Food poisoning in dogs – symptoms and prompt help

Overview

Food-borne illness is not one precisely defined disease: aflatoxin produced by mould, for example, causes toxin poisoning specifically. Commercial pet food or treats can also be contaminated with harmful bacteria. Diarrhoea signs alone cannot distinguish salmonellosis from other causes of stomach upset.

Salmonella is a relatively uncommon cause of diarrhoea in pets. However, an animal without symptoms can still carry and shed the bacterium.

Not every batch of ingredients or feed can be tested for every possible hazard.

Causes

Bacteria enter the body through the mouth

Salmonella infection occurs when faecal bacteria reach the dog's mouth through food, water or other contact. Infection may also come from undercooked food, contaminated water or an infected person. Homemade foods containing raw meat or eggs are more often contaminated with Salmonella than heat-treated commercial food.

Dried pig ears, for example, have also been identified as a source of Salmonella. Raw food may contain Listeria monocytogenes as well as Salmonella.

After ingestion, Salmonella bacteria can attach to the intestine and multiply in intestinal surface cells and tonsillar lymphoid tissue. Bacterial invasion into deeper mucosal layers damages the intestine and causes diarrhoea.

Mould toxins affect different organs

Mould growth can produce mycotoxins in food, poisonous substances formed by mould metabolism. Toxins causing neurological signs may occur in mouldy dairy products, nuts, pasta and compost waste, for example. These toxins disrupt signalling in the central nervous system.

Aflatoxins may be produced by Aspergillus mould growing in maize, peanuts and other grain ingredients. They can be present in food even when no mould is visible to the naked eye. Continued eating of the same contaminated food can lead to toxin accumulation in the body.

Risk factors

Risk increases if a dog can explore compost, rubbish or food scraps left accessible without supervision. Feeding raw meat increases the possibility of Salmonella exposure. Puppies may develop salmonellosis particularly after heavy bacterial exposure.

In adult dogs, clinical salmonellosis often involves another infection, debilitation from disease or hospitalisation. Infection during pregnancy can also threaten developing puppies. Aflatoxin exposure can continue for a long time if the dog eats the same contaminated food daily.

A puppy's still-developing intestinal microbiota and immune defences may increase susceptibility to Salmonella infection.

Typical symptoms

The combination of signs depends on the cause: not every food-borne illness looks the same. Common signs of bacterial intestinal inflammation include diarrhoea, abdominal pain and nausea.

• Your dog has diarrhoea, which may contain blood.

• Your dog vomits or drools more than usual.

• Appetite declines and your dog is more subdued than usual.

• The abdomen is painful and your dog may have a fever.

• Neurological mould-toxin exposure causes tremors, muscle twitches or unsteadiness.

• Your dog reacts unusually strongly to sounds or touch.

• A liver-damaging toxin may cause yellowish gums or whites of the eyes.

• Bruising or bleeding may develop without obvious injury.

Signs from neurological mould toxins may begin within 1–2 hours or only after several hours. Aflatoxin-related liver damage may cause no symptoms initially.

Complications and consequences

Dehydration, sepsis and tissue damage

Vomiting and diarrhoea can lead to dehydration and weight loss. With severe salmonellosis, bacteria can cross the intestinal lining into the blood and cause sepsis, sometimes called blood poisoning. Aflatoxins can impair liver function and blood clotting.

Seizures associated with severe mould-toxin poisoning can be fatal. Vomit entering the airways can cause aspiration pneumonia. Recovery from a neurological mould toxin can take a few days to several weeks. Rarely, dogs have retained an unsteady gait for months or even years.

A dog surviving aflatoxin poisoning may be left with long-term liver damage. Severe or rapidly developing aflatoxin poisoning can cause death before treatment begins.

A dog without symptoms can still spread Salmonella

Salmonella may be shed in faeces for weeks and sometimes months after visible signs end. A latent bacterial infection may reactivate, for example because of stress. Salmonella can also spread from a pet to a person.

Bacteria may reach the dog's muzzle, mouth and coat when it licks its rear end. Human infection does not require visible faeces because a very small number of bacteria may be enough.

Diagnosis at the vet

Investigating food eaten and the signs

The vet investigates the food eaten, other possible exposures and the nature of the signs. The food history includes treats and food given by other household members as well as the usual diet. Access to compost or rubbish is important when investigating sudden tremors.

Assessment of a neurological mould toxin relies on exposure history and typical signs. Similar signs can also result from pesticides and other poisons, for example. Routine blood counts and biochemistry may nevertheless remain within reference ranges.

Bacterial and toxin tests are chosen according to suspicion

Salmonella infection is primarily identified by bacterial culture of diarrhoeic faeces. Blood culture may be performed if sepsis is suspected. Bacterial shedding varies, so long-term carriage is investigated with faecal samples collected over several days. One negative faecal sample does not completely rule out Salmonella.

