Adverse effects of thiram-treated seed ingestion on the reproductive performance and the offspring immune function of the red-legged partridge

Thiram exposure: Disruption of the blood-testis barrier and altered apoptosis-autophagy dynamics in testicular cells via the Bcl-2/Bax and mTOR/Atg5/p62 pathways in mice

Thiram, a prevalent dithiocarbamate insecticide in agriculture, is widely employed as a crop insecticide and preservative. Chronic exposure to thiram has been linked to various irreversible damages, including tibial cartilage dysplasia, erythrocytotoxicity, renal issues, and immune system compromise. Limited research exists on its effects on reproductive organs. This study investigated the reproductive toxicology in mouse testes exposure to varying concentrations (0, 30, 60, and 120 mg/kg) of thiram. Our study uncovered a series of adverse effects in mice subjected to thiram exposure, including emaciation, stunted growth, decreased water intake, and postponed testicular maturation. Biochemical analysis in thiram-exposed mice showed elevated levels of LDH and AST, while ALP, TG, ALT, and urea were decreased. Histologically, thiram disrupted the testis' microarchitecture and compromised its barrier function by widening the gap between spermatogenic cells and promoting fibrosis. The expression of pro-apoptotic genes (Bax, APAF1, Cytc, and Caspase-3) was downregulated, whereas Bcl-2 expression increased in thiram-treated mice compared to controls. Conversely, the expression of Atg5 was upregulated, and mTOR and p62 expression decreased, with a trend towards lower LC3b levels. Thiram also disrupted the blood-testis barrier, significantly reducing the mRNA expression of zona occludens-1 (ZO-1) and occludin. In conclusion, chronic exposure to high thiram concentrations (120 mg/kg) caused testicular tissue damage, affecting the blood-testis barrier and modulating apoptosis and autophagy through the Bcl-2/Bax and mTOR/Atg5/p62 pathways. This study contributes to understanding the molecular basis of thiram-induced reproductive toxicity and underscores the need for further research and precautions for those chronically exposed to thiram and its environmental residuals.

Organic farming reduces pesticide load in a bird of prey

Human activities have led to the contamination of all environmental compartments worldwide, including bird species. In birds, both the environment and maternal transfer lead to high inter-brood variability in contamination levels of pollutants, whereas intra-brood variability is generally low. However, most existing studies focused on heavy metals or persistent compounds and none, to our knowledge, addressed the variability in contamination levels of multiple pesticides and the factors influencing it. In this study, the number of pesticides detected (of 104 compounds searched) and the sum of their concentrations in the blood of 55 Montagu's harrier (Circus pygargus) nestlings from 22 nests sampled in 2021 were used as metrics of contamination levels. We investigated the effect of organic farming at the size of male's home range (i.e., 14 km2) and chicks' sex and hatching order on contamination levels. We did not find a difference between inter-brood and intra-brood variability in pesticide contamination levels, suggesting a different exposure of siblings through food items. While chicks' sex or rank did not affect their contamination level, we found that the percentage of organic farming around the nests significantly decreased the number of pesticides detected, although it did not decrease the total concentrations. This finding highlights the potential role of organic farming in reducing the exposure of birds to a pesticide cocktail.

Molecular mechanism of thiram-induced abnormal chondrocyte proliferation via lncRNA MSTRG.74.1-BNIP3 axis

Thiram, a widely used organic pesticide in agriculture, exhibits both bactericidal and insecticidal effects. However, prolonged exposure to thiram has been linked to bone deformities and cartilage damage, contributing to the development of tibial dyschondroplasia (TD) in broilers and posing a significant threat to global agricultural production. TD, a prevalent nutritional metabolic disease, manifests as clinical symptoms like unstable standing, claudication, and sluggish movement in affected broilers. In recent years, there has been growing recognition of the regulatory role of long non-coding RNA (lncRNA) in tibial cartilage formation among broilers through diverse signaling pathways. This study employs in vitro experimental models, growth performance analysis, and clinical observation to assess broilers' susceptibility to thiram pollution. Transcriptome sequencing analysis revealed a significant elevation in the expression of lncRNA MSTRG.74.1 in both the con group and the thiram-induced in vitro group. The results showed that lncRNA MSTRG.74.1 plays a pivotal role in influencing the proliferation and abnormal differentiation of chondrocytes. This regulation occurs through the negative modulation of apoptotic genes, including Bax, Cytc, Bcl2, Apaf1, and Caspase3, along with genes Atg5, Beclin1, LC3b, and protein p62. Moreover, the overexpression of lncRNA MSTRG.74.1 was found to regulate broiler chondrocyte development by upregulating BNIP3. In summary, this research sheds light on thiram-induced abnormal chondrocyte proliferation in TD broilers, emphasizing the significant regulatory role of the lncRNA MSTRG.74.1-BNIP3 axis, which will contribute to our understanding of the molecular mechanisms underlying TD development in broilers exposed to thiram.

Wildlife ecological risk assessment in the 21st century: Promising technologies to assess toxicological effects

Despite advances in toxicity testing and the development of new approach methodologies (NAMs) for hazard assessment, the ecological risk assessment (ERA) framework for terrestrial wildlife (i.e., air-breathing amphibians, reptiles, birds, and mammals) has remained unchanged for decades. While survival, growth, and reproductive endpoints derived from whole-animal toxicity tests are central to hazard assessment, nonstandard measures of biological effects at multiple levels of biological organization (e.g., molecular, cellular, tissue, organ, organism, population, community, ecosystem) have the potential to enhance the relevance of prospective and retrospective wildlife ERAs. Other factors (e.g., indirect effects of contaminants on food supplies and infectious disease processes) are influenced by toxicants at individual, population, and community levels, and need to be factored into chemically based risk assessments to enhance the "eco" component of ERAs. Regulatory and logistical challenges often relegate such nonstandard endpoints and indirect effects to postregistration evaluations of pesticides and industrial chemicals and contaminated site evaluations. While NAMs are being developed, to date, their applications in ERAs focused on wildlife have been limited. No single magic tool or model will address all uncertainties in hazard assessment. Modernizing wildlife ERAs will likely entail combinations of laboratory- and field-derived data at multiple levels of biological organization, knowledge collection solutions (e.g., systematic review, adverse outcome pathway frameworks), and inferential methods that facilitate integrations and risk estimations focused on species, populations, interspecific extrapolations, and ecosystem services modeling, with less dependence on whole-animal data and simple hazard ratios. Integr Environ Assess Manag 2024;20:725-748. © 2023 His Majesty the King in Right of Canada and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Leucine improves thiram-induced tibial dyschondroplasia and gut microbiota dysbiosis in broilers

