Effects of ivermectin on development of Calliphora vicina, Robineau-Desvoidy 1830 (Diptera, Calliphoridae)

Ivermectin is one of the most widely used drugs for parasite control. Previous studies have shown a reduction in the abundance and diversity of "non-target" coprophilous organisms due to the presence of ivermectin (IVM) in bovine faecal matter (FM). Due to its breadth of behavioural habits, Calliphora vicina is a suitable dipteran species to evaluate the effects of IVM in FM. The aim of this work was to evaluate the effect of five concentrations of IVM in FM (3000, 300, 100, 30, and 3 ng/g) on the development of C. vicina. The following endpoints were evaluated: survival (between the first larval stage and emergence of new adults), larval development times to pupation and pupation times to adult, and adult emergence (% sex) and LC50. Sampling was performed from larval hatching at 60 and 120 min and at 3, 4, 5, and 12 h, and every 24 h specimens were weighed until pupae were observed. Data were analysed by ANOVA using a non-parametric Kruskal-Wallis test and as a function of elapsed development time and accumulated degree hours (ADH). Mortality at 3000 and 300 ng/g was 100% and 97%, respectively. There were statistically significant delays in adult emergence time (p = 0.0216) and in the ADH (p = 0.0431) between the control group (C) and 100 ng/g. The LC50 was determined at 5.6 ng/g. These results demonstrate the lethal and sub-lethal effects of IVM on C. vicina, while highlighting the usefulness of this species as a bioindicator for ecotoxicological studies.

Season-Long Simplification of Insect Communities in Dung From Cattle Treated With an Extended-Release Formulation of the Parasiticide Eprinomectin

Cattle treated with LongRange®, an injectable formulation of the parasiticide eprinomectin, fecally excrete insecticidal residues for an extended period post application. We examined the nontarget effect of these residues by comparing insect communities developing in dung of untreated cattle (week 0) with those developing in dung of cattle treated 1, 2, 4, 8, 12, 16, 20, and 24 or 25 weeks previously. Chemical analyses of dung showed that eprinomectin concentrations peaked at 1 week post application and were still detectable at 25 weeks. Results from two separate experiments showed that dung of untreated cattle supported more total insects (beetles, flies, parasitoid wasps) and insect species than did dung of cattle treated for ≤12 weeks (Experiment 1) and ≤25 weeks (Experiment 2) previously. For the two experiments, an effect of residue on individual taxa was either not detected (nine cases) or was determined to suppress insect development in dung of cattle treated for 8-12 weeks (two cases), 12-16 weeks (three cases), 16-20 weeks (two cases), or 24 or 25 weeks (six cases) previously. Flies and their parasitoid wasps were particularly sensitive to residues with suppression often at or near 100%. These results show that cattle treated with LongRange in spring will fecally excrete residues for the entire grazing season with an associated simplification of the dung insect community. The effect of this simplification on the long-term health on dung-breeding populations of insects on pastures and dung degradation was not examined in the present study, but merits future research. Environ Toxicol Chem 2023;42:684-697. © 2023 His Majesty the King in Right of Canada. Environmental Toxicology and Chemistry © 2023 SETAC. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

Effects of Avermectins on the Environment Based on Its Toxicity to Plants and Soil Invertebrates-a Review

Avermectins are pharmaceutical drugs widely used mainly in livestock to combat both ectoparasites and endoparasites. Drugs belonging to this family include ivermectin, abamectin, doramectin, selamectin, eprinomectin, and emamectin benzoate, and they share similar chemical characteristics. When administered to livestock, between 80 and 98% of the drug is estimated to leave the body without being metabolized in feces, thus reaching the soil. For this reason, concern for avermectin contamination in soil is increasing, and researchers are focused on estimating the effects on non-target organisms, such as plants and soil invertebrates. This review aimed to compile and discuss updated data of avermectin toxicity on non-target organisms to better comprehend its effect on the environment. Effects on plants are scarcely studied, since they were not believed to absorb these drugs. However, recent studies suggest that plants can be negatively affected. Regarding soil invertebrates, negative effects such as increased mortality and reduced reproduction are best known to dung-beetles. Recently, some studies have also suggested that earthworms, springtails, and enchytraeids can be adversely affected by avermectin exposure. Since ivermectin was the first avermectin marketed, most of the data refers to this product. According to new data on scientific literature, avermectins can now be considered harmful to non-target organisms, and its prudent use is recommended in order to reduce negative effects on the environment. For future investigations, inclusion of avermectins other than ivermectin, as well as field and "omics" studies is suggested.

Fitness consequences of the combined effects of veterinary and agricultural pesticides on a non-target insect

Pesticides and veterinary products that are globally used in farming against pests and parasites are known to impact non-target beneficial organisms. While most studies have tested the lethal and sub-lethal effects of single chemicals, species are exposed to multiple contaminants that might interact and exacerbate the toxic responses of life-history fitness components. Here we experimentally tested an ecotoxicological scenario that is likely to be widespread in nature, with non-target dung communities being exposed both to cattle parasiticides during the larval stage and to agricultural insecticides during their adult life. We assessed the independent and combined consumptive effects of varying ivermectin and spinosad concentration on juvenile life-history and adult reproductive traits of the widespread yellow dung fly (Scathophaga stercoraria; Diptera: Scathophagidae). Larval exposure to ivermectin prolonged development time and reduced egg-to-adult survival, body size, and the magnitude of the male-biased sexual size dimorphism. The consumption by the predatory adult flies of spinosad-contaminated prey showed an additional, independent (from ivermectin) negative effect on female clutch size, and subsequent egg hatching success, but not on the body size and sexual size dimorphism of their surviving offspring. However, there were interactive synergistic effects of both contaminants on offspring emergence and body size. Our results document adverse effects of the combination of different chemicals on fitness components of a dung insect, highlighting transgenerational effects of adult exposure to contaminants for their offspring. These findings suggest that ecotoxicological tests should consider the combination of different contaminants for more accurate eco-assessments.

A Historical Review of Management Options Used against the Stable Fly (Diptera: Muscidae)

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), remains a significant economic pest globally in situations where intensive animal production or horticultural production provide a suitable developmental medium. Stable flies have been recorded as pests of livestock and humans since the late 1800s to early 1900s. Over 100 years of research has seen numerous methodologies used to control this fly, in particular to protect cattle from flies to minimise production losses. Reduced milk production in dairy cows and decreased weight gain in beef cattle account for losses in the US alone of > $2000 million annually. Rural lifestyles and recreation are also seriously affected. Progress has been made on many control strategies against stable fly over a range of chemical, biological, physical and cultural options. This paper reviews management options from both a historical and a technical perspective for controlling this pest. These include the use of different classes of insecticides applied to affected animals as toxicants or repellents (livestock and humans), as well as to substrates where stable fly larvae develop. Arthropod predators of stable flies are listed, from which potential biological control agents (e.g., wasps, mites, and beetles) are identified. Biopesticides (e.g., fungi, bacteria and plant-derived products) are also discussed along with Integrated Pest Management (IPM) against stable flies for several animal industries. A review of cultural and physical management options including trapping, trap types and methodologies, farm hygiene, scheduled sanitation, physical barriers to fly emergence, livestock protection and amendments added to animal manures and bedding are covered. This paper presents a comprehensive review of all management options used against stable flies from both a historical and a technical perspective for use by any entomologist, livestock producer or horticulturalist with an interest in reducing the negative impact of this pest fly.

