POISONS

A poison is a substance which when introduced into or absorbed by an organism causes damage or injury. The usual implication is that relatively small amounts are dangerous.

Poisoning is often reported by clients, but true poisoning occurs infrequently ( we are a suspicious lot).

Poisoning types: Pesticides-45.5%-42.5% rodenticides

20% Insecticides

26% Herbicides

Pollutants 20.7%

Drugs 19.6%

Plants 14.2%

General treatment for poisonings

Monitor and if necessary take control of: Respiration, Circulation, Fluid deficits or imbalances, Central nervous system disorders, Pain.

Prevention:

Absorption

1) Topical- Clean any topical contamination with soap or oil remover. Be as quick as possible, but be methodical, and dry off to prevent hypothermia (but not too vigorously as towelling can cause skin circulation to increase). Try not to use organic solvents (Turps, white spirit) as they increase absorption. Best not to use kitchen oil as it may be eaten and then encourage absorption of the poison.

2) Emetics- useful only up to 2-3 hours after exposure. NOT if caustics or petrol has been ingested, or the animal is becoming drowsy. Emetics-

Salt 1-3 teaspoonfuls in warm water.

Apomorphine injection (dogs only)

Mustard in solution

Washing soda ( rarely found at home now)

Xylazine

Ipecachuana

3) Gastric lavage

Anaesthetise and intubate. Use 10ml/kg isotonic saline, warmed.

4) Purgatives

Use liquid paraffin by mouth or sodium sulphate enemas.

Elimination

Renal elimination can be forced using osmotic diuresis- intravenous 10% glucose or mannitol, and frusemide.

The pH of urine can be adjusted to reduce reabsorption of substances- Acid diuresis get rid of bases, and vice versa. (Ammonium chloride, ascorbic acid for acid diuresis; Sodium bicarb., Ringer's for alkaline diuresis.)

Peritoneal dialysis- 20-50ml/kg of saline infused into the peritoneum, left for 20 minutes then removed.

Neutralisation

Medicinal charcoal or BCK granules given by mouth as a slurry in water. Never give milk!

COLLECTION OF LAB SAMPLES

Unknown poison- whole carcase if possible.

From live animals- Vomit, blood sample, urine, nails or hair

Dead animals- Liver, stomach contents, kidney, fat, heart blood, brain, skin (epidermis particularly).

Pack samples in food grade bags or bottles, only use ice as a preservative, never use washed out bottles which have been used previously.

Take separate samples if histopathology is necessary.

SPECIFIC POISONING

NEUROLOGICAL

Caffeine- CNS stimulant, treat with sedatives, support.

Cyanide- usually arises from plants which contain cyanogenetic glycosides (bitter almond odour and taste). Causes convulsions and death. No antidote.

Lead- paint, waste oil or batteries. A cumulative poison, stored by the body. Initial signs may be gastrointestinal, but mainly seen as blindness, weakness, neurological abnormalities. Often seen in Swans and water birds due to lead shot (now illegal). Treated with EDTA injections, very successful if not too advanced.

Mycotoxins / Bacterial toxins- produced by spoilage of food, e.g. botulism. Cause weakness, paralysis. No antidote, but antiserum may be available for botulism.

Metaldehyde- Slug bait, used to kill snails / slugs, also found in firelighters. Causes convulsions and fitting, then loss of consciousness. Can be treated with an emetic up to 3 hours after ingestion, thereafter symptomatic treatment only with valium, phenobarbitone and aggressive diuresis.

Insecticides- Organochlorines, organophosphates and carbamates. OC's are now restricted due to severe environmental persistence and concentration in the food chain. Lindane, DDT, gamma BHC. Initially cause tremor, then fasciculations, then collapse and death. No antidote

Organophosphates- fenthion, dichlorvos, etc. Less toxic, and have stimulate the autonomic nervous system- salivation, tears, diarrhoea, tachycardia and miosis. Partial reversal of effects with atropine, and pralidoxime used as a specific antidote.

Carbamates, also anticholinesterases, atropine treats, but not pralidoxime.

Phenolic disinfectants (Dettol, TCP). CNS stimulation then depression, severe GI burns. Symptomatic care only.

Strychnine. Used as a mole killer, but most poisoning are malicious. Is a CNS disinhibitor, so causes spasms and convulsions then death, may respond to acid diuresis.

Chocolate (theobromine) CNS and sympathetic stimulant causing tachycardia and seizures. Surprisingly toxic to dogs- 2oz milk chocolate per kg can be fatal.

