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Sickness behavior, its mechanisms and significance

Published online by Cambridge University Press:  21 April 2008

Ian Tizard
Ian Tizard*
Affiliation:
Department of Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843, USA
*
E-mail: [email protected]
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Abstract

Recent studies have begun to clarify the pathogenesis of sickness behavior. Cytokines released by macrophages, dendritic cells and mast cells act on the brain to trigger behavioral changes in infected animals. The major cytokines, interleukin-1, tumor necrosis factor alpha, and others, all act on the hypothalamus to provoke alterations in the normal homeostatic condition. These include elevated body temperature, increased sleep, and loss of appetite as well as major alterations in lipid and protein metabolism leading to significant weight loss. Some of these changes are clearly directed towards enhancing the normal immune responses. The benefits of others such as appetite loss are unclear. It is also important to recognize that other animals may recognize sickness behavior as a sign of weakness and mark the victim out for targeting by predators. As a result, some prey species may work very hard to mask their sickness, a response that serves to complicate veterinary diagnosis.

Keywords

sicknessfevercachexiaanorexiacytokines
Type
Review Article
Information
Animal Health Research Reviews , Volume 9 , Issue 1 , June 2008 , pp. 87 - 99
Copyright
Copyright © Cambridge University Press 2008

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