Contributor: Gordon K. Klintworth
Cat scratch fever is caused by Bartonella henselae. The infection is transmitted by a bite or scratch of an infected cat. Cat scratch fever is a benign self-limiting illness characterized by lymphadenopathy that lasts about 3 weeks. A regional necrotizing granulomatous lymphadenitis is typical. An erythematous papular or pustular lesion usually forms at the sites of innoculation. This followed by a systemic pyrexial illness with malaise and lymphadenopathy. Less frequently splenomegaly, encephalopathy, hepatitis, pneumonia and osteomyelitis develop. Ophthalmic manifestaions are uncommon, but include Parinaud ocular glandular syndrome, follicular conjunctivititis [conjunctivitis - follicular], a neuroretinitis that resembles Leber idiopathic stellate neuroretinitis and small retinal or choroidal focal lesions. With fluorescein angiography these focal lesions show early blockage and late staining. The conjunctival reaction is often severe and characterized by intense acute and chronic inflammation, necrosis and vasculitis. Granulomas are uncommon in the conjunctiva. Preauricular lymph nodes can suppurate and drain. On healing they leave atrophic scars in the retinal pigment epithelium. A retinal branch vein occlusion or branch retinal artery occlusion may occur. Large necrotizing, stellate abscesses surrounded by granulomatous inflammation develop. To identify the small pathogen in tissue sections the Warthin-Starry stain is recommended.Infection follows inoculation, especially by the claws of cats, but sometimes the conjunctiva is contaminated by close contact with a cat, perhaps by licking around the eye.