006 Christmas Hazards for Dogs and Cats

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Likely higher incidence of poisoning around festive period, especially dogs
Three main scenarios:
•    Pet scavenges something poisonous
•    Well intentioned blissfully unaware pet carers offer their pet a poisonous holiday treat or two
•    Kids – or drunk adults! – do not comprehend the risk and give the pet something poisonous

Large number of potential poisons. Here are a few:

Chocolate

Toxic substance is theobromine: methylxanthine-derived alkaloid that occurs naturally in cacao beans and is found in chocolate, cocoa powder and other products produced from these beans.
Chocolate contains a lesser amount of caffeine which is also a methylxanthine
Theobromine concentration varies between types:
Plain (dark) chocolate and cooking chocolate generally contain significantly more than milk chocolate
Theobromine content of white chocolate is considerably lower; theobromine poisoning from white chocolate is rare
Cocoa beans, cocoa powder and cocoa shell mulches contain the highest concentrations of theobromine

Be vigilant as chocolate products may contain other potential hazards, e.g. raisins, currants or sultanas; diabetic chocolate products will most likely contain xylitol

Dose-dependent toxicity
Doses can be found in various online and offline resources

Theobromine stimulates the central nervous system with consequent neurological, muscular, cardiac and/or respiratory effects. Theobromine also causes smooth muscle relaxation, especially of the bronchi, and renal diuresis.

Clinical signs usually develop within 24 hours of ingestion and typically much sooner – within 4 hours. Signs may persist for 48-72 hours in some cases.
Commonly reported clinical signs include vomiting, abdominal discomfort, restlessness, excitability and hyperactivity, ataxia, tachycardia, and tachypnoea or panting. In more severe cases muscle rigidity, muscle tremors, hyperthermia, seizures and dysrhythmias have been reported. Urinary incontinence, polyuria and polydipsia may also occur. Severe seizures and/or cardiovascular compromise are typically reported in fatal cases.

Testing is not indicated in many cases. There are some patients in which doing some form of emergency database, and potentially an ECG, will be appropriate.

Treatment:

Routine GID indicated in appropriate cases. Gastrointestinal absorption is relatively slow in dogs, potentially taking up to 10 hours, so gastric empyting may be appropriate even after a significant delay. Avoid inducing emesis in animals that have contraindications such as significant hyperactivity, other forms of neurological compromise, respiratory issues and so on. Theobromine undergoes enterohepatic circulation so repeated use of charcoal may enhance elimination.
No specific antidote
Therapy is otherwise symptomatic and supportive e.g. intravenous fluid therapy, anti-emetic administration, sedation if excitability is excessive, and routine treatment of seizures. Anti-dysrhythmic therapy may also be indicated in some cases.

Prognosis: generally good with appropriate treatment but may be worse for animals showing marked cardiovascular or neurological signs at presentation.

Vitis vinifera fruits (Grapes, raisins, currants, sultanas)

Nephrotoxicity in dogs; no confirmed cases have been reported in cats thus far but they may be susceptible, unclear.

Same poisoning syndrome may occur following consumption of all types of these fruits including those manufactured organically and regardless of whether the product has been cooked or not. 
Exposure may occur through ingestion of products containing these fruits amongst their ingredients such as some chocolates, Christmas cakes, Christmas puddings, mince pies etc.

Toxin or toxins involved have yet to be identified; mechanism of toxicity is unknown.
Should be considered non-dose dependent or an idiosyncratic type of toxicity. Consider any dog at risk if they consume any of these fruits regardless of how much; not known whether a dog that has previously eaten these fruits and seemingly been fine could the next time they had some go on to develop acute kidney injury. All cases should be treated as soon as possible.

Clinical signs:

Vomiting reported in almost all cases, usually within 24 hours of ingestion. May be related to dietary indiscretion, azotaemia if acute kidney injury has occurred, but a specific effect of these fruits is also suspected given how common vomiting seems to be in these dogs.
Subsequently anorexia, lethargy, diarrhoea and abdominal pain have been reported as has hypersalivation.

Treatment:

Gastric emptying if not already vomiting, then activated charcoal
Hospitalise all cases on intravenous fluid therapy (e.g. 4-6 ml/kg/hour for 48-72 hours): empirical recommendation; not evidence-based but makes theoretical sense
Run baseline blood renal panel and perform urinalysis; repeat 48-72 hours later before discharging the patient. Even if the renal panel remains within normal limits it is worth looking at a urine sediment for casts before discharging the patient because they may suggest that that individual dog has suffered some degree of tubular injury that may prompt a change in the plan.
Standard management for acute kidney injury is indicated in cases in which this occurs

Xylitol

Naturally-occurring sugar alcohol found in low concentrations in various fruits and vegetables; extracted and used extensively commercially.
One main use is as a sweetener in low carbohydrate/low glycaemic index/diabetic products e.g. diabetic Christmas cakes or chocolates
Thought to reduce dental caries formation so increasingly used in various chewing gums, sweets, toothpastes and other oral care products
Also found in some prescription drugs, including veterinary ones as well as some vitamins and nutritional supplements and even canine oral hygiene products!

