Mould poisoning in dogs: mouldy food and compost

Overview

Mould poisoning is an umbrella term covering toxins with different effects. Tremorgenic means tremor-causing: these toxins disrupt nervous system function. Aflatoxicosis primarily involves liver damage and possible associated clotting disorders. The effects of all moulds therefore cannot be assessed using one symptom list.

Mycotoxins can occur in human food and animal feed. Mould growth needs a suitable material to grow on and sufficient moisture. Only some mould species produce toxins under suitable growth conditions. Aflatoxins can be present without visible mould. Tremor-causing Penicillium crustosum occurs widely in both Arctic and tropical regions.

Causes

Nervous system toxins develop in spoiling food

Penicillium moulds can produce tremorgenic substances in food and organic compost waste. Sources include mouldy nuts, dairy products, pasta, bread and spoiled fruit. Cases involving commercial dog food have also been described. An important neurotoxin is penitrem A, which crosses the blood–brain barrier from blood into the brain.

Penitrem A is rapidly absorbed from the gastrointestinal tract. After absorption, it has been found in the liver, kidneys, brain and blood serum, among other sites.

Toxins can alter nerve cell signalling and muscle function. Penitrem A affects potassium channels and neurotransmitter release, among other mechanisms. Other toxins found in canine samples include paxilline and cyclopiazonic acid. Several toxins may occur in one sample and contribute jointly to signs.

Aflatoxin exposure can continue through the same food

Aflatoxins produced by Aspergillus moulds can form in maize, peanuts and other cereal ingredients, for example. If your dog continually eats the same contaminated food, exposure continues day after day. The toxin can then damage liver tissue before outward signs appear. Contamination can begin during crop production or storage.

Risk factors

The greatest practical risk is access to decaying organic material. Scavenging food scraps exposes dogs both at home and outdoors. An open compost heap or food waste bin can provide a source. Spoiled food may also be found around stables, for example.

Moisture and a suitable temperature encourage toxin-producing mould growth. Aflatoxin risk extends beyond visibly mouldy scraps because packaged food can also be contaminated. Several animals eating the same food may be exposed to the same contaminated product. Damp or excessively warm storage can encourage mould in food kept at home too.

Typical symptoms

Tremorgenic poisoning signs may begin within 1–2 hours, or sometimes later. In individual confirmed cases, tremors started around 30 minutes after ingestion. Rapidly developing signs may include:

• Muscle tremors, twitching or whole-body shaking.
• Staggering and poor movement coordination, called ataxia.
• Unusual startle responses and sensitivity to touch or sound.
• Drooling or vomiting.
• Restlessness and confused-looking behaviour.
• Seizures, reduced consciousness or increased body temperature.

Not every case involves vomiting. Involuntary jerking eye movements, called nystagmus, may occur. Some dogs also have eyelid spasms, repeatedly squeezing the eyes tightly shut. Heart rate may also become faster than normal. Noise and extensive handling can intensify tremors.

With aflatoxin poisoning, your dog may instead initially be subdued, off food or have diarrhoea. As liver damage progresses, jaundice, bruising or bleeding may appear.

Complications and consequences

Strong, continuous muscle activity can raise body temperature and damage muscle tissue. This muscle cell breakdown is called rhabdomyolysis. Severe overheating can also involve a widespread clotting disorder. Inhaling vomit can cause aspiration pneumonia and complicate recovery.

Many dogs recover with treatment, but severe poisoning can be fatal. Some have had balance problems persisting for months or years. Aflatoxin exposure can cause long-term liver damage even after survival of the initial stage. Liver damage may progress during continuing exposure even while an animal initially has no signs.

Diagnosis at the vet

The sequence of events helps identify exposure

Your vet investigates what your dog may have eaten and how soon signs followed. Access to rubbish, compost, spoiled food or a stable can be a crucial clue. Suspected aflatoxins also require review of regularly fed dog food and possible exposure of other animals.

Temperature, consciousness, muscle tremors and walking are assessed as your dog's condition allows. Blood tests assess factors including blood cell counts, electrolytes and signs of organ and muscle injury. Routine blood tests can remain within reference ranges despite neurotoxic poisoning. Low blood glucose, calcium disorders or another neurological disease can resemble mould poisoning. Differential diagnoses also include slug bait and other pesticide poisoning.

Demonstrating a toxin requires separate laboratory analysis

There is no commercial in-practice rapid test for tremorgenic mycotoxins that replaces separate toxin analysis. Suspected food, vomit or stomach contents can be tested. Liquid chromatography combined with mass spectrometry identifies specific chemical toxins in a sample. Fungal culture can identify a growing mould, but finding it does not establish which toxin it produced. Confirming poisoning therefore distinguishes identifying the fungus from demonstrating its toxin.