Thiram, a commonly used agricultural insecticide and fungicide, has been found to cause tibial dyschondroplasia (TD) in broilers, leading to substantial economic losses in the poultry industry. In this study, we aimed to investigate the mechanism of action of leucine in mitigating thiram-induced TD and leucine effects on gut microbial diversity. Broiler chickens were randomly divided into five equal groups: control group (standard diet), thiram-induced group (thiram 80 mg/kg from day 3 to day 7), and different concentrations of leucine groups (0.3%, 0.6%, 0.9% leucine from day 8 to day 18). Performance indicator analysis and tibial parameter analysis showed that leucine positively affected thiram-induced TD broilers. Additionally, mRNA expressions and protein levels of HIF-1α/VEGFA and Ihh/PTHrP genes were determined via quantitative real-time polymerase chain reaction and western blot. The results showed that leucine recovered lameness disorder by downregulating the expression of HIF-1α, VEGFA, and PTHrP while upregulating the expression of Ihh. Moreover, the 16 S rRNA sequencing revealed that the leucine group demonstrated a decrease in the abundance of harmful bacteria compared to the TD group, with an enrichment of beneficial bacteria responsible for producing short-chain fatty acids, including Alistipes, Paludicola, CHKCI002, Lactobacillus, and Erysipelatoclostridium. In summary, the current study suggests that leucine could improve the symptoms of thiram-induced TD and maintain gut microbiota homeostasis.

Thiram exposure induces tibial dyschondroplasia in broilers via the regulation effect of circ_003084/miR-130c-5p/BMPR1A crosstalk on chondrocyte proliferation and differentiation

Thiram, an agricultural insecticide, has been demonstrated to induce tibial dyschondroplasia (TD) in avian species. Circular RNA (circRNAs), a novel class of functional biological macromolecules characterized by their distinct circular structure, play crucial roles in various biological processes and diseases. Nevertheless, the precise regulatory mechanism underlying non-coding RNA involvement in thiram-induced broiler tibial chondrodysplasia remains elusive. In this study, we established a broiler model of thiram exposure for 10 days to assess TD and obtain a ceRNA network by RNA sequencing. By analyzing the differentially expressed circRNAs network, we id entify that circ_003084 was significantly upregulated in TD cartilage. Elevated circ_003084 inhibited TD chondrocytes proliferation and differentiation in vitro but promote apoptosis. Mechanistically, circ_003084 competitively binds to miR-130c-5p and prevents miR-130c-5p to decrease the level of BMPR1A, which upregulates the expression of apoptosis genes Caspase 3, Caspase 9, Bax and Bcl2, and finally facilitates cell apoptosis. Taken together, these findings imply that circ_003084/miR-130c-5p/BMPR1A interaction regulated TD chicken chondrocyte proliferation, apoptosis, and differentiation. This is the first work to reveal the mechanism of regulation of circRNA-related ceRNA on thiram-induced TD, offering a key reference for environmental toxicology.

Mercury-Modulated Immune Responses in Arctic Barnacle Goslings (Branta leucopsis) upon a Viral-Like Immune Challenge

Historical mining activities in Svalbard (79°N/12°E) have caused local mercury (Hg) contamination. To address the potential immunomodulatory effects of environmental Hg on Arctic organisms, we collected newborn barnacle goslings (Branta leucopsis) and herded them in either a control or mining site, differing in Hg levels. An additional group at the mining site was exposed to extra inorganic Hg(II) via supplementary feed. Hepatic total Hg concentrations differed significantly between the control (0.011 ± 0.002 mg/kg dw), mine (0.043 ± 0.011 mg/kg dw), and supplementary feed (0.713 ± 0.137 mg/kg dw) gosling groups (average ± standard deviation). Upon immune challenge with double-stranded RNA (dsRNA) injection, endpoints for immune responses and oxidative stress were measured after 24 h. Our results indicated that Hg exposure modulated the immune responses in Arctic barnacle goslings upon a viral-like immune challenge. Increased exposure to both environmental as well as supplemental Hg reduced the level of natural antibodies, suggesting impaired humoral immunity. Hg exposure upregulated the expression of proinflammatory genes in the spleen, including inducible nitric oxide synthase (iNOS) and interleukin 18 (IL18), suggesting Hg-induced inflammatory effects. Exposure to Hg also oxidized glutathione (GSH) to glutathione disulfide (GSSG); however, goslings were capable of maintaining the redox balance by de novo synthesis of GSH. These adverse effects on the immune responses indicated that even exposure to low, environmentally relevant levels of Hg might affect immune competence at the individual level and might even increase the susceptibility of the population to infections.

Thiram-induced hyperglycemia causes tibial dyschondroplasia by triggering aberrant ECM remodeling via the gut-pancreas axis in broiler chickens

Pesticide thiram is widely used in agriculture and has been demonstrated to cause tibial dyschondroplasia (TD) in birds. However, the underlying mechanism remains unclear. This work used multi-omics analysis to evaluate the molecular pathways of TD in broilers that were exposed to low level of thiram. Integrative analysis of transcriptomic, proteomic, and metabolomic revealed thiram activity in enhancing pathological ECM remodeling via attenuating the glycolysis pathway and activating the hexosamine and glucuronic acid pathways. Intriguingly, we found hyperglycemia as a crucial factor for ECM overproduction, which resulted in the development of TD. We further demonstrated that high glucose levels are caused by islet secretion dysfunction in thiram-treated broilers. A combination of factors, including lipid disorder, low-grade inflammation, and gut flora disturbance, might contribute to the dysregulation of insulin secretion. The current work revealed the underlying toxicological mechanisms of thiram-induced tibial dyschondroplasia through blood glucose disorder via the gut-pancreas axis in chickens for the first time, which makes it easier to figure out the health risks of pesticides for worldwide policy decisions.

