Life-history traits, but not season, affect the febrile response to a lipopolysaccharide challenge in highveld mole-rats

Abstract

Fever is part of an acute phase response that organisms launch to defend themselves against an invasion by microbial pathogens such as bacteria and viruses. The elevation of an individual’s body temperature necessary to achieve a fever is considered energetically costly and variation in the expression of the febrile response has been reported with respect to season, sex and the reproductive status of an animal. The effect of these parameters on fever responses are well characterized for laboratory rodents but comparable data from wild rodents are currently lacking. We evaluated the febrile response of wild highveld mole-rats (Cryptomys hottentotus pretoriae) to lipopolysaccharide (LPS) during winter and summer. This social rodent retains its breeding potential throughout the year and exhibits a reproductive division of labour. Highveld mole-rats increased their body temperature to a greater degree in response to a dose of 1 mg kg-1 LPS than to saline or handling alone. The fever response did not differ between seasons while the stress-induced hyperthermia in response to handling was greater in summer compared winter. In contrast, males and breeders exhibited larger changes in body temperature following LPS administration than females and non-breeders, respectively. These findings are in accordance with those reported for laboratory species and suggest that general principles govern the modulation of innate immune responses such as fever among small mammals.