Snail Bait (Molluscicides)

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026
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Slug poison, also known as molluscicides, includes various chemical substances used to control snails and slugs. The most common active ingredients in commercial slug pellet preparations are metaldehyde, methiocarb, and iron phosphate. Metaldehyde in particular poses a significant danger to pets. This organic compound is synthesized from acetaldehyde and acts as a contact and stomach poison for slugs by disrupting their mucus production and leading to dehydration. In dogs and cats, on the other hand, metaldehyde causes serious neurological disorders because it can cross the blood-brain barrier and impair the activity of important neurotransmitters.

The most important facts at a glance

Poisoning by slug poison represents a serious and potentially life-threatening emergency situation for dogs and cats. The main active ingredient, metaldehyde, causes severe neurological symptoms through its neurotoxic effect, which can quickly lead to death without adequate treatment. Clinical signs typically develop within a few hours after ingestion of the poison and include gastrointestinal complaints, states of agitation, muscle tremors, convulsions, and hyperthermia.

The diagnosis is primarily based on the medical history and the characteristic clinical picture. Therapy must be initiated immediately and consists of decontamination, symptomatic treatment of neurological symptoms, and supportive measures to stabilize vital functions. Although no specific antidote exists, early and intensive treatment can significantly improve the chances of survival.

Preventive measures are of great importance to avoid cases of poisoning. Pet owners should avoid using slug pellet preparations containing metaldehyde and instead use pet-safe alternatives such as iron phosphate-based products or biological control methods. If slug poison poisoning is suspected, immediate action is required – the earlier treatment begins, the better the prospects for a full recovery.

Causes, development and progression

Poisoning from slug pellets is one of the most common types of intoxication in pets during the warmer months, when garden owners increasingly use slug control agents. Curious young animals and dogs that tend to ingest foreign substances are particularly at risk. The toxicity of metaldehyde is considerable: the median lethal dose (LD50 (lethal dose 50)) is approximately 100 mg/kg body weight for dogs and 207 mg/kg body weight for cats. In practice, this means that just one tablespoon of slug pellets can be enough to cause severe symptoms of poisoning in a 5 kg dog. Slug poison or slug pellets usually contain metaldehyde.
This is highly toxic for dogs and cats and can lead to fatal poisoning.
In the gastrointestinal tract, metaldehyde is partially converted into substances that can be excreted via the kidneys. However, a portion is absorbed and is able to cross the normal blood-brain barrier, causing severe neurological symptoms.

The main cause of slug poison poisoning in pets is the direct oral ingestion of slug pellet preparations. These are often spread in gardens, parks, or agricultural areas and are attractive to animals due to their smell and taste properties. Some preparations are supplemented with attractants that can also be appealing to pets.

The mechanism of action of metaldehyde is based on a disruption of the neurotransmitter system in the central nervous system. In particular, it inhibits the activity of GABA (gamma-aminobutyric acid), an inhibitory neurotransmitter that normally regulates neuronal excitability. The reduced GABA activity leads to excessive neuronal excitation, which manifests as muscle tremors (tremor), seizures, and other neurological symptoms. In addition, the function of the neurotransmitters norephedrine and serotonin is also impaired.

Metaldehyde is absorbed relatively quickly via the gastrointestinal tract. A portion is converted in the gastrointestinal tract into acetaldehyde, which can be excreted via the kidneys. However, the absorbed portion crosses the blood-brain barrier and exerts its neurotoxic effect there. The tremor triggered by the poisoning leads to increased muscle activity, which in turn causes hyperthermia (increase in body temperature) and metabolic acidosis (over-acidification of the body) – both factors that further worsen the condition of the poisoned animal.

Mechanism of action

Metaldehyde has an influence on the activity of neurotransmitters. The activity of the neurotransmitters GABA (gamma-aminobutyric acid), norephedrine, and serotonin is reduced, which is associated with states of agitation.
The accompanying tremor can lead to a critical increase in body temperature and an exacerbation of metabolic acidosis.
One gram of slug pellets contains 60 mg of metaldehyde.
The acute oral LD50 (lethal dose 50) for metaldehyde is 100 mg/kg body weight for dogs and 207 mg/kg for cats.
Signs of intoxication can be expected in a 5 kg dog after ingesting approx. one tablespoon of slug pellets.
The median lethal dose is given as 11.8 g of slug pellets / kg body mass.

