The benefits of high fever (fever) in increasing survival during infection
Studying rats infected with Pasteurella multocida, Vaughn and Kluger found that with a moderate increase in body temperature, their survival rate increases. With an increase in body temperature of 2.5 ° C from the initial level (equivalent to a body temperature of 39.2–39.4 ° C), they noted a statistically significant correlation between the magnitude of fever and survival.
With fever with a rise in body temperature of more than 2.5 ° C, mortality increased. This suggests that maximum survival is associated with an optimal level of fever. The authors emphasized that they showed only a correlation, but did not investigate a causal relationship.
In experiments conducted on cold-blooded animals, some effect of fever on survival was also found. As noted, poikilothermic animals develop a fever with infections. But it does not appear as a result of an increase in metabolic activity or a decrease in heat transfer, but when the animal is moved, if possible, to a warmer place.
The development of a fever in such an animal can be prevented if it is not allowed to take shelter in a warmer place. Thus, it is possible to study the fever without the undesirable influence of antipyretic drugs.
Covert showed that the survival of goldfish infected with bacteria (fish are cold-blooded creatures) is directly dependent on their body temperature. Infected fish usually choose water, the temperature of which is 2.2-3.3 ° C higher than the normal temperature of their body (28 ° C). At a water temperature of 28 ° C, more fish are killed than at a water temperature of 31 ° C.
When studying lizards infected with Aeromonas hydrophila, Bernheim noted that the prevention of fever by creating obstacles to the movement of animals to environments with higher temperatures contributes to a significant increase in mortality.