PCR can identify bacterial genetic material, but a positive result may also come from non-viable bacteria. Identifying the bacterial serotype, or subtype, may help trace the source. Feed, water and the surrounding environment may be tested to investigate the origin of infection.

One positive faecal sample from a dog without symptoms may indicate carriage and require repeat samples.

If aflatoxin is suspected, the vet assesses the liver and may recommend toxin analysis of a food sample. Specialist laboratories can look for neurological mould toxins in food, vomit or digestive contents. However, these specialist tests are not routinely available everywhere.

The food's batch code and date help investigate when contamination occurred and which other products may be affected.

Treatment

The vet assesses the safety of first aid

Stop feeding the suspected contaminated food immediately so exposure does not continue. The vet chooses treatment according to examination findings and the suspected exposure. Do not attempt to induce vomiting without case-specific veterinary guidance.

Inducing vomiting can cause aspiration pneumonia or damage the oesophagus and stomach. Salt must not be used because it can cause salt poisoning and brain swelling. The potential benefit depends on both the substance eaten and the time since ingestion.

Infection and toxin poisoning need different treatment

Most dogs with salmonellosis need supportive care without antibiotics. In severe systemic infection, the vet prescribes an appropriate antibiotic. Routine antibiotic use can disrupt the intestinal microbiota and prolong Salmonella shedding. Fluid therapy can correct dehydration and disturbances in the body's acid–base balance.

Unnecessary antibiotics can also select drug-resistant Salmonella strains, which threaten human health too.

Severe mould-toxin seizures and tremors need medication to control them. Intravenous fluids and temperature management may be needed in hospital. The vet may consider gastrointestinal decontamination using gastric lavage and activated charcoal. Protecting the airways during procedures is particularly important in a dog with neurological signs to prevent aspiration.

With prolonged tremors, muscle damage called rhabdomyolysis may be monitored. A seizuring dog can overheat, but its temperature can also fall too low during treatment. Medication to control tremors may still be needed after hospital discharge.

There is no specific antidote for aflatoxins. Treatment relies on stopping exposure and supportive care for identified blood and metabolic disturbances. Improving symptoms do not yet mean that possible long-term liver damage has resolved.

Prevention

Keep your dog away from compost, mouldy food and food waste. Wash hands with soap for at least 20 seconds before and after handling pet food. Wash bowls and measuring utensils with hot water and detergent after every use.

Use a separate washing-up brush for the food bowl from the one used for household dishes. Salmonella is killed by most dishwasher programmes above 60°C when dishwasher detergent is used. Raw food is more likely to contain harmful bacteria than processed food.

Refrigerate opened wet food promptly or dispose of it safely if unused. Keep dry food in a cool, dry place in its own carefully closed packaging. Do not buy damaged food packaging. Following storage instructions on the label is another way you can help maintain safety.

Important for dog owners

Keep the details and prevent further exposure

Keep the packaging, batch number and best-before date for any investigation. Do not give the suspected food to other animals either. Keep any food sample in its original packaging where children and animals cannot reach it.

Report a suspected feed-quality problem to the manufacturer or importer. Some authorities do not accept packaging opened or stored at home as an official sample because contamination after opening cannot be ruled out.

Record what your dog ate, when it happened and when signs began. Tell the vet whether other animals receiving the same food have shown symptoms. Consider possible access to rubbish or compost too. You can check whether a substance is poisonous for information on common substances unsuitable for dogs.

Collect a Salmonella-carrying dog's faeces carefully and wash hands afterwards. Do not allow the dog to lick people or sleep in a child's bed during infection. Children and immunocompromised people are more susceptible to infection.

Frequently asked questions

Is food poisoning the same as Salmonella?

No: Salmonella causes a bacterial infection, but food can also contain harmful mould toxins. Aflatoxins, for example, can damage liver function. The appearance of diarrhoea cannot reliably identify the cause, so Salmonella is confirmed through testing.

How quickly do signs begin?

Signs from neurological mould toxins may begin within 1–2 hours or later the same day. Aflatoxin-related liver damage, meanwhile, may initially progress without visible signs. An absence of symptoms immediately after suspected exposure therefore does not confirm food safety.

Can food be dangerous without visible mould?

Yes: aflatoxins can be present in pet food without visible mould growth. Repeated eating of the same food can increase toxin accumulation in the body. If food is suspected as the cause of symptoms, stop offering it and have your dog assessed by a vet.

Can I make my dog vomit at home?

Do not induce vomiting without case-specific veterinary instructions. Safety depends on the substance eaten, timing and the dog's condition. Vomit entering the airways is also a real risk. Do not use salt, as it can cause salt poisoning and brain swelling.

Can a dog's food-borne illness spread to people?

Salmonella can spread from pets to people, and dogs can still shed it after symptoms have ended. Bacteria can reach the muzzle and coat when the dog licks its rear end. Careful hand hygiene and faeces removal reduce exposure for others.