Sampling also affects results: mould and toxins may be unevenly distributed in compost. A clean compost sample collected later may therefore not represent the portion eaten earlier. Suspected aflatoxin exposure requires liver assessment and, when needed, food testing for the toxin.

Treatment

Tremors and seizures are controlled under supervision

Initial goals are stabilising your dog and controlling severe muscle tremors and seizures. Muscle relaxants and anticonvulsants may be used. Severe cases sometimes require anaesthesia to control otherwise unmanageable tremors. If medication depresses breathing, respiratory support may also be needed. Your vet decides medication and treatment duration.

Fluid therapy maintains hydration and corrects electrolyte disturbances. Antiemetics treat vomiting when needed to reduce the risk of inhaling vomit. Temperature is monitored and corrected because your dog may overheat during signs or cool during treatment. Acid–base balance and muscle breakdown markers are also monitored. In some clinical cases, intravenous lipid emulsion has been given alongside fluids and other symptomatic treatment.

Stomach emptying safety is assessed before intervention

A recently exposed dog without signs may sometimes have vomiting induced at the vet. Inducing vomiting in a dog with neurological signs can be dangerous because of seizures and aspiration. Gastric lavage may be used selectively, with airway protection essential. Activated charcoal is considered individually because its binding of penitrem A is uncertain.

Using salt to induce vomiting can itself cause salt poisoning and brain swelling. Do not try emetics or give treatment products at home without veterinary instructions. No specific antidote is known for tremorgenic mycotoxins, so care relies on stopping exposure and supporting vital functions. There is no antidote for aflatoxins either. Liver damage and biochemical disturbances are treated according to findings.

Discharge depends on signs settling

Hospital monitoring continues until tremors have largely resolved. Signs generally last around 24–72 hours, although longer recoveries are recognised. In a series of 5 laboratory-confirmed dogs, discharge occurred within 1–5 days. However, one still had mild tremors and cerebellar ataxia at discharge on day 4. In another individual case, the dog had no ongoing neurological signs at the 1-week check.

Prevention

Secure composters and food waste bins carefully and position them so your dog cannot eat their decaying contents. Dispose of spoiled food in a sealed bag in a lidded bin inaccessible to animals. Keep dry food cool and dry in its original packaging. Refrigerate opened wet food promptly or discard it if unused.

Do not try to make mouldy food safe by boiling or baking. In mouldy jam, for example, toxins can occur throughout the product beneath the visible mould layer. Do not feed suspected aflatoxin-contaminated food to other animals either. Drying and moisture control prevent mould growth, but already contaminated material must be removed from use.

Important for dog owners

Stop access to the suspected food and contact your vet immediately. Report the estimated time of eating, onset of signs and all foods or treats used. Keep a trembling dog's surroundings quiet and avoid unnecessary handling. Protect against falls during transport, but do not delay leaving to collect a sample.

Keep the suspected packaging, batch number and dates somewhere secure. Feed quality complaints can be directed to the manufacturer or importer. Under some national official sampling procedures, a package opened or stored at home cannot serve as an official sample because later contamination cannot be excluded. Your vet can still assess the need for clinical samples and other toxicological investigation.

After discharge, monitor walking, tremors, appetite and adherence to care instructions. New seizures, breathing difficulty, jaundice or bleeding need prompt reassessment. Check whether a substance is poisonous for information about common hazards.

Frequently asked questions

What if my dog ate mouldy food but looks normal?

Contact your vet immediately and explain what was eaten and when. Tremorgenic poisoning signs may start only after 1–2 hours or later. Early on, your vet can assess whether safe stomach emptying is still possible. Do not induce vomiting yourself.

Does boiling make mouldy food safe for dogs?

Ordinary heating or processing does not destroy mycotoxins already formed. Removing visible mould from jam, for example, does not remove toxin spread throughout it. Dispose of spoiled food so your dog cannot eat it from rubbish or compost.

Can a dog have mould poisoning without vomiting?

Yes. Not every dog with tremorgenic mycotoxin poisoning has digestive signs. Rapidly developing tremors, staggering or unusual sound sensitivity can still fit poisoning. Your vet investigates these signs because other toxins and metabolic disorders can also cause tremors.

Is dangerous mould always visible in dog food?

Aflatoxins can occur without visible mould growth. A dog continually eating the same contaminated food may be repeatedly exposed. Unusual lethargy, poor appetite, jaundice or unexplained bruising warrants veterinary investigation.

Can a dog fully recover from tremorgenic mould poisoning?

Many dogs recover with treatment, but the outcome depends on poisoning severity and its consequences. Signs commonly last around 24–72 hours. Persistent ataxia lasting months or years after exposure has been described in some dogs. Signs after discharge are assessed at agreed follow-up appointments.