The adaptive significance of Fever

Reese Clark

Why does fever occur?

Two hypothesis:

– Manipulation of the host by the pathogen.

– Adaptive defense against the infection.

Experimental Results

Vaughn et al.– Vaughn studied

behavioral responses of desert iguanas

Allowed iguanas to thermoregulate after injection of either saline or dead bacteria

Images from Freeman, S., Herron, J.C

Experimental Results

– Kluger et al. performed 2 studies

Desert Iguana infected with Aeromonas hydrophila and maintained and fixed temperatures.

Desert Iguana infected with A. hydrophila, treated with aspirin-like medicine.

Images from Freeman, S., Herron, J.C

Experimental Results

Manuel Banet– Studied effects of increased body temperature and

metabolic rates in rats. Rats had cooling devices implanted in either their brain or

spinal cord– Rats with cooling devices in their brains were able to develop

very high fevers and maintain somewhat normal metabolic rates.– Rats with cooling devices in their spinal cord showed greatly

increased metabolic rates without increasing body temperature.– He also closely monitored body temperatures and metabolic rates

in rats with and without implants, but none that were heated or cooled.

Experimental Results

Doran et al.– Studied the effects of fever on chicken pox in

children that were treated with a placebo and children that were treated with a fever reducer.

Image from Freeman, S., Herron, J.C

Experimental Results

Graham et al.– Studied adults infected with the common cold,

whom were treated with either a placebo or a variety of OTC medicines.

Images from Freeman, S., Herron, J.C.

Conclusions

Fever is a beneficial adaptation in ectotherms to infections by certain pathogens.

Fever in endotherms is an adaptive response to infection, however is not limited completely to core temperature increase, but many other effects on the immune system.

Fever is not beneficial in all infections and carries many costs.

Future Research Ideas

Decreased core temperature while allowing immune response continues as normal

Studies of the effects of presence or absence of fever in response to many different pathogens in endotherms and ectotherms.

References

Blatteis, C.M.2003. Fever: Pathological or Physiological, injurious or beneficial? Journal of Thermal Biology. 28: 1-

13. Freeman, S., Herron, J.C. 2007. Evolutionary Analysis. San

Francisco, CA. Pearson Benjamin Cummings. Jiang, D., Detolla, L. Sing, I.S., Gatdula, C., Fitzgerald, B.,

van Ruijen, N., Cross, A.S., Hasday, J.D. 1999. Exposure to Febrile Temperature upregulates expression of pyrogenic cytokines in endotoxin challenged mice. American Journal of Physiology. 276: 1653-1660.