Dung beetles and fecal helminth transmission: patterns, mechanisms and questions

First molecular identification of Haemonchus contortus (Nematoda: Trichostrongylidae), a blood-sucking gastric nematode of artiodactyles, in the ground beetle Carabus granulatus (Coleoptera: Carabidae)

Among gastrointestinal nematodes, Haemonchus contortus (Rudolphi) Cobb (order Strongylidae; family Trichostrongylidae) is one of pathogenic and economic importance in domestic and wild ruminants, including the European bison, Bison bonasus Linnaeus (order Cetartiodactyla; family Bovidae); a species on the International Union for Conservation of Nature's Red List of Threatened Species. Carabus granulatus Linnaeus (order Coleoptera; family Carabidae) is one of the most prevalent species of ground beetle, inhabiting a wide range of terrestrial ecosystems in Poland. Twenty-six ground beetles of this species inhabiting the Białowieża Primeval Forest in eastern Poland were screened for the presence of DNA of pathogenic gastrointestinal nematodes of ruminants. Extracted DNA was sequenced and compared to reference sequences. In six insects, the presence of H. contortus DNA was detected. The obtained nucleotide sequences were homologous to each other and to the majority of the published DNA sequences of H. contortus isolates. The sequences were also identical to a sequence of H. contortus isolated from European bison in Poland. The study provides the first molecular evidence of the presence of H. contortus DNA in C. granulatus. The finding suggests that ground beetles may play a role in the transmission dynamics of this parasite.

Hepatobiliary Ascariasis in a Piglet

PURPOSE

Ascariasis caused by the helminth Ascaris suum is the most common parasitosis of swine worldwide and it may involve all age categories of pigs. The present study reports an unusual localization of A. suum worms in the biliary system of a piglet slaughtered for human consumption.

METHODS

The liver was subjected to ultrasound scan and pathological examination. The isolated worms were morphologically examined and the DNA was extracted for the molecular identification of the species involved.

RESULTS

A total of 43 preadult nematodes were found within the gallbladder and the bile ducts. Parasites were morphologically identified as belonging to the genus Ascaris and molecularly as A. suum. At gross examination, the liver was moderately enlarged, with the bile ducts severely dilated. A chronic inflammatory infiltrate was noted, often centered around ectatic bile ducts (up to 5 mm in diameter), lined by hyperplastic epithelium and filled with sections of nematodes. The worm sections showed smooth cuticle, coelomyarian musculature, and an intestinal tract lined by columnar, uninucleated cells within a pseudocoelom. The ex vivo ultrasonographic examination of the liver allowed the visualization of several nematodes in the bile duct lumen and could be suggested for in vivo diagnosis. Unfortunately, the absence of the intestine did not allow to define the pathogenesis of the infection.

CONCLUSION

Although, given the unusual nature of this finding, it is difficult to identify predisposing factors for this A. suum localization, it suggests that ascariasis should be considered in the differential diagnosis of pigs with hepatobiliary disease.

Spatio-temporal modelling suggests that some dung beetle species (Coleoptera: Geotrupidae) may respond to global warming by boosting dung removal

In the current framework of changes to the global climate, information on the thermal tolerance of dung beetles is crucial to understand how they might cope with increases in land temperature in terms of survival and ecosystem service provision. In this spatio-temporal modelling study, we investigated the thermal tolerance and effect of temperature changes on dung removal by three dung beetle species (Coleoptera: Geotrupidae) living within the 600-1400 m altitudinal belt in the Italian Alps. We chose large tunneler beetles because of their pivotal role in dung removal and nutrient recycling, important ecosystem services for maintaining the viability and profitability of the Alpine pastoral system. Our study used experimental data on dung removal at different temperatures to predict changes to this ecosystem service in the future considering different climatic scenarios and changes in land use for the specific study area. The results show that the temperature increases incurred between 1981 and 2005 may have boosted rates of spring dung removal across the entire study area (expressed as average dung removal per pair per month), partially compensating for the reduction in grassland extent within pasture-based livestock farming systems. Despite the limitations related to modelling future climate change scenarios and uncertainties deriving from several interacting factors (e.g., the sensitivity of large-bodied species to land-use changes), our results suggest that the predicted increases in temperature over the next 80 years would continue to boost dung removal, revealing a resilience of this service. The increase in dung removal rates, for all three species, is mainly related to the most extreme scenario of carbon emissions and for the months spanning from May to October of the interval 2041-2100. Focusing on large tunnelers and adopting a dynamic approach that considers changes in dung removal over space and time can assist ecosystem service conservation planning.

