« 10 categories of plants poisonous to pets » | This article provides pet owners with a list of 10 categories of plants poisonous to pets.
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Why are some plants poisonous to pets?
Plants are poisonous to pets because they contain toxins leading to a wealth of negative effects for major organs of the body.
Most of those toxins do not have antidote readily available on the market. Thus, it is very important for pet owners to be aware of the risks those plants and alike might pose to their pet’s health and how it might affect them, as well as what to do and expect in term of veterinary care and vital prognosis.
When in doubt, pet owners should never hesitate to speak to a qualified vet to obtain further advice and information on what is the best course of action to help their pets. Most of all, in the majority of the situations listed below, prevention remains one of the best cure.
So, this article introduces 10 categories of plants poisonous to pets that can be found in their direct living environment.
Category 1: Blue-green algae aka cyanobacteria
Blue-green algae blooms can potentially be harmful due to their ability to produce toxins. Although most blooms are not responsible for toxicity, it would be hard to tell by only looking at them. Hence, it is safer to consider them all suspicious until proven otherwise by the relevant authorities.
Mycrocystins are toxic to the liver. They are found worldwide and mostly produced by some genera of blue-green algae such as Mycrocystis, Anabaena, Planktothrix and several others. Other toxins produced by blue-green algae, such as anatoxins, are toxic to the central nervous system.
Those toxins are dangerous to the extent they induce death of either humans or animals within minutes or days, depending on the toxin involved; with the neurotoxin leading to death faster than the hepatotoxin.
Mycrocystins trigger a series of liver related symptoms such as diarrhea, weakness, pale mucous membranes, icterus and shock whereas anatoxins induce a series of neurological signs such as muscle tremors, rigidity, paralysis, cyanosis and salivation.
Dogs are most affected pets, and this can be linked with ownership of private ponds of questionable levels of maintenance (blue-green algae proliferation) where pets may be tempted to drink from. Additionally, pets with a tendency to swim in affected areas (lakes, streams) will be more at risk.
The signs of toxicity may be visible as soon as 30 min after contact with the contaminated water. Prognosis is very poor despite emergency treatment and most cases lead to death.
Category 2: Plants containing cardiac glycosides
Digoxin and digitoxin are the most famous of cardiac glycosides among 400 of those reported substances. Many plants contain cardiac glycosides such as Desert rose, Dogbane, Purple or common foxglove, Giant milkweed, Kalanchoe, Lilly of the valley, Oleander, Star of Bethlehem, Wooly foxglove, Yellow oleander.
Concentration levels of the toxic substance will depend on the part of the plant, as well as the species involved. Since those plants can be found indoor (ornament) or outdoor (landscaping, nature), domestic animals can easily come in contact with them (chewing, ingestion of some parts of the plant).
The signs will appear rapidly, generally 30 min to a few hours after ingestion. All parts of all those plants must be considered toxic with varying levels of toxicity. It is worth noting that even the water in which bouquets are kept, is potentially toxic (pets often knock vases and drink the water).
Most frequent signs are hypersalivation, vomiting, diarrhea (+/- blood) and weakness. Cardiac signs occur such as the heart may slow down, show an abnormal ECG with blocks and arrhythmias or even stop, leading to death. Other signs involve neuromuscular issues as well as mydriasis (dilation of pupils not linked to a change in light levels)
Dogs with a particular gene mutation such as Collies and Australian shepherds will be more sensitive to the effects of those substances on their central nervous system.
If treated early, the prognosis is good for the pet. However, pet owners must note that a good recovery involves hospitalisation of their pet as a critical patient to provide all the necessary supportive care and on going required monitoring, especially that of the heart, blood pressure and serum electrolytes.
An antidote might be available, especially if Oleander has been ingested (higher cost involved). As a matter of prevention, pet owners are advised to learn and recognise the types of plants their pets may interact with at home or during walks.
Category 3: Plants belonging to the Lily family
Plants in this category are popular and found in houses as part of home ornaments (bouquets, floral baskets), gardens and in the wild. Most cases are reported in cats and involve all parts of the plant, including pollen as well as the water contained in vases and floral extracts.
