Animal poisons are considered as the organic irritant poisons. A number of animals present in nature are poisonous which possess toxic substances in them for their self defense from the predators. The poisons present in such animals is a result of natural selection for their survival. There are certain animal species which possess the toxin named ‘venom’.

The animal poison and venom are both toxic in nature and rich source of proteins, neurotransmitters, peptides, etc. among other organic compounds. Both are considered as zootoxins and can induce major damages to the prey’s/predator’s body. This is one of the mechanisms to kill their prey or predators.

Animal Poison & Venom

Animal poison and venom though have similar effects of killing but still are different because of their toxin delivery methods. Animal poisons are produced by the specialized cells or tissues of the animals which cause toxicity in the predators when they are ingested (such as cantharides, few amphibians, etc.), while venoms are secreted by dedicated glands of such animals and injected into the prey or predator through specialized apparatuses like fangs, stings, teeth, etc. via a process called envenomation (snakes, jellyfish, scorpions, etc.).

According to a study by Rusell in 2011, there are about 400 species of venomous snakes, around 1500 toxic marine animal species and n number of poisonous or venomous anthropods across the world.

Examples of poisonous animals are:

  • Microciona Prolifera (sea moss)
  • Leptoplana Tremellaris (flatworm)
  • Cantharis Vesicatoria (blister beetles)
  • Millipedes
  • Petromyzon Marinus (sea lamprey)
  • Rypticus Saponaceus (sopa fish)
  • Salamandra Salamandra (fire salamander)
  • Toads
  • Frogs and Tree Frogs
  • Eretmochelys Imbricata (hawksbill turtle)
  • Balaenopters Borealis (sei whale)
  • Thalarctos Maritimus (polar bear)

Examples of venomous animals:

  • Physalia Species (portuguese-man-of war)
  • Chironex Fleckeri (sea wasp)
  • Actinia Equina (sea anemone)
  • Conus Species (cone shells)
  • Octopus Maculous (spotted octopus)
  • Triatoma Species (kissing bugs)
  • Megalopyge Species (puss caterpillar)
  • Apis Species (honey bees)
  • Scolopendra Species (centipedes)
  • Loxosceles Species (black widow spider)
  • Scorpions 
  • Acanthaster Planci (Crown-of-thorns starfish)
  • Diadema Setosum (long-spined sea urchin)
  • Dasyatis Species (stingray)
  • Scorpaena Species (scorpion fish)
  • Snake Species (cobra, krait, viper)

Effects of Venom on Humans

  • Neurotoxic Effects– Venom affects the central nervous system where they interfere with the activity of ionic channels. Example of these venoms include scorpions, black-widow spider, octopus, centipedes, etc.
  • Necrotoxic Effects– Necrosis is induced in the cells which come in contact with the venom. Example of this venom include viper snake.
  • Cytotoxic Effects– The cells are killed by the components of venom. Example of this venom include honey bees, black-widow spiders, etc.
  • Myotoxic Effects – The venom binds with the muscle receptors and damages them. Example of this type of venomous animals include rattlesnake, lizards, etc.
  • Haemotoxic Effects– The blood vessels as well as the red blood cells are damaged by the venom components. Example of such animals include pit vipers.

The most common poisonous animals encountered are the cantharides, snakes and scorpions. 


Cantharides or spanish fly which are one of the poisonous arthropods commonly found in every environment. They are also known as blister beetles because the active principle of these insects called cantharidin causes blisters on the skin.

It is about 2 cm long and 0.75 cm broad with a shiny emerald green colored body. Cantharidin can be readily absorbed through any surface. The fatal dose is 15-50 mg of cantharidin or 1½ to 3 grams of  powdered cantharides and the fatal period is 24 to 36 hours.

The symptoms of toxicity of Cantharides depend on the route of administration.

  • If the route is skin, then blisters or vesicles are observed on the affected area within 2-3 hours. If the powder is swallowed then there would be a burning sensation in the mouth, throat, stomach and abdomen which is followed by intestine thirst.
  • Nausea and vomiting with blood stained materials, diarrhoea with bloody stools.
  • The poison also causes nephrotoxic effects which manifest a constant desire to micturate but only a small amount of urine passes out with blood traces.

The post-mortem appearances may include inflammation of the whole alimentary canal, kidneys and genitourinary tract. Edema in lungs and blood stained mucus in the air passage.


Snakes are the notorious venomous animals of nature. But not all the snakes are poisonous, there are certain species of snakes which are non-poisonous. The poisonous snakes are classified as elapids (cobra, krait, coral snake, etc.), vipers (pit and pitless viper) and sea snakes, depending upon the type of toxins they possess.

Elapids possess neurotoxic venom whereas vipers and sea snakes secrete haemotoxic and myotoxic venoms respectively. The toxic principles of snake venom include toxalbumins, proteolysins, fibrinolysins, cholinesterase, thromboplastins, agglutinins, coagulase, etc.

Poisonous snake bites and poisoning from snake bites may show different effects in human beings. The toxicity depends upon the size of the person, potency of the venom, amount of the venom, size, sex, and species of the snake, etc.

Also the season and time affect the toxicity of snake bites, such as the snakes returned from hibernation are less toxic and the nocturnal bites are more toxic than the day bites.

The fatal dose and fatal period depends on the species of snake. Usually the death from snake venom is instant or may occur within a few minutes to a few hours in case of cobra, while the vipers’ venom may cause death in a few days. The sea snakes are usually not fatal.

Postmortem appearances show 1-2 bite marks with blood oozing out the punctures. Endocardial haemorrhages, necrosis of renal tubules, swelling of the organs, etc.

Scorpions are the species of arthropods that are known for having venomous stings. The venom is more potent than the snake venom but the quantity injected is lower. The venom contains toxalbumin which have neurotoxic, haemotoxic and cardiotoxic ( only in red scorpion) effects.

The target feels the local irritation on the site of the bite with redness and burning pain. Nausea, vomiting, headache, giddiness, perspiration, excessive salivation, urticaria, dilated pupils, and muscular cramps are common symptoms of poisoning. Deaths are rare in adults while children may succumb to pulmonary oedema. 

Poisoning from venomous animals is usually accidental and sometimes homicidal. Suicidal poisoning is rarest of rare. 

There are certain animal poisons or venoms which have medicinal values such as antivenins are used in the case of snake bite poisoning. Cantharis are used as aphrodisiacs, counter-irritant to the skin in blistering plaster and abortifacient.

Categories: Toxicology


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