd’s health.