Feline keratitis and conjunctivitis (Proceedings) - Veterinary Healthcare


Feline keratitis and conjunctivitis (Proceedings)


Many and often the most severe cases of FHV-1 related disease seen at our clinics have a history of oral and/or topical use of steroidal medications that were prescribed for conjunctivitis. Both topical and/or systemic corticosteroids in the face of disease have been shown to increase viral shedding, the incidence of corneal sequestration (a surgical disease), and development of stromal keratitis (often a painful disease). Recurrent herpes viral conjunctivitis/keratitis and development of acute bullous keratopathy is often associated with immunosuppression and use of oral steroids (for diseases such as IBD, skin disease, etc). The point being: DO NOT USE TOPICAL CORTICOSTEROIDS IN CATS, ESPECIALLY IF FHV-1 IS SUSPECTED.

Nonulcerative causes of keratoconjunctivitis include Mycoplasma felis, Chlamydophila psittici, feline Calicivirus and Bartonella henselae). Mycoplasma is felt by some not be a primary infection and is only seen in association with FHV-1. This disease can start unilateral and become bilateral with time. There may or may not be an associated respiratory disease. Keratitis is not common. A "diphtheritic membrane" on the conjunctival surface is supposedly pathognomonic. Clinical signs of Chlamydia psittaci infection include conjunctival hyperemia and chemosis in one or both eyes often with formation of conjunctival follicles. Intracytoplasmic inclusion bodies may be found during the first 2-9 days after the onset of clinical signs, so conjunctival scrapings during initial outbreaks can be diagnostic. Polymerase chain reaction is available and appears more sensitive for detecting Chlamydophila infections. Treatment consists of topical tetracycline, chloramphenicol or erythromycin 4 times a day for 14 days. If Chlamydophila is present within a cattery, it may be necessary to treat all adult cats with 5 mg/kg doxycyline twice a day for 30 days to eliminate carriers since it is highly contagious and recovery from this infection does not necessarily translate to long-term protective immunity.

Reovirus and calicivirus conjunctivitis are also reported in the literature but clinical prevalence is not well documented. Reovirus infection may cause a serous ocular discharge associated with conjunctivitis, but appear to be of no long-term significance. Therapy is symptomatic as listed above. Calicivirus has been associated with the upper respiratory disease/conjunctivitis complex in cats, but some studies have shown that calici virus infection only rarely causes conjunctivitis in cats.

Recrudescent herpes virus disease is a very common clinical entity. 80% of cats infected with FHV-1 will be latently infected, and 45% will have spontaneous recurrences of clinical disease (and potential viral shedding). Stress (boarding, traveling) and immunosuppression (iatrogenic use of corticosteroids, other diseases, or FeLV/FIV), may cause acute recrudescence and clinical disease. Since the virus lays dormant in sensory nerve ganglia (trigeminal ganglia with distribution to the conjunctiva and cornea), recrudescence usually results in localized disease which may be unilateral or bilateral. Therapy is the same as for acute disease. DO NOT USE TOPICAL CORTICOSTEROIDS! In an attempt to mitigate severity of recurrent episodes, some will treat with l-lysine or topical antivirals prior to an anticipated stressful event.

Non-infectious causes for feline conjunctivitis include eosinophilic conjunctivitis, allergic conjunctivitis, hypersensitivity reaction and tear film disorders. All other infectious causes and treatments for viral infections should be performed before considering topical anti-inflammatories for these diseases in cats.

Corneal sequestrum is a unique clinical disease of cats and most often seen in the Asiatic breeds such as Persians, Himalayans, and the Burmese. There is light amber to dark black axial pigmentation of the corneal surface (localized necrosis of the epithelium and anterior stroma), which may progressively extend deep into the corneal stroma. This disease may be painful and elicit significant squinting, increased tearing, and often brown ocular discharge. Diffuse keratitis is often present as the disease progresses. It is thought that frictional irritation ("dry eye", entropion, exposure keratitis) is contributory. In research settings, inoculation with FHV-1 followed by topical and/or systemic corticosteroids resulted in sequestrum formation, as well as interstitial (stromal) keratitis (IOVS 30:1758-1768, 1989). Medical treatment can include treatment with broad spectrum topical lubricant antimicrobials to prevent infection, as the eye may slough the diseased cornea naturally. Corneal perforation is a risk with medical management alone. Surgical treatment options include superficial keratectomy and other supportive surgery (third eyelid flap, conjunctival graft, partial thickness keratoplasty, BioSIST) and medical therapy (antibiotics, antivirals). Since the disease may progress to affect the full thickness of the cornea, and involves often chronic and painful non-healing ulcers, surgical treatment options seem most appropriate in these cases.


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