EVALUATION OF THE ACUTE TOXICITY OF IVERMECTIN FORMULATION IN AMPHIBIANS

PISTONE C; SANCHEZ ES; ALVAREZ SM; ENRIZ D; GIANNINI F

Congreso; 40ma Reunión Anual de la Sociedad de Biologia de Cuyo; 2022

Amphibian populations are decreasing globally. The environmental contamination is one of the mayor factors that contributes to amphibious population declines. However, there is a great disagreement about if amphibious are good sentinels of ecological contamination or not, due a lot of ecotoxicological studies indicating that amphibians are generally less sensitive than fish and invertebrates to different groups of contaminants. Ivermectin is a broad-spectrum antiparasitic used as a treatment in humans and mainly in animals. It also recently gained importance in the framework of the 2020-2022 Covid-19 pandemic produced by the SARS-CoV-2 virus as a therapeutic alternative. On the other hand, cadmium (Cd) is a pollutant of global concern due to its high toxicity at low concentration. Various modern industrial activities cause serious Cd contamination because of its wide use in fields such as battery, pigments, coatings, plating and plastics.Our working group has been study over the years the toxicity of a commercial formulation of Ivermectin for humans and the toxicity of Cd. Previously, carried out the evaluation of the toxicity of both substances using two species of fish (Poecilia reticulata and Danio rerio) as experimental models. Here in, we present a study using amphibian larvae as experimental model. To evaluate these compounds, we use the technique recommended by the U.S. Fish and Wildlife Service (Johnson and Finley 1980) modified by our working group. The toxicity was evaluated in amphibian larval stages (V-VI according to Martin et al.) of Rhinella arenarum obtained by collection in the month of November in San Luis city. Ten specimens were exposed in duplicate to different concentrations (5-0.625 mg/L for Cd and 0.250-0.032 mg/L for ivermectin) for a period of 96 hours. The LD50 was determined according the ratio of mortality in 96hs of exposure using an online software that develops "probit analysis". The results obtained showed LD50=2.3 mg/L for Cd and LD50= 0.122 for ivermectin. Considering our previous studies in fish (Cd DL50=2-3 mg/L and ivermectin LD50= 0.0039 mg/L) amphibians have greater resistance than fish in the case of Ivermectin but similar to both fish species in Cd acute intoxication. Our results highlight the importance of testing the distinct nature and mechanism of toxicity of contaminants individually to be able to come to any conclusion on the relative toxicological sensitivity of amphibians and further investigate the sensitivity and consequences of the chronic exposure to these axenics.