Forensic Medicine & Applied Toxicology-6

Information about Forensic Medicine & Applied Toxicology-6

Published on August 11, 2014

Author: willismochieng



Forensic Classification of Poisons (6,7): Forensic Classification of Poisons (6,7) Dr. Willis Ochieng Toxicologist 11/08/2014 1 Forensic Classification of Poisons-6 Plant Poisons: Dosis sols facit venenum  applies to poisonous plants as it is for other poisons The principal exposure route is by ingestion Plant exposures may constitute a big fraction of illness or even death in most African countries The extent to which plant poisoning occurs in Kenya is not known Exposures to unidentified fruits or beans are common Potential and real intoxication with plant materials do occur Among all plant cases only a relatively small fraction is severe enough to require hospitalisation Every country should identify plants with the highest toxicological risks to provide data base for a more rational prevention, diagnosis and treatment of cases in the future Forensic Classification of Poisons-6 Plant Poisons 11/08/2014 2 Classification of Poisons-6 Phytotoxins: A poisonous plant or a herbal medicinal concoction, may contain one or a mixture of phytotoxins -- 1 essential oils which are perceived by human by sense of smell; 2 alkaloids , which are usually basic substances with nitrogen atom in the ring. Most of these exert physiological effects on human 3 300 non-protein amino acids , many of which are toxic to human and other animals. 4 Cyanogenic glycosides with the potential for the liberation of hydrogen cyanide 5 Cardioactive glycosides most of which are steroidal glycosides constitute a class of important medicinal agents many of which are used in traditional medicine. 6 Furanocoumarins are of toxicological importance because of their photosensitising properties. 7 Plant acids some of which are essential flavouring agents like those found in oranges and lemons while others are toxic e.g. oxalic acid are found in many plants. 8 Poly-acetylene compounds some of which have anti microbial activities as well as phototoxic effects and have been used for years as folk medicine. 9 Proteins and peptides which are essential for plant survival, act as a reserve protein for human while others are toxic. Toxic proteins, often referred to as toxalbumins , are only partially absorbed by gastrointestinal tract and may exert toxic actions in the cells. 10 saponins with haemolytic properties when ingested. 11 terpenes with a wide variety of toxic effects are found in different genera of African plants. Poisons are usually found in different parts of the plant in different concentrations . If present, the poisons are usually concentrated in plant organs such as nuts, seeds, beans, fruits, mushroom, flowers, leaves, stems and roots . Classification of Poisons-6 Phytotoxins 11/08/2014 3 Classification of Poisons-6 Impact of phytotoxic Poisoning in Africa-1: A number of plants of agricultural importance exhibit cyanogenesis whereby hydrogen cyanide is liberated when plant tissue is damaged Many people are poisoned by these plants because cyanogenesis has a very broad phylogenetic distribution . It occurs in well over 1000 species , representing some 80 families and 300 genera Many cyanophoric plants play important economic and nutritional roles in the tropical Africa Manihot , Phaseolus , Sorgum , Arachis , Pennisitum , Zea , Colacasia , Alocasia , Acacia, Bambusa , Macrosamia and Encephalartos , all are incorporated in human diet and contain varying levels of cyanogenic compounds and free hydrogen cyanide gas during cooking process An adult in regions where cassava forms the staple diet consumes as much as 750 grams of this food item daily, a quantity capable of generating 35 mg of hydrogen cyanide . This value is known to be approximately equal to half the lethal dose of hydrogen cyanide Correlation has been found to exist between dietary cyanogen contaminants and diseases such as tropical ataxic neuropathy, goitre, cretinism and mental retardation Evidence suggest that various health problems, including some forms of cancer , have their origins in the presence of toxic chemicals in herbal foods and medicines Classification of Poisons-6 Impact of phytotoxic Poisoning in Africa-1 11/08/2014 4 Classification of Poisons-6 Impact of phytotoxic Poisoning in Africa-2: Pyrrolizidine alkaloids are found in most African plants and are of great toxicological concern Pyrrolizidine alkaloids could be a contributing factor to the high incidence of liver cancer in certain parts of Africa Africa has over 300 species of Crotalaria , all of which examined so far contain pyrrolizidine alkaloids Other toxins present in foods are hypoglycin , dioscorine , sapotoxin , cycacin , mushroom toxin, capsaicin, halogeton toxin, and fluorooleic acid Ingestion of a