Implications of Endectocide Residues on the Survival of Aphodiine Dung Beetles: A Meta-Analysis

It is often difficult to compare studies examining the effects of endectocides on dung fauna because of different experimental approaches, for example, active ingredients (eprinomectin, doramectin, ivermectin, moxidectin) and formulations (injectable, pour-on, spiked). To gain a better understanding, we performed a quantitative meta-analysis using 22 studies to assess the overall effect of endectocide residues on the occurrence (presence or absence) and abundance of aphodiine dung beetles. Our results document a positive effect on the occurrence of adult beetles, indicating that adults tend to be attracted to dung with residues. Conversely, larvae are less likely to occur in the presence of residues. Thus, either adults that colonize dung with residues do not lay eggs or, more likely, the larvae that hatch from these eggs die early in development. Abundance of adult and larval stages was shown to be significantly reduced in dung containing residues. When individual endectocides were compared, only ivermectin demonstrated a significantly negative effect on the abundance of both adults and larvae, possibly owing to a small sample size for other agents. In laboratory studies, only dung "spiked" with endectocides reduced the abundance of larvae, whereas during field research, only pour-on applications were shown to reduce the abundance of larvae. The present study further documents the nontarget effects of endectocide residues on dung-dwelling organisms, provides robust evidence on the consequences of different application methods, and emphasizes the need for standardized methodological techniques in future studies. Environ Toxicol Chem 2020;39:863-872. © 2020 SETAC.

Concentration and environmental fate of ivermectin in floodplain wetlands: An ecosystem approach

Ivermectin (IVM) is commonly used for broad control of endo- and ecto- parasites in cattle. In wetlands of the Parana Medio River, cattle has been treated repeatedly with IVM for years and concerns have been raised on possible presence of the drug in these ecosystems. A field study was conducted to assess concentration of IVM in two wetlands subjected to different cattle use and frequency of IVM injection. Concentration of IVM in roots of macrophytes, Chironomus sp., Coelotanypus sp., Brachymesia furcata (larvae), Dero sp., Hyalella sp., Hirudinea, Planorbidae, Boana pulchella (larvae), Aphyocharax anisitsi and Serrapinnus calliurus were shown for the first time. Total concentration of IVM in the wetlands, and concentration in cattle manure, sediment, water and macrophytes increased with the number of treated cattle and frequency of IVM injections. Accumulation of IVM in aquatic assemblages is alarming because these organisms fulfill a key role in food webs, constituting a serious risk to human health. Management strategies should be implemented by farmers to keep recently treated animals away from watercourses to reduce the introduction of IVM into aquatic systems.

Sublethal effects of the parasiticide ivermectin on male and female reproductive and behavioural traits in the yellow dung fly

The veterinary pharmaceutical ivermectin is commonly used against parasites of livestock. Excreted in dung it can have lethal and sublethal effects on non-target organisms developing in and living around cattle dung. Research in this realm typically investigates the impact of pharmaceuticals on dung-feeding insects by looking at juvenile development and survival, while fitness effects of adult exposure are largely neglected. We conducted laboratory experiments to assess combined effects of ivermectin on life history and reproductive traits of juvenile and adult yellow dung flies (Scathophaga stercoraria). Two treatments (12 and 24 μg ivermectin/kg wet dung) were used for the larvae reared in dung, and one much higher concentration (3000 μg ivermectin/kg sugar) for the adult flies (in addition to uncontaminated controls). Juvenile ivermectin exposure lead to smaller body size of male and female flies. Adult feeding on ivermectin-contaminated dung additionally resulted in adult male flies with smaller testes (and likely fewer sperm) that experienced reduced mating durations, resulting in lower probability of producing offspring. Exposure of adult flies to ivermectin lowered offspring production and survival for both sexes. Thus, treatment of livestock with pharmaceuticals such as ivermectin appears to have even more far-reaching sublethal ecological consequences than previously assumed by affecting not only flies at their larval stage but also adult mating behaviour and reproduction.

Toxicological effect of ivermectin on the survival, reproduction, and feeding activity of four species of dung beetles (Coleoptera: Scarabaeidae and Geotrupidae) in Japan

We investigated the effects of the antiparasitic drug ivermectin on the dung beetles Copris acutidens Motschulsky, Onthophagus bivertex Heyden, O. lenzii Harold and Phelotrupes auratus auratus Motschulsky in Japan. Ivermectin was detected in cattle dung from 1 to 3 or 7 days post-treatment, with a peak at 3 days post-treatment in two pour-on administrations (500 µg kg-1). In C. acutidens, adult survivals and numbers of brood balls were significantly reduced in dung collected at 3 and 7 days post-treatment, and adult emergence rates were significantly decreased in dung collected at 7 and 14 days post-treatment. Feeding activity of C. acutidens was inhibited in dung collected at 3 days post-treatment, but was not significantly different from that seen in control dung at 7 and 14 days post-treatment. In O. bivertex and O. lenzii, there were no effects of ivermectin on adult survival or feeding activities, but the numbers of brood balls of O. bivertex constructed in dung collected at 3 and 7 days post-treatment were significantly lower than observed with control dung. The adult emergence rates of O. bivertex and O. lenzii were significantly reduced in dung collected at 1 to 3 and 1 to 7 days post-treatment, respectively. In P. auratus, there were no effects of ivermectin on adult survival, oviposition, feeding activity, or larval survival (until the third instar) in dung at 3 days post-treatment. The environmental risks affecting the populations of dung beetles in Japan are discussed.

Effects of eprinomectin on the survival, reproduction and feeding activity of the dung beetles, Onthophagus lenzii Harold, and rare species, Copris ochus Motschulsky (Coleoptera: Scarabaeidae)

Effects of the antiparasitic drug eprinomectin were studied on the dung beetles, Onthophagus lenzii Harold and the rare species, Copris ochus Motschulsky by pour-on administrations (500 µg kg-1) in Japan. Eprinomectin was detected in cattle dung from 1 to 7 or 14 days after treatment, with a peak at 1 day after treatment in two experiments. In O. lenzii, adult survivals and numbers of brood balls constructed were significantly reduced in dung from eprinomectin-treated cattle at 1 and 3 days post-treatment in experiment 1, and adult emergence rates were extremely reduced in dung at 1, 3, and 7 days post-treatment. In C. ochus, adult survivals were significantly reduced in dung at 3 days post-treatment (experiment 1), and equivalent levels to the control were restored in dung at 7 and 14 days post-treatment (experiment 2). Numbers of brood balls of C. ochus were nil in dung at 3 days (experiment 1), and significantly reduced in dung at 7 days (experiment 2) post-treatment compared with control. Adult emergence rates of C. ochus were 100 and 71.6% in dung from control cattle in experiments 1 and 2, respectively. However, no oviposition was observed in dung at 3 days post-treatment, and all offspring died at egg or the first instar larval stage in dung from 7 and 14 days post-treatment. Feeding activities of O. lenzii and C. ochus were significantly inhibited in dung from treated cattle at 1-3 days and 3 days post-treatment, respectively, returning to levels of the control at 7 days post-treatment.