Slug pellets represent a serious source of poisoning for dogs – and more rarely for cats. The product is usually granulated and provided with attractants, which makes it particularly attractive to dogs. The toxicity depends on the active ingredient contained. The most important toxic components are:

  • Metaldehyde (most common toxic ingredient)
  • Less common: Iron(III) phosphate or Methiocarb

The toxicological mechanism of action of metaldehyde, the most common toxic component, is described in detail below, as it is responsible for most poisoning cases in dogs and cats.

Toxicology of Metaldehyde

Metaldehyde is a polymer of acetaldehyde that can split back into free acetaldehyde molecules in the body. The toxic effect primarily affects the central nervous system (CNS (central nervous system)) and the metabolic system, leading to seizures, hyperthermia, and organ failure.

Mechanism of Action of Metaldehyde

Neurotoxic Effect on the CNS

  • After oral ingestion, metaldehyde is rapidly absorbed and crosses the blood-brain barrier.
  • It affects GABAergic neurotransmission:
    • GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter in the brain.
    • Metaldehyde lowers GABA concentration in the CNS, leading to uninhibited neuronal excitability.
    • Result: Muscle tremors, ataxia, seizures, hyperreflexia

Acetaldehyde Release

  • In the gastrointestinal tract and tissues, metaldehyde is partially converted to acetaldehyde
  • Acetaldehyde acts as:
    • Cytotoxic
    • CNS-activating
    • Hepatotoxic and nephrotoxic
    • Leads to disturbances in cellular respiration and metabolic stress

Hyperthermia and Metabolic Acidosis

  • Persistent muscular activity due to seizures causes massive heat production.
  • Additionally, lactic acidosis leads to an acidic pH in the blood, which exacerbates organ damage.
  • Hyperthermia can reach temperatures >42°C → thermal cell damage, coagulopathy, multi-organ failure

Further Effects

  • Hepatotoxicity: Enzyme elevation (ALT, AST), jaundice possible
  • Nephrotoxicity: due to acidosis, dehydration, and myoglobinuria resulting from muscle breakdown
  • Gastrointestinal irritation: due to direct contact → vomiting, salivation, diarrhea

Species Differences

Dog: Very Sensitive

  • Readily ingests snail bait, often in significant quantities
  • Symptoms within 30 minutes to 3 hours
  • Lethal dose of metaldehyde: 100–200 mg/kg BW

Cat: Rarely Affected, but Sensitive

  • Rarely intentionally ingests snail bait (no interest in attractants)
  • Ingestion usually by licking contaminated paws or prey animals
  • Symptoms are comparable, but usually occur with smaller amounts

Summary of the Toxic Mechanism

Target Structure Toxic Mechanism Clinical Consequence
CNS (primarily GABAergic pathways) Inhibition of GABA synthesis and release Seizures, tremors, neurological hyperexcitability
Muscles Persistent irritation due to CNS stimulation Hyperthermia, muscle breakdown (rhabdomyolysis)
Metabolism Lactic acidosis, electrolyte disturbances Organ failure, cardiac arrhythmias
Liver and Kidneys Secondary organ damage due to acidosis and hyperthermia Hepatopathy, acute kidney failure

Slug pellet poisoning – predominantly caused by metaldehyde – is a veterinary emergency in dogs with high lethality. The mechanism of action is based on central nervous overstimulation through GABA inhibition, accompanied by massive muscle activity, hyperthermia, and metabolic acidosis. Cats are less frequently affected, but they are sensitive even to small amounts. Without immediate symptomatic intensive therapy, the poisoning can be fatal within 24 hours.

