Mercury exists in a variety of organic and inorganic forms. Inorganic mercurials include the volatile elemental form of mercury (used in thermometers) and the salted forms (mercuric chloride [sublimate] and mercurous chloride [calomel]). Ingested inorganic mercury is poorly absorbed and low in toxicity. However, large amounts are corrosive and can cause vomiting, diarrhea, colic, and kidney damage. In rare cases of longterm inorganic mercurial poisoning, the central nervous system effects resemble those of organic mercury poisoning. Mercury vapor from elemental mercury causes respiratory and neurologic signs. Inducing vomiting, followed by administration of dimercaprol, is recommended after ingestion by mouth.

Inorganic mercury is converted to the organic forms, methylmercury and ethyl-mercury, by microorganisms in the sediment of rivers, lakes, and seas. Marine life accumulates the most toxic form, methylmercury, and fish must be monitored for contamination. There are reports of commercial cat food causing severe neurologic disturbances in cats fed an exclusive tuna diet for 7 to 11 months.

The organic mercurials are absorbed through all routes and accumulate in the brain, kidneys, and muscle. Animals do not show signs until several weeks after being poisoned by organic mercury. Signs can include blindness, excitement, abnormal behavior and chewing, lack of coordination, and convulsions. Cats show hindleg rigidity, lack of coordination, and tremors. Neurologic signs may be irreversible.

Laboratory tests are used to detect concentrations of mercury associated with poisoning in tissue (especially whole blood, kidney, and brain) and feed.

Dimercaprol and penicillamine are sometimes used in treatment.

Last full review/revision July 2011 by Barry R. Blakley, DVM, PhD; Cheryl L. Waldner, DVM, PhD; Rob Bildfell, DVM, MSc, DACVP; William D. Black, MSc, DVM, PhD; Herman J. Boermans, DVM, MSc, PhD; Cecil F. Brownie, DVM, PhD, DABVT, DABT, DABFE, DABFM, FACFEI; Raymond Cahill-Morasco, MS, DVM; Keith A. Clark, DVM, PhD; Gregory F. Grauer, DVM, MS, DACVIM; Sharon M. Gwaltney-Brant, DVM, PhD, DABVT, DABT; Larry G. Hansen, PhD; Safdar A. Khan, DVM, MS, PhD, DABVT; Garrick C. M. Latch, MASc, PhD; Gavin L. Meerdink, DVM, DABVT; Lisa A. Murphy, VMD; Frederick W. Oehme, DVM, PhD; Gary D. Osweiler, DVM, MS, PhD, DABVT; Mary M. Schell, DVM; David G. Schmitz, DVM, MS, DACVIM; Norman R. Schneider, DVM, MSc, DABVT