plant poison does not necessarily lead to poisoning Poisoning occurs when the poison reaches its target and when the body defence mechanisms or detoxification processes of the body is overcome Children below the age of 5 years are the most vulnerable to plant poisoning as a result of their inquisitiveness Adult poisoning is rare unless it is with suicidal intent Classification of Poisons-6 Impact of phytotoxic Poisoning in Africa-2 11/08/2014 5 Classification of Poisons-6 Herbal Medicines: Improvement brought by phytomedicines is usually mild and slow, but sometimes very drastic and helpfull in many cases . Side effects are rare. Those that do occur are mostly allergic reactions to natural substances. Therefore, herbal medicine is especially useful for the elderly patients and patients with physical complications The use of medicinal herbs in the West has increased over the past few years, and psychotropic herbs are among the most popular on the market Patients and doctors assume these products are safe. Problems that may occur with the use of psychotropic herbs include overuse or abuse, side effects, and herb-drug interactions Toxicity related to traditional medicines is becoming more widely recognised as these remedies become more and more popular. Accidental herbal toxicity occurs not only as a result of a lack of quality control in harvesting and preparation but also because herbal remedies are believed to be harmless Although there is a huge amount of data available documenting the pharmacologically active ingredients of many plants , it is seldom helpful to the toxicologist in an acute situation Analytical methods such as HPLC, GC-MS spectrometry, immunoassays provide identification of toxins in few cases in which history or symptoms give a clear lead In most cases of plant poisoning, treatment continues to be only of symptoms, with few specific antidotes available Classification of Poisons-6 Herbal Medicines 11/08/2014 6 Classification of Poisons-6 Mycotoxins: Fungal poisons believed to be involved in several chronic ill heaths such as mycotic infection of the heart Mycotoxins represent a diverse group of species-specific chemicals that can occur in a variety of plant foods Also occur in animal products derived from animals consuming contaminated foods Mouldy foods are consumed throughout the world during times of famine, as a matter of urgency and through ignorance of adverse health effects Acute or chronic effects are few Consumption of food contaminated with mycotoxins has a high potential to produce a variety of human diseases Classification of Poisons-6 Mycotoxins 11/08/2014 7 Poisons of Animal Origin-6 Zootoxins: A few zootoxins have been used in some cultures as zoomedicines . Many are used as zooweapons and therefore of forensic importance A ll phylogenetic classes of animals elaborate some sort of poisons except birds. All venomous animals are poisonous but not all poisonous animals are venomous Venom basically is a special type of poison produced and stored in a special site or organ for a special purpose and may be used for offence or defence In some animals, it is purposeless and is merely a product of metabolism Venom may contain amines, lipids, steroids, aminopolysaccharides , quinones , 5-HT, glycosides or other substances. Several of these may be present in venom elaborated by one animal The majority of venom is a complex of different substances often with different pharmacological and toxicological effects Proportion of substances in venom is such that one is preponderant over the others . As a result, most venom have a more particular effect on one or more several tissue sites and can thus be classified predominantly as either neurotoxic or cardiotoxic , haemotoxic , myotoxic , etc . Care should be taken to control the possible generalised effects in other organs. Envenomation thus presents a complex toxicosis . Poisons of Animal Origin-6 Zootoxins 11/08/2014 8 Poisons of Animal Origin-6 Insect Venom: Spiders , ants , bees and wasps produce poisonous secretions which may contain peptides, amines like histamine and hydroxytryptamine (5-HT), nonenzymatic proteins like kinins and several classes of enzymes exemplified by phospholipases and hyaluronidases Insect envenomation occurs world wide . Several deaths occur each year in Africa as a result of stinging by insects Stinging events involving bees and wasps are common. Most deaths or clinically important incidents involve only a few stings (< 10) and anaphylactic shock . Despite different venom composition in wasps and bees, both cause systemic damage and involve haemolysis , rhabdomyolysis , and acute renal failure With supportive care , most victims should be able to survive attacks from hundreds of wasps or approximately 1000 honey bees if not sensitised before Stinging may lead to