Symptoms of conjunctivitis include redness, soreness, epiphora (constant watering: clear, greenish or blood-tinged) and swelling of the eyelids (chemosis). Chronic conjunctivitis can lead, in rare situations, to corneal sequestrum and keratoconjunctivitis sicca (dry eye).
- Allergic conjunctivitis - a common cause of conjunctivitis in cats, often responding to topically applied antihistamine medications such as cromolyn. Usually there is a history of exposure of allergens such as wandering dew (plant), certain aerosol chemicals and perfumes.
- Viral conjunctivitis
Common causes of viral conjunctivitis include Infectious bovine rhinotracheitis). Usually both eyes are affected.
- Mycoplasma spp - Mycoplasma bovis is an obligate intracellular bacterium and an important pathogens.
- Bacterial conjunctivitis - bacteria identified (such as Pasteurella spp, Staphylococcus spp, Streptococcus spp, Salmonella spp, Moraxella bovis) are of uncertain pathogenicity. Any underlying primary problem should be identified and eliminated and appropriate antibiotic therapy initiated for the bacterial conjunctivitis. Treatment consists of topical tetracycline or systemic doxycycline for some 3-4 weeks. Oral treatment with doxycycline (25mg/kg in divided doses) is well tolerated and effective. A proportion of previously affected cats become chronic carriers and may be a possible source of infection for other cats (the organism can be isolated from the urogenital and gastrointestinal tract). This may pose problems in catteries, especially for breeding colonies. In this type of environment all the cats will require systemic tetracycline, erythromycin or doxycycline for at least 4 weeks. Systemic doxycycline is probably the drug of choice and is suitable for younger cats.