Sudden or Unexpected Death of Animals
Sudden or unexpected death of animals occur by unnatural (violence or poison or other harm) and natural causes.
- Unnatural death: always to be investigated by the police.
- Natural death: if they have occurred suddenly in apparently healthy animals and under suspicious circumstances, vetero legal investications are needed. The possibility of death as a result of disease and injury together has to be kept in mind. In such cases, a veterinary practitioner should not certify the cause of death without conducting a postmortem examination even if there is a string evidence of the disease.
Etiology of Sudden or Unexpected Death of Animals
Natural causes producing sudden death and diseases of the cardio vascular system:
- Acute myocarditis: due to infections like enteric fever (Typhoid) Diptheria, pericarditis Fathy degeneration of the myocardium Rupture of a myocardial infact or aneurysm.
- Left ventricular failure: associated with Aortic valvular disease, hyperthyroidism.
- Right ventricular failure: associated with chronic emphysema and lung diseases.
- Diseases of pericardium: Pericarditis.
- Congenital abnormal conditions of the heart in calves.
Classification of Death
Veterolegal deaths is accessed upon the concept that the cessation of the vital function depends upon tissue anoxia, which is brought about by four ways.
- Defective oxygenation of the blood in the lungs (or) anoxic anoxia
- Reduced oxygen carrying capacity of the blood
- Depression of the oxidative processes in the tissues
- Inefficient circulation of the blood through the tissues
1. Defective oxygenation of the blood in the lungs (or) anoxic anoxia
- Obstruction in the passage of air down the respiratory tract as in
- Strangulation
- Drowning
- Chocking from impaction of a foreign body.
- External compression of the chest and abdominal walls
- Eg. on being buried under earth (or) debris.
- Primary cessation of respiratory movements causing respiratory failure
- Eg. Narcotic poisoning, electrical shock.
- Breathing in a vitiated atmosphere containing excess of carbon dioxide or inert gases.
2. Reduced oxygen carrying capacity of the blood
Reduced oxygen carrying capacity of the blood, Anaemic anoxia occurring in acute poisoning by:
- Carbon monoxide
- Chlorates
- Nitrites
- Coal tar derivatives
3. Depression of the oxidative processes in the tissues
Depression of the oxidative processes in the tissues due to histotoxic anoxia occur in acute cyanide poisoning.
4. Inefficient circulation of the blood through the tissues
Inefficient circulation of the blood through the tissues-stagnant anoxia-occurring in death from:
- Traumatic shock
- Heat stress shock
- Acute and corrosive poisoning
All four types of anoxia produce circulatory failure and leads to death. The postmortem finding in all forms of death of vetero-legal nature can be divided into two types.
Basic pathological haemorrhages and Special pathological charges depending upon the particular type of death. Eg. Local injuries to the neck in throttling a strangulation.
The tissue anoxia induced, leads to circulatory failure. Hence, the fundamental pathological changes are uniform in all forms of death they vary in degree.
Sudden primary cardiac failure cause rapid death and the absence of visceral congestion when compared with death occurring slowly.
Chief Signs of death
An assessment of the various changes in the body, after death, enable us to arrive at an approximate idea as to the length of time that has elapsed since death. It is impossible to fix the exact moment of death.
Cessation of Circulation and Respiration
- Complete cessation of the circulation and respiration are the only reliable signs of death in early postmortem stages. In any case of doubt, the carcass should be left until some of the later signs appear which render the diagnosis absolute.
- Hibernating animals are known to resuscitate to life after having remained / for some time in a condition in which the action of heart and lungs was in abeyance and the muscles stiff and motionless. This state of suspended animation may last for a few seconds to half an hour or more may be found in cases of hysteria, sunstroke, concussion, drawing frozen, coma, electric shock, tetanus, convulsions, surgical shock and anesthesia. The animal can be revived by cardiac massage or electric stimulator accompanied by artificial respiration.
- Cessation of circulation can be tested by
- Auscultation of the heart
- Absence of a pulsation in the arteries
- Cessation of respiration may be tested by
- Holding a bright looking-glass infront of the open mouth and nostrils become dim due to the condensation of warm moist air exhaled from the lungs if animal respire.
- Hold a feather (or) cotton fibre infront of the mouth and nostrile, if respiration has stopped, these will be no movement.
Changes in the Eye
Soon after death, the eye loses its luster. The corneal reflex is lost.
Cornea become opaque and looks like dimmed glass. Such a condition may be present before death in uraemia and narcotic poisoning. Pupils may change their form and become oval, triangular or polygonal when pressure is applied by fingers on two or more sides of the eye balls of a dead animal.