Symptoms of intoxication

On average, 3 hours pass between the ingestion of snail bait and the onset of symptoms.
Symptoms include:

  • Irritation of the mucous membranes of the gastrointestinal tract
  • States of excitation
  • Anxiety
  • Coordination disorders
  • Muscle tremors
  • Seizures
  • Ataxia
  • Hyperthermia (increase in body temperature) due to tremors
  • Metabolic acidosis
  • Increased respiratory rate
  • Death due to respiratory failure

Clinical signs of slug poison poisoning usually appear within 1–3 hours after ingestion, but in severe cases, they can manifest after just 30 minutes. The course of poisoning is often dramatic and can lead to death within 4–24 hours without rapid veterinary intervention.

Characteristic symptoms of metaldehyde poisoning initially include gastrointestinal complaints such as vomiting, increased salivation, and abdominal pain, which are due to the direct irritant effect of the poison on the mucous membranes of the gastrointestinal tract. Neurological symptoms quickly follow and dominate the clinical picture: restlessness and anxiety, coordination disorders (ataxia), fine to coarse muscle tremors (tremor), which can escalate to generalized convulsions. Animals often show an increased respiratory rate (tachypnea) and heart rate (tachycardia), as well as significant hyperthermia with body temperatures exceeding 41°C, due to the increased muscle activity.

In advanced stages, disturbances of consciousness can occur, ranging from drowsiness to coma. Persistent seizures and hyperthermia lead to metabolic acidosis, which, together with dehydration and electrolyte shifts, can lead to circulatory failure and finally death by respiratory paralysis. It is particularly concerning that relapses can occur even after an apparent recovery, as metaldehyde can be stored in the body and released with a delay.

Diagnosis

The diagnosis of slug poison poisoning is primarily based on the medical history and the clinical appearance. Crucial to this is the collection of a thorough history, in which the pet owner is asked about possible contact with slug pellets or other molluscicides. Information about walks in gardens or parks where slug control agents were recently applied, as well as the accessibility of such products in the owner’s home, is particularly important.

The clinical examination focuses on assessing the neurological status and vital functions. Typical findings include increased body temperature, accelerated respiratory and heart rates, and neurological abnormalities such as muscle tremors, ataxia, and convulsions. However, these symptoms are not pathognomonic for metaldehyde poisoning and can also occur with other intoxications or neurological diseases.

Laboratory diagnostic tests primarily serve to rule out differential diagnosis and assess secondary damage. A blood count can provide evidence of dehydration (increased hematocrit), while blood chemistry provides information on liver and kidney function as well as the acid-base balance. Typical changes in metaldehyde poisoning include metabolic acidosis, electrolyte shifts, and possibly increased liver enzyme levels.

Definitive detection of metaldehyde is possible through toxicological analysis of stomach contents, vomit, or suspicious material, but is rarely performed in practice as therapy usually has to be initiated based on clinical symptoms and medical history. In unclear cases, a differential diagnosis from other poisonings (e.g., organophosphates, strychnine, ethylene glycol) or from primary neurological diseases (e.g., epilepsy, meningitis) may be necessary.

Therapeutic principles

There is no direct antidote.
Decontamination targets the gastrointestinal tract.
If assessable, decontamination should be performed for metaldehyde ingestion starting from 2 mg/kg body mass, but also as a precautionary measure in unclear circumstances.
Vomiting can be induced if the ingestion of snail bait occurred within the last 30 minutes and, crucially, no seizures have yet occurred.
If large amounts of snail bait are suspected to have been ingested, repeated gastric lavage under general anesthesia is advisable.
Symptomatic therapy primarily involves controlling tremors and seizures, and in this context, monitoring body temperature.
Regarding vital functions, the water, electrolyte, and acid-base balance are particularly important.
Initially, the following are indicated:

  • Sedatives
  • Anticonvulsants
  • Anesthetics
  • Intravenous fluid replacement
  • Correction of metabolic acidosis

Further therapy depends on other symptoms such as vomiting.

The treatment of slug poison poisoning requires a rapid and comprehensive therapeutic approach. Since no specific antidote exists for metaldehyde, therapy focuses on three main aspects: decontamination, symptomatic treatment, and supportive measures.

