Development of Dietary-Based Toxicity Reference Values to Assess the Risk of Chlorophacinone to Non-Target Raptorial Birds

Regulatory changes in the use of some second-generation anticoagulant rodenticides in parts of North America may result in expanded use of first-generation anticoagulant rodenticides (FGARs). Recent toxicological studies with captive raptors have demonstrated that these species are considerably more sensitive to the FGAR diphacinone than traditional avian wildlife test species (mallard, bobwhite). We have now examined the toxicity of the FGAR chlorophacinone (CPN) to American kestrels fed rat tissue mechanically amended with CPN, or rat tissue containing biologically-incorporated CPN, for 7 days. Nominal CPN concentrations in these diets were 0.15, 0.75, and 1.5 μg/g food wet weight, and actual CPN concentration in diets were analytically verified as being close to target values. Food intake was consistent among groups, body weight fluctuated by less than 6%, exposure and adverse effects were generally dose-dependent, and there were no dramatic differences in toxicity between mechanically-amended and biologically-incorporated CPN diets. Using benchmark dose statistical methods, toxicity reference values at which clotting times were prolonged in 50% of the kestrels was estimated to be about 80 μg CPN consumed/kg body weight-day for prothrombin time and 40 μg CPN/kg body weight-day for Russell’s viper venom time. Based upon carcass CPN residues reported in rodents from field baiting studies, empirical measures of food consumption in kestrels, and dietary-based toxicity reference values derived from the 7-day exposure scenario, some free-ranging raptors consuming CPN-exposed prey might exhibit coagulopathy and hemorrhage. These sublethal responses associated with exposure to environmentally realistic concentrations of CPN could compromise survival of exposed birds

Toxicity reference values for chlorophacinone and their application for assessing anticoagulant rodenticide risk to raptors

Despite widespread use and benefit, there are growing concerns regarding hazards of second-generation anticoagulant rodenticides to non-target wildlife which may result in expanded use of first-generation compounds, including chlorophacinone (CPN). The toxicity of CPN over a 7-day exposure period was investigated in American kestrels (Falco sparverius) fed either rat tissue mechanically- amended with CPN, tissue from rats fed Rozol bait (biologically-incorporated CPN), or control diets (tissue from untreated rats or commercial bird of prey diet) ad libitum. Nominal CPN concentrations in the formulated diets were 0.15, 0.75 and 1.5 µg/g food wet weight, and measured concentrations averaged 94 % of target values. Kestrel food consumption was similar among groups and body weight varied by less than 6 %. Overt signs of intoxication, liver CPN residues, and changes in prothrombin time (PT), Russell’s viper venom time (RVVT) and hematocrit, were generally dose-dependent. Histological evidence of hemorrhage was present at all CPN dose levels, and most frequently observed in pectoral muscle and heart. There were no apparent differences in toxicity between mechanically-amended and biologically-incorporated CPN diet formulations. Dietary-based toxicity reference values at which clotting times were prolonged in 50 % of the kestrels were 79.2 µg CPN consumed/kg body weight-day for PT and 39.1 µg/kg body weight-day for RVVT. Based upon daily food consumption of kestrels and previously reported CPN concentrations found in small mammals following field baiting trials, these toxicity reference values might be exceeded by free-ranging raptors consuming such exposed prey. Tissue-based toxicity reference values for coagulopathy in 50 % of exposed birds were 0.107 µg CPN/g liver wet weight for PT and 0.076 µg/g liver for RVVT, and are below the range of residue levels reported in raptor mortality incidents attributed to CPN exposure. Sublethal responses associated with exposure to environmentally realistic concentrations of CPN could compromise survival of free-ranging raptors, and should be considered in weighing the costs and benefits of anticoagulant rodenticide use in pest control and eradication programs

Toxicity reference values for chlorophacinone and their application for assessing anticoagulant rodenticide risk to raptors

