Equine Insect Toxicity Study Guide

Overview and Clinical Importance

Insect toxicosis represents a critical category of equine poisoning that practitioners must recognize rapidly. Two primary insect-related toxicoses dominate NAVLE content: cantharidin toxicosis (blister beetle poisoning) and Mare Reproductive Loss Syndrome (MRLS) associated with Eastern tent caterpillar ingestion. Both conditions can cause severe morbidity and mortality, making early recognition and intervention essential.

These toxicoses represent distinctly different pathophysiological mechanisms: cantharidin acts as a direct vesicant causing mucosal damage and electrolyte derangements, while tent caterpillar setae penetrate tissues and introduce bacteria systemically.

Part I: Blister Beetle Toxicosis (Cantharidin Poisoning)

Etiology and Epidemiology

Cantharidin toxicosis results from ingestion of blister beetles (family Meloidae), which contain the toxic compound cantharidin. More than 200 species exist in the continental United States, with the genus Epicauta most commonly implicated in equine poisoning cases.