Co-Exposure with the Herbicide 2,4-D Does Not Exacerbate Batrachochytrium salamandrivorans Infection in the Italian Crested Newt (Triturus carnifex)

Amphibians face a multitude of threats and therefore make a prime example of the current biodiversity crisis. Multiple amphibian stressors in anthropogenic landscapes include infectious diseases and agrochemicals. Synergic effects between these stressors may increase the negative impact of infections on amphibian health. In a 56-day trial, we assessed the impact of co-exposure to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and the pathogenic fungus <i>Batrachochytrium salamandrivorans</i> (<i>Bsal</i>) on infection parameters (infection intensity and disease severity) and health (body condition and telomere length) in Italian crested newts (<i>Triturus carnifex</i>). Twenty days post-inoculation with <i>Bsal</i>, newts were either exposed to 2,4-D for 12 days or not exposed (control). Most newts developed high infection loads that steadily increased towards the end of the trial. While body condition was negatively correlated with pathogen burden, only one out of 23 animals died. Telomere length remained unaffected by the pesticide and the pathogen. The 2,4-D treatment did not exacerbate <i>Bsal</i> infection. Most newts survived almost two months with significant pathogen loads; thus, even in a pesticide-infested environment, <i>T. carnifex</i> could be an important long-term <i>Bsal</i> reservoir for co-occurring species on the Italian peninsula, a urodele diversity hotspot.