Macroecology of Dung Beetles in Italy

The Italian fauna includes about 170 species/subspecies of dung beetles, being one of the richest in Europe. We used data on dung beetle distribution in the Italian regions to investigate some macroecological patterns. Specifically, we tested if species richness decreased southward (peninsula effect) or northward (latitudinal gradient). We also considered the effects of area (i.e., the species-area relationship), topographic complexity, and climate in explaining dung beetle richness. Finally, we used multivariate techniques to identify biotic relationships between regions. We found no support for the peninsula effect, whereas scarabaeines followed a latitudinal gradient, thus supporting a possible role of southern areas as Pleistocene refuges for this group of mainly thermophilic beetles. By contrast, aphodiines were more associated with cold and humid climates and do not show a distinct latitudinal pattern. In general, species richness was influenced by area, with the Sardinian fauna being however strongly impoverished because of its isolation. Faunal patterns for mainland regions reflect the influence of current ecological settings and historical factors (Pleistocene glaciations) in determining species distributions.

MOLECULAR IDENTIFICATION OF INSECT INTERMEDIATE HOSTS WITH POTENTIAL PARASITE TRANSMISSION TO THE DEFINITIVE HOST NORTHERN BOBWHITE (COLINUS VIRGINIANUS)

Grassland birds have been declining substantially for the past several years. Habitat loss, degradation, and fragmentation as well as climate change are all thought to be the main drivers of the decline. However, as the declines continue to accelerate, it is becoming imperative to examine other factors that may contribute to population fluctuations. The nematodes Oxyspirura petrowi, Aulonocephalus pennula, and Physaloptera sp. are commonly found infecting northern bobwhite (Colinus virginianus), a game species of economic importance, and all 3 nematodes use insects as an intermediate host. Here we used polymerase chain reaction techniques to determine the occurrence of the 3 nematodes in 7 insect orders to uncover epidemiological patterns of the greatest potential for transmission to northern bobwhite. Insects were collected from March through September using sweep nets and pitfall traps. An R × C chi-squared test with Monte Carlo simulation was used to determine differences in the occurrence of the parasites across taxa and time. The results of the statistical analysis showed the nematodes are predominantly found in the order Orthoptera, and A. pennula and Physaloptera sp. showed epidemiological patterns in insects. However, no such pattern was observed with O. petrowi. An explanation for the lack of epidemiological pattern in O. petrowi is proposed and the diversity of known insect hosts of the 3 nematodes is increased.

Larvae of Spirocerca lupi and another spirurid species in the same dung beetles: notes on species identification

Various dung beetle species of the family Scarabaeidae have been reported as intermediate hosts of Spirocerca lupi from different geographical locations, but there has been no data from south-east Asian countries. In the present study in Vietnam, by using morphological and molecular approaches, we identified the third-stage larvae of S. lupi for the first time in two dung beetle species, Catharsius molossus and Copris szechouanicus, adding them as new intermediate hosts of this nematode. In addition, both beetle species were infected with larvae of another spirurid nematode of Physocephalus sp. At large magnifications above 200×, these two spirurid larvae can be differentiated from each other by their body size (1880-2662 vs. 1417-1635 μm) and detailed morphological features of the anterior and posterior ends, such as the length of the buccal cavity, the position of the nerve ring and excretory pore, and tail characters. However, it is difficult to distinguish them at a lower magnification due to their minute size. Moreover, morphometric data of S. lupi larvae vary among reports and the body length may overlap with that of Physocephalus sp., thus, misidentification may occur, indicating the necessity of careful examination for accurate identification. The findings of the present study also supposed that larvae of S. lupi and more spirurid nematodes may be concurrently found in various dung beetle species, including C. molossus and C. szechouanicus, in other south-east Asian countries. Thus, more investigations in various countries should be conducted to identify spirurid larvae from dung beetles in order to fully understand their role as intermediate hosts of S. lupi and other spirurid nematodes.

