Metaldehyde Poisoning (with special reference to Waterfowl and Hedgehogs)

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Summary Information
Diseases / List of Toxic Diseases / Disease summary

This disease page is currently predominantly used in Wildpro to link different data types and demonstrate inter-relationships. Whilst basic information is available, It does not contain detailed information.

Alternative Names
  • Metaldehyde toxicity
  • Slug-bait toxicity
  • Slug-bait poisoning
  • Molluscicide toxicity
  • Molluscicide poisoning
Disease Agents
  • Metaldehyde (slug bait). Hydrolysed in the stomach to acetaldehyde polymers; these readily enter the brain (B101).
  • Metaldehyde is present as 3% in products for amateur (domestic/garden) use and 6% for commercial use. It is mixed with bran bait as an attractant to molluscs (also coloured blue to deter birds and with an olfactory repellent to deter mammals). (D86)
Infectious Agent(s) --
Non-infectious Agent(s)
Physical Agent(s) -- Indirect / Secondary
General Description Metaldehyde is a molluscicide (slug and snail killer) and is the substance used most commonly in the UK to protect crops and garden plants against molluscs (Mollusca - Molluscs (Phylum-Division)). (D86)


Clinical signs:

Mammals general:
  • Nervous signs: severe muscle tremors, ataxia/incoordination, hyperaesthesia, nystagmus (particularly in cats) and hyperpnoea.
  • Later opisthotonus and tonic convulsions (continuous).
  • May also be vomiting, hypersalivation, dyspnoea, tachycardia and hyperthermia (with profuse sweating seen in horses).
  • Severe acidosis due to acid metabolites and high level of muscle activity.
  • Death from respiratory failure (two to four hours), or later from liver failure (three to four days).
(B101, B283)


  • Hyperaesthesia, particularly to sound, tachycardia, anxiety, hypersalivation, ataxia, dysmetria, tremors, death.
  • Occasionally bluish-coloured faeces or vomit may be seen

(B284.6.w6, B151)

Cats and dogs:

  • CNS signs: muscle tremors, tonic seizures, opisthotonus, convulsions, pyrexia.
  • Autonomic signs: tachycardia, tachypnoea, panting, dyspnoea, salivation, vomiting. 
  • (J15.13.w2)
  • Abdominal pain, diarrhoea, sweating, tachycardia, incoordination, clonic spasms. (J15.13.w2)
  • Salivation, ataxia, hyperpnoea, tremors, convulsions, diarrhoea.(J15.13.w2)
  • Ataxia, recumbency, cyanosis, pyrexia, tremors, convulsions. (J15.13.w2)
  • Incoordination, torticollis. 
  • Spontaneous recovery or death.
  • (J3.67.w3).
  • Found dead (overnight deaths) with extreme opisthotonus - beak touching tail-base (J3.81.w1).

Gross Pathology:

In mammals:

  • Non-specific. (J15.13.w2)
  • Hepatic: Liver congestion and oedema.
  • Renal: Kidney congestion and oedema
  • Respiratory: Lung congestion and oedema.
  • Gastro-intestinal:
    • Intestinal haemorrhage, petechiation.
    • May be a formaldehyde-like odour when the stomach/rumen is opened.
  • Cardiac: May be passive subendocardial and subepicardial haemorrhage. (J15.13.w2)

    (B101, B283, J15.13.w2)

In Hedgehogs:

  • Gastrointestinal: Stomach contents smelling of acetaldehyde, bluish deposits within the gastro-intestinal tract. (B284.6.w6)

In Geese:

  • Gross Pathology:
    • Gastro-intestinal tract - petechiation at proventriculus-gizzard junction and around borders of heavily keratinised regions of the gizzard. Gross dilatation and engorgement of vessels on serosa of intestines and in mesentery.
    • Respiratory - lungs congested, patchy haemorrhages, blood-tinged fluid in air sacs.
    • Spleen: enlarged and congested in one of three geese.



In Geese:

  • Liver - marked centrilobular congestion, swelling of hepatocytes and coagulative degeneration of cytoplasm.
  • Brain - a few swollen axons in the medulla (one of three geese).