Despite widespread use and benefit, there are growing concerns regarding hazards of second-generation anticoagulant rodenticides to non-target wildlife which may result in expanded use of first-generation compounds, including chlorophacinone (CPN). The toxicity of CPN over a 7-day exposure period was investigated in American kestrels (Falco sparverius) fed either rat tissue mechanically- amended with CPN, tissue from rats fed Rozol bait (biologically-incorporated CPN), or control diets (tissue from untreated rats or commercial bird of prey diet) ad libitum. Nominal CPN concentrations in the formulated diets were 0.15, 0.75 and 1.5 µg/g food wet weight, and measured concentrations averaged 94 % of target values. Kestrel food consumption was similar among groups and body weight varied by less than 6 %. Overt signs of intoxication, liver CPN residues, and changes in prothrombin time (PT), Russell’s viper venom time (RVVT) and hematocrit, were generally dose-dependent. Histological evidence of hemorrhage was present at all CPN dose levels, and most frequently observed in pectoral muscle and heart. There were no apparent differences in toxicity between mechanically-amended and biologically-incorporated CPN diet formulations. Dietary-based toxicity reference values at which clotting times were prolonged in 50 % of the kestrels were 79.2 µg CPN consumed/kg body weight-day for PT and 39.1 µg/kg body weight-day for RVVT. Based upon daily food consumption of kestrels and previously reported CPN concentrations found in small mammals following field baiting trials, these toxicity reference values might be exceeded by free-ranging raptors consuming such exposed prey. Tissue-based toxicity reference values for coagulopathy in 50 % of exposed birds were 0.107 µg CPN/g liver wet weight for PT and 0.076 µg/g liver for RVVT, and are below the range of residue levels reported in raptor mortality incidents attributed to CPN exposure. Sublethal responses associated with exposure to environmentally realistic concentrations of CPN could compromise survival of free-ranging raptors, and should be considered in weighing the costs and benefits of anticoagulant rodenticide use in pest control and eradication programs

Bound To Shock: Protection from Lethal Endotoxemic Shock by a Novel, Nontoxic, Alkylpolyamine Lipopolysaccharide Sequestrant

Lipopolysaccharide (LPS), or endotoxin, a structural component of gram-negative bacterial outer membranes, plays a key role in the pathogenesis of septic shock, a syndrome of severe systemic inflammation which leads to multiple-system organ failure. Despite advances in antimicrobial chemotherapy, sepsis continues to be the commonest cause of death in the critically ill patient. This is attributable to the lack of therapeutic options that aim at limiting the exposure to the toxin and the prevention of subsequent downstream inflammatory processes. Polymyxin B (PMB), a peptide antibiotic, is a prototype small molecule that binds and neutralizes LPS toxicity. However, the antibiotic is too toxic for systemic use as an LPS sequestrant. Based on a nuclear magnetic resonance-derived model of polymyxin B-LPS complex, we had earlier identified the pharmacophore necessary for optimal recognition and neutralization of the toxin. Iterative cycles of pharmacophore-based ligand design and evaluation have yielded a synthetically easily accessible N1,mono-alkyl-mono-homologated spermine derivative, DS-96. We have found that DS-96 binds LPS and neutralizes its toxicity with a potency indistinguishable from that of PMB in a wide range of in vitro assays, affords complete protection in a murine model of LPS-induced lethality, and is apparently nontoxic in vertebrate animal models.This work was supported by NIH grant 1R01 AI50107

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Comparison of mixing methods and associated residual levels of zinc phosphide on cabbage bait for rodent management

