The number of rodenticide enquiries we receive increases as the weather starts to get colder, as rodents attempt to move indoors.
The most common type of rodenticides available are anticoagulants, which work by blocking the action of vitamin K, preventing the blood from clotting. Another common active ingredient in rodenticides (specifically for the control of mice) is alpha-chloralose, where the lethal action is due to depression of the central nervous system.
Commercial and professional products are available in a variety of forms. Some are presented as impregnated wheat or bran granules with an alpha-chloralose concentration between 2-4% w/w. These are often available in small sachets for easy use. Professional products may be available in larger containers and at higher concentrations. Some manufacturers colour their products green for identification purposes.
The most common clinical signs after ingestion of alpha-chloralose are profuse hypersalivation, ataxia, hyperaesthesia, hypothermia, constricted pupils, muscle tremors, convulsions and coma. Onset of these signs are often very rapid with effects sometimes being seen within 15 minutes, but more commonly within 1-2 hours.
We have had a few serious alpha-chloralose poisoning cases reported to us recently. Treatment is recommended in dogs for ingestion of >20 mg/kg of alpha-chloralose. The mainstay of treatment is the maintenance of the vital functions, stabilisation and decontamination. Anticonvulsant therapy is likely to be required in severe cases. The fatality rate is generally low if prompt treatment is provided.