A trait-based framework for dung beetle functional ecology

Traits are key for understanding the environmental responses and ecological roles of organisms. Trait approaches to functional ecology are well established for plants, whereas consistent frameworks for animal groups are less developed. Here we suggest a framework for the study of the functional ecology of animals from a trait-based response-effect approach, using dung beetles as model system. Dung beetles are a key group of decomposers that are important for many ecosystem processes. The lack of a trait-based framework tailored to this group has limited the use of traits in dung beetle functional ecology. We review which dung beetle traits respond to the environment and affect ecosystem processes, covering the wide range of spatial, temporal and biological scales at which they are involved. Dung beetles show trait-based responses to variation in temperature, water, soil properties, trophic resources, light, vegetation structure, competition, predation and parasitism. Dung beetles' influence on ecosystem processes includes trait-mediated effects on nutrient cycling, bioturbation, plant growth, seed dispersal, other dung-based organisms and parasite transmission, as well as some cases of pollination and predation. We identify 66 dung beetle traits that are either response or effect traits, or both, pertaining to six main categories: morphology, feeding, reproduction, physiology, activity and movement. Several traits pertain to more than one category, in particular dung relocation behaviour during nesting or feeding. We also identify 136 trait-response and 77 trait-effect relationships in dung beetles. No response to environmental stressors nor effect over ecological processes were related with traits of a single category. This highlights the interrelationship between the traits shaping body-plans, the multi-functionality of traits, and their role linking responses to the environment and effects on the ecosystem. Despite current developments in dung beetle functional ecology, many knowledge gaps remain, and there are biases towards certain traits, functions, taxonomic groups and regions. Our framework provides the foundations for the thorough development of trait-based dung beetle ecology. It also serves as an example framework for other taxa.

Gastrointestinal parasites in red-legged partridges (Alectoris rufa) hunted in Spain: a warning to game managers

Red-legged partridge (Alectoris rufa) populations are currently declining in the Iberian Peninsula, mainly due to habitat degradation and hunting pressure. In addition, the release of farm-reared partridges may introduce pathogens, including parasites, to wild populations. The presence of digestive parasites in red-legged partridges hunted in fifteen Spanish provinces was studied. Fecal samples and gastrointestinal tracts were collected, analyzed, and the morphometric identification of parasites was carried out. Eimeria spp. oocysts, nematode, cestode and trematode eggs were observed in fecal samples. Adult nematodes (Ascaridia galli, Ascaridia compar, Heterakis gallinarum, Heterakis tenuicauda, Trichostrongylus tenuis, Subulura spp., Cyrnea spp. and Aonchotheca caudinflata), tapeworms (Raillietina tetragona, R. echinobothrida, R. micracantha, Rhabdometra nigropunctata, and Choanotaenia infundibulum), and trematodes (Brachylaima spp., Brachylecithum spp., Dicrocoelium spp.) were identified in the gastrointestinal tracts. Significant statistical differences were found among climatic regions in the prevalence and intensity of Eimeria spp. infection, median intensity and the prevalence of indirect life cycle helminths, with Southern areas always showing higher infection values. The study provides information of the health status of red-legged partridges in Spain, highlighting the risk associated with the release of farm-reared partridges for restocking purposes. This should be taken into account to improve management strategies for the long-term conservation of the species.

Vertebrates as uninfected disseminators of helminth eggs and larvae

The passive dispersal of non-mobile organisms by vertebrates (zoochory) is a common mechanism used to explain their often widespread distribution. Transport occurs either internally via the vertebrate digestive tract (endozoochory), or externally be adhering to skin, feathers or fur (ectozoochory), and its success is due to both physiological and ecological factors associated with the disseminating 'hosting' animal. Helminth eggs and larvae are generally non-mobile stages that are largely dependent on the movement of another animal, typically a host, for geographical dissemination. Studies on the zoochory of helminths by vertebrates are extensive and particularly long-standing, stretching back to the 19th century, although this literature is often overlooked when considering the biogeography of parasites. This review assesses the potential of helminths to be dispersed passively by zoochory examining evidence from both laboratory and field studies. The physiological dynamics of the vertebrate intestines and skin surface as hostile environments, as well as the characteristics of eggs and larvae which may facilitate successful transport are evaluated. The various mechanisms of helminth endo- and ectozoochory are presented and the likelihood of long-distance dispersal determined. It is concluded that zoochory is a potentially important means of disseminating parasites.