Unexpected genetic integrity boosts hope for the conservation of the red-legged partridge (Alectoris rufa, Galliformes) in Italy

The red-legged partridge (Alectoris rufa) is a medium-sized galliform endemic to southwestern Europe. In the easternmost part of the species' range, the population inhabiting Elba Island (Tuscan Archipelago National Park, Italy) is of undisputed conservation value. While we found nuclear and maternal DNA introgression with the exotic chukar partridge (A. chukar) in previous studies based on microsatellite DNA (n = 25) and two mitochondrial markers (n = 103), respectively, we disclosed a limited or null admixture in a few Elban partridges (n = 4) in a recent genomic investigation relying on 168,675 Single Nucleotide Polymorphisms (SNPs). We herein carried out an extended microsatellite DNA survey including additional 65 samples (total, 90) and six loci (total, 11) to determine both spatial structure and genetic integrity of local A. rufa. A sharp divergence between the subpopulations inhabiting the two sides of the island was disclosed, and the microsatellites indicated that all Elban partridges were not admixed with the chukar, thus fully reflecting the picture inferred using SNPs. We hypothesized that the spreading of chukar genes was constrained by negative selection, with the persistence of only the maternal lineage being indicative of thermal adaptation. The two subpopulations should be treated as distinct Management Units, and an envisaged plan to secure a stock onto nearby Pianosa Island could not only warrant endurance of the Elban population but also establish a source of valuable founders for the ex-situ management of the species in Italy. Our study exemplifies how a suitable samples/loci combination is the key to solve wildlife issues dealing with introgression.

Evidence of environmental transfer of tebuconazole to the eggs in the house sparrow (Passer domesticus): An experimental study

Triazole compounds are among the most widely used fungicides in agroecosystems to protect crops from potential fungal diseases. Many farmland birds spend a significant part of their life cycle in agroecosystems, which may chronically expose them to pesticides. We experimentally tested whether exposure to environmental concentrations of tebuconazole could induce a contamination of the eggs in an agroecosystem sentinel species, the house sparrow (Passer domesticus). Wild-caught adult sparrows were maintained in captivity and exposed (exposed group) or not (control group) for seven months to tebuconazole through drinking water. Eggs were opportunistically collected for the determination of tebuconazole concentration by Liquid Chromatography coupled to tandem Mass Spectrometry in eggs. We found that eggs from exposed parents all contained tebuconazole with a mean concentration of 1.52 ng g^-1 dry weight. In eggs from control parents, the tebuconazole concentration was below the limit of quantification (0.23 ng g^-1 dry weight) for 11 out of 13 eggs. Thus, our study demonstrates for the first time that environmental exposure of female birds to tebuconazole can translate into egg contamination by this fungicide.

Feeding on grains containing pesticide residues is detrimental to offspring development through parental effects in grey partridge

Numerous toxicological studies have shown that ingestion of pesticides can induce physiological stress in breeding birds, with adverse consequences on egg laying parameters and offspring quality through parental effects. However, previous studies do not mimic current levels of pesticide residues in typical landscapes, and they do not consider potential cocktail effects of pesticides as they occur in the wild. Herein, we explored whether realistic pesticide exposure affected reproduction parameters and offspring condition through parental effects in Grey partridge. We fed 24 breeding pairs with either seeds from conventional agriculture crops treated with various pesticides during cropping, or organic grains without pesticide residues as controls. The conventional and organic grain diets mimicked food options potentially encountered by wild birds in the field. The results showed that ingesting low pesticide doses over a long period had consequences on reproduction and offspring quality without altering mortality in parents or chicks. Compared with organic pairs, conventional pairs yielded smaller chicks at hatching that had a lower body mass index at 24 days old. Additionally, these chicks displayed lower haematocrit when body mass index was higher. Therefore, ingestion of conventional grains by parents resulted in chronic exposure to pesticide residues, even at low doses, and this had detrimental consequences on offspring. These results demonstrate a sublethal effect of pesticide residues through parental effects. The consequences of parental exposure on chicks might partly explain the decline in wild Grey partridge populations, which raises questions for avian conservation and demography if current agrosystem approaches are continued.

Pesticide impacts on avian species with special reference to farmland birds: a review

For decades, we have observed a major biodiversity crisis impacting all taxa. Avian species have been particularly well monitored over the long term, documenting their declines. In particular, farmland birds are decreasing worldwide, but the contribution of pesticides to their decline remains controversial. Most studies addressing the effects of agrochemicals are limited to their assessment under controlled laboratory conditions, the determination of lethal dose 50 (LD₅₀) values and testing in a few species, most belonging to Galliformes. They often ignore the high interspecies variability in sensitivity, delayed sublethal effects on the physiology, behaviour and life-history traits of individuals and their consequences at the population and community levels. Most importantly, they have entirely neglected to test for the multiple exposure pathways to which individuals are subjected in the field (cocktail effects). The present review aims to provide a comprehensive overview for ecologists, evolutionary ecologists and conservationists. We aimed to compile the literature on the effects of pesticides on bird physiology, behaviour and life-history traits, collecting evidence from model and wild species and from field and lab experiments to highlight the gaps that remain to be filled. We show how subtle nonlethal exposure might be pernicious, with major consequences for bird populations and communities. We finally propose several prospective guidelines for future studies that may be considered to meet urgent needs.

