Effects of the Antiparasitic Drug Moxidectin in Cattle Dung on Zooplankton and Benthic Invertebrates and its Accumulation in a Water–Sediment System

Abstract

Two anthelmintic macrocyclic lactones-ivermectin and moxidectin-have revolutionized parasite control in cattle. These drugs are only partly metabolized by livestock, and the main route of excretion is via feces. In seasonally inundated floodplains, cattle feces come into direct contact with surface water. Important differences in pharmacokinetics and pharmacodynamics between these drugs may bear on their ecotoxicology in aquatic ecosystems. Moxidectin strongly binds to organic matter and thereby may be consumed in aquatic food webs, but there is a scarcity of data on toxicity to freshwater invertebrates. The objectives of this work were to determine the effect of moxidectin spiked in cattle dung on survival and growth of three representative aquatic invertebrates: the zooplankton Ceriodaphnia dubia, the amphipod Hyalella curvispina, and the snail Pomacea canaliculata. Moxidectin-laced dung was added in microcosms and concentrations were measured in water, sediment + dung, roots of the aquatic plant Salvinia biloba, and the aforementioned invertebrates. The influence of moxidectin on nutrient concentrations was also evaluated. Dung was spiked with moxidectin to attain concentrations of 750, 375 and 250 µg kg dung fresh weight, approximating those found in cattle dung at days 2, 3, and 5 following subcutaneous injection. Concentrations of moxidectin in dung during the first week of excretion were lethally toxic for the tested invertebrate taxa. The persistence of moxidectin in the sediment + dung and the uptake of the drug in roots of S. biloba increase its potential exposure to aquatic food webs. Moxidectin also reduced the rate of release of soluble reactive phosphorus to the water.

Drug dose and animal welfare: important considerations in the treatment of wildlife

“…However, moxidectin is highly toxic to aquatic organisms, such that inadvertent spillage of high volumes of product that ultimately enter waterways could have profound impacts, especially on fish. These may manifest as both acute toxicity and reproductive changes such as reduced egg hatching that could affect population dynamics in the longer term (Lumaret et al 2012;Mesa et al 2018;Muniz et al 2021). While more research into the ecotoxicological impacts of moxidectin are needed, in the short term, it would be prudent to clearly communicate to end-users that moxidectin pour-on should not be used near waterways, in volumes that inevitably lead to spillage, or during rain events that may lead to moxidectin being washed off the wombat or flooding of burrows.…”

Temperature moderates impact of formulated moxidectin on seed germination of three temperate grassland species

“…It has been shown that MLs, including moxidectin, can be absorbed by roots, distributed in the plant, partly metabolised and cause oxidative stress [ 53 – 55 ]. In a greenhouse pot experiment where soil was spiked with ivermectin, this could be found in the roots and leaves of soybean plants ( Glycine max ) but not in their fruits [ 55 ].…”

Parasites in Horses Kept in A 2.5 Year-Round Grazing System in Nordic Conditions without Supplementary Feeding

“…The objective in this study was to use pyrantel for treatment of endoparasites, due to the widespread resistance to benzimidazoles reported in cyathostomins [8] and the documented ecotoxic effect of macrocyclic lactones [13]. Pyrantel-only treatment was not successful in reducing cyathostomin egg excretion by 85%.…”