Euthanasia

Definition

Greek Eu= good Thanatos= death

One without pain and distress

Techniques should result in: Rapid unconsciousness

Cardiac arrest

Respiratory arrest

Loss of brain function

The technique should minimize stress and anxiety experiences by the animal prior to unconsciousness

Personnel should have appropriate training and experience in technique and animal handling

Method selected depends on: Species involved

Available means of restraint

Skill of personnel

Number of animals involved

Things to consider:

1. Ability to induce loss of consciousness & death without pain or stress.

2. Time required to induce unconsciousness. 3. Reliability of method. 4. Safety of personnel. 5. Irreversibility.

6. Emotional effect on observers or operators 7. Compatibility with subsequent evaluation or

use of tissue. 8. Drug availability. 9. Cost. 10. Human abuse potential.

Effects on People

Clinic setting

Humane Society/ Animal Control setting

Laboratory

Agents Cause death by:

1. Hypoxia: (Gas agents) Unconsciousness should precede loss of motor activity. Agents that provide muscle paralysis without unconsciousness should not be used.

2. Direct depression of Neurons vital for life function (injectable). They induce unconsciousness followed by death. Some of these agents “release” muscle control which may cause vocalization & muscle contraction.

3. Physical disruption of brain activity (external physical method). Direct destruction of the brain or electrical depolarization of neurons. Causes rapid unconsciousness – can be followed by exaggerated muscle activity.

Inhalant agents Any gas that is inhaled must reach a certain concentration

in the body before it is effective. Best if rapid exposure in enclosed receptacle. Disadvantages:

1. Hazardous to personnel

2. Slow time may cause agitation

3. Deep anesthesia level may induce seizures

4. Neonates appear resistant to hypoxia

Non-inhalant Pharmaceutical agents

I.V. is most rapid and reliable method Wild, fearful or aggressive animals should be

sedated first Intraperitoneal of non irritating solution when

I.V. is impractical Intracardiac only on unconscious animal I.M. and S.Q. not acceptable

Barbituates depress the Central Nervous System in descending order beginning with the cerebral cortex unconsciousness anesthesia apnea. cardiac arrest death.

Advantages: Speed of action

Minimal discomfort to animal

Less expensive than other euthanasia agents

Disadvantages: Requires trained personnel Each animal must be

individually restrained Strict accounting to DEA Movement, vocalization,

Gasp may occur in unconscious animal

Physical Methods

Appropriate in three general situations:

1. Easily handled small animals with anatomic features compatible with method used.

2. Large farm, wild or zoo animals.

3. In research where other methods might invalidate experimental results.

Methods Penetrating Captive Bolt: Used in ruminants,

horses and swine. Powered by gun powder or compressed air. Concussion and trauma to cerebral hemisphere and brain stem.

Advantage: Sudden, quick unconsciousness Disadvantages: Only stuns and should not be sole

means of death. Animal must be restrained and correct placement of bolt is critical.

Gunshot: In some circumstances may be only practical method. Shot should enter brain and cause instant unconsciousness.

Advantage: Instantaneous under field conditions Disadvantages: Dangerous to personnel;

aesthetically unpleasing; may miss target!

Cervical dislocation: Used on poultry, small birds, mice and small rats and rabbits. Technique causes separation of the cervical vertebrae from skull.

Advantages: rapid unconsciousness, quick death; does not chemically contaminate tissue.

Disadvantages: aesthetically unpleasing; limited species; Electrical activity for 13 seconds!

Decapitation: Rodents and small rabbits Advantages: Rapid unconsciousness; does not

contaminate tissue; anatomically undamaged brain tissue; rapidly accomplished.

Disadvantages: Handling and restraint stressful; electrical activity continues; possible injury to personnel; aesthetically displeasing to observers.

Electrocution: Used on cattle, sheep, swine, foxes, mink and dogs. Induces cardiac fibrillation causing cerebral hypoxia. Animals should be unconscious before electrocution.

Advantages: Economical; does not contaminate tissue; humane if unconscious.

Disadvantages; Dangerous to personnel; not useful for mass euthanasia; may not result in death.

Microwave Irradiation: Used primarily by neurobiologists on rats and mice.

Advantages: death in < 1 second; most effective method to fix brain tissue.

Disadvantages: Equipment expensive; only useful on animals the size of rats and mice.

Exsanguination: Draining of entire blood volume. Only to be used on unconscious or anesthetized animal.

Agents that result in tissue residue cannot be used in food animals.

Carcasses of animals euthanized by barbituates may contain potentially harmful residues

Poikilotherms - often difficult to ascertain death because of differences in metabolism, respiration and tolerance to hypoxia.

Each means has advantages and disadvantages and is never pleasant, but sometimes a necessary part of our job.