Epizootic Lymphangitis
Epizootic lymphangitis, caused by Histoplasma farciminosum, a fungal agent found mainly in Africa (see Chapter 53), is manifested as nodules and draining lesions of the subcutaneous lymphatic system.77 A conjunctival form of this disease results from deposition of the organism on the ocular mucous membranes by the biting flies of the Musca and Stomoxys species. Ocular signs
include serous to mucopurulent discharge, blepharedema, and conjunctival papules.77 Disease progression leads to ulceration of the papules, which may result in obstruction and erosion of the lacrimal duct or secondary keratitis. Diagnosis is mainly by cytology and culture, although serologic assays are also available.78 Amphotericin B is the treatment of choice, and a vaccine is available for horses in endemic areas