Decontamination aims to prevent further absorption of the poison. If ingestion occurred less than 30 minutes ago and the animal is not yet showing convulsions, vomiting can be induced under veterinary supervision, typically by administering apomorphine in dogs or xylazine in cats. For larger suspected amounts of poison or if ingestion occurred longer ago, gastric lavage under general anesthesia may be considered. The subsequent administration of activated charcoal (1–4 g/kg body weight) can reduce the absorption of poison not yet absorbed, whereby multiple doses may be useful due to the enterohepatic recirculation of metaldehyde.

Symptomatic therapy is primarily directed against neurological manifestations. To control muscle tremors and convulsions, anticonvulsants such as diazepam (0.5–2 mg/kg i.v.), phenobarbital (2–6 mg/kg i.v.), or propofol (1–6 mg/kg i.v. for induction, then 0.1-0.4 mg/kg/min as a continuous infusion) are used. In the case of therapy-resistant seizures, deep sedation or even controlled general anesthesia with intubation and mechanical ventilation may be necessary.

Supportive measures include intravenous fluid therapy to correct dehydration, electrolyte shifts, and metabolic acidosis. Sodium bicarbonate may be indicated in cases of severe acidosis. Active cooling using wet towels or fans is essential in cases of hyperthermia, and body temperature should be closely monitored. Additionally, depending on the clinical picture, antiemetics for vomiting, gastroprotectants to protect the gastric mucosa, and possibly antibiotics if aspiration pneumonia is suspected, may be used.

Prognosis & follow-up care

In an evaluation of 772 reported cases where dogs had ingested snail bait, 21.7% showed no symptoms, 61.7% of the dogs recovered, and 16.6% of the dogs died or were euthanized.
The prognosis should therefore be considered cautious.

The prognosis for poisoning by slug poison should be made with caution and depends on various factors. The amount of poison ingested, the time elapsed between ingestion and the start of treatment, and the response to initial therapy are decisive. Evaluations of clinical cases show that about 60–65% of affected dogs recover completely, while the mortality rate is 15–20%. The remaining animals may suffer long-term neurological deficits or organ damage.

Animals that respond to therapy within the first 12–24 hours and whose convulsions are controllable generally have a more favorable prognosis. Conversely, the occurrence of persistent status epilepticus, severe metabolic acidosis, renal failure, or disseminated intravascular coagulation (DIC) is associated with a poorer prognosis.

Aftercare plays an important role in full recovery. After stabilization, animals should be monitored as inpatients for at least 24–48 hours, as relapses can occur. Regular checks of body temperature, heart and respiratory rate, and neurological parameters are important. Laboratory tests to monitor renal and liver function as well as the acid-base balance should be repeated at appropriate intervals.

After discharge, a quiet environment is important for the animal to avoid further stress stimuli. Food and water intake should be normalized gradually. In animals showing persistent neurological symptoms, longer-term anticonvulsant therapy may be necessary, which is then gradually reduced. Follow-up examinations after 1–2 weeks and, if necessary, after one month serve to assess full recovery and rule out long-term consequences.

Research outlook

Research in the field of molluscicide poisoning in pets is currently focusing on several promising areas. On the one hand, new biomarkers are being investigated to enable early and more specific diagnosis. Studies on metabolic signatures in the blood of poisoned animals could in the future produce faster and more precise diagnostic tests that also allow for better differentiation from other intoxications.

Another research focus is on the development of more effective treatment protocols. Newer anticonvulsants such as levetiracetam show promising results in initial studies in controlling seizures triggered by metaldehyde and could supplement or partially replace conventional therapies. Innovative detoxification procedures such as specific lipid emulsion therapies are also being investigated for their effectiveness against lipophilic toxins like metaldehyde.

In parallel, scientists are working on developing safer slug control agents. In addition to the already available iron phosphate-based products, new formulations are being researched that are toxic to slugs but harmless to mammals. Biological control methods, such as the use of nematodic parasites or natural predators, are also gaining importance as environmentally friendly and pet-compatible alternatives.

Last but not least, research is dedicated to improving prevention strategies. Epidemiological studies analyze risk factors and seasonal patterns of poisoning cases to enable more targeted awareness campaigns. Innovative product designs with improved warning labels, child-resistant packaging, and formulations unattractive to pets could further reduce the risk of poisoning in the future.

