Animal Chronicles Summer 2007

Is that toxic to my pet?

by Steve Dana, DVM

A challenging part of emergency veterinary medicine is managing the patient exposed to a poison, or caring for those who are already demonstrating toxic signs from a poison. Without a doubt, the most important advice I can give you when it comes to poisoning is to act immediately: If you have witnessed ingestion of a potentially harmful agent, or even suspect this because of exposure, contact your veterinarian immediately to determine an appropriate course of action. Accidental ingestion of human prescription drugs or even inadvertent or excessive ingestion of veterinary medications — such as chewable anti-inflammatories for instance — also qualify as toxicities.

Early decontamination (washing skin or eyes for topical exposure to irritants, or induced vomiting for the non-caustic poisons that have been swallowed), and either specific or supportive treatment, can alter the prognosis and make the difference between simple exposure, and serious or prolonged illness. Always bring the product in question along with you and your pet when seeking veterinary assistance. Listed below are a few of the more common and lesser-known ingested poisonings that we often see and treat.

Mushrooms: Amanita phalloides, or “death cap” mushrooms, are common in Northern California and grow essentially all year round — our largest caseloads at the Pet Emergency & Specialty Center of Marin occur in the summer and fall months when these mushrooms thrive in our moist marine environment. Untreated ingestion of even a small portion of this mushroom can be fatal due to overt liver injury and failure. Amanita toxicity accounts for 95 percent of all mushroom-related fatalities in people and dogs. Identification of these mushrooms is unreliable since their appearance varies and even trained mycologists are fooled. We treat any mushroom ingestion early and aggressively. Suspected mushrooms can be saved for later identification in paper rather than plastic, but remember that immediate decontamination by inducing vomiting and giving activated charcoal is essential, along with critical supportive care and monitoring.

Rodenticide: Because there are rats in Marin, the ingestion of rat poison is common in dogs. Cats can be indirectly exposed when they ingest the poison from the gastrointestinal tract of rodents they may catch. If a pet is not decontaminated immediately, these agents are absorbed into the blood and ultimately alter the ability of blood to clot normally. Signs of poisoning are associated with internal bleeding into body cavities or can be outwardly seen as blood from the nose, in urine, or bruising, for example. Vitamin K is an antidote used depending upon exposure history, decontamination or signs of toxicity. Again, it’s vital to get your pet to the vet immediately.

Marijuana (THC): Compared to humans, dogs are extremely sensitive to small amounts of ingested marijuana or similar agents containing the active agent THC. Signs can include drowsiness, a drunken appearance, urinations/urine incontinence, and low heart rates. Treatment is supportive once signs are recognized. When in doubt, we often perform a urine toxicological screen for this and other “recreational” drugs in order to assist in a diagnosis.

Xylitol (sugar-free gums): Used as an artificial sweetener, xylitol, once ingested and absorbed from the gut of dogs, can stimulate elevated insulin levels which result in lowered blood sugar and can cause serious blood salt (electrolyte) changes. Signs can progress from weakness to even seizures and require supportive care in the hospital.

Macadamia Nuts: An unknown agent in these nuts can cause muscle weakness, drowsiness, joint pain, stiffness and tremors. There is no antidote; treatment is supportive and signs are often self-limiting.

Chocolate: A problem in dogs for two reasons — gastrointestinal upset from fats and sugar, as well as heart and nervous system effects from agents known as methylxanthines. These agents have no antidote, and serious acute and delayed signs include excitement, agitation, seizures, coma and heart rhythm disturbances. Beyond early decontamination, care is supportive.

Permethrins in Cats: Cats are sensitive to certain spot-on topical flea products labeled for dogs, particularly those containing the synthetic pyrethroid insecticide. After mistakenly applied to a cat rather than a dog, neurological excitement and tremors develop, often progressing to seizures requiring supportive care in the hospital and removal of the product from the coat and skin.

Grapes and Raisins: Dogs are sensitive to grapes ingested in all their forms, including dried as raisins. The exact toxic element remains unknown, but ingestion can result in serious kidney injury and can cause failure of kidney function demanding aggressive kidney supportive measures.

Tremorgenic Mycotoxins: Molds/fungi that grow in garbage, compost and weathering fruit on the ground (particularly walnuts in our area) can produce metabolites that, when ingested, cause muscle tremors, spasms, seizures and elevated temperature that appear similar to the symptoms caused by snail bait (metaldehyde poisoning) or strychnine poisoning. The diagnosis is often made on clinical signs and history, and treatment often requires supportive hospital care for one to three days.

Dr. Steve Dana is the Medical Director at Pet Emergency & Specialty Center of Marin.

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