Toxins lurking in plain sight Print E-mail
News - Rubrieke
Tuesday, 22 August 2017 14:21
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Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

We have to be aware that cats and dogs are not just smaller versions of people. The metabolism and organ function vary across species making some things toxic for one and not the other.

Additionally, in veterinary science we often use the expression, “cats are not small dogs which climb trees”. Cats are very different to dogs, not only in behaviour and nutritional requirements but also in how they metabolise certain drugs.

Chocolate: More cocoa equals worse clinical signs, so dark chocolate and home-made puddings can cause signs in relatively small amounts in susceptible patients. The symptoms are stimulation and cardiac arrhythmias and diarrhoea. Bakers and dark chocolate are the most toxic, and milk chocolate can be dangerous if ingested in large amounts.

Xylitol: This sweetener is available in bulk as well as in sugarless chewing gum and sweets, medications and nasal sprays and causes a rapid drop in blood sugar and liver failure in dogs (and in birds – do not put into feeders).

Excessive intake of macadamia nuts can cause transient neurological signs characterised by vomiting, ataxia or weakness, fever, muscle tremors and depression. Dogs are the only species in which signs have been reported.

Human anti-inflammatory drugs are far too strong for dogs and ingestion results in stomach ulcers and kidney failure. Cats are even less able to metabolise the drugs so any dose is too much.

Over-the-counter cough, cold and allergy medications may contain acetaminophen (Panado®) or decongestants, such as pseudoephedrine or phenylephrine, which are especially toxic. 

Cycads are extremely toxic to dogs. Any part of the plant, if eaten, can cause severe bloody diarrhoea and liver failure. The liver failure can be rapid or the damage can be mild and progressive. This is a very dangerous plant to have in your garden where dogs can access it.

Onions and garlic are toxic to dogs if taken in moderate to large quantities. They cause damage to the red blood cells, which decreases its ability to bind and carry oxygen, and if severe may cause the cells to break up, causing anaemia. If a large amount of toxin is ingested the anaemia may cause symptoms and the urine may become red as iron containing proteins from damaged red blood cells are excreted in the urine. Accidental ingestion is usually with tomato and onion gravy and stews being fed to dogs.

Rodenticides (rat poison): These block vitamin K, an essential component in activating clotting factors in the body. They cause internal bleeding, usually about three to four days after being eaten and the dog will collapse and be in shock. Sometimes bleeding can be seen from the teeth or from small injuries.

Grapes and raisins: These harmless human foods may cause kidney damage in dogs.

Glucosamine joint supplements: Overdoses of these sometimes tasty products typically only cause diarrhoea. However, in rare cases, liver failure can develop.
Medications can cause tremors, seizures, cardiac problems and death in pets.

Cats are generally more sensitive to any substances which need to be broken down by the liver, as they are deficient in some of the enzymes required to break certain drugs down and utilise alternative pathways.

Plants in the Lilium species, such as Easter, tiger, and Asiatic lilies, cause kidney failure in cats. Any part of the plant, including the pollen, is toxic. So, cut flowers in the home can also cause poisoning. All cat owners need to be aware of these highly toxic plants.

Flea and tick spot-on products for dogs are very toxic in cats. Those that are pyrethroid-based and organophosphates cause tremors and seizures and can be deadly to cats.

Antidepressants: Cats seem strangely drawn to these medications, which can cause severe feline neurologic and cardiac effects on ingestion.

Cats are even more sensitive to anti-inflammatory drugs than dogs. Even veterinary specific NSAIDs, such as Metacam (meloxicam), should be used with caution.

Acetaminophen, contained in Panado and other over-the-counter cough, cold and headache medications, is especially toxic to cats, as they damage red blood cells and cause liver failure. Even a low dose – a quarter tablet – can cause severe symptoms.

Glow sticks and glow jewellery are irresistible “toys” to cats but contain a chemical called dibutyl phthalate. When it contacts the mouth, pain and excessive foaming occurs, but the signs quickly resolve when the cat eats food or drinks water.


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