How to recognise poisoning

This is never easy because of the myriad of potentially toxic substances likely to be present on a farm, however always look for the most common and obvious first.

A poison may only affect an individual animal within a group because it was the only one inadvertently exposed to it. For example a toxic dose of medicine was administered by mistake.

Similarly most or all the pigs in a pen, a number of pens or a complete building may be affected, indicating a much wider exposure. Finally a complete herd may be affected - invariably associated with a common feed, water source or airborne pollution.

Step 1- Study the history carefully

Consult with your veterinarian

  • Is the onset rapid - usually within 48 hours? If so, are a number of pigs affected?
  • Is only a particular age group affected, for example gilts, sows, sucking piglets? If so, what is common to the group?
  • What routines, medicines, management procedures have been applied to the group recently?
  • Is a particular area of the farm or a number of pens affected? If so are there any common factors?
  • Does the appearance of the condition coincide with the introduction of a new batch of feed or feed ingredients, a change in water or other local change?

Step 2 - Clinical signs

  • List the clinical signs. (See Fig.13-1 and Fig.13-2).
  • Common features of poisoning include:
  • Rapid onset - (There are however exceptions depending on the dose level and period of exposure).
  • A defined group of pigs affected.
  • A number of pigs with identical clinical signs.
  • Not a recognisable disease.
  • Rectal temperatures are usually normal.

Clinical signs of different poisons

A broad outline of how different poisons affect different systems of the pig is given in Fig.13-1.

This can be used to help identify possible causes, particularly if used in conjunction with Fig.13-2. Specific systems of the body may be affected and develop the following signs:

Circulatory system

  • Anaemia.
  • Cyanosis (blue discoloration of skin).
  • Increased respiration.
  • Jaundice.
  • Haemorrhage.

Digestive system

  • Abdominal pain.
  • Diarrhoea - with or without haemorrhage.
  • Rectal prolapse.
  • Salivation.
  • Vomiting.

General effects

  • Generalised malaise.
  • Reduced feed intake or complete inappetence.
  • Reduced growth.

Locomotor system

  • Abnormal gait.
  • Ataxia.
  • Incoordination.
  • Lameness.

Nervous system

  • Blindness.
  • Excitation.
  • Fits.
  • Incoordination.
  • Spasmodic movements.

Reproductive system

  • Abnormal oestrus.
  • Swollen vulva.
  • Abortion.
  • Embryo reabsorption.
  • Failure of fertilisation.

Respiratory system

  • Coughing.
  • Difficulty breathing.
  • Pneumonia (found at post-mortem examination).
  • Sneezing, nasal discharge.


  • Colour.
  • Haemorrhage.
  • Irritation.
  • Vesicles.

Urinary system

  • Blood in the urine.
  • Cystitis / pyelonephritis (found at post-mortem examination).
  • Excess mineral deposits (found at post-mortem examination or in the urine).
  • Pus.

Step 3 - Post-mortem examinations and records of mortality

Post mortem examinations may assist in differentiating between a specific disease and toxic conditions. Samples from tissues are probably required for further laboratory tests. The number of deaths and whether they are sudden or after a short or prolonged illness may characterise certain poisons.

The information assessed from steps 1 to 3 will raise a suspicion of poisoning.

Step 4 - Identify the possible sources of the poison

  • List the chemicals on the farm - sprays, pesticides etc.
  • List the medicines on the farm.
  • What injections have been given?
  • Are rodenticides used and available?
  • Are parasecticides used?
  • Could any sources of feed be suspected?
  • Is there evidence of spoiled or mouldy feed or mould in the feed delivery system?
  • Consider water, bedding and other environmental contaminants.
  • Are sprays / disinfectants used.
  • In out-door herds consider plants, water and environmental contaminants.
  • Do any of the signs fit into Fig.13-1 or Fig.13-2?

Step 5 - Identify the toxin

Use Fig.13-1 to identify the potential toxin or toxins, together with the history and symptoms.

Step 6 - Read about the poison

Refer to the poison in the text and administer treatments in conjunction with veterinarian advice.

Step 7 - Confirm the poison

Refer samples to a lab for confirmation. (Fig.13-3).