Thiram exposure in environment: A critical review on cytotoxicity

Thiram is used in large quantities in agriculture and may contaminate the environment by improper handling or storage in chemical plants and warehouses. A review of the literature has shown that thiram can affect different organs in animals and its toxic mechanisms can be elucidated in more detail at molecular level. We have summarized several impacts of thiram on animals: the effects of the perspectives of oxidative stress, mitochondrial damage, autophagy, apoptosis, and the IHH/PTHrP pathway on regulating abnormal skeletal development in particular tibial dyschondroplasia and kyphosis; angiogenesis inhibition was investigated from the perspective of angiogenesis factor inhibition, PI3K/AKT signaling pathway and CD147; the inhibition effect of thiram on fibroblasts and erythrocytes via the perspective of oxidative stress, mitochondrial damage and inhibition of growth factors in animal skin fibroblasts and erythrocytes; studied fertilized egg size, reduced fertility, neurodegeneration, and immune damage from the perspectives of CYP51 inhibition and dopamine-b-hydroxylase inhibition in the reproductive system, vitamin D deficiency in the nervous system, and inflammatory damage in the immune system; embryonic dysplasia in terms of thyroid hormone repression in animal embryonic development and repression of the SOX9a transcription factor. The elucidation of the mechanisms of toxicity of thiram on various organs of animals at molecular level will enable a more detailed understanding of the mechanisms of toxicity of thiram in animals and will facilitate the exploration of the treatment of thiram poisoning at molecular level.

Residue of thiram in food, suppresses immune system stress signals and disturbs sphingolipid metabolism in chickens

Thiram, a well-known sulfur containing organic compound is frequently and extensively used in agriculture because of high biological activity to control different pests. In certain cases, due to long persistence in the environment pesticides and other environmental contaminants induce undesirable toxic impacts to public health and environment. To ascertain the potential mechanisms of toxicity of thiram on different immune organs of broilers, a total of 100 one-day-old chicks were obtained and randomly divided into two groups including thiram group (50 mg/kg) and untreated control group. Thymus and spleen tissues were collected at the age of 14 days from the experimental birds. At necropsy level, thymus was congested, enlarged and hyperemic while spleen had no obvious lesions. The results on mechanisms (apoptosis and autophagy) of immunotoxicity showed significantly increased expression of bax, caspase3, cytc, ATG5, beclin1 and p62 in spleen of treated mice. Results indicated significantly decreased expression of m-TOR and bcl2 to activate apoptosis and autophagy. The expressions of bax, p53 and m-TOR were up-regulated in the thymus while the expressions of ATG5 and Beclin1 were down-regulated to mediate cell apoptosis and inhibit autophagy. The results on different metabolome investigation showed that the sphingolipid metabolism in the thymus of chicks exposed to thiram was disrupted resulting in up-regulation of metabolites related to cell membrane components such as SM, galactosylceramide and lactosylceramide. The results of our experimental research suggest that thiram can interfere with the sphingolipid metabolism in thymus and angiogenesis, inhibit the proliferation of vascular endothelial cells to induce potential toxic effects in chicken.

Field evidence of UK wild bird exposure to fludioxonil and extrapolation to other pesticides used as seed treatments

We determine the exposure of wild birds to pesticides via consumption of fludioxonil-treated winter wheat seeds following autumn drilling. We recorded the density of seeds left on the soil surface, bird density, and consumption of pesticide-treated seed by birds using camera traps. We calculated the dose ingested by each bird species in a single feeding bout and if they ate treated seeds exclusively for 1 day. We extrapolated this for an additional 19 pesticides commonly used as seed treatments, assuming equal consumption rates. All three fields contained grains on the soil surface (mean 7.14 seeds/m² on sowing day). In total, 1,374 granivorous birds spanning 18 different species were observed in the fields, with 11 species filmed eating the seeds. Fludioxonil appears to pose a low risk to birds, with <1.14% of the LD50 potentially ingested by a bird for a daily maximum amount of seeds. Analysis of the further 19 pesticides commonly used as seed dressings suggests that the neonicotinoid insecticides imidacloprid, clothianidin, and thiamethoxam represent the highest risk for granivorous birds. For example, chaffinch (Fringilla coelebs) could consume 63% of LD50 of imidacloprid in a single feeding bout, and 370% in a day. Further investigation is clearly required to determine whether seeds treated with these other pesticides are consumed as readily as those treated with fludioxonil, as if so this is likely to cause significant harm.

Bird exposure to fungicides through the consumption of treated seeds: A study of wild red-legged partridges in central Spain

Sown seeds are a key component of many farmland birds' diets due to natural food shortages in autumn and winter. Because these seeds are often treated with pesticides, their ingestion by birds can result in toxic effects. For risk assessment, data on treated seed toxicity should be combined with information about exposure risk for wild birds and the factors that modulate it. We characterized the exposure of red-legged partridges to pesticide-treated seeds through the analysis of digestive contents of birds shot by hunters (n = 194) in an agricultural region in central Spain. We measured the contribution of sown seeds to the partridges' diet and how it related to pesticide exposure. Moreover, we evaluated the influence of landscape composition on the intake of sown seeds and pesticides by partridges. During peak sowing time, seeds constituted half (50.7%) of the fresh biomass ingested by partridges, which consumed mostly winter cereal seeds (42.3% of biomass). Residues of seven fungicides and one insecticide (active ingredients) were detected in 33.0% of birds. The presence of pesticides in digestive contents was linked to the ingestion of cereal sown seeds. Moreover, dietary exposure of birds to pesticides was modulated by landscape characteristics, being lower in areas with heterogeneous landscapes, greater habitat mosaic and more natural vegetation. The estimated dietary intake of pesticides resulting from our field observations, in combination with experimental data on pesticide toxicity, raise concerns about the risks that pesticide-treated cereal seeds pose to granivorous bird populations. Our results highlight the importance of farming landscape composition and diversification, which should be considered as a priority in the agricultural policy to mitigate pesticide risks to farmland birds through the consumption of treated seeds.

Novel genome reveals susceptibility of popular gamebird, the red-legged partridge (Alectoris rufa, Phasianidae), to climate change

We produced a high-quality de novo genome assembly of the red-legged partridge A. rufa, the first reference genome of its genus, by utilising novel 10× Chromium technology. The estimated genome size was 1.19 Gb with an overall genome heterozygosity of 0.0022; no runs of homozygosity were observed. In total, 21,589 protein coding genes were identified and assigned to 16,772 orthologs. Of these, 201 emerged as unique to Alectoris and were enriched for positive regulation of epithelial cell migration, viral genome integration and maturation. Using PSMC analysis, we inferred a major demographic decline commencing ~140,000 years ago, consistent with forest expansion and reduction of open habitats during the Eemian interglacial. Present-day populations exhibit the historically lowest genetic diversity. Besides implications for management and conservation, this genome also promises key insights into the physiology of these birds with a view to improving poultry husbandry practices.