Alcohol- CNS depressant. Brings out the worst in a dog. Sadly, no treatment for overdose.

Alphachloralose- Mouse poison, causes brief excitement, then sedation, and coma. Kills by hypothermia. Treat with emetics, then CV stimulants as necessary.

GASTROINTESTINAL

Most poisons are caustic on ingestion- Acids / Alkalis / detergents / selective herbicides such as phenoxyacetic acids 2,4,D 2,4,5,T.

Paraquat is particularly unpleasant causing vomiting, ulceration and bleeding. If this resolves, then the lungs often develop a progressive fatal scarring

HEPATOTOXINS

Paracetamol (+/- aspirin). Very toxic to cats, 1/2 a human tablet can be fatal. Liver necrosis develops, also facial oedema and damage to haemoglobin. Treat with emetics if early, then with intravenous acetylcysteine.

Blue- green algae - Seen in summer in swimming dogs. Supportive treatment only.

Halothane!

NEPHROTOXINS

Heavy metals- Arsenic, Mercury, Lead cause necrosis.

Ethylene glycol (antifreeze). Said to be sweet and attractive to dogs and cats. Metabolism in the liver produces deposits of insoluble oxalate in renal tubules. Treated early by infusion of alcohol which forces excretion of the ethylene glycol unchanged.

Drugs- Neomycin, Gentamycin, Polymixin, Sulphonamides.

Calciferol (rodenticide) is a vitamin type drug causing accumulation of calcium in soft tissues. Symptomatic treatment only with low Ca diets, diuresis.

Blood system Toxins

Sodium chlorate- total weed killer. Causes chemical damage to haemoglobin (-> methaemoglobin), then haemolysis. Not very toxic, but Very palatable. Signs are chocolate coloured blood / urine. Treated with methylene blue infusion and acid diuresis.

Aspirin, Chloramphenicol, Oestrogens, Phenylbutazone. All can cause aplastic (non- regenerating) anaemia in occasional individuals.

Rodenticides - Warfarin derivatives, usually end in -coum e.g. difenacoum. Toxicity varies a lot between different compounds. Cause bleeding by blocking vitamin K and preventing the activation of prothrombin. Signs are haemorrhage in joints, mouth, skin, lungs etc. Treat with Vit K3, by injection and by mouth, sometimes for months.

Respiratory Toxins

Ammonia, Chlorine, Acrolein, Burnt Teflon. All cause lung damage.

Febrile Syndrome

Caused by a group of herbicides known as Dinitrophenols. These attack cellular metabolism and kill by hyperthermia. Rare as they degrade very quickly after application.

A list of Some Poisonous Plants

Colocasia (Elephants Ear) - Gastrointestinal irritation

Amaryllis - Toxic alkaloids in bulb- Vomiting and Diarrhoea

Black Bryony - contain histamine, causes vomiting

White Bryony- contains glycosides- fatal heart poison

Arum Lily - Irritant to mouth.

Cherry Laurel - Cyanogenetic glycosides in leaves

Daffodil - Bulbs cause vomiting, occasionally coma and death.

Deadly nightshade -atropine- causes severe heart rhythm change.

Dieffenbachia - Intense oral irritation, ++ oedema from sap

Rubber plant - Irritant sap

Holly- multiple poisons in berries. 20 berries can kill a large dog.

Lily of the Valley - 20 toxins, damage the heart.

Mimosa - Vomiting and irritant, seeds most toxic.

Swiss Cheese Plant - Irritant sap

Poinsettia - Irritant and toxic sap - vomiting

Tulip - Bulbs cardiotoxic, oral irritant.

INSECT AND ANIMAL POISONING

Adders

Usually April- September, bites on nose and legs. Lots of toxins and enzymes which damage tissue. Local oedema develops rapidly, but this then becomes hard and cold. Treat locally with cold compresses, and give iv fluids to support the circulation. Anti venin is available, but risky to use.

Bees and Wasps

Stings contain histamine and enzymes. Pain in 30 seconds and oedema for 24 hours. Remove the sting by grasping at the skin, not by the poison sacs. Bathe bee stings with bicarbonate, and wasp stings with vinegar.

Hairy caterpillars

Various moth species, the hairs release histamine and cause ulceration and irritation.

Toads

Cutaneous glands secrete mixed toxins which cause irritation the cardiac arrhythmias. Usually animals appear salivating profusely as the secretions of the toad are very bitter.

Diseases confused with Poisoning:

Acute gastroenteritis

Epilepsy

All vague disease!

Haemorrhagic diseases

Ulcerative diseases of the mouth and skin.