Impact of veterinary drug and pesticide residues on populations of the European common toad (Bufo Bufo)

Common toads (Bufo bufo) are facing a widespread decline, which is expected to affect ecosystem functions and services. Few studies have suggested an impact of various agricultural contaminants, including veterinary drugs and pesticides. This study aimed to evaluate the effects of residues of major drugs and pesticides on Common toad populations. Water samples from 10 ponds with declining populations and 10 ponds with stable populations in Flanders (Belgium) were analyzed for 112 pesticides and 61 veterinary drugs. Samples were collected at 3 timepoints (March, May and June 2024) corresponding to different developmental stages of the Common toad. A targeted analysis of 112 pesticides was performed using a validated SPE-LC-MS/MS method. Furthermore, a targeted and validated SPE-UHPLC-MS/MS method was used for the analysis of 15 antiparasitic drugs. Additionally, 46 antimicrobial drug residues were analyzed using a targeted and validated SPE-UHPLC-Orbitrap-HRMS methodology, combined with a suspect screening of additional veterinary pharmaceuticals and pesticides using an in-house database. Results of this analysis will be presented at the conference. Additionally, the impact of detected contaminants will be linked to the population status of Common toads.