Comparative effects of the parasiticide ivermectin on survival and reproduction of adult sepsid flies

Ivermectin is a veterinary pharmaceutical widely applied against parasites of livestock. Being effective against pests, it is also known to have lethal and sublethal effects on non-target organisms. While considerable research demonstrates the impact of ivermectin residues in livestock dung on the development and survival of dung feeding insect larvae, surprisingly little is known about its fitness effects on adults. We tested the impact of ivermectin on the survival of adult sepsid dung fly species (Diptera: Sepsidae) in the laboratory, using an ecologically relevant and realistic range of 69-1978 µg ivermectin/kg wet dung, and compared the sensitivities of larvae and adults in a phylogenetic framework. For one representative, relatively insensitive species, Sepsis punctum, we further investigated effects of ivermectin on female fecundity and male fertility. Moreover, we tested whether females can differentiate between ivermectin-spiked and non-contaminated dung in the wild. Adult sepsid flies exposed to ivermectin suffered increased mortality, whereby closely related species varied strongly in their sensitivity. Adult susceptibility to the drug correlated with larval susceptibility, showing a phylogenetic signal and demonstrating systemic variation in ivermectin sensitivity. Exposure of S. punctum females to even low concentrations of ivermectin lowered the number of eggs laid, while treatment of males reduced egg-to-adult offspring survival, presumably via impairment of sperm quality or quantity. The fitness impact was amplified when both parents were exposed. Lastly, sepsid flies did not discriminate against ivermectin-spiked dung in the field. Treatment of livestock with avermectins may thus have even more far-reaching sublethal ecological consequences than currently assumed via effects on adult dung-feeding insects.

Ivermectin residues disrupt dung beetle diversity, soil properties and ecosystem functioning: An interdisciplinary field study

Ivermectin is the most common endectocide used to control parasites affecting livestock. Short-term physiological and behavioural effects of ivermectin on dung beetles may have long-term consequences for beetle populations and ecosystem functioning. Long-term effects of the use of ivermectin can be estimated by comparing dung assemblages and ecosystem functions in areas with conventional ivermectin-treated livestock and environmentally similar areas in which livestock are not treated with veterinary medical products (organic farming). In this study, we investigated both short-term and long-term effects of the administration of ivermectin on the characteristics of dung beetle assemblages and the services they provided in a protected area (Doñana National Park, SW Spain). We examined short-term dung colonization, dwelling, relocation, and disaggregation rates and the associations between these processes and the key assemblage parameters of species richness, abundance, biomass and functional diversity. Furthermore, we analysed changes in soil physical-chemical properties and processes. Short-term differences were observed in the total amount of dung relocated by dung beetles at different colonization vs. emigration stages, suggesting that dung beetles in this area were affected by the recent treatments of livestock with ivermectin. Moreover, short-term effects could also be responsible for the significant differences in dung spreading rates between sites. Conventional use of ivermectin disrupted ecosystem functioning by affecting species richness, abundance and biomass. The decrease in diversity parameters was related to a reduction in the functional efficiency, which resulted in the long-term accumulation of dung on the ground and considerable changes in soil functionality.

Modelling the impact of targeted anthelmintic treatment of cattle on dung fauna

The insecticidal properties of many anthelmintics pose a risk to dung fauna through the effects of drug residues in dung on the activity, oviposition and development of dung-dwelling invertebrates. Reductions in dung fauna numbers can inhibit dung degradation, which may impact biodiversity and nutrient cycling on farms. A simulation model was created to predict the impact of antiparasitic drugs on cattle dung fauna, and calibrated using published data on the dung-breeding fly Scathophaga stercoraria. This model was then tested under different effective dung drug concentrations (EC) and proportions of treated cattle (PT) to determine the impact under different application regimens. EC accounted for 12.9% of the observed variation in S. stercoraria population size, whilst PT accounted for 54.9%. The model outputs indicate that the tendency within veterinary medicine for targeted selective treatments (TST), in order to attenuate selection for drug resistance in parasite populations, will decrease the negative impacts of treatments on dung fauna populations by providing population refugia. This provides novel evidence for the benefits of TST regimens on local food webs, relative to whole-herd treatments. The model outputs were used to create a risk graph for stakeholders to use to estimate risk of anthelminthic toxicity to dung fauna.

Quantifying immediate and delayed effects of anthelmintic exposure on ecosystem functioning supported by a common dung beetle species

Dung beetles (Coleoptera: Scarabaeoidea) support numerous ecosystem functions in livestock-grazed pastures. Exposure to veterinary anthelmintic residues in livestock dung can have lethal and sublethal effects on dung beetles, and can reduce rates of dung removal, but the immediate and longer-term consequences for other dung beetle mediated functions have rarely been studied. We investigated the consequences of anthelmintic exposure on survival of the dung beetle Aphodius fossor and its delivery of four ecosystems functions that underpin pasture production: dung removal, soil fauna feeding activity, primary productivity, and reduction of soil compaction. We tested whether anthelmintic exposure had immediate or delayed effects on these functions individually and simultaneously (i.e., ecosystem multifunctionality). We found no evidence that ivermectin residues had a lethal effect on adult beetles. For dung removal, we found a significant interaction between the timing of exposure and functioning: while dung removal was impaired by concurrent exposure to high levels of ivermectin, functioning was unaffected when beetles that had been exposed previously to the same concentration of anthelmintic later interacted with untreated dung. Other ecosystem functions were not affected significantly by anthelmintic exposure, and there was no evidence to suggest any persistent impact of anthelmintic exposure on ecosystem multifunctionality. While anthelmintic residues remain a significant threat to dung beetle populations, for adult beetles, we found no evidence that residues have detrimental consequences for ecosystem functioning beyond the immediate point of exposure.

Ivermectin alters reproductive success, body condition and sexual trait expression in dung beetles

Ivermectin is a very common parasiticide used in livestock. It is excreted in the dung and has negative effects on survival and reproduction of dung-degrading organisms, including dung beetles. Here we exposed the dung beetle Euoniticellus intermedius to different concentrations of ivermectin in the food and evaluated reproductive success and the expression of traits associated with survival and reproduction under laboratory conditions. It is the first time the effects of ivermectin were evaluated on offspring physiological condition and the expression of a secondary sexual trait. We also registered the number of emerged beetles, sex ratio and body size of emerged adult beetles. Besides reducing the number of emerged beetles and body size, as found in the same and other insects, ivermectin at high doses reduced muscle mass while at intermediate doses it increased lipid mass. Ivermectin changed offspring sex ratio and at high doses increased the size of male horn, which is an important trait defining the male mating success. Our results highlight the importance of regulating parasiticide usage in livestock in order to maintain ecosystem services provided by dung beetles and confirm that contaminants impose new environmental conditions that not only impact on wild animal survival, but also on evolutionary processes such as sexual selection.

