Analysis and dissipation of the antiparasitic agent ivermectin in cattle dung under different field conditions

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In biodiversity assessments, especially of small-bodied organisms for which taxonomic expertise is lacking, identification by genetic barcoding may be a cost-effective and efficient alternative to traditional identification of species by morphology, ecology, and behavior. The authors tested the feasibility and accuracy of such an approach using dung insects of practical relevance in ecotoxicological assessments of veterinary pharmaceutical residues in the environment. They produced 8 known mixtures that varied in absolute and relative composition of small-bodied and large-bodied species to see whether mitochondrial cytochrome c oxidase subunit 1 barcoding picks up all species qualitatively and quantitatively. As demonstrated before in other contexts, such metabarcoding of large numbers of dung insect specimens is principally possible using next-generation sequencing. The authors recovered most species in a sample (low type I error), at minimum permitting analysis of species richness. They obtained even quantitative responses reflecting the body size of the species, although the number of specimens was not well detected. The latter is problematic when calculating diversity indices. Nevertheless, the method yielded too many closely related false positives (type II error), thus generally overestimating species diversity and richness. These errors can be reduced by refining methods and data filtering, although this requires bioinformatics expertise often unavailable where such research is carried out. Identification by barcoding foremost hinges on a good reference database, which does not yet exist for dung organisms but would be worth developing for practical applications. Environ Toxicol Chem 2016;35:1970-1977. © 2015 SETAC.

Section: Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Is qualitative and quantitative metabarcoding of dung fauna biodiversity feasible?

Blanckenhorn¹,

Rohner²,

Bernasconi

et al. 2016

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“…However, the number of replicates used per substance treatment should be at least 10. Also, although ivermectin breaks down very slowly in nature and this was therefore not done in the present study, it could be informative to monitor actual substance concentrations analytically detectable in the dung over the course of such an experiment in case of spiking too, as done by Wohde et al . Replicating the experiment seasonally could further be beneficial, because results can be expected to (systematically) differ over the season because of different compositions of the community or winter diapause responses of many taxa in autumn.…”

Section: Discussionmentioning

confidence: 98%

A field test of the effect of spiked ivermectin concentrations on the biodiversity of coprophagous dung insects in Switzerland

Jochmann

Lipkow²,

Blanckenhorn

2015

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Veterinary medical product residues can cause severe damage in the dung ecosystem. Depending on the manner of application and the time after treatment, the excreted concentration of a given pharmaceutical varies. The popular anthelmintic drug ivermectin can be applied to livestock in several different ways and is fecally excreted over a period of days to months after application. In a field experiment replicated in summer and autumn, the authors mixed 6 ivermectin concentrations plus a null control into fresh cow dung to assess the reaction of the dung insect community. Taxon richness of the insect dung fauna emerging from the dung, but not Hill diversity ((1) D) or the total number of individuals (abundance), decreased as ivermectin concentration increased. Corresponding declines in the number of emerging insects were found for most larger brachyceran flies and hymenopteran parasitoids, but not for most smaller nematoceran flies or beetles (except Hydrophilidae). Parallel pitfall traps recovered all major dung organism groups that emerged from the experimental dung, although at times in vastly different numbers. Ivermectin generally did not change the attractiveness of dung: differences in emergence therefore reflect differences in survival of coprophagous offspring of colonizing insects. Because sample size was limited to 6 replicates, the authors generally recommend more than 10 (seasonal) replicates and also testing higher concentrations than used in the present study as positive controls in future studies. Results accord with parallel experiments in which the substance was applied and passed through the cow's digestive system. In principle, therefore, the authors' experimental design is suitable for such higher-tier field tests of the response of the entire dung community to pharmaceutical residues, at least for ivermectin. Environ Toxicol Chem 2016;35:1947-1952. © 2015 SETAC.

“…In the present study, however, residue concentrations were measured as reported by Wohde et al . Thus, the effects of residues on insect taxa were further examined using regression analyses to estimate mean lethal concentration (LC50) values.…”

Section: Methodsmentioning

confidence: 99%

“…Results were generally consistent across countries and support formal adoption of the method by the European Union to assess the effects of veterinary medical product residues on the composition and diversity of insects occurring in dung of treated livestock. Other studies in the present special section, Effects of Ivermectin , report the concentrations of residues detected in dung used for the present study , the effect of these residues on soil organisms , and the effect of these residues on community function (dung degradation ).…”

Section: Introductionmentioning

confidence: 99%

Validation of a standard field test method in four countries to assess the toxicity of residues in dung of cattle treated with veterinary medical products

Floate

Düring

Hanafi

et al. 2015

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Registration of veterinary medical products includes the provision that field tests may be required to assess potential nontarget effects associated with the excretion of product residues in dung of treated livestock (phase II, tier B testing). However, regulatory agencies provide no guidance on the format of these tests. In the present study, the authors report on the development of a standardized field test method designed to serve as a tier B test. Dung was collected from cattle before and up to 2 mo after treatment with a topical application of a test compound (ivermectin). Pats formed of dung from the different treatments were placed concurrently in the field to be colonized by insects. The abundance, richness, and diversity of insects developing from egg to adult in these pats were compared across treatments using analysis of variance tests. Regression analyses were used to regress abundance, richness, and diversity against residue concentrations in each treatment. Results of the regression were used to estimate mean lethal concentration (LC50) values. The robustness of the method and the repeatability of its findings were assessed concurrently in 4 countries (Canada, France, Switzerland, and The Netherlands) in climatically diverse ecoregions. Results were generally consistent across countries, and support the method's formal adoption by the European Union to assess the effects of veterinary medical product residues on the composition and diversity of insects in dung of treated livestock. Environ Toxicol Chem 2016;35:1934-1946. © 2015 Crown in the right of Canada. Published by Wiley Periodicals Inc., on behalf of SETAC.