Zinc phosphide is a toxicant that is used extensively for rodent management throughout many parts of the world. Some rodent species, such as Belding\u27s ground squirrels (Urocitellus beldingi Merriam, 1888), often avoid zinc phosphide grain baits, leaving green vegetation such as cabbage as the only viable carrier for rodenticides. However, to date, ambiguity has existed as to the most appropriate mixing strategy for zinc phosphide-coated cabbage baits, and it is unknown how rapidly zinc phosphide degrades on these green carriers. Following laboratory and field-enclosure trials, we detected no significant difference in mean zinc phosphide concentrations or variability in zinc phosphide concentrations between mechanical and hand mixing strategies. However, the use of a mechanical mixer was determined to be the more practical option given that it is quicker and requires less effort for mixing large quantities of bait, it minimized worker exposure to phosphine, and because it yielded mean concentrations that were closer to target values. Both the moisture content of cabbage and zinc phosphide concentrations diminished over time, resulting in a fairly minimal window of exposure for non-target wildlife. Field investigation of this exposure risk, as well as an assessment of efficacy of zinc phosphide-coated cabbage baits for Belding\u27s ground squirrel management, are warranted

Development of Dietary-Based Toxicity Reference Values to Assess the Risk of Chlorophacinone to Non-Target Raptorial Birds

Regulatory changes in the use of some second-generation anticoagulant rodenticides in parts of North America may result in expanded use of first-generation anticoagulant rodenticides (FGARs). Recent toxicological studies with captive raptors have demonstrated that these species are considerably more sensitive to the FGAR diphacinone than traditional avian wildlife test species (mallard, bobwhite). We have now examined the toxicity of the FGAR chlorophacinone (CPN) to American kestrels fed rat tissue mechanically amended with CPN, or rat tissue containing biologically-incorporated CPN, for 7 days. Nominal CPN concentrations in these diets were 0.15, 0.75, and 1.5 µg/g food wet weight, and actual CPN concentration in diets were analytically verified as being close to target values. Food intake was consistent among groups, body weight fluctuated by less than 6%, exposure and adverse effects were generally dose-dependent, and there were no dramatic differences in toxicity between mechanically-amended and biologically-incorporated CPN diets. Using benchmark dose statistical methods, toxicity reference values at which clotting times were prolonged in 50% of the kestrels was estimated to be about 80 µg CPN consumed/kg body weight-day for prothrombin time and 40 µg CPN/kg body weight-day for Russell’s viper venom time. Based upon carcass CPN residues reported in rodents from field baiting studies, empirical measures of food consumption in kestrels, and dietary-based toxicity reference values derived from the 7-day exposure scenario, some free-ranging raptors consuming CPN-exposed prey might exhibit coagulopathy and hemorrhage. These sublethal responses associated with exposure to environmentally realistic concentrations of CPN could compromise survival of exposed birds

Zinc Phosphide-coated Cabbage for Managing Belding’s Ground Squirrels (Abstract)

Belding’s ground squirrels (Urocitellus beldingi) cause extensive damage in alfalfa and other hay crops throughout substantial portions of the Intermountain West. Recent management efforts have largely focused on shooting, burrow fumigation, and occasionally grain baits. However, these tools are often either too costly to implement or ineffective. In 2015, the California Department of Pesticide Regulation approved a Special Local Needs permit to use zinc phosphide-coated cabbage for managing Belding’s ground squirrels in Siskiyou, Modoc, and Lassen Counties. This baiting strategy could provide a cost effective and efficacious management approach, although efficacy data were lacking. Therefore, we established a study to assess the importance of spatial variability of location sites, prebaiting, and ground squirrel density on efficacy of zinc phosphide-coated cabbage for Belding’s ground squirrel management across impacted hay-growing regions in northeastern CA. We also assessed potential differences in bait mixing strategies (in a tub via hand mixing vs. the use of a commercial-style cement mixer) on targeted zinc phosphide concentrations, as well as the degradation rate of zinc phosphide and moisture content of cabbage under environmental conditions. We did not detect a significant difference between hand and mechanical mixing. However, mechanical mixing was closer to the target level (mean = 101% vs. 115% for mechanical and hand mixing, respectively), was more precise, and allowed for the mixing of larger batches. As such, mechanical mixing was the strategy we used for field application. Furthermore, both moisture content (0.29% loss per hour) and zinc phosphide concentration (31% loss in 48 hours) steadily declined during a three-day observation period, indicating a fairly minimal window of exposure for nontarget species. See Baldwin et al. (2018) for additional details on lab testing of mixing methods and residual zinc phosphide levels associated with cabbage bait. During field trials, we found that prebaiting increased overall efficacy by approximately 18%, with efficacy 23% greater in the western (eastern Siskiyou and western Modoc Counties) vs. eastern portions (south-central Modoc County) of the study area. The tested bait was also substantially more efficacious when initial ground squirrel populations were larger, presumably due to a greater need for forage at high densities. Ground squirrel activity was relatively consistent throughout the day, although peaks were noted from 09:00 to 11:00 and from 13:00 to 15:00. Consumption of cabbage bait diminished throughout the day after initial application. Consumption was again high the following morning, but again diminished throughout the remainder of the day. Ideal times for bait application were likely before 09:00 and again before 13:00, although ground squirrels continued to feed on bait throughout the day. Zinc phosphide-coated cabbage bait appears to be an effective management option when prebaiting is used in Siskiyou County and in western portions of Modoc County. Additional research is needed to determine methods to increase efficacy in central and eastern Modoc County. See Baldwin et al. (2019) for additional details on this study