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

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.

Treating cattle with antibiotics affects greenhouse gas emissions, and microbiota in dung and dung beetles

Antibiotics are routinely used to improve livestock health and growth. However, this practice may have unintended environmental impacts mediated by interactions among the wide range of micro- and macroorganisms found in agroecosystems. For example, antibiotics may alter microbial emissions of greenhouse gases by affecting livestock gut microbiota. Furthermore, antibiotics may affect the microbiota of non-target animals that rely on dung, such as dung beetles, and the ecosystem services they provide. To examine these interactions, we treated cattle with a commonly used broad-spectrum antibiotic and assessed downstream effects on microbiota in dung and dung beetles, greenhouse gas fluxes from dung, and beetle size, survival and reproduction. We found that antibiotic treatment restructured microbiota in dung beetles, which harboured a microbial community distinct from those in the dung they were consuming. The antibiotic effect on beetle microbiota was not associated with smaller size or lower numbers. Unexpectedly, antibiotic treatment raised methane fluxes from dung, possibly by altering the interactions between methanogenic archaea and bacteria in rumen and dung environments. Our findings that antibiotics restructure dung beetle microbiota and modify greenhouse gas emissions from dung indicate that antibiotic treatment may have unintended, cascading ecological effects that extend beyond the target animal.

A review on the effect of macrocyclic lactones on dung-dwelling insects: Toxicity of macrocyclic lactones to dung beetles

Avermectins and milbemycins are commonly used in agro-ecosystems for the control of parasites in domestic livestock. As integral members of agro-ecosystems with importance in maintaining pasture health through dung burial behaviour, dung beetles are an excellent nontarget bio-indicator taxon for examining potential detrimental effects of pesticide application. The current review focuses on the relative toxicity of four different anthelmintics (ivermectin, eprinomectin, doramectin and moxidectin) in dung residues using dung beetles as a bioindicator species. One of the implications of this review is that there could be an effect that extends to the entire natural assemblage of insects inhabiting and feeding on the dung of cattle treated with avermectin or milbemycin products. Over time, reduced reproductive rate would result in decreased dung beetle populations and ultimately, a decrease in the rate of dung degradation and dung burial.

Effects of large herbivores on grassland arthropod diversity

Both arthropods and large grazing herbivores are important components and drivers of biodiversity in grassland ecosystems, but a synthesis of how arthropod diversity is affected by large herbivores has been largely missing. To fill this gap, we conducted a literature search, which yielded 141 studies on this topic of which 24 simultaneously investigated plant and arthropod diversity. Using the data from these 24 studies, we compared the responses of plant and arthropod diversity to an increase in grazing intensity. This quantitative assessment showed no overall significant effect of increasing grazing intensity on plant diversity, while arthropod diversity was generally negatively affected. To understand these negative effects, we explored the mechanisms by which large herbivores affect arthropod communities: direct effects, changes in vegetation structure, changes in plant community composition, changes in soil conditions, and cascading effects within the arthropod interaction web. We identify three main factors determining the effects of large herbivores on arthropod diversity: (i) unintentional predation and increased disturbance, (ii) decreases in total resource abundance for arthropods (biomass) and (iii) changes in plant diversity, vegetation structure and abiotic conditions. In general, heterogeneity in vegetation structure and abiotic conditions increases at intermediate grazing intensity, but declines at both low and high grazing intensity. We conclude that large herbivores can only increase arthropod diversity if they cause an increase in (a)biotic heterogeneity, and then only if this increase is large enough to compensate for the loss of total resource abundance and the increased mortality rate. This is expected to occur only at low herbivore densities or with spatio-temporal variation in herbivore densities. As we demonstrate that arthropod diversity is often more negatively affected by grazing than plant diversity, we strongly recommend considering the specific requirements of arthropods when applying grazing management and to include arthropods in monitoring schemes. Conservation strategies aiming at maximizing heterogeneity, including regulation of herbivore densities (through human interventions or top-down control), maintenance of different types of management in close proximity and rotational grazing regimes, are the most promising options to conserve arthropod diversity.

Ivermectin sensitivity is an ancient trait affecting all ecdysozoa but shows phylogenetic clustering among sepsid flies

Avermectins are potent and popular veterinary pharmaceuticals used globally to fight parasites of livestock and humans. By disturbing ion channel transport through the membrane, avermectins are effective against endo- and ectoparasitic round and horsehair worms (Nematoida), insects, or ticks (Arthropoda), but not against Plathelminthes, including flatworms (Trematoda) and tapeworms (Cestoda), or segmented worms (Annelida). Unfortunately, excreted avermectins have strong nontarget effects on beneficial arthropods such as the insect community decomposing livestock dung, ultimately impeding this important ecosystem function to the extent that regulators mandate standardized eco-toxicological tests of dung organisms worldwide. We show that the ancient phylogenetic pattern and qualitative mechanism of avermectin sensitivity is conserved and compatible with most recent phylogenomic hypotheses grouping the Nematoida with the Arthropoda as Ecdysozoa (molting animals). At the species level, we demonstrate phylogenetic clustering in ivermectin sensitivities of 23 species of sepsid dung flies (Diptera: Sepsidae). This clustered 500-fold quantitative variation in sensitivity may indicate recent lineage-specific responses to selection, but more likely reflects pre-existing genetic variation with pleiotropic effects on eco-toxicological responses to pollutants. Regardless, our results question the common practice in eco-toxicology of choosing single test species to infer detrimental effects on entire species communities, which should ideally assess a representative taxonomic sample.

Soil Nutrients, Bacteria Populations, and Veterinary Pharmaceuticals across a Backgrounding Beef Feedlot

Beef cattle backgrounding operations that grow out weaned calves for feedlot finishing contain several environmentally significant constituents. A better understanding of these constituents and their environmental distribution will aid in the development of effective management guidelines for sustainable beef production. This research investigated soil nutrients, bacterial, and veterinary pharmaceutical concentrations across a small backgrounding beef feedlot on a karst landscape. Results indicated that all contaminants were highly concentrated in the feeder area (FD) and were lower in the other feedlot areas. The FD soils had a pH of 8.2, 59 mg kg soil organic matter (SOM), 2002 mg kg soil test phosphorus (STP), 99.7 mg kg NH-N, and 18.3 mg kg NO-N. The other locations were acidic (5.9-6.9 pH) and contained 39 mg kg SOM, 273 mg kg STP, 21.5 mg kg NH-N, and 2.0 NO-N mg kg. Bacteria populations in the FD averaged 2.7 × 10 total cells, 3.9 × 10 spp., 2.9 × 10 spp, and 4.5 × 10 cells per gram of soil. spp. and spp. concentrations were 1 to 4 orders of magnitude lower at the other locations. showed lower dynamic range and was generally uniformly distributed across the landscape. Antibiotic and parasiticide concentrations in the FD were 86.9 ng g monensin, 25.0 ng g lasalocid, and 10.3 ng g doramectin. Their concentrations were 6- to 27-fold lower in the other feedlot locations. Contaminant management plans for this small feedlot will therefore focus on the feeder and nearby grazing areas where soil nutrients, bacteria populations, and veterinary pharmaceuticals were most concentrated.