Pupils retain their round form in a living animal. Eyes look sunken due to reduction of intra- ocular tension.
Cooling of the Body
After death, the body starts losing its heat by conduction, convection and radiation and gradually attains the same temperature as that of its surrounding medium. The loss of heat from the body cannot be considered as a certain sign of death until the body has lost 15 to 20 degrees of the normal heat viz 80 ºF for a rectal temperature. The body surface will be cold in 8 to 12 hours. The rate of cooling of the body may be influenced by age, condition of the body, manner or mode of death and surroundings of the body.
Fat and large well-nourished bodies retain heat much longer than lean and weak bodies. In general small and emaciated animals loose their warmth rapidly in cold surroundings. Freezing temperature accelerates the loss of the body heat.
Cooling of the body is more rapid in deaths occurring from severe haemorrhage, chronic and wasting diseases, whereas the body stays warm for a long time, when death has resulted from Asphyxia as in lightning, suffocation or poisoning by carbondioxide.
Cadaveric Changes in the Muscles
- After death, Muscular tissues of the body pass through 3 stages:
- Primary flaccidity or relaxation.
- Rigor mortis or cadaveric rigidity.
- Secondary flaccidity.
- Primary flaccidity:
- Soon after death, the whole muscular system begins to relax. Hence, we notice that the lower jaw falls, the eye lids lose their tension, the extremities become soft, and flay and the joints flexiable. But, the muscles are contractile and react to external stimuli, mechanical or electrical due to their retaining molecular life after somatic death. This stage lasts for 3 to 6 hours, but the average is 2 or 3 hours.
- Rigor mortis or cadaveric rigidity:
- Is also known as death stiffening. Rigor mortis comes on immediately after the muscles have lost the power of contractility (both voluntary and involuntary muscles). Adenosine triphosphate plays on fundamental role in the normal contraction, relaxation of the living muscle and it also determines the physical condition of the muscle protein, myosin. Mnocle protein consists of two protein myosin and actin. Their combined form is called actomyosin, which possesses the property of contractility and relaxation in the presence of ade-nosine triphisphate which is closely bound to the muscle protein and potassium chloride (Kcl).
- Secondary Flaccidity:
- Secondary flaccidity is characterized by the relaxation of the muscle which is synchronous with the onset of putrefaction. The muscles do not respond to any electrical stimuli.
- Putrefaction or Decomposition:
- It is the last stage in the resolution of the body. It is a slow process which is brought about by the action of ferments, produced by living saprophytic micro-organisms which resolve the complex organized tissues of the body into simpler inorganic compounds. Aerobic and gas forming anaerobic micro organisms in the living animal are found in large numbers in the alimentary cannal but within a short time after death are found scattered in all the tissues and organs and even in the blood. Unless special care is taken to prevent the spread of micro-organisms, they may cause putrefaction of the carcass.
- Factors responsible for the process of putrefaction:
- Temperature: Most favourable temperature for putrefaction is 100ºF.
- Access of air: Presence of air promotes putrefaction and vice versa.
- Moisture: Presence of moisture in the air promotes putrefaction. Asence of moisture in the air promotes mummification.
- Age: Young animals carcass putrefy more rapidly. Old animals carcass do not decompose very rapidly.
- Cause of death: Putrefaction is rapid in sudden death. Poisoning by Arsenic and Antimony in animals retard the putrefaction changes.
- Signs of putrefaction:
- Distension of the adomen due to the formation of gasses.
- Blood stained fluid from the mouth and nostrils.
- Liquefaction of the eye balls.
- Development of foul-smelling gases.
- Thoracic and abdominal carities will burst, protruding out the stomach and intestiness.
- Conversion of the tissues into a semifluid mass.
Adipocere
Adipocere is formed when the carcass is kept in moist condition. It is due to the gradual hydrogenation of pre-existing fats.
The fat is converted into palmitic, stearic and hydro stearic acid. Mixture of these substances constitutes adipocere. Adipocere has a distrinct rancid or sweetish smell which is quite characteristic. It floats in water and dissolves in ether and alcohol.
Adipocere is formed first in the subcutaneous tissues and later in the adipose tissues elsewhere in the body. It does not occur naturally in the viscera or in the nonfatty tissues.
Mummification
Desiccation or shriveling of the carcass from the evaporation of water is mummification. Mummification occur, when the carcass is in dry surrounding like sandy soil or a cool dry place.
Consumption by Insects and Animals
Insects and animals may begin to consume a body soon after death. Flies, maggots and beetles attach open areas of the body. They gather an soft body tissues. An entomologist’s study of the insect larvae on a body can help estimate the time of death.
