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Pre-existing bacterial infections, not stress fever, influenced previous studies which labeled Gerrhosaurus major an
A E Muchlinski1, R Gramajo, C Garcia
1Department of Biology and Microbiology, California State University, Los Angeles 90032, USA. amuchli@calstatela.edu
Abstract:
Early studies indicated that the Sudan plated lizard, Gerrhosaurus major, did not exhibit a febrile response when challenged with bacterial pyrogen. More recent results indicated that a 14-day antibiotic treatment regime produced a significant decrease (0.5 +/- 0.1 degree C) in the mean selected body temperature (MSBT) for this species (31.3 +/- 0.2-30.8 +/- 0.2 degrees C). The antibiotic treatment results suggested that G. major already had a fever caused by a pre-existing bacterial infection. The current study was designed first to determine if a sub-population of G. major, with a higher mean pre-antibiotic treatment MSBT would exhibit a greater decrease in MSBT after antibiotic treatment. A 14-day antibiotic treatment regime for G. major (N = 7) with MSBTs > or = 31.9 degrees C (mean 32.4 +/- 0.2 degrees C) produced a significant decrease of 1.7 +/- 0.4 degrees C in MSBT to 30.7 +/- 0.3 degrees C. Analysis of the combined antibiotic treatment MSBT data from [13] and the current study demonstrated that the magnitude of the change in MSBT after antibiotic treatment was dependent upon the pre-antibiotic treatment MSBT. These data imply that animals with a greater pre-treatment MSBT and greater MSBT change had a greater magnitude fever. In the second portion of this study the MSBT for individual lizards was measured during separate experiments using both indwelling cloacal thermocouples taped to the tail of the lizard and telemeters implanted into the peritoneal cavity of the lizard. This second study was designed to determine if measurement of Tb using thermocouples induced a stress fever which may have masked a portion of the pyrogen-induced fever. The MSBT measured using indwelling cloacal thermocouples (30.5 +/- 0.3 degrees C) was not significantly greater (T > 0.05) than the MSBT increased using telemeters (31.0 +/- 0.2 degrees C). The results of the experiments from this study demonstrate that the previously reported afebrile state for G. major was the result of animals having pre-existing bacterial infections. G. major does exhibit a febrile response similar to other lizard species.
Insights
Sudan plated lizards, Gerrhosaurus major, do exhibit a febrile response, contrary to early beliefs. Antibiotic treatment revealed pre-existing infections caused elevated temperatures, indicating a fever response in this lizard species.
Area of Science:
- Herpetology
- Animal Physiology
- Infectious Disease
Background:
- Early studies suggested Gerrhosaurus major lacked a febrile response to pyrogens.
- Recent findings indicated antibiotic treatment lowered mean selected body temperature (MSBT), implying pre-existing infections.
- This study investigated the febrile response and temperature measurement methods in G. major.
Purpose of the Study:
- To determine if higher pre-antibiotic MSBT in G. major correlates with a greater temperature decrease post-treatment.
- To assess if temperature measurement techniques induce stress fever, potentially masking febrile responses.
- To confirm if G. major exhibits a febrile response.
Main Methods:
- Administered a 14-day antibiotic treatment to G. major with high MSBTs.
- Analyzed changes in MSBT before and after antibiotic treatment.
- Compared MSBTs measured via indwelling cloacal thermocouples versus intraperitoneal telemeters.
Main Results:
- Higher pre-antibiotic MSBT lizards showed a significant decrease (1.7°C) after treatment.
- The magnitude of MSBT change was dependent on pre-antibiotic MSBT, suggesting fever intensity.
- No significant difference in MSBT was found between thermocouple and telemeter measurements, indicating no induced stress fever.
Conclusions:
- G. major does exhibit a febrile response, previously masked by bacterial infections.
- The febrile response magnitude is linked to the pre-treatment body temperature.
- Standard temperature measurement methods do not appear to induce significant stress fever in this species.