Dung beetle community composition affects dung turnover in subtropical US grasslands

An important service in many ecosystems is the turnover and degradation of dung deposited by cattle. Dung beetles are the primary group of insects responsible for dung turnover, and factors affecting their abundance and distribution thus impact dung degradation. Lands lost to grazing due to dung buildup and pasture contamination total millions of acres per year in US pastures.We evaluated the structural differences in dung beetle assemblages in natural grasslands versus a managed agroecosystem in subtropical southeastern Florida (USA). We measured the direct effect of dung longevity when dung beetle fauna normally inhabiting dung pats were excluded.Our results indicate dung beetle abundance, functional diversity, and species richness have a substantial impact on the rate of dung turnover in subtropical pastoral lands with ~70% of dung removed from the soil surface after three months. Functional diversity and evenness did not have a significant positive effect on dung removal in managed, versus natural grasslands demonstrating a strong relationship between dung beetle assemblage composition and delivery of a key ecological process, dung degradation.We suggest the importance of trees, which provide a thermal refuge for beetles, should be dispersed within matrixes of open pasture areas and within proximity to adjacent closed-canopy hammocks to facilitate the exchange of dung beetles between habitats and therefore maintain the provisioning of dung degradation services by dung beetle assemblages.

A Systematic Review of Zoonotic Enteric Parasites Carried by Flies, Cockroaches, and Dung Beetles

Filth flies, cockroaches, and dung beetles have been close neighbors with humans and animals throughout our joint histories. However, these insects can also serve as vectors for many zoonotic enteric parasites (ZEPs). Zoonoses by ZEPs remain a paramount public health threat due to our close contact with animals, combined with poor water, sanitation, and hygiene access, services, and behaviors in many global regions. Our objective in this systematic review was to determine which ZEPs have been documented in these vectors, to identify risk factors associated with their transmission, and to provide effectual One Health recommendations for curbing their spread. Using PRISMA guidelines, a total of 85 articles published from 1926 to 2021 were reviewed and included in this study. Qualitative analysis revealed that the most common parasites associated with these insects included, but were not limited to: Ascaris spp., Trichuris spp., Entamoeba spp., and Cryptosporidium spp. Additionally, prominent risk factors discovered in the review, such as poor household and community WASH services, unsafe food handling, and exposure to domestic animals and wildlife, significantly increase parasitic transmission and zoonoses. The risk of insect vector transmission in our shared environments makes it critically important to implement a One Health approach in reducing ZEP transmission.

A Review of Dung Beetle Introductions in the Antipodes and North America: Status, Opportunities, and Challenges

Following the introduction of cattle, exotic dung beetles (Coleoptera: Aphodiidae, Geotrupidae, Scarabaeidae) were imported into the Antipodes (Australia and New Zealand) and North America (primarily the United States) to accelerate the degradation of cattle dung on pastures. The history of dung beetle introductions between the two regions is similar but has not previously been assessed: this is important as new introductions are continuing in the regions. Here, we review these introduction programs, report on their current status, and discuss methodological advances. In doing so, we examine the accidental introduction of exotic (i.e., adventive) species and the contribution of both deliberately introduced and adventive species to endemic dung beetle faunas. Further, we provide a list of pest and parasite species whose populations can be reduced by dung beetle activity. We also identify a combined total of 37 introduced and 47 adventive dung beetle species that have become established in the Antipodes and North America, with exotic species dominating dung beetle assemblages from pasture habitats. Climatic and edaphic matches, the size of founding populations, abiotic and biotic stressors, and the time of year when releases are made are all critical determinants that affect the success of dung beetle introduction programs. Finally, we discuss opportunities, plus the risks and challenges associated with dung beetle introductions. We hope that this review will aid in the success of future introduction programs, either to enhance ecosystem services in areas that they are needed, or potentially to reestablish native species in regions where they have been extirpated.