Evaluation of eco-toxicological effects of the parasiticide moxidectin in comparison to ivermectin in 11 species of dung flies

A standardized bioassay previously developed with ivermectin for the yellow dung fly (Scathophagidae) and the face fly (Muscidae) was applied to test the response of 11 dung fly species to the presumably less toxic parasiticide moxidectin. The results were compared to existing data for the same species tested with ivermectin, albeit two new species (Scathophaga suilla and Musca domestica) were tested here with both the substances. Estimated lethal effect concentrations LC50 at which 50% of the flies died ranged more than tenfold from 0.012 mg moxidectin/kg fresh dung for Sepsis neocynipsea (Sepsidae) to 0.140 mg moxidectin/kg fresh dung for the house fly Musca domestica (Muscidae). In most of the species, we additionally revealed sub-lethal effects at lower moxidectin concentrations in terms of retarded growth and development and reduced body size. Mortality thresholds were about ten times higher for moxidectin than for ivermectin, hence moxidectin is indeed less toxic than ivermectin in absolute terms. Crucially, we obtained strong correlations among the 11 tested fly species in both lethal and sub-lethal responses to the two substances, such that species relatively sensitive to ivermectin were also relatively sensitive to moxidectin. Such correlations are expected if the two substances are structurally related and function in the same manner by disturbing ion channel transport. Methodologically speaking, all species used proved suitable for toxicological testing of parasiticides.

Occurrence of ectoparasiticides in Australian beef cattle feedlot wastes

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous analysis of 6 ectoparasiticides - 2 synthetic pyrethroids (deltamethrin, cypermethrin) and 4 macrocyclic lactones (abamectin, doramectin, ivermectin and eprinomectin) in biosolids. The method was used to investigate the occurrence of these ectoparasiticides in beef cattle feedlot wastes in Australia from 5 commercial feedlot operations which employ varying waste management practices. Deltamethrin and cypermethrin were not detected in any of the samples while abamectin, ivermectin, doramectin and eprinomectin were detected in some of the samples with concentrations ranging from 1 to 36 μg/kg dry weight (d.w.) freeze dried feedlot waste. Levels of macrocyclic lactones detected in the feedlot wastes varied and were dependent on sample type. The effect of seasonal variations and waste management practices were also investigated in this study.

Standardized laboratory tests with 21 species of temperate and tropical sepsid flies confirm their suitability as bioassays of pharmaceutical residues (ivermectin) in cattle dung

Veterinary pharmaceuticals excreted in the dung of treated livestock can have strong non-target effects on the dung organism community. We report results of ecotoxicological tests with ivermectin for 21 species of temperate (Europe, North America) and tropical (Asia, Central America) black scavenger flies (Diptera: Sepsidae), using standardized methods developed previously for the yellow dung fly and the face fly. Our study documents great variation in ivermectin sensitivity of more than two orders of magnitude among species and even populations within species: estimated lethal effect concentrations LC(50) (at which 50% of the flies died) ranged from 0.05 to 18.55 μg/kg dung fresh weight (equivalent to 0.33-132.22 μg/kg dung dry weight). We also show that controlled laboratory tests can--within reasonable limits-be extended to the field or to laboratory settings without climate control, as obtained LC(50) were roughly similar. In addition to lethal effects, our study revealed relevant sub-lethal effects at lower ivermectin concentrations in terms of prolonged development, smaller body size and reduced juvenile growth rate. Finally, oviposition choice experiments showed that females generally do not discriminate against dung containing ivermectin residues. We conclude that sepsid flies are well suited test organisms for pharmaceutical residues in the dung of livestock due to their ease and speed of rearing and handling, particularly in the tropics, where high-tech laboratory equipment is often not available.

Efficacy of cyromazine to control immature stable flies (Diptera: Muscidae) developing in winter hay feeding sites

Hay mixed with manure and urine residues at sites where hay has been provided as supplemental winter feed for cattle provide an excellent substrate for the development of immature stable flies, Stomoxys calcitrans (L.). Such sites are primary sources of early summer stable flies in the central United States and no effective measures are currently available to control fly development in them. A single application of granular cyromazine in May provided 97% reduction in the number of adult stable flies emerging from hay feeding sites. Stable fly control did not decline during the 12 wk season. A small decline in control was observed relative to anthomyiid, sarcophagid, and syrphid flies developing in the hay feeding sites. However, none of those flies are considered to be pests and > or = 50% control of those flies was maintained for 65 d after application. Cyromazine offers a safe and affordable option for the control of immature stable flies developing in winter hay feeding sites. Controlling those flies should reduce the estimated $2 billion per year of lost production in U.S. cattle industries attributable to stable flies.

Field effects of faecal residues from ivermectin slow-release boluses on the attractiveness of cattle dung to dung beetles

A 2-year study was performed in two sites in southern France to assess the effect of ivermectin residues on the attractiveness of cattle dung to colonizing insects. Insect captures were compared between pitfall traps baited with dung from untreated cattle and dung from cattle that had been treated with a slow-release (SR) bolus of ivermectin. Cattle dung was collected at different times after treatment (4, 14, 42, 70 and 98 days). Excretion showed a plateau, with levels ranging between 0.688 µg and 1.123 µg ivermectin per gram of wet dung. Faecal residues affected insect captures at both sites. Effects were independent of the time dung was collected after treatment, except for one result subsequent to a severe drought during the baiting period. Ivermectin-contaminated dung showed a significant attractive effect, with increased captures regardless of the guild to which beetles belonged. This study demonstrates the attractiveness of ivermectin residues over a long period after the treatment of animals. It draws attention to the danger of widespread use of this endectocide-based SR bolus, which is attributable to the preferential attraction of insects to treated dung, which potentially puts at risk the survival of their offspring.

Environmental monitoring of ivermectin excreted in spring climatic conditions by treated cattle on dung fauna and degradation of faeces on pasture

The effect of ivermectin excreted in faeces of cattle treated in late winter on the arthropods and the degradation of faeces on pasture were evaluated. Four calves of similar age and weight were allocated to two groups, one group was treated subcutaneously with ivermectin and the other group remained as untreated control. From faeces collected from both groups at 3, 7, 14, 21 and 28 days post-treatment (dpt), three faecal pats of 1 kg each were made and deposited on a mixed paddock. One quarter of each faecal pat was removed at 10, 20, 30 and 60 days postdeposition (dpd) to determine the concentration of ivermectin, the organic matter content, and to collect colonising dung arthropods. Concentrations at days 3 and 7 pt were significantly higher than at the other dpt (p<0.05). The highest ivermectin concentrations were found in samples from 3 dpt (p<0.05). The organic matter percentage was not significantly different between treatments. An edaphic fauna characterised the colonisation of the faeces by organisms. Although arthropods' abundance differences were not significant except for the 28 dpt at 30 dpd (p<0.0003), fewer organisms were collected from the ivermectin group at all times.

