Uveitis: viral

• Cause: viral uveitis is one of the most common causes of uveitis in the cat, with 4 viruses being especially prevalent - Feline Infectious Peritonitis virus (FIP Feline corona virus: FIP), Feline Leukemia virus (FeLV Feline leukemia virus), Feline Immunodeficiency virus (FIV Feline immunodeficiency virus) and (probably less common) Feline Herpes virus (FHV Feline herpes virus: feline rhinotracheitis virus ).
• Signs: varied.
• Diagnosis: difficult - may require paracentesis of aqueous, serology looking for rising antibody titer, histopathology.
• Treatment: topical anti-inflammatory medication.
• Prognosis: guarded.

• Usually presented as change in eye color or appearance  - discomfort not always present.

• Occasionally uveitis noted as sequel to another disease process.

Morbidity

• Low, many cats show few signs of discomfort with the condition.
• Occasionally, signs of visual deficit are noticed, signs of other organ disease, cataract Cataract or glaucoma Glaucoma.

• Etiologic diagnosis involves serological examination for evidence of the most common causes of uveitis, plus assessment of systemic disease, and may be expensive.

• Toxoplasmosis Toxoplasmosis.
• FIP Feline infectious peritonitis.
• FeLV Feline leukemia virus disease (often neoplastic syndrome present).
• FIV Feline immunodeficiency virus disease.
• Herpes virus Feline herpes virus: feline rhinotracheitis virus.
• Idiopathic.
• Crytococcosis.

• Complex - involves immune reaction of the uvea, which acts as an accessory lymph node - hypersensitivity type III implicated with FIP, causing pyogranulomatous vasculitis.
• Most other causes involve type II hypersensitivity and uveal sensitization, so that immune-mediated uveitis is the most common etiology, and is often idiopathic.

• Often acute onset, but chronic timecourse.

• These diseases are systemic diseases, which affect the uvea via vascular system.

• Often non-diagnostic.

• Mild pupil miosis   (compare with canine uveitis), anterior chamber protein (aqueous flare), iris hyperemia and/or view small vessel formation (technical term: rubeosis iridis), iris swelling, mild corneal edema.

• Reddened conjunctival and episcleral blood vessels   , lowered intraocular pressure, posterior synechia formation  , hypopyon, hemorrhage, keratitic precipitates  adherent to the ventral corneal endothelium.

• Posterior segment signs, including vitreal infiltration, vasculitis, perivascular inflammation or hemorrhage, retinal degeneration consistent with old chorioretinitis, cataractous changes after initial disease.

Serology

• Serology and serum protein electrophoresis essential, as is routine WBC and blood biochemistry.
• Toxoplasma gondii antibody titers in aqueous humor samples may be useful in diagnosis.
• Early tests into the use of PCR detection of antigen in aqueous humor have been developed (Lappin 2000).

2-D Ultrasonography

• Further tests required as necessary include ultrasonography, anterior chamber paracentesis, fluorescein angiography, further blood tests as decided from the initial screen.

Histopathology

• Ideal for confirmation of FIP but not possible if eye is to be retained.
• Lymphocytic plasmacytic infiltrates in ciliary body are common (possibly due to immune reaction).

Definitive diagnostic features

• Diagnosis difficult, involves presence of serological reaction to the antigen, plus anterior chamber antibody in some cases (mostly herpes virus and toxoplasma at present) - may require histopathology to produce absolute confirmation.
• Perform a Goldmann Witme test (aqueous titer/serum titer) or better still:
  • (aqueous titer against uveitogenic virus/aqueous titer against feline parvovirus) x (serum titer against feline parvovirus/aqueous titer against uveitogenic virus).

• Evidence of classical histopathological signs with sometimes systemic evidence of disease. May be neoplastic cells in the Leukemia-lymphosarcoma complex.

• Pyogranulomatous inflammation and perivasculitis associated with FIP, usually requires systemic findings to confirm. Presence of lymphosarcoma suggests FeLV, and requires serologic evidence. Evidence of inflammatory infiltration of uvea is a frequent finding, and again requires confirmation by serology for FIV FIV test /FHV /FeLV FeLV test (non-neoplastic form).

• Differentials for uveitis include viral, bacterial, fungal, protozoal, parasitic and rickettsial infection, neoplasia, systemic inflammation, immune-mediated disease, trauma, hypertension Hypertension, hyperlipidemia, lens disease.

• Treatment for uveitis involves topical anti-inflammatory medication, atropine and possibly antibiotic therapy (clindamycin Clindamycin) if toxoplasma suspected.
• Topical glucocorticoids are often effective but in resistant disease subconjunctival or even systemic treatment may be necessary.
  There is a risk of exacerbating systemic infection by the use of high dose glucocorticoids.
• Systemic anti-inflammatories may be useful particularly with posterior segment signs, but beware systemic disease.

• Clinical examinations, plus repeated serological examinations, and assessment of systemic signs.

• Guarded until diagnosis established, and presence of systemic signs evaluated.

• Not predictable, requires monitoring. Chronic low grade uveitis may lead to secondary glaucoma and related lens luxation.

• Due to poor response of uvea to treatment, overwhelming inflammation, secondary glaucoma, neoplasia requiring enucleation.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Maggs D J (2009) Feline uveitis. An 'intraocular lymphadenopathy'. J Fel Med Surg 11 (3), 167-182 PubMed.
• Lappin M R (2000) Feline infectious uveitis. J Feline Med Surg 2 (3), 159-163 PubMed.
• Heider H J, Pox C, Loesenbeck G et al (1998) Ophthalmological findings in association with different virus infections in the cat. European Journal of Companion Animal Practice 8 (2), 35-42 VetMedResource.
• Chavkin M K, Lappin M R, Powell C C et al (1992) Seroepidemiologic and clinical observations of 93 cases of uveitis in cats. Progress in Veterinary & Comparative Ophthalmology 2 (1), 29-36 VetMedResource.
• Davidson M G, Nasisse M P, English R V et al (1991) Feline anterior uveitis - a study of 53 cases. JAAHA 27 (1), 77-83 VetMedResource.
• Peiffer R L Jr. & Wilcock B P (1991) Histopathologic study of uveitis in cats - 139 cases (1978-1988). JAVMA 198 (1), 135-138 PubMed.

Other sources of information

• Petersen-Jones S & Crispin S (2002) BSAVA Manual of Small Animal Ophthalmology. 2nd edn. British Small Animal Veterinary Association. ISBN 0 905214 54 4