Body temperature, behavior, and plasma cortisol changes induced by chronic infusion of Staphylococcus aureus in goats.
Most experimentally induced fevers are acute, usually lasting approximately 6-12 h, and thus do not mimic chronic natural fevers, which can extend over several days or more. To produce a model of chronic natural fever, we infused eight goats (Capra hircus) intravenously with 2 ml of 2 x 10(11) cell walls of Staphylococcus aureus (S. aureus) for 6 days using osmotic infusion pumps (10 microl/h) while measuring changes in body temperature, behavior, and plasma cortisol concentration. Seven control animals were infused with sterile saline. Abdominal temperature-sensitive data loggers and osmotic infusion pumps were implanted under halothane anesthesia. To compare our new model with existing models of experimental fever, we also administered 2-ml bolus intravenous injections of 2 x 10(11) S. aureus cell walls, 0.1 microg/kg lipopolysaccharide (Escherichia coli, serotype 0111:B4), and sterile saline in random order to six other goats. Bolus injection of lipopolysaccharide and S. aureus induced typical acute phase responses, characterized by fevers lasting approximately 6 h, sickness behavior, and increased plasma cortisol concentration. Infusion of S. aureus evoked prolonged fevers, which lasted for approximately 3 days, starting on day 4 of infusion (ANOVA, P < 0.05), and did not disrupt the normal circadian rhythm of body temperature. However, pyrogen infusion did not cause plasma cortisol concentration to rise (ANOVA, P > 0.05) or the expression of sickness behavior. In conclusion, infusion of S. aureus produced a fever response resembling that of sustained natural fevers but did not elicit the cortisol and behavioral responses that often are described clinically and during short-term experimental fevers.
Mphahlele
Noko R
NR
School of Physiology, Univ. of the Witwatersrand, 7 York Road, Parktown 2193, South Africa. mphahlelen@physiology.wits.ac.za
Fuller
Andrea
A
Roth
Joachim
J
Kamerman
Peter R
PR
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology*; D002473:Cell Wall / Q000737:chemistry; D002940:Circadian Rhythm / Q000502:physiology; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology; D005334:Fever / Q000139:chemically induced / Q000503:physiopathology; D006041:Goats; D006854:Hydrocortisone / Q000097:blood*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D011187:Posture / Q000502:physiology; D011749:Pyrogens / Q000494:pharmacology; D011863:Radioimmunoassay; D012768:Shivering / Q000187:drug effects / Q000502:physiology; D013203:Staphylococcal Infections / Q000503:physiopathology* / Q000523:psychology*; D013211:Staphylococcus aureus
D008070:Lipopolysaccharides; D011749:Pyrogens; D006854:Hydrocortisone