Environmental risk assessment of ivermectin: A case study

The veterinary parasiticide ivermectin was selected as a case study compound within the project ERAPharm (Environmental Risk Assessment of Pharmaceuticals). Based on experimental data generated within ERAPharm and additional literature data, an environmental risk assessment (ERA) was performed mainly according to international and European guidelines. For the environmental compartments surface water, sediment, and dung, a risk was indicated at all levels of the tiered assessment approach. Only for soil was no risk indicated after the lower tier assessment. However, the use of effects data from additional 2-species and multispecies studies resulted in a risk indication for collembolans. Although previously performed ERAs for ivermectin revealed no concern for the aquatic compartment, and transient effects on dung-insect populations were not considered as relevant, the present ERA clearly demonstrates unacceptable risks for all investigated environmental compartments and hence suggests the necessity of reassessing ivermectin-containing products. Based on this case study, several gaps in the existing guidelines for ERA of pharmaceuticals were shown and improvements have been suggested. The action limit at the start of the ERA, for example, is not protective for substances such as ivermectin when used on intensively reared animals. Furthermore, initial predicted environmental concentrations (PECs) of ivermectin in soil were estimated to be lower than refined PECs, indicating that the currently used tiered approach for exposure assessment is not appropriate for substances with potential for accumulation in soil. In addition, guidance is lacking for the assessment of effects at higher tiers of the ERA, e.g., for field studies or a tiered effects assessment in the dung compartment.

Effects of ivermectin-spiked cattle dung on a water-sediment system with the aquatic invertebrates Daphnia magna and Chironomus riparius

A two-species test using a water-sediment test system was performed to investigate chronic effects of the parasiticide ivermectin on Daphnia magna and Chironomus riparius. To simulate exposure by direct excretion of cattle into surface waters, ivermectin was applied via spiked cattle dung. The parasiticide was applied once, at concentrations ranging from 11 to 1314 microg kg(-1) dung dry weight. The highest concentration corresponds to the maximum concentration in dung 3 days after topical application to cattle. Test vessels were stocked with chironomid larvae and daphnids of defined, mixed age. Replicates were sampled 10, 24, 38 and 51 days post application. Survival, growth and emergence of chironomids, and abundance and biomass of daphnids were evaluated. In case of extinction of the D. magna population in all replicates of a concentration level, daphnids were re-introduced into the remaining vessels of this concentration to simulate immigration. In addition, a second batch of chironomid larvae was introduced into the vessels on day 27 post application. At 1314 microg ivermectin kg(-1) dung dry weight, survival, larval growth and emergence of the initially stocked chironomids were strongly affected. A significant effect on emergence was also observed for the second batch of chironomids. The two highest test concentrations led to 100% mortality of the initially stocked daphnids. At 1314 microg kg(-1) dung dry weight, no daphnids survived following re-introduction on days 11, 28 and 42. At 263 microg kg(-1) dung dry weight, the daphnids that were re-introduced on day 11 survived and reproduced, but abundance and biomass were reduced. The results of the present study indicate that following single application, toxic ivermectin concentrations persisted for an extended period. Possible effects on aquatic invertebrates, which may be caused by direct excretion of ivermectin-containing dung into surface water, deserve further attention.

Veterinary medicines and the environment

Veterinary medicines may be emitted either directly or indirectly into the environment, following its use. As veterinary medicines are biologically active compounds, there is a concern that their occurrence in the environment may have an adverse impact on aquatic and terrestrial organisms. This chapter reviews the major sources by which veterinary medicines enter the environment, the fate, behaviour and occurrence of veterinary medicines in the environment and the potential effects on environmental and human health. Finally, gaps in the current knowledge are identified and recommendations provided on priorities for future research.

Effects of faecal residues of moxidectin and doramectin on the activity of arthropods in cattle dung

Dung invertebrate colonization and degradation levels of faeces from cattle treated with endectocides were studied. Faeces of control and doramectin (DRM) (subcutaneous) and moxidectin (MXD) (subcutaneous and topical) treated animals were deposited on the field from 3 to 21 days post-treatment (pt). Pats were recovered after 6 to 42 days post-deposition (pd). Faecal weight, dry matter, arthropods number, and drugs concentrations were determined. Total arthropods number was higher in control (P<0.0001) than in the other groups from days 3 to 21 pt. Total number of insects recovered on days 3, 11, and 21 pt from control pats was significantly (P<0.001) higher than in treated-animal pats during all the trial. At day 21 pt, the insects' number in dung voided by DRM-treated cattle was (P<0.05) lower than in the other groups. Comparisons of dung degradation among treatments were inconclusive. A lower adverse effect was observed for MXD compared with DRM. No significant degradation of MXD or DRM was observed during the present trial.

Seasonal abundance and reproductive output of the dung flies Neomyia cornicina and N. viridescens (Diptera: Muscidae)

The seasonal abundance and reproductive output of two common, but little studied, dung-breeding flies, Neomyia cornicina and N. viridescens, were examined in artificial cow pats in pastures in southwest England in 2001 and 2004. In 2001, the numbers of both Neomyia species increased slowly over summer to show a sharp seasonal peak in late August and early September. There was no significant effect of mean temperature, mean relative humidity or dung water content on abundance or seasonally de-trended abundance. High levels of aggregation were seen between pats and, when present, greater numbers of N. cornicina emerged than N. viridescens. Neomyia cornicina was present in 13% of 240 artificial standardized pats put out in 2001, at a median of 19 adults per colonized pat; N. viridescens was present in 8% of artificial pats at a median of three adults per colonized pat. In 2004, N. cornicina emerged from 46% of the 94 artificial pats put out at a median of three adults per colonized pat, while N. viridescens emerged from only 12% of pats at a median of one adult per colonized pat. Flies were also collected in 2004, using sticky-traps and hand nets. Again, free-flying N. cornicina appeared to be more abundant in the field than N. viridescens; 162 N. cornicina were caught compared to 44 N. viridescens over the same sampling period. The size of each adult female was recorded and ovarian dissection was used to determine the numbers of eggs matured. Female N. viridescens were significantly larger than the N. cornicina and matured significantly higher numbers of eggs. Gravid N. viridescens matured a mean of 37.1 (+/-16.9) eggs, whereas gravid N. cornicina matured a mean of 28.8 (+/-13.2) eggs. The reasons why the larger, more fecund, N. viridescens adults are less abundant in the field or emerging from pats than N. cornicina are unknown. Further work is required to identify the nature and cause of the mortality experienced by the larvae of these species and the ecological differences and functional specialisation which allows co-existence to be maintained.