Feeding partridges with organic or conventional grain triggers cascading effects in life-history traits

Farmland birds are declining across Europe and North America and the research of factors behind is the subject of extensive researches. Agricultural intensification is now recognized as a major factor governing the loss of biodiversity with strong evidence that pesticides induced direct bird mortality at a high dose. However, less attention has been given to the long-term effects of chronic exposure to low dose of pesticides. Here, we used an experimental procedure in which grey partridges were fed with untreated grains obtained from either organic (no pesticide) or conventional agriculture (with pesticide) for 26 weeks, thus strictly mimicking wild birds foraging on fields. We then examined a suite of life-history traits (ecophysiological and behavioural) that may ultimately, influence population dynamics. We show for the first time that ingesting low pesticide doses over a long period has long-term consequences on several major physiological pathways without inducing differential mortality. Compared to control partridges, birds exposed to chronic doses i) had less developed carotenoid-based ornaments due to lower concentrations of plasmatic carotenoids, ii) had higher activated immune system, iii) showed signs of physiological stress inducing a higher intestinal parasitic load, iv) had higher behavioural activity and body condition and v) showed lower breeding investment. Our results are consistent with a hormetic effect, in which exposure to a low dose of a chemical agent may induce a positive response, but our results also indicate that breeding adults may show impaired fitness traits bearing population consequences through reduced breeding investment or productivity. Given the current scale of use of pesticides in agrosystems, we suggest that such shifts in life-history traits may have a negative long-term impact on wild bird populations across agrosystems. We stress that long-term effects should no longer be ignored in pesticide risk assessment, where currently, only short-term effects are taken into account.

Agricultural pesticides and ectoparasites: potential combined effects on the physiology of a declining aerial insectivore

Agricultural pesticides usage has been increasing globally. These compounds have been developed to disrupt pest species physiology, but because their specificity is limited, they can also have adverse effects on non-target organisms. Recent studies have shown that the damaging toxicological effects of pesticides can be amplified in stressful environments. However, few studies have documented these effects in natural settings where organisms are simultaneously exposed to pesticides and to other environmental stressors such as parasites. In this study, we assessed both pesticide and ectoparasite effects on the physiology of a free-ranging bird. We measured physiological markers including haematocrit, bacteria-killing ability (BKA) and leucocyte counts, as well as exposure to haematophagous Protocalliphora larvae, in tree swallow nestlings (Tachycineta bicolor), a declining aerial insectivore, in southern Québec, Canada, for over 3 years. We found that combined exposure to pesticides and Protocalliphora larvae was negatively related to haematocrit, suggesting possible synergistic effects. However, we found no such relationships with BKA and leucocyte counts, highlighting the complexity of physiological responses to multiple stressors in natural settings. Populations of several aerial insectivores are declining, and although sublethal pesticide effects on physiology are suspected, our results suggest that exposure to other factors, such as parasitism, should also be considered to fully assess these effects, especially because pesticides are increasingly present in the environment.

Genome-wide markers redeem the lost identity of a heavily managed gamebird

Heavily managed wildlife may suffer from genetic homogenization and reshuffling of locally adapted genotypes with non-native ones. This phenomenon often affects natural populations by reducing their evolutionary potential and speeding up the ongoing biodiversity crisis. For decades, the red-legged partridge (Alectoris rufa), an intensively managed gamebird of conservation concern and considerable socio-economic importance, has been subjected to extensive releases of farm-reared hybrids with the chukar partridge (Alectoris chukar) and translocations irrespective of subspecific affinity. These practices have led to serious concerns that the genetic integrity and biogeographic structure of most red-legged partridge populations are irreversibly affected, as suggested by previous studies based on few genetic markers. Using over 168 000 genome-wide loci and a sampling across the entire A. rufa range, we detected unexpectedly limited and spatially uneven chukar introgression as well as significant intraspecific structure. We demonstrate that species widely feared to have irretrievably lost their genetic identity are likely to be much less affected by unsuitable management practices than previously assumed. Our results spell the need for a radical re-think on animal conservation, possibly restoring native status to populations long treated as compromised. Our study exemplifies how the application of innovative conservation-genomic methods is key to solving wildlife management problems dealing with introgressive hybridization worldwide.

Birds feeding on tebuconazole treated seeds have reduced breeding output

Drilled seeds are an important food resource for many farmland birds but may pose a serious risk when treated with pesticides. Most compounds currently used as seed treatment in the EU have low acute toxicity but may still affect birds in a sub-chronic or chronic way, especially considering that the sowing season lasts several weeks or months, resulting in a long exposure period for birds. Tebuconazole is a triazole fungicide widely used in agriculture but its toxicity to birds remains largely unknown. Our aim was to test if a realistic scenario of exposure to tebuconazole treated seeds affected the survival and subsequent reproduction of the red-legged partridge (Alectoris rufa). We fed captive partridges with wheat seeds treated with 0%, 20% or 100% of tebuconazole application rate during 25 days in late winter (i.e. tebuconazole dietary doses were approximately 0.2 and 1.1 mg/kg bw/day). We studied treatment effects on the physiology (i.e. body weight, biochemistry, immunology, oxidative stress, coloration) and reproduction of partridges. Exposed birds did not reduce food consumption but presented reduced plasmatic concentrations of lipids (triglycerides at both exposure doses, cholesterol at high dose) and proteins (high dose). The coloration of the eye ring was also reduced in the low dose group. Exposure ended 60 days before the first egg was laid, but still affected reproductive output: hatching rate was reduced by 23% and brood size was 1.5 times smaller in the high dose group compared with controls. No significant reproductive effects were found in the low dose group. Our results point to the need to study the potential endocrine disruption mechanism of this fungicide with lagged effects on reproduction. Risk assessments for tebuconazole use as seed treatment should be revised in light of these reported effects on bird reproduction.