The organ affected is the kidney, through what is called renal tubular necrosis. The associated symptoms with ingestion of lilies are vomiting, anorexia, lethargy, decrease urination, acute renal failure and, on some rare occasion, pancreatitis. Associated neurological signs consist of ataxia (loss of balance), tremors and seizures. Signs will usually develop within 6 to 12h of exposure.
In the absence of an antidote, treatment consists of emergency decontamination, such as removing pollen, inducing vomiting (release ingested parts of the plant), aggressive supportive care and monitoring to help prevent severe damages to the kidneys.
Delaying treatment will reduce the chances of recovery for the cat and lead to renal failure. Once renal symptoms appear, the chance of recovery becomes significantly poorer. It is reported that mortality rates from Easter lily toxicosis are as high as 100% when pet owners fail to seek immediate treatment.
Category 4: Some species of mushrooms
Although, strictly speaking, mushrooms are not actual plants, we have included them as part of this review. Pets can encounter and ingest species of mushrooms in gardens or during outdoor walks.
Among the thousands of mushroom species, a minority is toxic. Such as the blue-green algae, it would be difficult for untrained people to tell the poisonous ones from the non-poisonous.
Several toxins produced by mushrooms and affecting pets are reported:
- Amanitins: lead to liver failure within 36 – 48h post exposure, after initial gastrointestinal disease and a « false recovery » stage. Amanita phalloides (Death cap) and Amanita ocreata (Destroying angel) are most involved types of mushrooms and can lead to sudden death of the animal (within 24h) depending on the quantity ingested. Puppies are more vulnerable.
- Muscarine: invlove signs such as salivation, lacrimation, vomiting, diarrhea, bradycardia and miosis and does not present a high risk in term of poisoning.
- Muscimol and ibotenic acid will induce ataxia, sedation, muscle spasms and seizure. Appropriate supportive treatment will help recovery within 24 to 48h.
- Psilocybin: toxin contained in hallucinogenic mushrooms with animal exhibiting signs such as ataxia, vocalisation, agressivity, nystagmus (a rapid movement of the eyes) and a higher body temperature. The prognosis for full recovery is good with supportive care.
Besides, amanitins are highly toxic to humans with rates of mortality reaching 20 to 40%. It is worth noting that cooking or freezing those mushrooms will not destroy the toxin.
Category 5: Plants producing insoluble oxalate crystals
Plants in this category belong to the Araceae family and gather about 200 species. Those plants are often present in households where people use them for decorative purpose. Hence, pets are highly likely to come in contact with them, through chewing and/or swallowing.
The problem: those plants contain insoluble oxalate crystals which are released when the plant is chewed. Those needle-sharp crystals form part of the defence apparatus of the plant. They act as both mechanical and chemical irritants, triggering all sorts of complications in both cats and dogs who happen to chew them.
Signs appear almost immediately, following the mechanical irritation, with oral pain, hypersalivation and development of anorexia, vomiting, swelling of lips, tongue or pharynx. Some respiratory signs may sometimes be involved, due to the swelling. Eyes could be affected if the liquid contained in the plant comes in contact with them, leading to pain and swelling.
Nevertheless, the prognosis is good since the symptoms are mild to moderate and do not last. Appropriate treatment relies on adequate decontamination (washing the mouth) and relevant supportive care. Best course of action is to remain aware of such plants and keep them out of reach of pets.
Category 6: Plants producing soluble oxalate crystals
Even though most of the plants in this category consist of weed, some of them are grown as household plants, which means pets may come in contact with them. Those plants contain oxalic acid and oxalate salts, substances poisonous to both cats and dogs, in the event they manage to consume significant amounts.
Most common species involve garden rhubarb, star fruit and shamrock plant as well as hybrids. The problem with soluble oxalate salts is that they enable a decrease in serum calcium levels by binding with systemic calcium, which in turn provokes a condition called nephrosis, as well as renal failure. Besides, oxalic acid will trigger gastrointestinal tract irritation showing up as vomiting and diarrhea.
