SUBJECT FORENSIC SCIENCE Paper No. and Title PAPER No.10: Forensic Toxicology Module No. and Title MODULE No.8: Organic Poisons- II: Animal Poisons Module Tag FSC_P10_M8 FORENSIC SCIENCE PAPER No.10: Forensic Toxicology MODULE No.8: Organic Poisons: Animal Poisons TABLE OF CONTENTS 1. Learning Outcome 2. Introduction to Animal Poisoning 3. Forensic Issues 4. Categorization of Venomous Animals 4.1 Vertebrates 4.1.1 Reptiles 4.1.2 Fishes 4.1.3 Amphibians 4.1.4 Birds 4.2 Non- Vertebrates 4.2.1 Arthropods 4.2.2 Arachnids 4.2.3 Cnidaria (or Coelenterates) 4.2.4 Molluscs 5. Summary FORENSIC SCIENCE PAPER No.10: Forensic Toxicology MODULE No.8: Organic Poisons: Animal Poisons 1. Learning Outcomes After studying this module, you shall be able to know about – The toxins of Animal origin. General introduction of certain animal toxins Forensic significance of animal poisoning 2. Introduction to Animal Poisoning Largely it talks about the poisons originated from living organisms which are obviously animals. While there is so much diversity in the animal kingdom, the methods of predation and self-protection is varies from species to species. Similarly, some animals use poisons as a weapon of predation or self-defence or both. Snakes are the most popular among these type creatures besides other known venomous organisms like, fishes, insects, etc. In India, deaths as a result of snake-bite are mainly accidental in nature. Venoms used in an offensive posture are generally associated with the oral pole, as in the snakes and spiders, while those used in a defensive function are usually associated with the aboral pole or with spines, as in the stingrays and scorpion fishes. In the snake, the venom provides a food-getting mechanism. Its secondary function is its defensive status. In contrast, in venomous spiders, toxin is used to paralyze the prey before the extraction of hemolymph and body fluids. The venom is not primarily designed to kill the prey, but it is only to immobilize the organism for feeding. The same can be said for scorpions, although they do use their venom in defense. In fishes, such as the scorpion fishes and stone fishes, and in elasmobranches, such as the stingray, the venom apparatus is generally used in the animal’s defense. Poisonous animals, on the other hand, usually derive their toxins through the food chain. As such, poison is often a metabolite produced by microorganisms, plants, or animals. 3. Forensic Issues Practically almost all cases of animal bites reported from around the world are accidental in nature, and the vast majority are due to unintentional or deliberate provocation of the animal by humans itself. Likewise Snakes, rarely if ever, attack human beings on their own. A number of occupations are associated with increased risk of snake bites like grass-cutting, working in rubber, coconut, areca- nut, and tea & coffee plantations. Perhaps, the only recorded case of suicide accomplished with the help of a venomous snake is that of Queen Cleopatra of Egypt (69 – 30 BC), who is said to have deliberately prompted a snake (an adder) to bite her. While homicides can be accomplished by using a venomous snake as an instrument but actual instances of murder committed by such an unusual method are rare. Deaths due to snakebites are regarded as medicolegal in nature, and a forensic autopsy is mandatory. Unfortunately, precised characters of envenomation may be lacking in such cases, and even fang marks may not always be visible. FORENSIC SCIENCE PAPER No.10: Forensic Toxicology MODULE No.8: Organic Poisons: Animal Poisons Today, immuno-diagnosis with the help of, ELISA makes it possible to conclusively diagnose death due to snakebite by analysing tissues around bite site, or blister fluid, or even body fluids such as blood and urine for venom antigens. 4. Categorization of Venomous Animals Several species of animals, with or without backbones, produce venoms or contain certain toxins that may be dangerous to humans, either externally by stinging, biting or by ingestion. Both the categories are discussed as following: 4.1 VERTEBRATES 4.1.1 REPTILES 4.1.1.1 SNAKES Snakes belong to the class Reptilia, order squamata, and sub-order Serpentes. Snakes are found all over the world except New Zealand, Ireland and in Arctic lands. Of the 2500-3000 species of snakes distributed world-wide, about 500 are poisonous to Humans. The three main families of poisonous snakes exists are the Elapidae (cobras), the Viperidae (vipers) and the Crotalidae (pit vipers). The elapids cover around half the world’s species of venomous snakes and contain the Cobras and the Mambas. Genera of the elapid family are found in Asia, the Pacific, the Americas and Africa. The existent vipers, Viperidae, of which the common viper is the best known, inhabit Europe, Asia and Africa. The Pit Vipers, Crotalidae, are largely found in North, Central and South America and include the Rattlesnake genera Crotalus and Sistrurus. There are 238 species of snakes in India out of which only 52 are poisonous. Of these 52 poisonous species majority of bites and consequential mortality is