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This article was published in 1967
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Pinkeye in Cattle
C. E. J. WALKER, B.V.Sc., Veterinary Research Officer, Glenfield
For years, the term "Pinkeye" has been used for inflammation of the superficial ocular tissues of ruminants with the connotation that the syndrome is a single disease entity.
This is far from the case. At least seven conditions are known, with conspicuous ocular lesions. These are listed in the accompanying table.
The character of systemic / non-systemic involvement, sporadic / epizootic incidence, conjunctival sac bodies / no bodies and conjunctivitis / keratitis aid distinction of the syndromes.
1. Bovine malignant catarrh has outspoken systemic signs; the remainder do not.
2. I.B.R. virus causes a predominantly serious conjunctivitis, epizootic in nature, often in adult cattle and usually in winter.
3. In Thelazia infection the lesions are predominantly a keratitis, and the worms (up to 2 cm. long) may be seen moving across the cornea or conjunctiva at any time during the course of the disease.
A Thelazid worm (probably Thelazia gulosa) has been recovered recently from a two to three-month-old blind calf in the Julia Creck district of Queensland.
| BMC | IBR | M.bovis | Thelazia | U/v light & Phenothiazine | Foreign Bodies | Ocular S. cell carcinoma | ||
|---|---|---|---|---|---|---|---|---|
| Ocular Discharge | Serous | +++ | +++ | +++ | ||||
| Muco-purulent | +++ | ++ | ++ | + | ||||
| Photophobia | + | + | +++ | |||||
| Conjunctival oedema | + | +++ | + | ++ | ||||
| Conjunctivitis | +++ | ++ | ++ | + | ||||
| Corneal erosion | Central | +++ | ||||||
| Elsewhere | + | + | ++ | Var. | ||||
| Corneal opacity | Focal | +++ | +++ | |||||
| Diffuse | ++ | ++ | ++ | Var. | ||||
| Limbal ring | + | |||||||
| Corneal vascularisation | + | ++ | + |
Parasitic keratitis is of an epizootic nature in South African and Nigerian cattle, but may occur only in isolated sporadic cases in Australia. The life cycle is: gravid female worms in conjunctival sac, embryonated eggs in lachrymal secretions, hatching on soiled cheek hairs, ingestion of larvae by flies (Musca spp.), development to infective stage within fly in 15-30 days, release of infective larvae from fly's proboscis during feeding, growth to maturity in lachrymal duct, naso-lachrymal canal and under 3rd eyelid of primary host in 20-40 days. Adult worms survive in the conjunctival sac of cattle for several months, and possibly for a year.
4. Foreign body kerato-conjunctivitis is self-explanatory. Cancer eye may predispose to a high incidence of this condition when cattle are grazing stubble paddocks as the eye preservation reflex is often slowed.
5. Moraxella bovis infection is predominantly a bacterial keratitis with serous exudation and probably accounts for 75 per cent of "pinkeye" in young cattle and calves seen every summer in N.S.W. and Victoria.
In conclusion, it is well to remember that antibiotics are just that—antibacterial drugs—and do not inhibit or remove inflammatory fluid or cells from the cornea.
The signs of Pinkeye are those of inflammatory changes in a transparent tissue and there is no drug yet known which will remove these signs faster than the repair response to inflammation.