Frequently asked questions (FAQs)

  1. How quickly do symptoms of snail bait poisoning appear?
    The first symptoms typically appear within 1–3 hours after ingestion of the poison. In severe cases, the first signs such as salivation or restlessness can appear after just 30 minutes.
  2. Which snail baits are safe for my pets?
    Iron phosphate-based slug agents are considered significantly safer for pets than products containing metaldehyde or methiocarb. Nevertheless, these should also be kept out of reach of animals, as they can cause gastrointestinal complaints if ingested in excess.
  3. What should I do if I suspect my pet has ingested snail bait?
    Contact your veterinarian or a veterinary emergency clinic immediately. Do not attempt to induce vomiting yourself, as this can be dangerous if neurological symptoms are already present. If possible, take the packaging of the slug agent with you to the veterinary practice.
  4. Can my pet fully recover from snail bait poisoning?
    With early and adequate treatment, full recovery is possible in about 60–65% of cases. The prognosis depends on the amount of poison ingested, the time until treatment, and the individual response to therapy.
  5. How long does my pet need to stay at the veterinary hospital after slug bait poisoning?
    Inpatient monitoring usually lasts 24–48 hours but can vary depending on the severity of the poisoning and the occurrence of complications. Close monitoring is important as relapses can occur.
  6. Are there long-term consequences after recovering from poisoning?
    Most animals recover without permanent damage. In some cases, however, persistent neurological deficits, liver or kidney damage can occur, requiring longer-term treatment.
  7. How can I protect my pet from snail bait poisoning?
    Avoid using slug agents containing metaldehyde or methiocarb in areas where your pets have access. Store garden products safely and keep your animals away from freshly treated areas. Consider alternative slug control methods such as coffee grounds, beer traps, or the use of natural predators.
  8. Are certain animal species or breeds more susceptible to slug bait poisoning?
    Dogs are generally more frequently affected than cats due to their exploratory behavior. Young, curious animals and breeds with a pronounced hunting or play instinct are particularly at risk. Small breeds can be more severely affected even by smaller absolute amounts of poison.
  9. How effective are biological alternatives for slug control?
    Biological methods such as the use of nematodes, setting up beer traps, or promoting natural predators can be effective if used consistently, but usually require more time and patience than chemical agents. Their effectiveness can vary depending on weather conditions and the type of slug.
  10. Can slug bait poisoning also endanger humans?
    Yes, metaldehyde is also toxic to humans, especially children. Symptoms of poisoning are similar to those in animals. Therefore, slug agents should always be kept out of reach of children and protective gloves should be worn during application.

Literature

  • Bates, N., Rawson-Harris, P. and Edwards, N., 2015. Common questions in veterinary toxicology. Journal of Small Animal Practice, 56(5), pages 298–306.
  • Bates, N. S., Sutton, N. M. and Campbell, A., 2012. Suspected metaldehyde slug bait poisoning in dogs: a retrospective analysis of cases reported to the Veterinary Poisons Information Service. Veterinary Record, 171(13), page 324.
  • Berny, P., Caloni, F., Croubels, S. et al., 2010. Animal poisoning in Europe. Part 2: Companion animals. The Veterinary Journal, 183(3), pages 255–259.
  • Dolder, L. K., 2003. Metaldehyde toxicosis. Veterinary Medicine, 98(3), pages 213–215.
  • Gupta, R. C., 2018. Veterinary Toxicology: Basic and Clinical Principles. 3rd Edition. Cambridge, MA: Academic Press.
  • Löwe, G. and Löwe, O., 2021. Poisoning in dogs and cats – A veterinary Guides. 2nd Edition. Kreuztal: Kynos-Verlag. 208 pages.
  • Vetpharm – Toxicological database of the University of Zurich. Plant data sheet on metaldehyde. Available online at: https://www.vetpharm.uzh.ch/CLINITOX/TOXDB/KLT_010.HTM?Submit=done [Accessed July 6, 2025].
  • Yas-Natan, E., Segev, G. and Aroch, I., 2007. Clinical and neurological manifestations of metaldehyde toxicosis in dogs. Journal of Small Animal Practice, 48(8), pages 438–443.