Two-dimensional self-assembled Au-Ag core-shell nanorods nanoarray for sensitive detection of thiram in apple using surface-enhanced Raman spectroscopy

The development of substrate with high sensitivity and good reproducibility for surface-enhanced Raman scattering (SERS) detection of contaminants in foods has attracted more and more attention. Herein, a stable two-dimensional (2D) Au-Ag core-shell nanorods (Au@Ag NRs) nanoarray substrate with high-performance SERS activity was developed based on interface self-assembly strategy and successfully applied to the detection of thiram in apple sample. A broad linearity range of 0.01-10 mg/L and a low limit of detection of 0.018 mg/L were achieved for thiram solution. The substrate was stable and exhibited satisfactory sensitivity after preserving at ambient temperature for 4 weeks. Furthermore, this method presented the comparable result to that acquired from high-performance liquid chromatography (HPLC) with satisfactory recoveries of 93-116%. The study indicated that the prepared Au@Ag NRs nanoarray substrate was promising for SERS detection of contaminants such as pesticides in foods.

Egg Overspray with Herbicides and Fungicides Reduces Survival of Red-Legged Partridge Chicks

Within the environmental risk assessment conducted for pesticide registration in the European Union (EU), avian reproductive toxicity is characterized after exposing adults. However, eggs of ground-nesting species can be exposed when pesticide applications occur during laying or incubation. We simulated environmentally realistic exposure of red-legged partridge (Alectoris rufa) eggs to an herbicide (2,4-D) and a fungicide (tebuconazole) applied to winter cereal crops during the breeding season of most farmland birds. We analyzed the effects on hatching success, offspring survival, and physiology. Exposure by overspray led to greater pesticide accumulation in the eggshell or content than exposure through contact with treated soil (3.1-13.7 times higher, depending on the pesticide and target sample). Egg overspray with tebuconazole significantly increased chick mortality, which was 26% higher than that of controls. 2,4-D caused a similar but a close to significant increase (chick mortality 24% higher than controls). Exposure to either pesticide through contact with treated soils did not affect chick survival but altered some biochemical parameters posthatching. Our experiment shows that egg spraying with pesticides should be considered as a relevant exposure scenario in risk assessment procedures, given its potential to affect the reproductive success of ground-nesting farmland birds.

Ameliorative effect of naringin against thiram-induced tibial dyschondroplasia in broiler chicken

Tetramethyl thiuram disulfide (thiram) is widely used in agricultural production as an insecticide and fungicide, which can also lead to tibial dyschondroplasia (TD) in poultry. TD is characterized by leg disorders and growth performance retardation, and no targeted drugs have been found to treat TD until now. Therefore, the objective of the present study was to explore the ameliorative effect of traditional Chinese medicine naringin on thiram-induced TD chickens. A total of 180 one-day-old Arbor Acres (AA) broiler chickens were randomly divided into three equal groups (n = 60): control group (standard diet), thiram-induced group (thiram 50 mg/kg from day 3 to day 7), and naringin-treated group (naringin 30 mg/kg from day 8 to day 18). During the 18-day experiment, the growth performance, tibial bone parameters, antioxidant property of liver, serum biochemical changes and clinical symptoms were recorded to evaluate the protective effect of naringin in thiram-induced TD broiler chickens. Additionally, mRNA expressions and protein levels of Ihh and PTHrP genes were determined via quantitative real-time polymerase chain reaction and western blot. Administration of naringin showed significant results by alleviating lameness, increased growth performance, recuperated growth plate (GP) width, and improved functions and antioxidant enzyme level of liver in broilers affected by TD. Moreover, naringin treatment restored the development of damaged tibia bone via downregulating Ihh and upregulating PTHrP mRNA and protein expressions. In conclusion, our study determines naringin could be used as an effective medicine to treat TD.

Trichoderma atroviride as a promising biocontrol agent in seed coating for reducing Fusarium damping-off on maize

AIMS

The objective of this work was to identify a fungal strain showing potential biocontrol abilities against two Fusarium damping-off agents and to test it as a Biological Control Agent (BCA) in maize seed coating under field conditions.

METHODS AND RESULTS

A collection of native fungal strains associated with maize in Belgium was screened for antagonistic potential against Fusarium avenaceum and Fusarium culmorum. The strain with highest biocontrol potential was identified as an endophytic Trichoderma atroviride BC0584. In greenhouse, it significantly improves the emergence of seedlings infected by F. avenaceum or F. culmorum pathogens. In most field trials carried out during the season 2017, it significantly increased the emergence rate of infected seedlings compared to untreated seeds. One slurriable powder formulation allows BCA conidia to survive over a 6-month storage period at 4°C.

CONCLUSIONS

The fungal BC0584 strain is a promising BCA that could be an alternative to synthetic fungicides. It is adapted to local environmental conditions, is easily and cheaply produced and can be stored in a low-cost formulation.

SIGNIFICANCE AND IMPACT OF THE STUDY

In Belgium, this is the first study to use a T. atroviride native strain against Fusarium damping-off on maize crop. Modes of action and required conditions for ensuring high biocontrol activity in the field have still to be investigated.

Uptake, Metabolism, and Elimination of Fungicides from Coated Wheat Seeds in Japanese Quail (Coturnix japonica)

Pesticides coated to the seed surface potentially pose an ecological risk to granivorous birds that consume incompletely buried or spilled seeds. To assess the toxicokinetics of seeds treated with current-use fungicides, Japanese quail (Coturnix japonica) were orally dosed with commercially coated wheat seeds. Quail were exposed to metalaxyl, tebuconazole, and fludioxonil at either a low dose (0.0655, 0.0308, and 0.0328 mg/kg of body weight, respectively) or a high dose (0.196, 0.0925, and 0.0985 mg/kg of body weight, respectively). Fungicides were rapidly absorbed and distributed to tissues. Tebuconazole was metabolized into tert-butylhydroxy-tebuconazole. All compounds were eliminated to below detection limits within 24 h. The high detection frequencies observed in fecal samples potentially offer a non-invasive matrix to monitor pesticide exposure. With the summation of total body burden across plasma, tissue, and fecal samples, less than 9% of the administered dose was identified as the parent fungicide, demonstrating the importance to monitor both active ingredients and their metabolites in biological samples.