First detection of Gongylonema species in Geotrupes mutator in Europe

The detection of three Gongylonema sp. infective larvae in two specimens of the dung beetle Geotrupes mutator (Marsham, 1802) from western Spain is reported here for the first time in Europe. Scanning electron microscopy confirmed that the analyzed specimens belong to the genus Gongylonema, but it was not possible to determine the species identity by the lack of morphological information in the literature and because many of the phenotypic characteristics had not yet fully developed at this juvenile stage. Nevertheless, a phylogenetic analysis using amplified cox1 nucleotide sequences has revealed that the studied larvae could be clearly discriminated (< 89% identity) from all the other Gongylonema cox1 sequences available in public genetic databases. While our results are limited by the scarcity of genetic information available for this genus, the possibility that the analyzed specimens might correspond to a new species should not be ruled out, and more studies are needed. The results provided in this report indicate that G. mutator is involved in the transmission cycle of Gongylonema sp. to vertebrates in Europe.

First report of Spirocerca lupi larva in dung beetles (Scarabaeus armeniacus) in the central region of Iran: A morphological and molecular identification

Dung beetles as detritivores insects, naturally use feces of vertebrates as foods and reproduction beds. This leads to frequent contacts between dung beetles and parasitic helminths. The current study was carried out to assess infections of dung beetles with larval stages of helminths in rural areas of Taleqan County, Alborz Province, Iran. A total number of 200 dung beetles were collected randomly in June 2017 from the highlands of Taleqan County. Beetles were dissected in normal saline and carefully studied using a stereomicroscope. Morphological characteristics of the recovered larvae were drawn using a camera lucida equipped microscope at 400× magnification. Then, genomic DNAs of the recovered larvae extracted and PCR amplifications of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene were carried out and the amplicons were sequenced. All collected dung beetles identified as Scarabaeus armeniacus from the Scarabaeidae family (55.5 % were male and 44.5 % female). Three females of the beetles have been found to be naturally infected with the third stage larvae of Spirocerca lupi. The average length and width of the larvae were 2.95 (2.81-3.15; CI 95 %) and 0.12 (0.1-0.15; CI 95 %) mm, respectively. The phylogenetic analysis showed that S. lupi belonged to a clade within the Spirocercidae family. In the current study, S. armeniacus introduced as a potential biological vector for transmission of S. lupi to vertebrates in the region. To the best of the authors' knowledge, this is the first report on the larval stages of S. lupi in S. armeniacus.

Insects dispersing taeniid eggs: Who and how?

Taeniosis/cysticercosis and echinococcosis are neglected zoonotic helminth infections with high disease burden caused by tapeworms which circulate between definitive and intermediate host reflecting a predator-prey interaction. Taeniid eggs can remain vital for months, allowing arthropods to mechanically transport them to intermediate hosts. However, the multiple routes that arthropods provide as carriers of taeniid eggs are still often unregarded or not considered. This review focuses on the prevalence and importance of arthropods as carriers and spreaders of taeniid eggs in the epidemiology of taeniosis/cysticercosis and echinococcosis. Current scientific knowledge showed a relevant role of houseflies (Muscidae), blowflies (Calliphoridae), dung beetles (Scarabaeoidea), darkling beetles (Tenebrionidae), ground beetles (Carabidae) and skin beetles (Dermestidae) in the spread of taeniid eggs in the environment, which may favor the infection of new hosts through the direct ingestion of an insect or of contaminated food and water. At last, key research challenges are highlighted, illustrating that further knowledge on the topic is needed to develop and improve guidelines and actions to prevent taeniid infections worldwide.

