Fever response in North American snakes

Selection of an increased body temperature (T-b) following injection of dead bacteria and placement into a photothermal gradient was first reported for reptiles in the lizard Dipsosaurus dorsalis. Subsequent to the study on D. dorsalis, a fever response was demonstrated in other lizard species, in turtles and in a crocodilian, however, the only previous study conducted with snakes did not show significant increases in selected T-b following injection of dead bacteria or endotoxin. The objective of the current study was to examine six species of snakes, representing two geographic regions (California and Pennsylvania) and different habitat types (desert and mesic environment) for the presence or absence of a fever response after injection with a single dosage of dead Aeromonas sobria bacteria. Body temperatures for individuals of each species were measured for 24 h under saline injection conditions and for 48 h under bacteria injection conditions using 36 gauge type K thermocouples and a computerized data acquisition system. A substrate type thermal gradient provided a range of available surface temperatures from 13 to 40 C. Two of the desert species, Pltuophis melanoleucus and Arizona elegans, did exhibit a fever response during at least one of the four 12 h periods following bacteria injection. One of the mesic species, Thamnophis sirtalis, exhibited a significant hypothermia in response to bacteria injection. One desert species, Lampropeltis getulus and two mesic species, Elaphe obsoleta and Nerodia sipedon, did not exhibit any change in T-b following bacteria injection. The results of this study indicate that the behavioral fever response can now be confirmed in snakes. Short acclimation periods, inadequate selection of a proper pyrogen and the use of a photothermal gradient may have contributed to negative results in the previous study on snakes. Use of only a single dosage of bacteria may have produced negative results in some species during this study.