Tibial growth plate vascularization is inhibited by the dithiocarbamate pesticide thiram in chickens: potential relationship to peripheral platelet counts alteration

The widespread use of thiram has raised concerns for health and its toxic effects, but the underlying toxicity mechanism on platelets and bones is poorly defined. Here, we found a significant increase in the number of platelets in chickens with the thiram intake, due to the increased expression of thrombopoietin mRNA in the dysfunction liver. Furthermore, the decreased vascular distribution and cell death of chondrocytes in the tibial growth plates (TGPs) were observed, resulting in bone growth inhibition, which is associated with the abnormal activation of platelets leading to the extraordinary decrease of vascular endothelial growth factor A (VEGFA) and angiopoietin-1 protein were released and their corresponding receptors VEGFR2 and Tie-2 expressions were also reduced in the TGPs. Taken together, these findings revealed that thiram has an adverse effect on bones and platelets, which may have a high risk of thrombosis and osteoarthritis.

Variation in PFAA concentrations and egg parameters throughout the egg-laying sequence in a free-living songbird (the great tit, Parus major): Implications for biomonitoring studies

Over the past decades, there has been growing scientific attention and public concern towards perfluoroalkyl acids (PFAAs), due to their widespread presence in the environment and associations with adverse effects on various organisms. Bird eggs have often been used as less-invasive biomonitoring tools for toxicological risk assessments of persistent organic pollutants, including some PFAAs. Hereby, it is typically assumed that one random egg is representative for the PFAA concentrations of the whole clutch. However, variation of PFAA concentrations within clutches due to laying sequence influences can have important implications for the egg collection strategy and may impede interpretations of the quantified concentrations. Therefore, the main objective of this paper was to study variation patterns and possible laying sequence associations with PFAA concentrations in eggs of the great tit (Parus major). Eight whole clutches (4-8 eggs) were collected at a location in the Antwerp region, situated about 11 km from a known PFAA point source. The ∑ PFAA concentrations ranged from 8.9 to 75.1 ng g^-1 ww. PFOS concentrations ranged from 6.7 to 55.1 ng g^-1 ww and this compound was the dominant contributor to the total PFAA profile (74%), followed by PFDoA (7%), PFOA (7%), PFDA (5%), PFTrA (4%) and PFNA (3%). The within-clutch variation (70.7%) of the ∑ PFAA concentrations was much larger than the among-clutch variation (29.3%) and concentrations decreased significantly for some PFAA compounds throughout the laying sequence. Nevertheless, PFAA concentrations were positively and significantly correlated between some egg pairs within the same clutch, especially between egg 1 and egg 3. For future PFAA biomonitoring studies, we recommend to consistently collect the same egg along the laying sequence, preferably the first or third egg if maximizing egg exposure metrics is the main objective.

Limited reproductive impairment in a passerine bird species exposed along a perfluoroalkyl acid (PFAA) pollution gradient

Although bird eggs have been used in biomonitoring studies on perfluoroalkyl acids (PFAAs), effects of environmental concentrations on reproduction remain largely unknown in wild birds. In the present study we examined the associations between the concentrations of 4 perfluoroalkyl sulfonic acids (PFSAs) and 11 perfluoroalkyl carboxylic acids (PFCAs) in the eggs of great tits (Parus major), collected along a distance gradient from a pollution source, and multiple reproductive parameters (including the start of egg laying, clutch size, hatching success, fledging success and total breeding success) along with egg shell thickness and body condition of the nestlings. The PFAA concentrations measured at the plant site were among the highest ever reported in wild bird eggs. PFAA concentrations decreased sharply with increasing distance (0-11 km) from the plant, but remained relatively elevated in the adjacent sites. PFAAs were grouped into principal components (PCs) to prevent collinearity. High concentrations of PFOS, PFDS, PFDoDA, PFTrDA and PFTeDA (grouped as PC1) were associated with a reduced hatching success of nests where at least one egg hatched, thinner egg shells and increased survival of the hatched chicks. High concentrations of PFDA (PC2) were associated with a reduced hatching success, especially in nests where no eggs hatched, an earlier start of egg laying and a reduction of total breeding success, mainly caused by the failure in hatching. Although the major manufacturer of PFAAs phased out the production of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and related products in 2002, concentrations appear to have increased since previous measurements. Surprisingly, despite the very high concentrations close to the fluorochemical plant, there was no clear evidence for reproductive impairment as the observed associations between PFAA concentrations and reproductive parameters were rather limited compared to previous studies in songbirds. These findings also suggest potential differences in sensitivity between species. CAPSULE: Despite the very high PFAA concentrations at the perfluorochemical hotspot, correlations with reproductive parameters were limited.

Effect of tetramethyl thiuram disulfide (thiram) in relation to tibial dyschondroplasia in chickens

Tetramethyl thiuram disulfide (thiram) is one of the important pesticides, which is extensively used in agriculture, but if it is combined with the cell membrane, then it causes membrane damage, bone morphogenic inactivation, and inhibited angiogenesis. Thiram has been considered a common cause of tibial dyschondrolplasia (TD) in various avian species, because it becomes the part of feed due to environmental contamination and its overuse in agriculture as pesticides or fungicide. However, there is no systematic study on the changes of the correlation indexes with toxic effect of the thiram in chickens. Therefore, we evaluated the toxic effects of thiram on growth performance of chickens, viscera organ index, pathological changes in tissue, and gene expression associated with osteoblast differentiation, vascularization, and tibial bone development. For this study, 1-day chickens (n = 300) were randomly distributed into two equal groups, control group (normal basal diet) and thiram group (adding thiram 40 mg/kg in basal diet). The result presented that thiram group chickens were looking unhealthy, lazy, and showing clinical symptoms like lameness. Thiram treatment significantly reduced the performance of chickens, liver index, and tibial length compared with control group. The toxic effect of thiram increased the visceral organ index (spleen and cardiac), tibia index, and TD severity considerably. It also increased serum Ca²⁺ and P³⁺ concentration and decreased tibial density compared to control chickens but the difference was not significant. Histopathology of tibia and liver showed that there were severe lesions due to toxic effect of thiram. Furthermore, HIF-1α and VEGF antibody localizations were increased and WNT4 localization was reduced significantly in immunohistochemical analysis. This systemic study of toxic effects of thiram in chicken concluded that thiram reduced the growth performance of chickens through decreasing liver index, whereas increasing kidney, cardiac, and spleen index, and induced TD by changing the expressions of VEGF, HIF-1α, and WNT4.

