Stress

Objective:

To review the causes (specific reference to capture, transport and holding) and the basic physiology behind the stress repsonse in live vertebrates. Also includes a discussion on the pathophysiology of capture myopathy.

 

Contents:

 

 

Introduction:

For the capture and holding of animals for brief or prolonged periods; for the manipulation of wild or domestic (purpose bred) animals YOUR PRIMARY GOAL IS TO REDUCE STRESS BY MINIMIZING PAIN AND DISTRESS.

 

 

STRESS

Stress is the reactions of the body to forces of a deleterious nature, infectious nature, and various abnormal states that tend to disturb the normal physiological equilibrium.

  1. fear or fright or rage activates the hypothalamus
  2.  massive discharge of the sympathetic nervous system (to prepare body for vigorous muscle activity)

 

Stress response includes:

  1. increased arterial pressure
  2. increased blood flow to muscles and decreased blood flow to other organs
  3. increased cellular metabolism
  4. increased blood glucose
  5. increased glycolysis
  6. increased muscle strength
  7. increased mental activity
  8. increased rate of blood coagulation

 

Stress Responses are Caused by:

Release of vasoactive substances and hormones:

 

Benefit of cortisol?

The benefit of cortisol is not entirely clear and some effects, if prolonged, are detrimental:

  1. Rapid mobilization of amino acids and fats from cellular stores for increased energy and to mobilize amino acids for new protein construction.
  2. Promotes gluconeogenesis -- the formation of carbohydrate from protein or fat.
  3. Potent anti-inflammatory effect -- reduces circulating lymphocytes and stabilizes membranes. This effect is often sought in certain therapies when the need for a potent anti-inflammatory effect calls for the administration of corticosteroids. However, every clinician knows that overuse of corticosteroids may cause immunosuppression.
  4. Cortisol is all right and even important for the short duration -- may actually feel some euphoria.
  5. Over a subacute time frame you may see gastric ulcers and adrenal hemorrhage.
  6. If persistent or chronic -you may see immunosuppression, muscle wasting, and behavioral changes.

 

Minimizing stress should be self evident simply because of the problems you are liable to encounter. Stress alters the "normal" physiology of an animal and will produce subclinical problems that will affect the reliability of your data. If prolonged, you are liable to see clinical symptoms that may result in clinical disease, possibly by organisms not usually considered pathogenic. For example: wild caught snow geese held in temporary holding pens in the field have died from Aspergillosis; arctic ground squirrels carrying Salmonella sp broke with clinical Salmonellosis following trapping and transportation.

 

 

Capture Myopathy

Capture myopathy is an important stress induced disease occasionally encountered in some wildlife species, particularly ungulates and birds. Although problems associated with physical injury, trauma, hyperthermia, hypothermia, anesthetic problems, and other effects of stress are more commonly seen during capture of wildlife, understanding capture myopathy is critical. This is, in part, so as not to inadvertently attribute capture mortalities to this disease when death was caused by something else! Understanding how to prevent this disease leads to better capture operations and fewer overall mortalities regardless of the cause!

Synonyms:

Overstraining disease, Capture disease, Stress myopathy, Exertional rhabdomyolysis

 

Cause:

Stress. A combination of fear and anxiety with muscle exertion

 

Pathogenesis:

Precise cause and pathogenesis is unclear.

 associated with exertion and fear that occurs during capture and confinement

 metabolic acidosis due to elevated levels of lactic acid as a result of anaerobic glycolysis in skeletal muscle.

 increasing levels of serum potassium combined with catecholamine effects leads to reduced cardiac output, poor tissue perfusion and severe muscle hypoxia and necrosis

 

Pathology:

The characteristics of the animal and the severity of the insult will affect the course of the disease and the lesions that develop. Clinical signs and pathology can be quite variable. This disease is an excellent illustration that what we see at necropsy (post-mortem examination) is a single "snap shot" yet disease is a dynamic process that occurs over a time continuum.