Zinc Phosphide-coated Cabbage for Managing Belding’s Ground Squirrels (Abstract)

Belding’s ground squirrels (Urocitellus beldingi) cause extensive damage in alfalfa and other hay crops throughout substantial portions of the Intermountain West. Recent management efforts have largely focused on shooting, burrow fumigation, and occasionally grain baits. However, these tools are often either too costly to implement or ineffective. In 2015, the California Department of Pesticide Regulation approved a Special Local Needs permit to use zinc phosphide-coated cabbage for managing Belding’s ground squirrels in Siskiyou, Modoc, and Lassen Counties. This baiting strategy could provide a cost effective and efficacious management approach, although efficacy data were lacking. Therefore, we established a study to assess the importance of spatial variability of location sites, prebaiting, and ground squirrel density on efficacy of zinc phosphide-coated cabbage for Belding’s ground squirrel management across impacted hay-growing regions in northeastern CA. We also assessed potential differences in bait mixing strategies (in a tub via hand mixing vs. the use of a commercial-style cement mixer) on targeted zinc phosphide concentrations, as well as the degradation rate of zinc phosphide and moisture content of cabbage under environmental conditions. We did not detect a significant difference between hand and mechanical mixing. However, mechanical mixing was closer to the target level (mean = 101% vs. 115% for mechanical and hand mixing, respectively), was more precise, and allowed for the mixing of larger batches. As such, mechanical mixing was the strategy we used for field application. Furthermore, both moisture content (0.29% loss per hour) and zinc phosphide concentration (31% loss in 48 hours) steadily declined during a three-day observation period, indicating a fairly minimal window of exposure for nontarget species. See Baldwin et al. (2018) for additional details on lab testing of mixing methods and residual zinc phosphide levels associated with cabbage bait. During field trials, we found that prebaiting increased overall efficacy by approximately 18%, with efficacy 23% greater in the western (eastern Siskiyou and western Modoc Counties) vs. eastern portions (south-central Modoc County) of the study area. The tested bait was also substantially more efficacious when initial ground squirrel populations were larger, presumably due to a greater need for forage at high densities. Ground squirrel activity was relatively consistent throughout the day, although peaks were noted from 09:00 to 11:00 and from 13:00 to 15:00. Consumption of cabbage bait diminished throughout the day after initial application. Consumption was again high the following morning, but again diminished throughout the remainder of the day. Ideal times for bait application were likely before 09:00 and again before 13:00, although ground squirrels continued to feed on bait throughout the day. Zinc phosphide-coated cabbage bait appears to be an effective management option when prebaiting is used in Siskiyou County and in western portions of Modoc County. Additional research is needed to determine methods to increase efficacy in central and eastern Modoc County. See Baldwin et al. (2019) for additional details on this study