DEFINITION

INCIDENCE

The incidence varies from year to year, but spread within a group of animals is usually very rapid and the morbidity can be as high as 80%.

AETIOLOGY

Several microbiological agents have been recovered from cases of infectious bovine keratoconjunctivitis. Moraxella bovis is the bacterium most commonly isolated from affected eyes. Several species of Mycoplasma have also been associated with the disease.

CLINICAL SIGNS

Bilateral tear production and mild conjunctivitis are the first clinical signs noted. The eye is obviously painful. Within 1-2 days, a small greyish white opacity appears in the centre of the cornea. The grey opacity may enlarge to cover a large area of the cornea with a grey/white spot developing in the centre of the cornea. Occasionally in severe cases deep corneal ulceration may occur. Rarely complete perforation of cornea ensues. In the older lesion, many small blood vessels can be seen in the peripheral areas of the cornea. Healing of large ulcers is accompanied by extensive corneal vascularisation. The animal, if not blind in the affected eye, certainly suffers impaired vision.

Affected animals are usually dull, with a reduction in appetite and a resultant weight loss. Although adult dairy cows are rarely affected, there is a reduced milk yield in affected animals. Economically the disease is important because of the reduced weight gains in calves and fattening animals, up to 10% compared to unaffected animals in the same group.

EPIDEMIOLOGY

The disease is virtually confined to animals less than two years old but occasionally adult animals are affected. It occurs in most parts of the world and is most common in the summer and autumn months. Because the disease is more prevalent in the summer months, flies are considered to be important in the transmission of the disease. Carrier animals are thought to be responsible for the carry over of the disease from year to year. Severe outbreaks of infectious keratoconjunctivitis can occur during the winter especially where large number of animals are closely confined together.

DIAGNOSIS

Diagnosis in very early stages may present some difficulty, but if a group of young animals is showing excess lacrimation and conjunctivitis with no other signs of systemic or upper respiratory infection, it should be presumed to be infectious keratoconjunctivitis. 

TREATMENT

In the majority of cases, the lesions of IBK will resolve following treatment with locally applied antibiotics and several methods of application are available.

Ointments. Special formulations are available which will maintain therapeutic concentrations for up to 48 hours when a repeat treatment should be used.

Subconjunctival injection. Will produce therapeutic concentrations in the eye for periods of 24-48 hours. Often effective but may require repeated dose and can produce local reactions.

Parenteral injection. Therapeutic concentrations can be attained following parenteral administration of oxytetracyclines, tylosin and sulphadimidine. Severely ulcerated eyes may also require surgical closure to save the eye.

CONTROL

The recommended method of controlling an outbreak of IBK is by prompt antibiotic treatment of affected animals. Little success has been achieved in eradication of infection from groups using local or parenteral antibiotics.

Vaccines have been described and used commercially in other countries but their efficacy has yet to be proved.