Most cases result from the poison being swallowed. In a few instances poison may be taken in through a wound of the skin, or even through the unbroken skin, e.g. phenol preparations. Malicious poisoning is most frequently carried out against dogs and cats, although horses and ruminants also sometimes suffer.

The use of poison to control vermin — rabbits, foxes, rats, mice, etc. — is a hazard, for when the poisoned bait is accessible to domesticated animals, cases of poisoning may result. It should be remembered that the exposure of such poison above ground constitutes an offence.

The constituents of common and commercial rat-poisons are mentioned under RODENTS – Rodenticides.

Many cases of poisoning result from the careless use of sheep-dips, paints, weed-killers and insecticides, which, in powder, paste, or solution, are left about in places to which animals have access. Cattle are notoriously inquisitive, and will lick at anything they find, sometimes with fatal consequences.

It is perhaps not widely enough realised that cattle seem to like the taste of lead paint — 1 heifer helped herself to a whole pint of it — and that very small quantities spattered on the ground can kill several beasts. Even the contents of old, discarded paint tins can be lethal. In one instance, children found such tins and scraped out the residue on to pasture, killing 5 yearlings. In another instance, cattle licked out old paint tins on a rubbish dump in a pit to which they found their way. A recently painted fence is also a danger.

Thirsty cattle will drink almost anything: diesel oil and a copper-containing spray liquid have each caused death in these circumstances. Salt poisoning is certainly no myth, and pigs should never be kept short of drinking water.

Some insecticides, such as TEPP and Parathion, are totally unsuitable for use on livestock. Fatal poisoning of a herd of cattle sprayed with TEPP has been reported from Texas. A farmer in Ireland used aldrin as an orf-dressing, and killed 105 out of 107 lambs. Fatal poisoning of cattle has also occurred through the application to their backs of a carbolic-acid-arsenic preparation against flies. (See also HERBICIDES; WEEDKILLERS.)

Near factories and chemical works, grass, etc., may become impregnated with fluorine compounds, copper, lead or other metals, and lead to chronic poisoning of any animals grazing nearby. The same thing applies in orchards after spraying of fruit-trees. Pasture may be contaminated by spray-drift or dusting operations, particularly from the air, and the chemicals used may cause poisoning. This applies also to other treated green crops which animals may eat. DDT and BHC and other insecticides (used in home and garden) of the CHLORINATED HYDROCARBON group may poison birds, cats and dogs. (See also ORGANOPHOSPHORUS POISONING; FARM CHEMICALS; FLUOROSIS.)

The use of pitch (the poisonous ingredient of clay-pigeons) or coal tar on the walls and floors of piggeries is a cause of poisoning. Some wood preservatives cause hyperkeratosis.

Poisoning may result from indiscretion on the part of owners or attendants in the use of patent or other animal medicines, or from the administration to animals of tablets, etc. intended for human use, e.g. paracetamol, caffeine.

Dogs and Cats

Dogs and Cats may also be poisoned by gaining access to unsecured medicines (pills, tablets, etc.) intended for human use. For home and garden hazards to pet animals (including cage birds), see under CARBON MONOXIDE; ‘FRYING PAN’ DEATHS; ANTIFREEZE; CREOSOTE; LEAD POISONING; METALDEHYDE; BHC POISONING; BENZOIC ACID POISONING; WARFARIN; DDT; HOUSE PLANTS; HOUSE DECORATING. If one considers dogs out for walks, one should add DIELDRIN; PARAQUAT; FARM CHEMICALS. As regards dog and cat foods, poisoning has resulted from biscuit meal made from corn dressed with dieldrin, from stored food contaminated by rats’ urine containing warfarin, from aflatoxins, and from horse-meat containing barbiturates or choral hydrate. In the cat, food containing benzoic acid as a preservative has caused poisoning.

Fodder poisoning

Excess of fodder beet may cause scouring in both pigs and cattle, and the after-effects may be serious. In sows just farrowed, the milk supply may almost disappear. Beet tops have caused the deaths of cattle when given unwilted, and even when wilted they should be strictly rationed. Kale and rape poisoning can occur in cattle and sheep; these must be used sparingly and not constitute an animal’s sole diet, and hay in particular is necessary in addition. Deaths have occurred in horses and cattle restricted to rye-grass pasture. Sheep have been fatally poisoned by feeding them surplus pig-meal containing a copper supplement; a heifer likewise. Pigs have been poisoned by giving them medicated meal intended for poultry and containing nitro-phenide against coccidiosis. Which all goes to show that medicated feeds are by no means always interchangeable between different species of livestock, since there are genetic differences between them as regards susceptibility to poisoning, depending in part upon possession or absence of some enzyme which can readily detoxify the poison. (See GROUNDNUT MEAL.)