Ivermectin as a rodent feed-through insecticide for control of immature sand flies (Diptera: Psychodidae)

Ivermectin was evaluated as a potential rodent feed-through for the control of immature stages of Phlebotomus papatasi. The survival of sand fly larvae fed feces of Syrian hamsters (Mesocricetus auratus) that had been fed a diet containing 0, 2, 6, 10, 20, 60, or 100 ppm ivermectin was measured. Sand fly larvae fed the feces of ivermectin-treated hamsters had significantly reduced survival, with 100% mortality of larvae fed feces of hamsters fed a diet containing 20, 60, and 100 ppm ivermectin. The results of this study suggest that a control strategy using rodent baits containing ivermectin to control phlebotomine sand flies may be possible. Because rodent reservoirs and sand fly vectors of Leishmania major live in close association in many parts of the Middle East, the control of transmission of the agent of zoonotic cutaneous leishmaniasis also may be possible.

Toxicity of abamectin and doramectin to soil invertebrates

This study aimed at determining the toxicity of avermectins to soil invertebrates in soil and in faeces from recently treated sheep. Abamectin was more toxic than doramectin. In soil, earthworms (Eisenia andrei) were most affected with LC50s of 18 and 228 mg/kg dry soil, respectively, while LC50s were 67-111 and >300 mg/kg for springtails (Folsomia candida), isopods (Porcellio scaber) and enchytraeids (Enchytraeus crypticus). EC50s for the effect on reproduction of springtails and enchytraeids were 13 and 38 mg/kg, respectively for abamectin, and 42 and 170 mg/kg for doramectin. For earthworms, NOEC was 10 and 8.4 mg/kg for abamectin and doramectin effects on body weight. When exposed in faeces, springtails and enchytraeids gave LC50s and EC50s of 1.0-1.4 and 0.94-1.1 mg/kg dry faeces for abamectin and 2.2->2.4 mg/kg for doramectin. Earthworm reproduction was not affected. This study indicates a potential risk of avermectins for soil invertebrates colonizing faeces from recently treated sheep.

Adverse effects of ivermectin on the dung beetles, Caccobius jessoensis Harold, and rare species, Copris ochus Motschulsky and Copris acutidens Motschulsky (Coleoptera: Scarabaeidae), in Japan

Effects of the antiparasitic drug, ivermectin, on the dung beetles, Caccobius jessoensis Harold, 1867 and the rare species, Copris ochus Motschulsky, 1860 and Copris acutidens Motschulsky, 1860 were studied in laboratory and field experiments in Hokkaido, Japan. Ivermectin was detected in dung from 1 to 21 or 28 days following treatment, with a peak on the first day after treatment in two pour-on administrations (500 microg kg(-1)), although there were considerable differences between the two peaks. In C. jessoensis, brood balls constructed by the female were not reduced in the dung of treated cattle except for seven days after treatment in experiment 2. Also, there was no significant difference in the mean weight of brood balls between dung from treated and control cattle. However, the emergence rates were significantly reduced in dung 1-3 days after treatment. In the field study, brood balls constructed by C. jessoensis were more abundant in dung from treated cattle in experiment 1, but adult emergence was significantly reduced at one and seven days after treatments. Adult mortality of C. ochus Motschulsky at 90 days after the beginning of rearing was 11.1% in dung from control cattle with 22 brood balls constructed, whereas it was 84% in dung from treated cattle with no brood balls and/or ovipositioning. Also, in C. acutidens Motschulsky, adult mortality at 90 days after the beginning of rearing was 3.6% in dung from control cattle with 13 brood balls constructed, whereas it was 94.1% in dung from treated cattle with no brood balls or ovipositioning. The environmental risk in the use of ivermectin during breeding period of dung beetles in pasture is discussed.

A screening level index for assessing the impacts of veterinary medicines on dung flies

Veterinary parasiticides are administered to livestock to control a wide range of parasites. Following excretion, these substances may persist in the environment and impact nontarget organisms. This paper describes a simple screening-based index for predicting the effects of veterinary parasiticides on dung flies using data on parasiticide toxicity, animal husbandry, and parasiticide use. The utility of the index has been assessed, at the farm scale for a number of dipteran species, using data from a survey of farms in England and insect ecology and ecotoxicological data. The results indicate that a large proportion (35%) of parasiticide treatments in England will have no impact on dung fly populations. In terms of individual parasiticides, the macrocyclic lactone doramectin was predicted to have the highest impact on English dipteran populations with a maximum reduction in the population of horn flies on one farm of 28%. Ivermectin pour-on had the next highest impact (6.8%), followed by eprinomectin (6.4%), and ivermectin injection (4.1%). Due to a lack of data, it was not possible to assess the effects of the benzimidazole parasiticides (oxfendazole and fenbendazole), morantel and permethrin. The approach is simple, nondata-intensive and has the potential to be a valuable tool for use in environmental risk assessment or management of new and existing veterinary parasiticides.

Pasture and grazing land: assessment of sustainability using invertebrate bioindicators

Impacts of practices frequently used to manage Australian pastures are reviewed with the aim of determining which groups are responsive to changes in grazing regime, fertiliser use, pasture types, tree clearing, pesticide use, liming and irrigation. Invertebrate groups sensitive to pasture management regimes may be potential candidates for use as bioindicators of ecological sustainability of these pasture types. This review concentrates on the more intensively utilised temperate pastures of southern Australia, as very little work has been done on the impact of the grazing animal and pasture management on invertebrate fauna on the extensive rangelands of the arid and semiarid zones. Background to the relative importance of invertebrates in the functioning of the pasture ecosystem is given. This has culminated in the construction of food webs for two temperate perennial pastures (an unfertilised, native and a fertilised, sown pasture) at Armidale, NSW, for which there is comprehensive data available. Invertebrate bioindicators of pasture sustainability emerged from the consideration of grazing lands and invertebrate responses. Currently, only four groups would seem to be likely candidates as bioindicators of sustainability of pastures. These are soil nematodes, earthworms, protozoa and Collembola. The main difficulty in monitoring these groups is that it requires specialist expertise, and services provided by commercial laboratories for routine biological soil tests are still in their infancy. There are gaps in our knowledge of how invertebrate fauna react to the pressing issues of soil acidity and salinity.

