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Metaldehyde Poisoning

By

Barry R. Blakley

, DVM, PhD, Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan

Last full review/revision Oct 2020 | Content last modified Oct 2020

Metaldehyde is the active ingredient in molluscicides, which are mostly used during the wet season for slug and snail control. In certain locations, metaldehyde is also used for rat control. Metaldehyde comes as a liquid or bait combined with bran, either as flakes or pellets, and is tasty to pets and farm animals. Some products also contain arsenic or an insecticide. All species are susceptible to metaldehyde poisoning, with dogs being the species most frequently poisoned (3 ounces of bait is enough to poison a 30-pound dog). Depending on stomach contents and the rate of stomach emptying, signs can vary greatly.

Signs of poisoning are similar in all mammals. Initial signs can include muscle tremors, lack of coordination, heightened senses, a rapid heartbeat, fever, and deep or fast breathing. The eyes may move rhythmically (most severe in cats), and muscle spasms can cause backward arching of the head, neck, and spine. All species develop vomiting (except horses), diarrhea, excessive drooling, metabolic abnormalities, and difficulty breathing. Horses also sweat a large amount.

Inducing vomiting in severe exposure may not be necessary because metaldehyde is a stomach irritant. However, the stomach is usually flushed with sodium bicarbonate. Fluid treatment is used to prevent possible liver damage. Medications are used to calm the animal and to reduce muscle activity and pain. Cold water rinses are recommended when fever is severe. Prognosis is good if fever and seizures can be controlled, but intensive treatment is usually needed for 4 or more days.

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