Effects of herbicides and ranavirus on survival and health of juvenile freshwater turtles

Background/Question/Methods

Emerging pathogens within the genus Ranavirus (family Iridoviridae) are carried by and can be lethal to ectotherms including amphibians, reptiles, and fish. Impacts of this virus in reptiles are under-studied, and factors contributing to pathogen virulence and host susceptibility are not well understood.  We conducted a controlled laboratory experiment to examine the interactive effects of ranavirus and herbicides on turtle health and survival.  Twenty juvenile Red Eared Sliders (Trachemys scripta elegans) were assigned to each of eight groups containing all combinations of treatments for ranavirus (exposure, control) and three herbicides (ShoreKlear®, 2,4-D, Atrazine, control).  Growth, survival, and condition of these 160 turtles were monitored for four weeks post-exposure.  Necropsies were performed at the conclusion of the experiment, and tissues from internal organs were test for presence of ranavirus.

Results/Conclusions

We found no difference in either survival or swelling of the neck and axillary region (a common symptom of ranavirus) due to either ranavirus or chemical exposures.  Similarly, neither treatment impacted growth in mass or shell length during the experiment.  There was little to no growth in turtles over this period.  Among turtles exposed to ranavirus, chemical treatments did not impact whether turtles tested positive or negative for ranavirus at the conclusion of the experiment. These results suggest that low concentrations of the herbicides used in this experiment may not impact growth or survival of juvenile turtles exposed to ranavirus. However, we hesitate to make broader conclusions and recommendations based on this study, because of the lack of growth in our study and the death of some turtles in our control treatments.  We suspect that cool rearing temperatures may have impacted the general health of turtles across treatments.