Xylitol poisoning reported in DOGS; no published reports of feline poisoning

Two phases to toxicity:

Hypoglycaemia:

Due to dose-dependent increase in pancreatic insulin production that may result in hypoglycaemia +/- hypokalaemia, hypophosphataemia
Usually occurs quickly, certainly within a few hours, but it can be delayed – this will partly depend on the form in which the xylitol was ingested
Rapid gastrointestinal absorption but also some slow-release products; absorption also depends for example on how well the food item was chewed before being swallowed

Hepatotoxicity:

May cause liver insufficiency or failure
Mechanism(s) unclear
More delayed onset (e.g. 72 hours)
Difficult to predict which dogs will develop liver complications. Not all dogs that develop hypoglycaemia go on to have liver complications; on the flipside a dog may not suffer clinically significant hypoglycaemia but significant hepatotoxicity occurs.

Hepatotoxicity may be dose-dependent but still remains unclear, consider it a non-dose dependent idiosyncratic toxicity at this time. Recommend aggressive treatment for all cases as hepatotoxicity potentially fatal.

Treatment:

Routine gastrointestinal decontamination; tenuous evidence base for activated charcoal but risk-benefit profile positive as is usually the case!
Routine approach to management of hypoglycaemia with parenteral and/or enteral supplementation as indicated
Standard symptomatic and supportive approach to management of hepatotoxicity including appropriate management if coagulopathy develops, possible use of hepatoprotectants, and treatment for hepatic encephalopathy if required. 

Prognosis:

Hypoglycaemia alone: generally good with timely and appropriate management. Likely to be worse if repeated bouts of hypoglycaemia occur, especially when associated with central nervous system signs.
Prognosis worse with sustained elevations in liver enzymes; guarded to poor with evidence of hepatic dysfunction; grave for acute hepatic failure.

Dangerous foods potentially more accessible around festive period

Allium species (onions, garlic, leeks, shallots, chives)

These can be harmful even when cooked causing vomiting/diarrhoea but potentially also a non-immune mediated haemolytic anaemia in both dogs and cats. Some of the less obvious sources of exposure include for example sage/onion stuffing, onion gravy.

Nuts

Some nuts (e.g. peanuts, macademia nuts) may cause vomiting/diarrhoea but potentially also more severe signs affecting the nervous system or muscles.
Potential hazard of chocolate-coated nuts and even chocolate-coated nut and raisin combos!

Mouldy food

May cause neuromuscular signs as a result of tremorgenic mycotoxins; potentially fatal toxidrome that requires aggressive management including intravenous lipid emulsion.

Plants:

Lilies:

  • All types of lily can cause renal toxicity in cats but not dogs
  • Non-dose dependent idiosyncratic toxicity so all cases should be treated as soon as possible; approach is basically the same as already described for grapes in dogs
  • All parts of the plant can be toxic; also e.g. licking pollen off feet; drinking vase water

Mistletoe: may cause drooling or vomiting but generally not much else in dogs and cats; 

Poinsettia: gets a lot of attention on the internet but usually only causes irritation of the stomach/intestines in cats. Can be more serious but typically isn’t.

If parts of Christmas trees are eaten the ‘needles’ can cause damage and potentially obstruction of the stomach/intestines; rare but be aware!

Potential ‘foreign bodies’: dogs in particular may eat decorations or wrapping paper this may cause drooling, vomiting or diarrhea but in the worst case scenario could cause gastrointestinal obstruction; this is especially the case if a cat tries to eat some tinsel for example and develops a linear foreign body situation.

Weather-related hazards: in countries where Christmas occurs during cold spells, some potential risks include:

Antifreeze (ethylene glycol):

  • Dose-dependent renal toxicity in both dogs and cats
  • All cases should be treated as soon as possible; often by the time patients present the prognosis is grave.

Poisoning from human medications that may be used more during cold periods, e.g.

  • Paracetamol (acetaminophen): cats are much more susceptible
  • Aspirin and other ‘NSAIDs’ (e.g. ibuprofen)
  • Over-the-counter decongestants can be an issue
  • Etc.

May be self-exposure by pet or misguided administration by carer.

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