acute anaphylaxis and repeated stings may result in a fatal anaphylactic reaction. Those not sensitive to bee sting may tolerate up to about 100 simultaneous stings without medical intervention Antihistamines, adrenaline, corticosteroid cream and analgesics are required for treatment. Bees have been used as biological weapons Bee venom phospholipase A 2 represents the major antigen or allergen of honey bee venom A lot of insect repellents have been developed to control venomous insects and disease vectors Poisons of Animal Origin-6 Insect Venom 11/08/2014 9 Poisons of Animal Origin-6 Snakes, (Ophidae): Although most feared, the majority of snakes are harmless Have been used as torture objects by police in some countries Approximately 60% of the world’s snakes are colubrids most of which are not poisonous The only African snake poisonous in this class is boomslang Almost all elapids are poisonous with African black mamba being deadly A few members like the African Puff Adder in viperidae class occur in Africa with rattle snakes ( crotalid sub-class) almost non-existent A few fresh-water and marine snakes ( hydrophids ) have been reported in lakes and marine shores particularly in mangrove swamps Poisons of Animal Origin-6 Snakes, ( Ophidae ) 11/08/2014 10 Poisons of Animal Origin-6 Snake venom: A snake venom is a complex mixture containing active proteins and peptides. The majority of snakes spit haemotoxin Haemostatically active components are distributed widely in the venom of many different snake species Venom components can be grouped into several categories depending on their haemostatic effect The venom may contain- Blood coagulants, anticoagulants, and agglutinins which may affect the red cells and cause coagulation of blood Also contain vasculotoxic cytolysins , proteolysins and bactericidin Neurotoxins affecting nervous system and myoneural junctions- Cholinesterase & anticholinesterase Cardiotoxin Hyaluronidase is a common ingredient for the purpose of facilitatating the spread of venom in the tissue Acute renal failure can often occur following envenomation by vipers or crotalids , sea snakes or some elapids Poisons of Animal Origin-6 Snake venom 11/08/2014 11 Poisons of Animal Origin-6 Development Of Venom Fangs: Snakes had legs which retracted over the years Could they have been lizard-like prior to their involvement with Adam and Eve? There are more than 200 different species of snakes in eastern Africa They occupy practically every habitat from desert to jungle, tops of trees to beneath the soil, lakes and ocean All snakes are carnivorous and prey upon other animals Some kill prey by constriction method These snakes usually specialise in mammals, and they include the well known pythons The African rock python is the largest snake in Africa, growing to more than 5 meters in length Some use venom as a tool for immobilisation of the prey This provides us with a basis for determining the classification of poisonous snakes Poisons of Animal Origin-6 Development Of Venom Fangs 11/08/2014 12 Poisons of Animal Origin-6 Odontological Classification Of Snakes: Based on the type of fang (tooth) evolved, we have at least three useful groups of snakes Back fanged snakes Most of these snakes are non-poisonous. Bites leave only a few scratches. It is the class with the majority of the world’s snakes. Most belong to colubrid family Immovable fanged snakes All are poisonous and inject much poison following a quick nip due to biological position of the fang Foldable front fanged snakes Most are large and venomous Contain the most feared and dangerous snakes like mambas and cobras Most of these inject large quantities of neurotoxic venom and kill their prey quickly. Fangs stick outside due to their biological position Poisons of Animal Origin-6 Odontological Classification Of Snakes 11/08/2014 13 Poisons of Animal Origin-6 Symptomatology : The syndromic presentation may include no clinical envenomation , painful swelling, weakness, venom ophthalmia and other presentations Extensive oedema may follow bites of many vipers and the spitting cobras ( haemotoxic ) and the volume of swelling represents blood fluids lost from the general circulation. In severe cases the depletion of blood fluids causes stress to many vital organs and may result in permanent injury or fatality Do not suck the site of the bite since this removes very little poison, if any at all, it can be dangerous for the health worker. Neurotoxic venom paralyses muscles and may present with a stiff chest . This must be considered an urgent symptom as it is difficult to reverse, and the use of serum must be resorted to straight away . In some severe cases, artificial respiration may be necessary for several days. Symptoms of nerve poisoning can manifest themselves in a fairly short time , and in the exceptionally