Further Information
  • Metaldehyde toxicity may be overdiagnosed in hedgehogs. (B284.6.w6)
  • Metaldehyde toxicity may be underdiagnosed in hedgehogs due to rapid metabolism and therefore lack of detection on analysis. (B291.12.w12)


  • Ingestion of metaldehyde by waterfowl may be direct (by eating slug bait containing metaldehyde) or indirect/secondary (by eating slugs/snails which have consumed the bait). (J3.67.w3, J3.81.w1).
  • Hedgehogs are known to eat bread and may be considered likely to eat bran-based slug pellets containing metaldehyde. (J3.128.w2)
  • The possibility of indirect intoxication (via poisoned slugs or snails) must be considered. (B291.12.w12)


In Waterfowl:
  • Estimated consumption in geese (with lethal effect) 0.8g.kg bodyweight (J3.81.w1)
In Hedgehogs:
  • It has been estimated that consumption of 5g of pellets containing 50-60g metaldehyde per kg pellets would be potentially lethal (J3.128.w2)
  • It has been suggested that for a 1kg bodyweight hedgehog, based on an LD50 of 500 mg/kg bodyweight, poisoning would require ingestion of 490 pellets. (D86)
  • It has been suggested that consumption of poisoned slugs would not in itself cause toxicity (J3.128.w2, B156.7.w7).
  • Hedgehogs which ate up to 200 treated slugs failed to show any signs of metaldehyde poisoning or behavioural disorders. Some hedgehogs offered dead slugs ate few or none of the slugs. It was concluded that the risk of secondary poisoning in hedgehogs was very low. (J173.47.w1)


  • Clinical signs and a history of access to metaldehyde. (J15.13.w2)
  • Detection of toxic/potentially toxic quantities of metaldehyde in the stomach (e.g. 40mg/kg) or liver. (J3.128.w2, J15.13.w2)
    • Fresh material is required for diagnosis. (J3.128.w2)
    • A distinctive formaldehyde-like smell of acetaldehyde may be noted from stomach contents or vomit. (J15.13.w2)
  • Levels of metaldehyde in plasma are not useful for diagnosis due to the rapid metabolism of the compound. (J15.13.w2)


  • Symptomatic treatment only. (J15.13.w2)
  • Sedatives or anaesthetics to reduce excitement/convulsions.(B101)
    • Diazepam 2-5 mg/kg to effect is preferred; acepromazine has been used successfully. (B283)
    • N.B. barbiturates compete with acetaldehyde metabolism. (B283)
  • Removal of ingested material if possible. (B101)
    • Induction of vomiting (cats, dogs) or in large animals use of laxatives. (J15.13.w2)
    • Emetics may not be required as metaldehyde is a gastric irritant. (B283)
  • High dose mineral oil (since metaldehyde is oil-soluble) to reduce further absorption of the metaldehyde;(B101, B283)
  • Activated charcoal is recommended in large animals to reduce further absorption of the metaldehyde. (B283)
  • Intravenous fluid therapy is essential to reverse acidosis and to prevent dehydration. (J15.13.w2)
    • Aggressive fluid therapy with sodium lactate (to reduce acidosis).(B283)
  • Calcium borogluconate or glucose may be given to protect against liver damage. (B283)
  • Cold-water rinses if the animal is severely hyperthermic. (B101, B283)

In Hedgehogs:

  • Sedatives or anaesthetics to reduce excitement/convulsions; (B228.11.w11)
    • Diazepam, 2-3 mg/kg bodyweight (to reduce muscle fasciculations and the associated hyperthermia). (B284.6.w6)
  • Apomorphine as an emetic has been suggested. (B228.11.w11)
  • Fluid therapy using Hartmann's solution to correct acidosis. (B151, B284.6.w6)
    • Additional bicarbonate of soda may be required to counteract metabolic acidosis. (B151)
  • Stomach flushing with milk, sodium bicarbonate or charcoal to decrease absorption of the metaldehyde.(B151, B284.6.w6)
  • Calcium gluconate (by intraperitoneal drip in hedgehogs) has been suggested to combat liver damage. (B228.11.w11)
  • Oxygen therapy may be required. (B284.6.w6)
  • Vitamin B12 injection may assist in recovery. (B284.6.w6)
  • Supportive treatment including warmth. (B151)


  • Use of alternative forms of slug control will reduce hedgehog exposure to metaldehyde-based molluscicides. (D86, D101)
Techniques linked to this disease
Host taxa groups /species
Disease has been reported in either the wild or in captivity in the following Species:
  • Ducks, geese (J3.67.w3, J3.81.w1).
  • Hedgehogs (Erinaceus europaeus - West European hedgehog)(J3.128.w2, B151)
  • Hedgehogs have been presented to a wildlife hospital in the UK with signs of metaldehyde poisoning: excitement, tremors and some stiffening of the muscles followed by partial paralysis. (B259.w7)
  • Three hedgehogs Erinaceus europaeus were diagnosed with metaldehyde poisoning at post mortem examination in a study of 74 dead hedgehogs collected July 1976- November 1986 in the UK. Two animals had stomachs containing more than 40 mg/kg of the metaldehyde metabolite acetaldehyde while the third had 80 mg/kg in the liver. (J3.128.w2)
  • Metaldehyde toxicity is seen in hedgehogs (Erinaceus europaeus) in the UK. (J15.21.w1)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken).

Host species with further information available are listed below:

Disease has been reported in free-ranging populations of the following Species:

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken).

Host species with further information available are listed below:

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