Biological methods for the control of gastrointestinal nematodes

Gastrointestinal nematodes (GIN) are a cause of significant losses in animal production worldwide. In recent years, there have been important advances in the biological control of GIN of ruminants and horses. While these measures are still relatively under-utilised in practice, interest will undoubtedly grow due to the emergence of drug resistant parasite populations, the rise in demand for organically farmed products (which does not allow prophylactic use of drugs, including anthelmintics) and legislation, which regulates and restricts the use of anthelmintics. This review provides an overview of the most promising biocontrol agents of GIN of grazing animals including nematophagous fungi, dung beetles, earthworms, predacious nematodes and nematophagous mites. Recent advancements in these fields are evaluated, and the potential reasons for the delayed development and slow uptake of biocontrol agents are discussed. It is now widely believed that no method of GIN control is sustainable alone, and a combination of strategies (i.e. integrated pest management) is required for long term, effective parasite control. This review shows that, although their efficacies are lower than those of conventional anthelmintics, biological control agents are an important adjunct to traditional GIN control.

Trade-Offs with Growth Limit Host Range in Complex Life-Cycle Helminths

AbstractParasitic worms with complex life cycles have several developmental stages, with each stage creating opportunities to infect additional host species. Using a data set for 973 species of trophically transmitted acanthocephalans, cestodes, and nematodes, we confirmed that worms with longer life cycles (i.e., more successive hosts) infect a greater diversity of host species and taxa (after controlling for study effort). Generalism at the stage level was highest for middle life stages, the second and third intermediate hosts of long life cycles. By simulating life cycles in real food webs, we found that middle stages had more potential host species to infect, suggesting that opportunity constrains generalism. However, parasites usually infected fewer host species than expected from simulated cycles, suggesting that generalism has costs. There was no trade-off in generalism from one stage to the next, but worms spent less time growing and developing in stages where they infected more taxonomically diverse hosts. Our results demonstrate that life-cycle complexity favors high generalism and that host use across life stages is determined by both ecological opportunity and life-history trade-offs.

Coprophagous Insects and the Ecology of Infectious Diseases of Wildlife

A diversity of macro- and microparasitic species exert strong influences on wildlife population density, community structure, and ecosystem functioning, all through their impacts on individual host fitness. Through consuming, manipulating, and relocating wildlife feces, over 7,000 species of coprophagous dung beetles interact with a staggering diversity of wildlife parasites with fecal-oral transmission in ways that both increase and decrease transmission. Here, we review the mechanisms by which dung beetles influence micro- and macroparasite transmission and outline a future research framework that integrates theory and empirical insights to advance our understanding of how these relationships may interact with ongoing environmental change drivers to further influence wildlife populations and community structure. Any organism that significantly influences parasite transmission will impact multiple levels of biological organization. Therefore, improving our understanding of the role of dung beetle interactions within disease ecology will be key to future efforts to understand the overall dynamics of infection in wildlife and how parasites contribute to the maintenance of ecosystem structure and function and evolutionary processes in wild animals.

Prevalence of Toxoplasma gondii and Potentially Zoonotic Helminths in Wild Boars (Sus scrofa) Hunted in Central Italy

Our aim was to evaluate the risk of human toxoplasmosis via meat consumption from wild boars by estimating the seroprevalence of Toxoplasma gondii in animals hunted in central Italy. Using a modified agglutination test, 213 sera from wild boars were examined for anti-Toxoplasma IgG antibodies. Diaphragm samples (n=65) from seropositive and seronegative animals were tested by nested-PCR to detect T. gondii DNA. Toxoplasma DNA from diaphragms was genotyped by PCR-RFLP using 12 genetic markers. Moreover, the aim of the study was also to identify helminth infections of wild boars in the selected area and to evaluate their hazard for humans. Examination of sera revealed a seroprevalence of 12.2%. Only one T. gondii strain could be genotyped from a seropositive animal and PCR-RFLP revealed that it belonged to type II. Analysis of 50 samples of faeces and 32 small intestines revealed that 78% and 15.6% of the samples harboured parasites, respectively, with the occurrence of parasites potentially dangerous for humans. These latter included Ascaris suum, Macracanthorhynchus hirudinaceus, Trichuris suis, and Metastrongylus spp. A significant association was found between coprological positivity and male sex. These results indicate that T. gondii infection may be present in wild boar tissues and consumption of undercooked or raw wild boar meat may expose humans to risk of toxoplasmosis in the study area. Furthermore, the study highlights that wild boars are hosts of helminths of veterinary and medical importance transmissible to pigs and humans.