severe case of the black mamba, even within 10 or 15 minutes . If, however, someone looks as if he is suffering from a nerve poisoning straight after a bite, it is most probably because he is scared out of his wits. Poisons of Animal Origin-6 Symptomatology 11/08/2014 14 Poisons of Animal Origin-6 Treatment Of Snake Bite:   The occurrence of snakebite is occasionally unrecognised by the patient and health worker, resulting in delayed or inadequate treatment, or even in death Investigations including creatine kinase , clotting profile and venom detection kit should be performed in cases of suspected snakebite where possible A severe clinical diathesis may result either from envenomation or from the release of an inappropriate tourniquet applied as 'first-aid' often several hours before presentation to hospital. Abnormalities of clotting are associated with both events A normal thromboelastogram (TEG) provides early recognition of patients in whom the clinical course is likely to be benign . An abnormal TEG identifies patients of whom 50% will develop a severe clinical diathesis The doctor or any other health worker has to balance the dangers of oversimplification against the dangers of confusion The management of poisonous snake bites includes first aid and clinical medical treatment. First aid consists of reassurement of the patient, immobilisation of the bitten limb and rapid transport to the nearest hospital to monitor the vital functions. In no case suction, incision or tight bandages be applied The degree of envenomation can be classified in three categories : no symptoms , only local non-progressive symptoms, and systemic or local rapidly progressive symptoms Antivenin therapy is indicated in severe envenomation . Antivenin should be given with great caution. Antibiotic therapy and tetanus prophylaxis may be necessay Poisons of Animal Origin-6 Treatment Of Snake Bite 11/08/2014 15 Poisons of Animal Origin-6 Antivenin Treatment: There is no serum available or needed for most snake bites and reommend a symptomatic approach , attending to symptoms , dressing the wound and treatment for shock . Serum is only effective against the poison of the species of snakes used in its manufacture, or, in some cases, closely related species. It is extremely bad practice to use serum for a bite against which it is ineffective . The use of antidotes e.g. antivenin is hazardous when allergic reactions occur. Clinical assessment must be done well to decide on how much antiserum is required . The use of antiserum should be avoided if possible . It is produced from serum of animals (usually horses) Attempts are being made to produce them monoclonally . Anti-serum should be used only when other alternative treatment is considered ineffective . Anaphylaxis can usually be allayed by first suppressing the body's defences with hydrocortisone or better still with 0.25 ml of 1:1000 adrenaline given subcutaneously immediately before administration of antivenom serum. Snake bite carries with it a fairly strong risk of infection , requiring limiting dose of hydrocortisone to 100mg. A syringe with adrenaline should always be at the ready in case shock does occur. Snake poison, once injected, spreads rather rapidly. The serum, on the other hand is exactly the opposite . There is therefore no alternative to injecting the serum straight into a vein . The best way to administer anti-serum is in a saline drip . A full 50 ml is needed for both adults and children . Children seem to have more serious local and systemic complications than adults and this may indicate the need to use a higher dose of antivenom than that being used at present Poisons of Animal Origin-6 Antivenin Treatment 11/08/2014 16 Poisons of Animal Origin-6 Tourniquet and Drug Therapy : Can delay the spread of neurotoxins, but may augment toxicity of haemotoxins Know the type of venom before the application of tourniquet Do not make incisions over the site of the bite Antibiotics only used with those snakebite patients with necrosis Being bitten by a snake is a very frightening experience , and this can lead to all manner of manifestations and complications Sometimes people collapse in an awful state from the bites of harmless snakes or even totally imaginary bites Sedative administration is therefore needed to allay fears . A sedative with antihistaminic properties like promomethazine , is suggested Placebo injections may be useful in these cases. This is where and when witchdoctors do wonders Under no circumstances should the patient be asked direct questions Asking whether victim has any difficulty in breathing, for instance, is likely to produce an instant tight chest Poisons of Animal Origin-6 Tourniquet and Drug Therapy 11/08/2014 17 The End: The End 11/08/2014 18

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