Poison cases in large animals occur less often than in other species but are usually more time consuming and frustrating to manage. Generally, an animal is found dead in the stall or pasture, or a sudden outbreak of illness occurs in a herd of animals.

A rapid response is necessary, especially in herd cases, to eliminate the toxicant, treat affected animals appropriately, and prevent the development of further cases. The initial history is frequently limited, yet owners, trainers, barn managers, elevator owners, and others may demand an immediate answer.

The simple act of finding a toxicant does not necessarily mean it is the causative agent or that it is even related to the problem at hand. Concluding thus without further evidence could skew the investigation and result in an inaccurate diagnosis and further illness in or death of other animals. A complete toxicologic investigation, including a thorough history, clinical signs, clinicopathologic testing (including necropsy if available), and analytic testing, should be undertaken in a careful and systemic manner. Internet websites can be used to provide accurate and rapid sources of toxicologic information to aid in the investigation and provide treatment options^1,2 (Table 54.1). An established working relationship with a diagnostic laboratory providing advanced testing and access to a board-certified toxicologist specializing in large animals will increase the likelihood of a positive diagnosis.