The Effects of Road Salt on Lithobates clamitans Tadpoles

In areas that see heavy snowfall and icy roads, road salt is used to improve driving conditions. However, after snow melts, road salt does not disappear. Instead, it dissolves into melted snow and flows into bodies of water where amphibians breed and live. Altering the salinity of the environment has been seen to affect different species of frogs. It is unclear, however, whether those findings generalize to other anurans. Here, we examined how exposure to road salt affects the development of green frog tadpoles (L. clamitans). We caught 80 L. clamitans tadpoles at the Ross Biological Reserve near Purdue University. We divided 60 tadpoles of average Gosner stage 37 into three treatments: control (well water), road salt (860 mg Cl/L), and an alternative road deicing salt product (beet juice/20% salt brine mixture). To examine the effects of salt exposure at earlier developmental stage, 20 younger tadpoles (average Gosner stage 30) were exposed to road salt. These tadpoles were kept at 3 degrees Celsius for 21 days and warmed up post-exposure mimicking natural conditions at the end of the winter. Preliminary results revealed no significant differences in the developmental rate or size (mass and total length) of the tadpoles across all treatments. Following the individuals as they complete metamorphosis will provide more insights about the long-term effects to road salt. Overall this study will provide insights about the effect of road salt on green frog development and the consequences of using a relatively recently developed method for more efficient road deicing

Effect of salts on the deadly amphibian chytrid fungus Batrachochytrium dendrobatidis

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) is a parasitic fungus that infects and kills amphibians worldwide. Bd causes electrolyte imbalance by destroying the keratin in the skin and causes cardiac arrest. Past studies have shown that Bd growth and motility can be inhibited by increased NaCl concentrations. In most studies, NaCl is the only type of salt used but Bd is exposed to other types of salts. In North American wetlands, runoff from road salts during winter and spring when Bd hosts (amphibians) often experience high levels of infection prevalence. This study investigated how different road salts at various concentrations affect the growth and motility of Bd. We predict that Bd growth will be inhibited more by road salts that contain more de-icing chemicals such as CaCl2 and that Bd growth will be the greatest in salts that are more environmentally friendly, such as Beet salt. Bd was reared in NaCl, CaCl2, and Beet salt at concentrations of 0.5, 1.0, 1.5, and 2.0 ppt. Growth was then quantified through counting and measuring of the area of growth and compared across treatments. Bd growth is greater in the absence of any salt than in the presence of either Beet salt, CaCl2, or NaCl. Bd growth at 14C was greater than at 22C. Our findings suggest several types of roads salts may have negative effects on Bd life history traits that could translate to lower infections in amphibians. Future studies should explore how road salts affect amphibians exposed to road salts, and how infection dynamics change when both host and pathogen are in the presence of these salts

Drivers of Winter Infection Dynamics of an Amphibian Pathogen

Infectious diseases are becoming increasingly common and problematic for wildlife populations in many parts of the world. Disease prevalence and severity fluctuate over time, often due to the ubiquitous pressure of seasonality, or the cyclic changes in ecological systems. However, for many host-pathogen systems, our understanding of important seasonal drivers of disease remains fragmented. For example, when seasonality of a disease is studied in medium and high latitudes, winter is often neglected, despite this being a period of physiological and immunological challenges associated with extreme environmental conditions. Therefore, my aim is to examine drivers of winter infection dynamics of the amphibian fungal pathogen Batrachochytrium dendrobatidis. First, B. dendrobatidis infection prevalence was measured from spring through fall to understand local infection levels and anthropogenic influences (Chapter 1). Next, laboratory experiments examined the effects of B. dendrobatidis on critical thermal minimum of two anuran species to identify how this pathogen influences the ability of hosts to survive winter (Chapter 2). Another laboratory experiment tested how road de-icing salt (commonly used in winter) influences B. dendrobatids and a tadpole host condition and subsequent host-pathogen interactions (Chapter 3). Finally, a field-based exploration of B. dendrobatidisinfection dynamics was conducted during winter to understand how infections vary during in this season and between two overwintering strategies (Chapter 4). Winter infection dynamics in many host-pathogen systems are largely understudied, but the knowledge gained by this work can demonstrate how harsh environmental conditions of winter that can exacerbate otherwise benign infections, and affect the ability of hosts to sustain infections during winter. This work can therefore inform predictions and investigations of infection dynamics in subsequent seasons to better understand the seasonality of wildlife diseases

Thigh-length compression stockings and DVT after stroke

Controversy exists as to whether neoadjuvant chemotherapy improves survival in patients with invasive bladder cancer, despite randomised controlled trials of more than 3000 patients. We undertook a systematic review and meta-analysis to assess the effect of such treatment on survival in patients with this disease