The use of surplus seed corn for pig-feeding has led to fatal poisoning — the mercury dressing having been overlooked! (See DIELDRIN for poisoning from seed dressings, and FLOOR SWEEPINGS; also MONENSIN SODIUM.)

Hay contaminated with foxgloves or ragwort is a source of fatal poisoning. Silage contaminated with ragwort has similarly caused death. Silage contaminated with hexoestrol has caused abortion. (See under HORMONES IN MEAT PRODUCTION.)

Poisonous plants

Poisonous plants growing in pastures, in swampy or marshy places, in the bottoms of hedges, on waste land and in shrubberies and gardens, are other very common sources of poisoning. In the early spring, when grass is scarce, and when herbivorous animals are let out for the first time after wintering indoors, the tender succulent growths attract them, often with serious consequences. Similar results may be seen during a very dry summer when grass is parched. Ragwort and bracken are the most common causes of plant poisoning in cattle; in sheep, bracken can cause night blindness and neoplasia as well as true poisoning. (See BRACKEN.)

Clippings from shrubs, especially from yew, rhododendrons, aconite, boxwood, lupins, laurel, laburnum, etc., should never be thrown ‘over the hedge’, because in some of these the toxic substances are most active when the clippings have begun to wither, and animals are very prone to eat them in this condition. It is a safe rule to regard all garden trimmings as unsafe for animals, with the exception of vegetables, such as cabbages and turnips. (See under ACONITE; BITTERSWEET; FOXGLOVE; HEMLOCK; LABURNUM; POTATO; RAGWORT; WATER DROPWORT; YEW; LOCOWEED, etc.)


The symptoms of each of the more common poisonous agents are given under their respective headings.

It must be emphasised that the symptoms of some illnesses are the same as those of some poisons, and vice versa. For example, not only vomiting and diarrhoea but also cramp, fever, rapid breathing, convulsions, hysteria, jaundice, salivation, blindness, and deafness are common to both. A professional diagnosis is therefore important.

Irritant poisons produce acute abdominal pain, vomiting (when possible), purging, rapidly developing general collapse, and often unconsciousness, perhaps preceded by convulsions.

Narcotics produce excitement at first, unsteady movements, interference with sight; and later, stupor and unconsciousness appear; coma, with or without spasmodic or convulsive movements, supervenes, and death occurs in many cases.

Narcotic irritants produce symptoms of irritation in the first place, and later, delirium, convulsions, and coma.

As a general rule poisoning should be suspected when an animal becomes suddenly ill, soon after feeding; when put out to pasture for the first time in the season after dipping; or when a change of food has recently taken place. Newly purchased animal feeds may be followed by an outbreak of illness, and such results point to the inclusion of some harmful substance. Fungal poisoning may occur as a result of mouldy barley, etc.


In suggesting simple first-aid measures, it should be emphasised that they necessarily differ from — and are likely to be less effective than — those the veterinary surgeon will take. It should be realised, too, that against some poisons there are no effective antidotes.

Where it is suspected that poisoning has arisen from use of some proprietary product, take the container (or the label from it) to your veterinarian (or write down the name of the manufacturer and product) so that he or she may ascertain the chemical ingredients and, if necessary, consult the manufacturer as to the recommended antidote.

If it is suspected that poisoning may have resulted from a skin dressing, wash this off with warm soapy water to prevent further absorption. (See CARBOLIC ACID POISONING.)

Where a poison is believed to have been taken by mouth, give an emetic. However, emetics should be avoided if strong acids or alkalis are involved.

Emetics which may be safely used are: for pigs, a dessertspoonful of mustard in a cupful of water; for dogs, a strong salt solution (ordinary household salt), or a crystal of washing soda; for cats, the latter.

To hinder absorption in the horse, ox, or sheep, strong black tea or coffee which has been boiled may be given. These, all of which contain tannic acid or tannates, are useful against vegetable poisons.

To counteract the effects of irritants, use demulcents (olive oil, milk, milk and eggs, or liquid paraffin). Yellow phosphorus is an exception to this rule; oily substances favour its absorption and must be avoided; copper sulphate should be given instead. Against narcotics, stimulants are needed, e.g. strong coffee or black tea, given by the mouth as a first-aid measure.

Advice on poisons

In the UK, veterinary surgeons may obtain information and advice concerning poisonous compounds, and their antidotes, if any, from the National Poisons Information Service, Avonley Road, London SE14 5ER.

Confirmation of poisoning

No matter how strong circumstantial evidence seems to be, it is always essential that a post-mortem examination be made, and that necessary samples of the stomach contents, portions of the liver and perhaps other organs, should be submitted to a qualitative and quantitative chemical examination by an analyst, before a suspected case of poisoning can be considered to be definitely proved. The necessity for this procedure is obvious when legal proceedings are contemplated.