Conjunctitivis is a common eye disease of cats, defined as an inflammation of the conjunctival membranes surrounding the eye, is a very common disease in cats. Sometimes secondary blepharitis can occur.
There are a wide range of causes including allergies, scratches from other cats and objects, autoimmune diseases (eosinophilic granuloma complex), viral infections (FHV, FCV and rarely FIP), bacteria (Chlamydia) and other parasite infections such as Toxoplasma. 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 Feline herpes virus) and more rarely, Calicivirus infection. Usually both eyes are affected and in older cats, often the right eye only (due to the right trigeminal nerve (where FHV resides during dormancy)hyperactivity in cats, who like humans are more right-handed and chew with the right side of their mouth.
- Chlamydia - Chlamydophila felis is an obligate intracellular bacterium and an important pathogens. Clinical signs may be observed in cats from 4 weeks old onward. Clinical signs are of a unilateral conjunctivitis initially, which becomes bilateral several days later. Initially there is a serous discharge with obvious chemosis and conjunctival hyperaemia, later the discharge can become mucopurulent and other organisms may be isolated. There is no corneal involvement and no primary respiratory disease, although mild rhinitis may be present.
- Eosinophilic keratitis
- Bacterial conjunctivitis - bacteria identified (such as Pasteurella spp, Staphylococcus spp, Streptococcus spp, Salmonella spp, Moraxella spp) 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.
- Mycoplasma spp a less common cause of feline conjunctivitis. The condition is often self-limiting and usually resolves within 30 days, although the cat may remain infectious for up to 60 days. Mycoplasma felis can be isolated from the conjunctiva of both normal cats and those with conjunctivitis, so it is important to ensure that no other potential pathogens are present in suspect cases. The clinical appearance if often spectacular as chemosis, hyperaemia and conjunctival thickening are marked. Slit lamp examination may reveal papillary hypertrophy in the initial stages. In an untreated case, the hyperaemia becomes less obvious after 14 days and the conjunctiva becomes pale with a friable white diphtheritic membrane (pseudomembrane) as an obvious feature.