attributed to 5 species viz. Ophiophagus hannah (King Cobra), Naja naja (Common Cobra), Daboia rusellii (Russell’s Viper), Bungarus caeruleus (Krait) and Echis carinatae (Saw- Scaled viper). Venom The snake venom is the secretion of the racemose salivary glands that is a modification of the parotid salivary gland of other vertebrates, and is usually situated on each side of the head below and behind the eye, invested in a muscular sheath. It is provided with large alveoli in which the venom is stored before being conveyed by a duct to the base of the channelled or tubular fang through which it is ejected. Poison is a clear limpid fluid of a pale straw or amber colour, more rarely greenish, sometimes with a certain amount of suspended matter, is exhausted after several bites, and the glands have to recuperate. The venom retains its poisonous properties for several years in dried state. The Cobra venom is slightly viscous and when exposed to sun it becomes a little turbid. FORENSIC SCIENCE PAPER No.10: Forensic Toxicology MODULE No.8: Organic Poisons: Animal Poisons The venom of Russell’s viper is usually white or yellow. Venoms of different species of poisonous snakes vary in the toxicity, composition and antigenic structure. It is basically a mixture of one or more of the toxic substances, toxalbumins and enzymes in varying proportions such as: (1) Proteolysins: It causes liberation of histamine from the damaged muscular endothelium leading to dissolution of walls of blood vessels with extravasation of blood in the tissue space, also causes digestion of tissue proteins and peptides and produces marked tissue destruction. (2) Fibrinolysins: It enhances the coagulation process. (3) Neurotoxins: It is mainly found in elapidae venom producing curare like effect causing paralysis especially of respiratory centre. (4) Cholinestrase: It is also found in elapidae venom causing hydrolysis of acetylcholine to choline and acetic acid thus causes impairment of neuromuscular transmission. (5) Haemolysin: It is found chiefly in viper venom causing widespread haemolysis in presence of lecithinase. (6) Cytolysin: It is mainly found in viprine venom and causes lysis of cell structures of blood and tissues. (7) Agglutinins: It causes agglutination of Red Blood Corpuscles. (8) Phosphatidases: It produces haemolysis and toxic effects on heart and circulation with haemorrhage from lungs. (9) Proteinases: It has trypsin like action, causing tissue damage. It produces anticoagulant effect from destruction of fibrinogen. It also catalyses the conversion of prothrombin to thrombin thus producing coagulant effect. (10) Phospholipase: It acts as a catalyst in hydrolysis of lipids. By destroying phospholipids in nervous tissues, it alters neuromuscular conduction. It also helps in penetration of neurotoxin in to nervous tissue. (11) Hyaluronidase: It helps in rapid spreading of the venom from the local site of bite and thereby quick absorption. It is present in all snake venoms. (12) Ribonuclease and deoxyribonuclease: It helps in rapid spreading of the venom from the local site of bite and thereby quick absorption. It is present in all venoms. FORENSIC SCIENCE PAPER No.10: Forensic Toxicology MODULE No.8: Organic Poisons: Animal Poisons (13) Protease: It causes dissolution of vascular wall and help in spreading of red blood cells and serum in the tissues. (14) Lecithinases: It acts on the lipid layer of the cells causing increasing fragility and permeability leading to cell destruction. The cobra venom in Neurotoxic and produces muscular paralysis involving firstly the muscles of the mouth, throat and lastly muscles of respiration, seats the action of venom being upon the motor nerve cells, the action resembling curare. It consists of: (i) Neurotoxin (ii) Cholinesterase (iii) Proteases (iv) Phosphatidases (v) Hyaluronidase (vi) Ribonuclease (vii) Thromboplastin (viii) Fibrinolysin (ix) Proteolysin (x) Cardiotoxin (xi) Phospholipase- A. Cobra venom produces convulsions and paralysis, while krait venom produces only muscular paralysis. The viperine venom is predominantly haemolytic and hemotoxic. It causes lysis of red cells and other tissue cells and coagulation disorders bringing about coagulation of the blood and clotting of the pulmonary arteries. There will be haemorrhage from the site of bite, associated with the necrosis of renal tubules, convulsions from intra-cerebral haemorrhage. It consists of: (i) Proteases (ii) Hyaluronidase (iii) Haemorrhagin (iv) Haemolysin (v) Leucolysin (vi) Lecithinase (vii) Cytolysin (viii) Thromboplastin (ix) Phospholipase- A (x) Proteinases. Fatal doses of various bites are: (i) Dried cobra venom : 12 - 15 mg (ii) Dried viper venom : 15 - 20 mg (iii) Dried krait venom : 5 - 6 mg (iv) Dried Saw Scaled viper venom : 8 mg Fatal Period: The death may occur instantaneously from neurogenic shock resulting from fright otherwise the fatal period is: (i) In colubrine bite : ½ - 24 hours (ii) In viperine bite : 2 - 4 days Antivenoms Antivenoms are prepared by immunizing horses with venom from poisonous snakes and extracting the serum and purifying it.