Mushroom poisoning in dogs – symptoms and urgent treatment

Overview

Mushroom poisoning covers several different toxic conditions affecting different parts of the body. Many mushrooms are non-toxic, but some can cause fatal poisoning. Even a non-toxic or spoiled mushroom may irritate the digestive tract because mushrooms are poorly digested.

Among 421 dogs followed in Norway with confirmed mushroom ingestion, 98.6% survived. This figure includes dogs eating different species, rather than severe poisonings alone. Urgency depends on mushroom species and exposure.

The Norwegian ingestion follow-up included 121 different mushroom species.

Causes

Different mushroom toxins damage different organs

Poisoning usually follows swallowing a mushroom or part of one. Destroying angels and death caps contain amatoxins. Amanitins in Galerina marginata also damage liver cells. Amanitins inhibit cellular RNA polymerase II and thereby protein production. Liver cells, rapidly renewing intestinal cells and kidney tubular cells are particularly vulnerable.

Orellanine in the deadly webcap is strongly toxic to the kidneys. Ibotenic acid and muscimol in fly agaric and panther cap affect the central nervous system. Muscarine in fibrecaps instead excessively stimulates peripheral acetylcholine receptors. Gyromitrin in false morels becomes monomethylhydrazine in the body. This reduces the nervous system's inhibitory neurotransmitter GABA.

Toxin concentration can vary with species and mushroom part. A death cap's cap may contain a lethal quantity of amanitins for an animal. Muscarine does not cross the blood–brain barrier, so its effects mainly occur outside the brain. Muscimol instead activates brain GABA receptors and can suppress the central nervous system.

Amanitins undergo little metabolism and are mainly excreted unchanged in urine.

Risk factors

Dogs that taste everything from the ground or roam freely are readily exposed. Puppies and young dogs therefore need particular supervision where mushrooms grow. Among the confirmed Norwegian ingestions, 72% of dogs were under 1 year old. Their median age, the middle value, was 5 months.

The same amount poses a greater poisoning risk to a small dog than a large one. Risk also depends on species and quantity eaten. Wild mushrooms can appear in gardens as well as forests in late summer and autumn.

Destroying angels grow particularly in spruce-dominated forest, often among thick moss.

Typical symptoms

Signs from gastrointestinal irritant mushrooms usually begin within 15 minutes–3 hours. Neurological signs from fly agaric and panther cap may begin within 30–120 minutes. Signs from muscarine-containing mushrooms often start within 5–30 minutes.

At home, you may notice the following signs:

• Vomiting, diarrhoea or blood in diarrhoeic stools.

• Clearly increased drooling and watery eyes.

• Abdominal pain or reduced appetite.

• Unsteadiness, confusion or muscle twitches.

• Unusual restlessness or marked tiredness.

• Seizures or reduced consciousness.

• With muscarine poisoning, pupils may be smaller than usual.

• Increased drinking and urination with kidney damage.

Webcap poisoning signs may begin 2–14 or 3–14 days after ingestion.

As kidney damage progresses, urine volume may decrease.

Vomiting, diarrhoea and neurological signs from false morels may begin after 6–12 hours. Psilocybin in Psilocybe mushrooms can cause unusual aggression or vocalisation. Psilocybin signs usually begin within 0.5–1 hour, but sometimes only after 3 hours.

Complications and consequences

Temporary improvement can mislead in amatoxin poisoning

With amanitin poisoning, a dog may initially have no symptoms for 6–12 hours. Apparent recovery after gastrointestinal signs may occur at 24–48 hours. The liver and kidney damage phase usually follows within 36–72 hours. Severe deterioration after destroying angel poisoning may begin within 36–48 hours.

Severe liver failure can involve a clotting disorder. Blood sugar can also fall dangerously low. Liver dysfunction may cause brain signs, or encephalopathy. Puppies or dogs eating large quantities of amanitins may die within 24 hours.

Untreated death cap poisoning is fatal in almost 100% of cases. After serious liver or kidney injury, recovery or death may occur 7–14 days after ingestion.

Mortality associated with amatoxin-related liver or kidney failure may exceed 50%.

Respiratory problems and other organ damage

Fibrecap poisoning can cause breathing difficulty, circulatory shock and death. Canine deaths from fly agaric have also been identified. Orellanine-damaged kidneys may be left with chronic failure. Severe vomiting and diarrhoea can cause dehydration and impaired circulation.

Muscarine-related breathing difficulty results from increased airway secretions and bronchoconstriction. The heart rate may also become slower than normal. Blood pressure can fall excessively too. False morel poisoning can also cause red blood cell breakdown and resulting anaemia. Liver injury may cause yellow skin or mucous membranes.

Diagnosis at the vet

Ingestion timing and a mushroom sample guide investigation

Possible exposure, symptom onset and mushroom identification are central to diagnosis. A photograph where it grew and a sample help identification. Mushroom remains in vomit can also be used. However, chewing, stomach acid and activated charcoal can alter appearance.

An expert may be needed to identify spores and species. An image-recognition app's result must be confirmed with other information. Destroying angels can be confused with some white Agaricus species.

