University of Alicante study: Antiparasitic Ivermectin six times more toxic than Moxidectin

Ivermectin is six times more toxic than Moxidectin for insects in charge of the recycling of organic matter. For the first time ever, there is scientific evidence based on physiological studies and this should be taken into account when using antiparasitic agents for livestock.

This is the conclusion of a study carried out by the multidisciplinary research group led by José R. Verdú, Professor of Zoology and researcher at the University of Alicante Latin American Centre for Biodiversity (CIBIO) with the participation of scientists from CIBIO and the UA Department of Physiology, Genetics and Microbiology, as well as from the University of Jaén, Université Paul Valéry Montpellier 3, the National Museum of Natural Sciences-CSIC, the University of Granada and the IUCN-Centre for Mediterranean Cooperation.

The results have just been published in the article First assessment of the comparative toxicity of ivermectin and moxidectin in adult dung beetles: Sub-lethal symptoms and pre-lethal consequences, included in Nature journal Scientific Reports. By means of a comparative study on the toxicity of Ivermectin and Moxidectin molecules in adult dung beetles, scientists have concluded that the Ivermectin molecule is six times more toxic than Moxidectin. Based on these results, scientists recommend to veterinarians and ranchers that they should use Moxidectin as an alternative to cattle parasite treatment, replacing Ivermectin and thus to avoid serious consequences in biodiversity.

Ivermectin is a highly effective antiparasitic, used preventively in cattle, since its discovery in 1981. The product has experienced an exponential growth, until becoming a standard treatment against parasites, even in humans ever since. The World Health Organization (WHO) has considered it as an essential medication.

Ivermectin is currently the most widely used molecule worldwide and also one of the most toxic for beneficial fauna, according to José R. Verdú. The scientists compared the two molecules and found that Moxidectin would be a good alternative to Ivermectin, as it affects a lot less the insect physiology. The study has been carried out both at the physiological and behavioral levels of dung beetles, obtaining direct results on how it affects coleoptera. The physiological (sub-lethal) study analyses whether it affects the organs, antennas, etc., and the behavioral (pre-lethal) study takes into account whether the legs are uncoordinated or if the beetle gets paralyzed.

The work methodology followed, as Verdú detailed, consisted in two tests: an electroantennagraphy, which consists of testing how healthy the antennae and the smell of insects are. For this purpose, they had individuals who had ingested different concentrations of these molecules and, in this way, were able to see how the antennas receive the stimulus and what the antennas conditions were.

The second test tried to assess the motility behavior, that is, walking, stretching antennas, moving legs. Researchers have detected several symptoms, such as partial paralysis, ataxia or total paralysis and, depending on this, they take notes on how many days were required for the paralysis to manifest. "In the case of Ivermectin, ataxia occurs much earlier in time."

The UA researcher affirms that, although this molecule was proved to be less toxic, it had not been applied in beetles at the physiological level". The appropriate parameters were used in the echo toxicity analyses carried out, the limits of toxicity, which is much more reliable. They are parameters that are used in eco toxicity tests. Eco toxicity studies the effect of toxic chemical compounds on living beings, especially in terms of populations, communities and ecosystems, with the aim of predicting the effects of pollution so that to prevent any environmental deterioration effect that may be identified.

Ivermectin is used in more than 90% of cases. Many pharmaceutical companies have commercialized it because it is much more effective but also more harmful to the coprophage organisms that eliminates livestock manure. Verdú states that Moxidectin has a similar effect in deworming. It is the veterinarians who have to take this alternative into account, the research says.

In 2017, the same multidisciplinary team already confirmed how Ivermectin is affecting the decline of coprophage fauna, whose scientific results were published in the study "Ivermectin residues disrupt dung beetle diversity, soil properties and ecosystem functioning: An interdisciplinary field study".Science of The Total Environment. Thus, livestock treated with Ivermectin causes the accumulation of five times more excrement per hectare and per year than organic or ecological livestock.

Previously, in 2015, the research team published "Low doses of ivermectin cause sensory and locomotor disorders in dung beetles" in the journal Scientific Reports. On that occasion, they analyzed the effect of Ivermectin on Scarabaeus cicatricosus populations, a key coprophagous beetle in Mediterranean ecosystems. The study showed that arthropods that ingest this substance, even in low doses, lose their ability to interact with the environment because they get their locomotory and sensory capacities altered, a fact that may explain the decline that these beetle species are suffering.