 

Capture myopathy is often classified by the time frame:

Peracute: Metabolic acidosis and increased potassium causes cardiac fibrillation circulatory collapse and death within minutes. May require a prior "chase" or stressor to sensitize the cardiac muscle by exposure to epinephrine. Minimal, if any, gross lesions. Histological lesions are present in muscles.

Acute: Muscle stiffness, depression, rapid heart and respiratory rate with death in approximately 12 hours from pulmonary edema. On gross examination, may see slightly swollen, pale, turgid muscles to pale streaking and "dry" appearance to muscles. Muscle rupture with severe hemorrhage may occur.

Subacute: Pronounced damage to skeletal muscles as well as internal organs so that the animals are paralyzed. Death may result from renal failure caused by myoglobinuria. Myoglobin is directly toxic to tubular epithelium.

Chronic: Fibrotic lesions in skeletal and cardiac muscle.

 

Specimens to submit for diagnostics:

Serum for biochemical profiling, specifically for electrolytes (potassium) and muscle enzymes. Please note that even slight hemolysis of red cells can artificially increase serum potassium levels unrelated to clinical disease.

Histology is critical. Collect fresh tissues and fix in 10% buffered formalin: Minimal collection includes skeletal muscle (backstrap, hindleg, shoulder) and cardiac muscle, liver. Of course this sampling is insufficient for evaluating other causes of death so do not commit yourself to the diagnosis of capture myopathy at the gross post-mortem - BE THOROUGH OR INVOLVE SOMEONE WHO CAN DO A THROUGH EXAMINATION.

 

Treatment:

 Treatment is unrewarding so prevention is the key!

 Intravenous sodium bicarbonate to treat the metabolic acidosis. The dose should be calculated using the base deficit but it is rare to know what it is; therefore, most administration of sodium bicarbonate will result in alkalosis. For conservative therapy, to be done only by someone familiar with clinical assessment, try 4-6mEq/kg body weight repeated in an hour.

 IV fluids - Normal saline (do not use Ringers since it has potassium in it)

 Vitamin E/Selenium

 

Prevention:

 Minimize exertion.

 Avoid handling in hot weather (or inclement weather).

 Do not confine animals/birds in sacks or under nets.

 Reduce psychological stress:

 If you must hold animals/birds for any length of time, provide feed and water.

 

 

STRESS AND THE HOLDING OR TRANSPORT OF ANIMALS

 

 For short term holding in field you should consider using pens as opposed to cages.

 Containers must protect from injury and allow animal to assume a normal posture without excessive crowding.

 Holding and shipping containers will vary but you must consider: 

If using ground transport you may need to incorporate stops and rest periods.

 

Release back to the wild after temporary holding?

  May not be allowed by the management agency. If you wish to do this it must be requested in your permit application to the management agency(ies) involved.

  Check with management agency about concern regarding disease.

  Will depend upon length of captivity, where animals are held captive, and procedures performed.

  If you do this they should be returned to the capture site, otherwise you are conducting a translocation.

 

 

References

  1. Guide for the Care and Use of Laboratory Animals. 1996. National Academy Press, Washington D.C. 1996.
  2. American Society of Mammalogists Animal Care and Use Guidelines (available in pdf format)
  3. Guidelines for the Use of Wild Birds in Research
  4. Guidelines for the Use of Fishes in Field Research
  5. Guidelines for the Use of Live Amphibians and Reptiles in Field Research
  6. Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching. 1988. Consortium for Developing a Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching. 74pp.
  7. The Well-Being of Agricultural Animals in Biomedical and Agricultural Reseaarch. Proceeding from a SCAW-sponsored conference, Agricultural Animals in Research, held September 6-7, 1990, Washington, D.C. 112pp.
  8. Guide to the Care and Use of Experimental Animals, Volume 1, 2nd Edition. 1993. Canadian Council on Animal Care.
  9. Guide to the Care and Use of Experimental Animals, Volume 2. 1984. Canadian Council on Animal Care.
  10. Spraker, T. Pathogenesis of

 

 

Last modified on Monday February 12, 2001 4:57 PM by John Blake