Blood and urine tests look for organ damage

Severe gastrointestinal signs prompt assessment of fluid balance and blood electrolytes, or salts. Amanitin poisoning may increase liver enzymes and bilirubin. Webcap poisoning requires monitoring of kidney values and acid–base balance. Urine may contain blood, protein or glucose, for example.

Specialist laboratories can detect amanitin in samples such as blood, urine or stomach contents. Urine amanitin concentrations peak on day 1 in dogs. It may remain detectable in urine 4 days after exposure. Urinary muscarine measurement can support diagnosis of muscarine poisoning.

Specialist mass-spectrometry testing can look for ibotenic acid and muscimol in urine or stomach contents. Orellanine is mainly detectable in urine within 24 hours of exposure. A long symptom-free interval can therefore make detection difficult once illness begins.

Amanitin can be detected in canine plasma as early as 1 hour after ingestion. In orellanine poisoning, liver enzymes usually remain normal despite kidney damage. The kidneys' urine-concentrating ability may decline as a result.

Treatment

Reducing absorption requires veterinary care

There is no universal antidote effective against every mushroom toxin.

Treatment depends on species and the dog's signs. A vet may induce vomiting in a symptom-free dog very soon after exposure. For some mushroom poisonings, gastrointestinal emptying is considered even more than 2 hours after ingestion. Salt must not be used to induce vomiting. Activated charcoal can reduce toxin absorption from the digestive tract.

With webcap poisoning causing symptoms days later, gastrointestinal decontamination is no longer useful. Treatment then targets kidney failure and gastrointestinal signs.

Hospital care supports fluid balance and organ function

Intravenous fluids correct dehydration and support treatment. The vet may give anti-nausea medicines. Gastric protectants may reduce irritation where needed. Amatoxin poisoning may require glucose for low blood sugar. Severe clotting disorders may require blood products and vitamin K.

Silibinin may reduce amanitin uptake into liver cells. Acetylcysteine may also be considered for liver support, but its effectiveness in mushroom poisoning is uncertain. Neurological signs from false morel poisoning may be treated with pyridoxine.

Large quantities of pyridoxine carry a nerve-damage risk, so vitamin treatment also requires veterinary supervision.

Dialysis may be considered for severe orellanine-related kidney damage.

Neurological and respiratory signs need close monitoring

In severe muscarine poisoning, atropine reduces excessive muscarinic effects. Atropine is unsuitable for fly agaric poisoning. Medicines controlling muscimol-related seizures may also worsen respiratory depression. A severely affected dog may therefore require mechanical ventilation.

Muscarine treatment particularly monitors improved breathing and reduced airway secretions. Excessive atropine effects can increase heart rate. They can also raise body temperature too far. A quiet, dim environment may reduce treatment needs in mild psilocybin poisoning. Body temperature is monitored in a symptomatic dog for possible overheating.

Follow-up and recovery

Signs from gastrointestinal irritant mushrooms alone usually ease within a few hours or 1–2 days. Fly agaric poisoning signs usually last around 24 hours. However, returning to a symptom-free state may take 24–48 hours.

Prevention

Prevent wild-mushroom eating even when mushrooms look harmless. Supervise your dog in the garden too, particularly in warm, damp weather. Promptly remove mushrooms appearing in the garden from reach. Among confirmed Norwegian ingestions, 62% occurred in the dog's own garden.

Dogs strongly inclined to eat things found outdoors need particular attention. Freezing, drying or boiling does not destroy orellanine. Also prevent inhalation of puffball spore dust because spores can cause lung inflammation.

You can check whether a substance is poisonous for other poisoning risks at home and outdoors.

Important for dog owners

Call the emergency vet immediately and give your dog's weight, estimated ingestion time, possible quantity and current signs. Photograph the mushroom where it grew and pack any sample separately, out of reach. Do not spend time identifying it if this delays treatment. Record apparent improvement and renewed deterioration too. At discharge, confirm when liver or kidney values will be rechecked and which signs require an immediate return to hospital.

Treatment and monitoring are planned with a vet even when the dog vomits up the mushroom itself.

Frequently asked questions

Should I wait for symptoms before calling a vet?

No: amanitin poisoning, for example, may cause no signs for 6–12 hours. With webcaps, signs may begin only days later. Suspected ingestion is therefore a reason to contact a vet immediately even if your dog behaves normally.

Is a small piece harmless?

Not necessarily: even a small taste of a fibrecap can cause moderate poisoning, for example. The dangerous quantity depends on mushroom species and dog size. The same amount poses a proportionally greater risk to a smaller dog than a large one.

Can I make my dog vomit with salt?

No: salt must not be used to induce vomiting. The vet assesses suitability according to exposure timing and signs. If a dog that ate fly agaric already has neurological signs, treatment closely monitors central nervous system function and breathing.

Does improvement mean the danger has passed?

Not always: amatoxin poisoning can include apparent recovery. Liver failure, a clotting disorder and kidney damage may follow. Further investigation and treatment therefore depend on species, timing and the overall clinical picture.

Why bring the mushroom or a photograph?

Species helps assess poisoning risk and select appropriate treatment. A photograph where it grew and an intact matching mushroom help identification. A chewed mushroom mixed with stomach contents or stained by charcoal may be much harder to identify reliably.