Got Dung? Resource Selection by Dung Beetles in Neotropical Forest Fragments and Cattle Pastures

Both the impact of habitat modification on the food preferences of species and its impact on ecosystem functioning are poorly understood. In this study, we analyzed food selection by dung beetles in 80 tropical forest fragments and their adjacent cattle pastures in the Los Tuxtlas Biosphere Reserve, Mexico. Ten pitfall traps were placed at each site, half baited with human dung and the other half with fish carrion. We assessed dung beetle food selection and classified any specialization in resource use quantitatively using a multinomial classification model. We collected 15,445 beetles belonging to 42 species, 8747 beetles (38 species) in forest fragments and 6698 beetles (29 species) in cattle pastures. Twenty-five species were present in both habitats. Of all the beetles captured, 76% were caught in dung traps (11,727 individuals) and 24% in carrion traps (3718 individuals). We found 21 species of dung specialists, 7 carrion specialists, 8 generalists, and 6 species too rare to classify. The bait most frequently selected by beetles in this study was dung in both forests and pastures. Specialists tended to remain specialists in both habitats, while generalists tended to change their selection of bait type depending on the habitat. In summary, our results show that replacing forests with cattle pastures modifies the patterns of resource selection by dung beetles and this could affect ecosystem functioning.

Multitrophic diversity effects of network degradation

Predicting the functional consequences of biodiversity loss in realistic, multitrophic communities remains a challenge. No existing biodiversity–ecosystem function study to date has simultaneously incorporated information on species traits, network topology, and extinction across multiple trophic levels, while all three factors are independently understood as critical drivers of post‐extinction network structure and function. We fill this gap by comparing the functional consequences of simulated species loss both within (monotrophic) and across (bitrophic) trophic levels, in an ecological interaction network estimated from spatially explicit field data on tropical fecal detritus producer and consumers (mammals and dung beetles). We simulated trait‐ordered beetle and mammal extinction separately (monotrophic extinction) and the coextinction of beetles following mammal loss (bitrophic extinction), according to network structure. We also compared the diversity effects of bitrophic extinction models using a standard monotrophic function (the daily production or consumption of fecal detritus) and a unique bitrophic functional metric (the proportion of daily detritus production that is consumed). We found similar mono‐ and bitrophic diversity effects, regardless of which species traits were used to drive extinctions, yet divergent predictions when different measures of function were used. The inclusion of information on network structure had little apparent effect on the qualitative relationship between diversity and function. These results contribute to our growing understanding of the functional consequences of biodiversity from real systems and underscore the importance of species traits and realistic functional metrics to assessments of the ecosystem impacts of network degradation through species loss.

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.

Genetic identification of mammalian meal source in dung beetle gut contents

Coprophagous dung beetles are a numerically and functionally important group. Their obligatory use of mammalian dung has broad ecological implications, including providing economically and epidemiologically relevant ecosystem services. Beetle-mammal ecological networks are critically important in determining the resilience of dung beetle communities and the supply of beetle-mediated ecosystem functions. However, our understanding of dung beetle trophic networks remains incomplete. Here we report on a pilot study to evaluate the effectiveness of DNA-based analyses in identifying the source of dung beetle meals. Using beetles collected from dung piles of known provenance, we hypothesized that molecular analysis of gut content would correctly identify the mammal host, and that beetle body size would increase the odds of successful detection of mammalian DNA. We analyzed 90 specimens belonging to six beetle species. Most samples yielded mtDNA sequences from the expected mammalian species, suggesting that these methods can be an efficient tool for the investigation of dung beetle diet.

