NAVLE Hemic and Lymphatic

Equine Epizootic Lymphangitis Study Guide

Epizootic lymphangitis (EL) is a chronic, contagious fungal disease affecting horses, mules, and donkeys, caused by Histoplasma capsulatum var. farciminosum.

Overview and Clinical Importance

Epizootic lymphangitis (EL) is a chronic, contagious fungal disease affecting horses, mules, and donkeys, caused by Histoplasma capsulatum var. farciminosum. This dimorphic fungus creates characteristic pyogranulomatous skin lesions that follow lymphatic vessels, producing the pathognomonic 'cord-like' appearance.

The disease remains endemic in parts of sub-Saharan Africa, particularly Ethiopia, and poses significant welfare and economic challenges for working equids. While eradicated from most developed countries, it represents an important differential diagnosis for lymphangitis in horses.

Form Frequency Location Key Features
Cutaneous Most common (greater than 90%) Limbs, neck, chest Cord-like lymphatics, ulcerating nodules, honey-like discharge
Ocular 5-10% of cases Conjunctiva, eyelids Medial canthal swelling, mucopurulent discharge, conjunctival papules
Respiratory Rare (less than 5%) Nasal cavity, lungs Purulent nasal discharge, pyogranulomatous pneumonia
Asymptomatic Up to 18% (subclinical) Systemic No visible lesions, positive serology/PCR

Etiology and Pathophysiology

Causative Agent

Histoplasma capsulatum var. farciminosum is a thermally dimorphic fungus with distinct environmental and tissue forms:

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