Pm examination of veterolegal case

MODE OF COLLECTION AND DESPATCH OF TOXICOLOGICAL SPECIMENS FOR DIAGNOSIS OF POISONING
Generally every veterinarian is encountered with two types of cases in poisoning of farm animals. (1) Accidental poisoning and (2) Malicious poisoning. The necropsy of the animals and the rapid diagnosis is helpful in the treatment of other affected animals in case of accidental poisoning. In case of malicious poisoning, which may turn up into medico legal case, the identification of poison is a must to establish the cause of death. In all poisonous cases, chemical analysis of the biological specimens is essential to know the cause of death or illness. Therefore, every veterinarian should know the salient points in collection and despatch of toxicological specimens to a laboratory.
History of the case is of great importance in the diagnosis of poisoning. This includes the number of animals in the farm, number of affected, method of feeding, regularity of feeding, recent changes in the rations or attendants, whether pastures have been sprayed with pesticides or fertilizers, if rodenticides have been used and remnants of the bait removed and disposed properly, storage of poisonous substances etc.
Inspection of the surroundings for empty pesticides or paint containers that are not really empty, presence of poisonous plants in the farm environment. Also, the possibility of industrial effluents coming in contact with grazing/watering sources should be given thought of.
POST MORTEM PROPER
Necropsy by routine procedure is to be performed as soon as possible after the death of animal. Examine the animal externally and note incisions (for sui poisoning, snake bite etc.,) on the skin or mucous membranes
Examine the oral cavity for corrosive lesions (acids/alkali) or changes in colour of mucous membrane (nitrate, co, cyanide poisoning). As most of the toxins gain entry through gut, examination of gut mucosa, the contents, their smell, colour and pH (acids, alkali, urea) is a valuable guide in diagnosing toxicoses. Poisoning by salts of heavy metals results in significant post mortem lesions but poisoning by alkaloids like strychnine produces very feeble lesions.
The natural orifices, sub-cutaneous fat tissue, muscles, bones and teeth (in fluorine poisoning), body cavities, and internal organs should be examined. The stomach should be punctured rather than cut open for organoleptic examination to note the character of smell. Puncture ensures greater accuracy and a longer time smell. Some of the poisons which emit characteristic smell are: bitter almond -hydrogen cyanide poisoning, garlic odour - phosphorus poisoning, rotten garlic or horse radish smell - selenium, tobacco odour –nicotine, acetylene odour - zinc phosphide and ammoniacal odour- urea.
Check the pH of the stomach contents by pH paper. Any variation in the normal pH of the sps. being examined indicates abnormality. (In urea poisoning-alkaline pH is observed in rumen liquor due to release of ammonia).
The colour of stomach contents also indicates the cause of poisoning. Copper salts impart a greenish blue colour whereas picric and nitric acid impart yellow colour to the contents.
The contents of the stomach vary from traces to flakes of paints or lead objects, grains or baits, seeds etc., like wise small and large intestine should be examined. Blood should be examined for its colour and clotting characters. Cyanide poisoning imparts cherry red colour, arsenic imparts rose red colour and nitrate poisoning turns blood brown in colour. In abrus and cyanide poisoning-blood remains fluid after death.
Examination of other visceral organs should be done in relation to their size, colour etc. eg: - spleen size is decreased and colour is changed to dark brown or black in copper poisoning and spleen size is increased in T-2 mycotoxicoses.
Lymph nodes are swollen, haemorrhagic, oedematous and dark upon exposure to radiation. Bone marrow becomes pale and gelatinous with yellowish tint.
The description of morphological changes should be noted clearly and absence of changes should be notified. The most important lesions found should be underlined.
COLLECTION OF SAMPLES FOR ANALYSIS
A sample feed/suspected bait to establish source of poisoning.
Rumen contents/vomitus to establish that the toxin has been ingested.
Liver, spleen and blood - to establish absorption.
Kidney, urine, milk - to establish excretion.
In case of small animals (poultry, small dogs, lab animals) the cadavers are sent as it is, in case of large animals the stomach contents are collected from the vicinity of patho anatomic changes in the gastric mucosa. If there are no changes a representative sample is collected, but in medium sized animals the stomach tied at oesophageal and duodenal end, intestine tied at both ends and bladder with tied ends is sent separately.
All the specimens are to be taken in separate containers (polythene jars/covers), securely tied, properly labelled with particulars of date, case No., organs collected, species, name of preservative used etc. A sample of the preservative used, brief history of the case along with treatment given particulars should be sent.

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Kind of sample Quantity
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Whole blood 10-20 ml
Serum 10-20 ml
Milk 50-100 ml
Urine 50-100 ml
Water 200 ml
Faeces 50 g
Feed 0.5 - 1kg.
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It is always preferable to send the specimens through a special messenger. In medico legal cases, the specimens should be sealed in the presence of a witness.
Mode of preservation
1. Ice/72 hrs.
2. Alcohol (95% ethyl alcohol) 1 ml/g of tissue is the ideal preservative for toxicological specimens. Formaline should never be used as it hardens the tissue without giving scope for scraping and interferes in the analysis. Blood and serum should be refrigerated and never frozen. A sample of the preservative used should be sent. It is always better to have a duplicate sample stored properly in a refrigerator for future reference.
Type of poison Organs to be collected
Arsenic - Liver, kidney, feed, stomach contents, urine.
Lead - Bone, blood, and stomach contents
Fluoride - Urine, stomach contents, forages and water sample
Nitrate - Water, forage, silage, whole blood, plant material, frozen and sent without chopping in a ploythene cover
Copper - Kidney, liver, whole blood, faeces
Cyanide -Blood, liver, forage, stomach contents in1% mercuricchloride and refrigerated
Organo phosphorus pesticides - Body fat, stomach contents, blood (heparinised), urine, feed and half brain.
Organochlorine pesticides - Fat, stomach contents, liver, kidney, whole blood, serum.
Carbon monoxide - Blood (refrigerated).
Urea - Blood (refrigerated), rumen liquor (frozen).