New screening test to predict the potential impact of ivermectin-contaminated cattle dung on dung beetles

According to European Union recommendations, a test method has been developed to evaluate the effects of veterinary pharmaceuticals on dung feeding insects. This test method was evaluated with the dung beetle Aphodius constans by using fecal residues of ivermectin after a pour-on administration. Dung of different age (and thus containing different concentrations of ivermectin) as well as mixtures of highly-contaminated spiked dung with untreated control dung were studied in five test runs in two laboratories. The concentration of ivermectin (active substance; a.s.) in the dung samples was verified analytically. The main test endpoint was the survival of first instar larvae. The LC50 using dung directly obtained from treated cattle ranged from 470 to 692 microg a.s. kg(-1) dung (dry weight; d.w.) and 67 to 97 microg a.s. kg(-1) dung (fresh weight; f.w.). Using mixtures, the outcome of two tests was almost identical: 770 to 781 microg a.s. kg(-1) dung (d.w.); 109 to 132 microg a.s. kg(-1) dung (f.w.). In comparison to the LC50 values obtained when ivermectin was spiked in control dung at several concentrations (LC50 880-985 microg a.s. kg(-1) dung (d.w.)), the LC50 values were again very similar. Three conclusions can be drawn from these results. The proposed test method seems to be robust and allows for the initiation of an international validation process (including ringtesting). Because of only small differences found in tests in which the test substance was spiked into control dung and those in which dung from treated cattle was applied, the use of a standard test method is proposed. The effects of ivermectin on ecologically relevant dung beetles obtained in a standardised test method reflect the results from field studies and are in the range of environmentally relevant concentrations.

Environmental impact of ivermectin excreted by cattle treated in autumn on dung fauna and degradation of faeces on pasture

The effect of ivermectin excreted in faeces of treated cattle on dung fauna and dung degradation on pasture during autumn was evaluated. Two groups of calves were used. One group was treated subcutaneously with ivermectin while the other remained as untreated control. Faeces deposited on 1, 3, 7, 14 and 21 days post-treatment (dpt) were removed on 1, 3, 7, 14, 21, 30 and 60 days post-deposition (dpd) and were used to determine the concentration of ivermectin and the percentage of organic matter and for the collection of colonising organisms. Samples from 1 and 3 dpt contained the highest drug concentration and percentage of organic matter compared to the control group (p<0.05). Faeces from the treated group showed lesser abundance and diversity of arthropods (p<0.05) than the control group. A reduction in numbers and diversity of dung fauna in faecal samples from treated animals was most remarkable at 1, 3 and 7 dpt, coinciding with the highest concentration of ivermectin and organic matter percentage.

Cow-dung colonization and decomposition following insect exclusion

The rate of dung-pat degradation in cattle pastures in south west England was examined between May and September 2002, using batches of standardized, 1.5 kg, artificially-formed cow pats. In pats in which insects were allowed free access, the rate of disappearance, measured as ash-free dry weight, was faster in spring than summer and the loss of organic matter ranged between 0.69 and 1.99% per day, equating to an estimated time for complete disappearance of 57-78 and 88-111 days in spring and summer, respectively. To assess the role of colonizing insects on decomposition, six batches of pats were constructed and either left uncovered or, using fine mesh cages, were covered for 2, 7 or 14 days following deposition to exclude colonizing insects, after which they were uncovered. After 35 days all pats were then retrieved from the field, the composition of the invertebrate community within each pat was determined and the degree of degradation, measured as ash-free dry weight, was assessed. Covered pats had significantly higher rates of ash-free dry weight loss than uncovered pats. From the 180 pats that were recovered and searched, larvae of Aphodius (Coleoptera: Scarabaeidae) were the most numerous taxon collected (1435 individuals). Aphodius larvae were significantly more abundant in pats that remained uncovered or were covered for 2 days only, compared to pats that had been covered for 7 or 14 days. The results show that the exclusion of insects for as little as two days following deposition causes a significant reduction in both the insect population and the subsequent rate of pat degradation.

Insecticidal activity of synthetic pyrethroids, organophosphates, insect growth regulators, and other livestock parasiticides: an Australian perspective

The present review is restricted to the collation and evaluation of information describing the excretion profile and ecotoxicity of veterinary medicines developed specifically for the control of either internal or external parasites of livestock. It identifies numerous gaps in our knowledge and highlights our poor understanding of the environmental fate of many of these chemicals, especially those developed for the control of ticks, lice, and/or biting flies. Residues of most anthelmintics are largely harmless to dung-feeding arthropods, but those of many ectoparasiticides, especially the synthetic pyrethroids, are highly toxic to fly larvae and adult dung beetles. Organophosphates, because they are metabolized extensively and eliminated mostly in urine, are considered to be unlikely to have a major impact on the development or survival of dung-dwelling organisms. The present review stresses the need for better information regarding spatial and temporal usage patterns of veterinary parasiticides, and it examines the role of ecotoxicological models for evaluating their impact on populations of dung-dependent arthropods.

Quantification of dung carbon incorporation in a temperate grassland soil following spring application using bulk stable carbon isotope determinations

Herbivore dung constitutes a substantial input of C to temperate grassland soils, and its fate must be determined in order to fully understand nutrient cycling in this ecosystem. This experiment used changes in bulk delta13C values of the 0-1 cm and 1-5 cm soil horizons of a dung-treated temperate grassland soil to approximate percentage applied dung C incorporation over 372 days. Natural abundance 13C-labelled C4 dung (delta13C - 12.6%) and C3 dung (delta13C - 31.3% were produced in a monitored diet switch from ryegrass silage (delta13C - 30.1%) to maize silage (delta13C - 11.6%). The dung was applied to a C3 grassland (delta13C 0-1 cm - 29.9%, 1-5 cm - 30.6%), and dung remains and soil cores from beneath the treatments were sampled at intervals. delta13C values were used to estimate a maximum of 12% applied dung C incorporation in the top 5 cm of the soil after 112 days, which declined to around 8% at the end of the experiment. A significant increase in percentage applied dung C was observed in the top 1 cm of soil, compared with the 1-5 cm horizon, after a substantial rain event after 30 days. However, results of forage fibre analyses of the two dung types revealed significant differences in composition which may affect subsequent calculations of percentage dung incorporation based on bulk delta13C values.

Effect of the antiparasitic drugs fenbendazole and ivermectin on the soil nematode Pristionchus maupasi

Pristionchus maupasi, a soil nematode, was used to elucidate the potential ecotoxic effect of the two anthelmintics fenbendazole and ivermectin in cattle dung. The population growth of P. maupasi was greater in faeces from cattle harbouring active Panacur- or Ivomec-boli, which are releasing fenbendazole and ivermectin to the rumen, respectively, compared to the growth in control faeces. In dose-response experiments it could be shown that the pure chemical compound of fenbendazole was increasingly nematocidal to P. maupasi in concentrations from 10 to 20 microg/g faeces (ww, i.e. wet weight) and the pure compound of ivermectin was effective above 3 microg/g faeces (ww). The results indicate that neither fenbendazole nor ivermectin have any acute toxic effect on P. maupasi in naturally excreted concentrations of the pure drugs, together with their metabolites in faeces from bolus-treated cattle. Both drugs are excreted in concentrations that are non-toxic to P. maupasi.

Fecal residues of veterinary parasiticides: nontarget effects in the pasture environment

Residues of veterinary parasiticides in dung of treated livestock have nontarget effects on dung-breeding insects and dung degradation. Here, we review the nature and extent of these effects, examine the potential risks associated with different classes of chemicals, and describe how greater awareness of these nontarget effects has resulted in regulatory changes in the registration of veterinary products.