The Role of More Sensitive Helminth Diagnostics in Mass Drug Administration Campaigns: Elimination and Health Impacts

Diagnostics play a crucial role in determining treatment protocols and evaluating success of mass drug administration (MDA) programmes used to control soil-transmitted helminths (STHs). The current diagnostic, Kato-Katz, relies on inexpensive, reusable materials and can be used in the field, but only trained microscopists can read slides. This diagnostic always underestimates the true prevalence of infection, and the accuracy worsens as the true prevalence falls. We investigate how more sensitive diagnostics would impact on the management and life cycle of MDA programmes, including number of mass treatment rounds, health impact, number of unnecessary treatments and probability of elimination. We use an individual-based model of STH transmission within the current World Health Organization (WHO) treatment guidelines which records individual disability-adjusted life years (DALY) lost. We focus on Ascaris lumbricoides due to the availability of high-quality data on existing diagnostics. We show that the effect of improving the sensitivity of diagnostics is principally determined by the precontrol prevalence in the community. Communities at low true prevalence (<30%) and high true prevalence (>70%) do not benefit greatly from improved diagnostics. Communities with intermediate prevalence benefit greatly from increased chemotherapy application, both in terms of reduced DALY loss and increased probability of elimination. Our results suggest that programmes should be extended beyond school-age children, especially in high prevalence communities. Finally, we argue against using apparent or measured prevalence as an uncorrected proxy for true prevalence.

Big dung beetles dig deeper: trait-based consequences for faecal parasite transmission

Observational evidence suggests that burial of faeces by dung beetles negatively influences the transmission of directly transmitted gastrointestinal helminths. However, the mechanistic basis for these interactions is poorly characterised, limiting our ability to understand relationships between beetle community composition and helminth transmission. We demonstrate that beetle body size and sex significantly impact tunnel depth, a key variable affecting parasite survival. Additionally, high parasite loads reduce the depth of beetle faeces burial, suggesting that the local prevalence of parasites infecting beetles may impact beetle ecosystem function. Our study represents a first step towards a mechanistic understanding of a potentially epidemiologically relevant ecosystem function.

New insights in cysticercosis transmission

Taenia solium infection causes severe neurological disease in humans. Even though infection and exposure to swine cysticercosis is scattered throughout endemic villages, location of the tapeworm only explains some of the nearby infections and is not related to location of seropositive pigs. Other players might be involved in cysticercosis transmission. In this study we hypothesize that pigs that carry nematodes specific to dung beetles are associated with cysticercosis infection and/or exposure. We carried out a cross-sectional study of six villages in an endemic region in northern Peru. We euthanized all pigs (326) in the villages and performed necropsies to diagnose cysticercosis. For each pig, we counted cysticerci; measured anti-cysticercus antibodies; identified intestinal nematodes; tabulated distance to nearest human tapeworm infection; and recorded age, sex, productive stage, and geographic reference. For the purpose of this paper, we defined cysticercosis infection as the presence of at least one cysticercus in pig muscles, and cysticercosis exposure as seropositivity to anti-cysticercus antibodies with the presence of 0–5 cysticerci. Compared to pigs without nematode infections, those pigs infected with the nematode Ascarops strongylina were significantly associated with the presence of cysticerci (OR: 4.30, 95%CI: 1.83–10.09). Similarly, pigs infected with the nematode Physocephalus sexalatus were more likely to have cysticercosis exposure (OR: 2.21, 95%CI: 1.50–3.28). In conclusion, our results suggest that there appears to be a strong positive association between the presence of nematodes and both cysticercosis infection and exposure in pigs. The role of dung beetles in cysticercosis dynamics should be further investigated.

In endemic areas, pigs acquire cysticercosis when ingesting Taenia solium eggs that have been released into the environment in the feces of a person infected with T. solium. The present study has found evidence that players, such as dung beetles, might be involved in further dissemination of the parasite into the environment. Specifically, we found an association between helminths, for whom dung beetles act as an intermediate host, and porcine cysticercosis infection and exposure after adjusting for other porcine cysticercosis predictors such as distance to tapeworm carrier and age. Although the study does not evaluate dung beetles directly, parasites specific to dung beetles serve as a novel proxy to evidence the potential role of dung beetles in the epidemiology of cysticercosis. Therefore, it is important that further studies elucidate the role of other players in cysticercosis transmission in order to better explain the reemergence and persistence of cysticercosis after elimination and control efforts. In addition, vector populations could potentially be used as markers for cysticercosis in the communities.