Behavior of Sickness Animal

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• Animal owner and Handle frequently use behavioral
  sign as an indicator -
• depress
• lethargic
• little interest in eating food or drinking water
  (inappetite or anorexia)
• febrile - not specific to any particular species

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• non - immunologic disease-fighting behavioral
  strategies - the first line of defense before
  immune system
• sick animal - wild ancestor -- living in an
  environment without medical or supportive care
• behavior as facilitating fever response by
  putting all of animals resources into killing
  pathogen

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• When infected with pathogen, febrile response
  coupled with
• reduction of plasma iron (effect of inhibiting
  the growth of at least some virus or pathogenic
  bacteria)
• potentiating the immune system

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• Fever response (when animal expose to pathogenic
  organism) initiated by the release of
  endogenous pyogens (EPs) from
• fixed tissue macrophages
• blood monocytes
• phagocytic cells of the liver and spleen
• granular lymphocytes

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• Interleukin-I (IL-1) - primary EP
• inaddition to causing fever, IL-1 induces other
  fever-related responses,
• lowering the plasma iron concentration
• the excretion of Na
• activating the non-specific immune reaction to
  pathogen

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• Fever response is best characterized as part of a
  cluster of physiologic reaction including
• the release of glucocorticoid from adrenal gland
• the release of proteins from liver, called
  acute-phase response
• fever develop due to EPs change the hypothalamic
  thermoregulatory set point so that an animal
  feels cold at previously normal temperature

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• change the hypothalamic thermoregulatory set
  point
• animal shunts blood from peripheral tissue to
  internal organs and piloerection or shivering
• A new thermal equilibrium conserve body heat

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• Cold-blooded reptiles
• the rate of survival of bacterial infected
  lizards given in cold environment lt warm
• treated with antipyretic (prevent fever) -- died
• Warm-blood animal - a general phenomenon
  throughout the animal kingdom
• febrile rabbit was given with antipyretic -- died
  gt control subject

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• 2 mechanisms -
• fever may facilitate an animals ability to
  combat infectious disease by
• potentiating immunologic response
• increased bacterial killing by neutrophil,
• enhanced lymphocyte proliferative response to
  antigen and mitogen
• enhanced antibody synthesis
• potentiation of IL-1 induction of T-cell
  proliferation -- enhanced by fever

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• 2 mechanisms -
• second mechanism relates to the optimal
  temperature for pathogens growth (same as or
  below normal body temperature)
• febrile response -- may suppress the growth
• but febrile temperature do not suppress the in
  vitro growth of all pathogenic organisms

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• combination of febrile temperature and reduced
  iron availibility -- suppress organism growth
• Prolonged temperature above 41oC can associated
  with tissue damage - CNS, liver, spleen, heart

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• During fever reaction, there is an obligatory
  increase metabolic rate
• metabolic increase 30-50
• estimated cost of about 13 for each 1oC rise in
  body temperature
• further metabolic cost -- shivering (raise body
  temp)
• in dogs, when body temp must be raised by
  shivering, the metabolic rate is increase 5-fold

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• Some question, febrile animal needs calories to
  elevated body temp, but not consuming food?
• Not thirsty or hungry animal -- little movement
  (save energy)
• It appears as though the same physiological
  process that produces fever
• injection of IL-1 produces a transient anorexia
  and administration -- does not block this effect
  of IL-1

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cytokines
Hypothalamic Nuclei

cytokines
leptin
Macrophage
Energy expenditure
_
White Adipose
Food Intake
insulin
glucose
Pancreas
Pathogen
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• It appears as though the same physiological
  process that produces fever
• other cytokine have anoretic effect - IL-6 and
  tissue necrosis factor alpha (TNF-a)
• increase slow-wave sleep (SWS)
• muramyl peptide and lipopolysaccharide component
  of bacterial cell wall -- enhance SWS

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• Dog and Cat often curl up when sick -
• reduces the body surface
• cut heat loss by convection and radiation
• piloerection which increases the insulation
  values
• have a scruffy-looking hair coat (reduction in
  grooming activity)

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oF
Body Temperature
Physiological Changes Thermoregulation Set
Point Plasma Iron Concentration
Behavioral Changes Slow-wave Sleep
Activity Appetite
Inhibited Growth of Pathogens
Macrophage and Monocyte
A
B
C
Infection by Pathogen
Removal of Pathogens by Immune System