Risk assessment of lead poisoning and pesticide exposure in the declining population of red-breasted goose (Branta ruficollis) wintering in Eastern Europe

The red-breasted goose Branta ruficollis is a globally threatened species (IUCN Vulnerable) and the only European goose species currently in decline. Working on the wintering grounds on the Black Sea Coast, we address two potential causes of decline of this species for the first time: lead poisoning, and contamination from pesticides. We quantified the densities of spent Pb shot in three wetlands used by the geese in north-east Bulgaria, and analysed the Pb concentration in the faeces of red-breasted geese and the more abundant greater white-fronted geese Anser albifrons, using Al concentration as an indicator of soil ingestion. Pb shot densities in sediments were low, and we found no evidence for Pb shot ingestion in red-breasted geese. On the other hand, we found that the geese were feeding on wheat whose seeds were treated with four fungicides: thiram, tebuconazole, difenoconazole and fludioxonil, and the two first were even detected in geese faecal samples. Using data on the daily food intake, we estimated the exposure levels of the geese to these fungicides, both by measuring the concentrations remaining on seeds and by estimating the amount used to coat the seeds at the time of sowing. We found that the exposure rates estimated during the sowing period for both geese species can exceed the recognized hazardous doses for thiram, and to a lesser extent for tebuconazole, which indicates that some pesticides may be playing a previously overlooked role in the decline of red-breasted geese.

Specific carotenoid pigments in the diet and a bit of oxidative stress in the recipe for producing red carotenoid-based signals

Colorful ornaments have been the focus of sexual selection studies since the work of Darwin. Yellow to red coloration is often produced by carotenoid pigments. Different hypotheses have been formulated to explain the evolution of these traits as signals of individual quality. Many of these hypotheses involve the existence of a signal production cost. The carotenoids necessary for signaling can only be obtained from food. In this line, carotenoid-based signals could reveal an individual’s capacity to find sufficient dietary pigments. However, the ingested carotenoids are often yellow and became transformed by the organism to produce pigments of more intense color (red ketocarotenoids). Biotransformation should involve oxidation reactions, although the exact mechanism is poorly known. We tested the hypothesis that carotenoid biotransformation could be costly because a certain level of oxidative stress is required to correctly perform the conversion. The carotenoid-based signals could thus reveal the efficiency of the owner in successfully managing this challenge. In a bird with ketocarotenoid-based ornaments (the red-legged partridge; Alectoris rufa), the availability of different carotenoids in the diet (i.e. astaxanthin, zeaxanthin and lutein) and oxidative stress were manipulated. The carotenoid composition was analyzed and quantified in the ornaments, blood, liver and fat. A number of oxidative stress biomarkers were also measured in the same tissues. First, we found that color and pigment levels in the ornaments depended on food levels of those carotenoids used as substrates in biotransformation. Second, we found that birds exposed to mild levels of a free radical generator (diquat) developed redder bills and deposited higher amounts of ketocarotenoids (astaxanthin) in ornaments. Moreover, the same diquat-exposed birds also showed a weaker resistance to hemolysis when their erythrocytes were exposed to free radicals, with females also enduring higher oxidative damage in plasma lipids. Thus, higher color production would be linked to higher oxidative stress, supporting the biotransformation hypothesis. The recent discovery of an avian oxygenase enzyme involved in converting yellow to red carotenoids may support our results. Nonetheless, the effect could also depend on the abundance of specific substrate carotenoids in the diet. Birds fed with proportionally higher levels of zeaxanthin showed the reddest ornaments with the highest astaxanthin concentrations. Moreover, these birds tended to show the strongest diquat-mediated effect. Therefore, in the evolution of carotenoid-based sexual signals, a biotransformation cost derived from maintaining a well-adjusted redox machinery could coexist with a cost linked to carotenoid acquisition and allocation (i.e. a resource allocation trade-off).

Residues of plant protection products in grey partridge eggs in French cereal ecosystems

The contamination of the eggs of farmland birds by currently used plant protection products (PPPs) is poorly documented despite a potential to adversely impact their breeding performance. In this context, 139 eggs of 52 grey partridge Perdix perdix clutches, collected on 12 intensively cultivated farmlands in France in 2010-2011, were analysed. Given the great diversity of PPPs applied on agricultural fields, we used exploratory GC/MS-MS and LC/MS-MS screenings measuring ca. 500 compounds. The limit of quantification was 0.01 mg/kg, a statutory reference. A total of 15 different compounds were detected in 24 clutches. Nine of them have been used by farmers to protect crops against fungi (difenoconazole, tebuconazole, cyproconazole, fenpropidin and prochloraz), insects (lambda-cyhalothrin and thiamethoxam/clothianidin) and weeds (bromoxynil and diflufenican). Some old PPPs were also detected (fipronil(+sulfone), HCH(α,β,δ isomers), diphenylamine, heptachlor(+epoxyde), DDT(Σisomers)), as well as PCBs(153, 180). Concentrations ranged between <0.01 and 0.05 mg/kg but reached 0.067 (thiamethoxam/clothianidin), 0.11 (heptachlor + epoxyde) and 0.34 (fenpropidin) mg/kg in some cases. These results testify an actual exposure of females and/or their eggs to PPPs in operational conditions, as well as to organochlorine pollutants or their residues, banned in France since several years if not several decades, that persistently contaminate the environment.Routes of exposure, probability to detect a contamination in the eggs, and effects on egg/embryo characteristics are discussed with regard to the scientific literature.