Symptoms appear when those substances are ingested in large quantities and trigger renal issues, due to the formation of calcium oxalate crystals. Not all parts of those plants are edible, and so the situation will also depend on which parts are eaten by pets. For example, rhubarb leaves are not edible.
When calcium oxalate crystals are formed, they trigger acute renal failure with symptoms developing from 24 to 48h after ingestion, such as increased drinking, increased urination or absence of urination, with presence of blood and protein in the urine.
A significant drop in calcium levels (hypocalcemia) will be responsible for signs such as depression, weakness, tremors, tetany and coma.
Treatment is supportive, as to avoid deterioration, especially with those pets showing hypocalcemia and oxaluria. The major goal is to prevent renal failure. If treated early, the prognosis will be good and pets will recover. However, if renal failure develops before the pet can benefit from emergency veterinary care, the prognosis will be guarded. Some cases may develop chronic renal failure.
Category 7: Plants of the Ericaceae family
This family gathers species such as Rhododendrons and Azaleas. Those are also used as household decor. Those plants are toxic because of the grayanotoxins they contain. Absolutely all parts of those plants are toxic and will impact the cardiovascular function within a few hours of comsumption.
The literature reports that swallowing the equivalent of 0.2% of the pet’s body weight is enough to trigger symptoms starting with gastrointestinal signs, then followed by lowering of blood pressure as well as general disruption of the heart’s activity, including cardiac arrest. Additionally, neurological signs can arise.
Treatment relies on decontamination and supportive care as there is no antidote. If the situation is not complicated by cardiac signs, then the prognosis is good, however, neurological signs might take some time to disappear.
The best way for owners to avoid accidental intoxication of their pets is to keep their households and gardens free of such hazardous plants, especially away from cats. Those may have a tendency to play with flowering plants.
Category 8: The Sago palm plant
The Sago palm plant, also known as the Cycad palm plant is toxic to pets through ingestion. All the parts are toxic, especially the seeds, as they contain higher levels of cycasin.
Effects are dose-dependent and involve liver failure. The cycasin is ingested and transformed into a molecule which triggers liver toxicity. The symptoms take between 2 and 3 days to develop into acute and severe hepatic necrosis.
Prior to this, pets will show signs of vomiting and diarrhea. Consequently to liver impairment, neurological signs can develop and pets will show loss of balance, seizure or even fall into a coma.
Since there is no antidote against this toxin, decontamination and supportive therapies are indicated, as well as monitoring of the liver function.
Prognosis will depend on the part of the plant and the quantity swallowed. Literature report that 42% of intoxicated pets may recover after emergency treatment and monitoring. However, in some cases, there are warnings that some recovered pets may still die within 8 to 12 weeks after the initial intoxication with parts of a sago palm plant.
Category 9: Yew species aka the "Tree of Death"
With such a name, no wonder yew is toxic. It is of the upmost importance to avoid exposure to it, although small animals are rarely intoxicated with its toxins: Taxine A and Taxine B. Because Taxine A and B are calcium and sodium channel blockers, they directly impact the activity of the heart.
Yew affects all species of animals, more specifically horses and cattle. It is reported that a dog could die of yew intoxication by ingesting as little as one ounce of leaves or just by chewing on its branches.
Unfortunately, intoxication with yew leads extremely rapidly to death, thus supportive treatment is rarely an option in such situation. There is also no antidote. Unless decontamination is practiced immediately after ingestion, there is little chance of saving the animal.
Category 10: Cannabis sativa in its "recreational" form
It is not unusual to treat pets involved with either ingestion of marijuana (through dried flowers and leaves, baked goods such as cakes and cookies or cigarettes) or inhalation of the smoke. The impact of the toxin tetrahydrocannabinol (THC) is dose-dependent.
When ingested, THC induces signs such as gastric irritation leading to vomiting. Other signs can include depression, disorientation and even a coma. The heart may slow down or accelerate and body temperature might decrease or increase, depending on cases.
The signs may occur rapidly, within minutes and generally take 1 to 3h to become visible; they can last for up to 3 days. Supportive treatment in hospital might become necessary, although on the positive side, intoxication with marijuana usually resolves well and pets should be able to make a full recovery.
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