Toxicological responses to sublethal anticoagulant rodenticide exposure in free-flying hawks.

An important component of assessing the hazards of anticoagulant rodenticides to non-target wildlife is observations in exposed free-ranging individuals. The objective of this study was to determine whether environmentally realistic, sublethal first-generation anticoagulant rodenticide (FGAR) exposures via prey can result in direct or indirect adverse effects to free-flying raptors. We offered black-tailed prairie dogs (Cynomys ludovicianus) that had fed on Rozol® Prairie Dog Bait (Rozol, 0.005% active ingredient chlorophacinone, CPN) to six wild-caught red-tailed hawks (RTHA, Buteo jamaicensis), and also offered black-tailed prairie dogs that were not exposed to Rozol to another two wild-caught RTHAs for 7 days. On day 6, blood was collected to determine CPN's effects on blood clotting time. On day 7, seven of the eight RTHAs were fitted with VHF radio telemetry transmitters and the RTHAs were released the following day and were monitored for 33 days. Prothrombin time (PT) and Russell's viper venom time confirmed that the CPN-exposed RTHAs were exposed to and were adversely affected by CPN. Four of the six CPN-exposed RTHAs exhibited ptiloerection, an indication of thermoregulatory dysfunction due to CPN toxicity, but no signs of intoxication were observed in the reference hawk or the remaining two CPN-exposed RTHAs. Of note is that PT values were associated with ptiloerection duration and frequency; therefore, sublethal CPN exposure can directly or indirectly evoke adverse effects in wild birds. Although our sample sizes were small, this study is a first to relate coagulation times to adverse clinical signs in free-ranging birds.

Acute hemorrhage and death in calves following chlorophacinone exposure.

Three calves were submitted to the Iowa State University Veterinary Diagnostic Laboratory for diagnostic evaluation following an abrupt increase in morbidity and mortality in a calf herd associated with epistaxis and widespread hemorrhage. Each of the submitted calves had moderate-to-severe hemorrhage within various tissues and body cavities, including the thymus, subcutaneous region of the neck, mediastinum, lungs, pericardial sac, heart, spleen, perirenal fat, urinary bladder, and skeletal muscle, including the diaphragm. An anticoagulant rodenticide screen was performed on the livers of each calf. Significant concentrations of chlorophacinone were detected at 4.2, 3.6, and 2.9 ppm in liver. Multiple piles and an open pail of white powdery material were present within the facility in which the calves were housed and were identified as the sources of chlorophacinone. Acute hemorrhage and death occurred in fourteen 1.5-mo-old, crossbred calves following ingestion of the vitamin K antagonist chlorophacinone.

Accidental chlorophacinone exposure of lactating ewes: Clinical follow-up and human health dietary implications.

Anticoagulant rodenticides are widely used for rodent control in agricultural and urban settings. Their intense use can sometimes result in accidental exposure and even poisoning of livestock. Can milk, eggs or meat derived from such accidently exposed animals be consumed by humans? Data on the pharmacokinetics of chlorophacinone in milk of accidently exposed ewes were used to estimate the risk associated with its consumption. Three days after accidental ingestion, chlorophacinone was detected in plasma of 18 ewes, with concentrations exceeding 100 ng/mL in 11 animals. Chlorophacinone was detected in milk on day 2 post-exposure and remained quantifiable for at least 7 days in milk of these 11 ewes. Concentrations in milk were much lower than in plasma and decreased quickly (mean half-life of 2 days). This study demonstrated dose-dependent mammary transfer of ingested chlorophacinone. Variation in prothrombin time (PT) on Day 3 suggested that some of the ewes that ingested chlorophacinone may have been adversely affected, but PT did not facilitate estimation of the quantity of chlorophacinone consumed. Using safety factors described in the literature, consumption of dairy products derived from these ewes after a one-week withdrawal period would pose low risk to consumers.

Acute toxicity and clotting times of anticoagulant rodenticides to red-toothed (Odonus niger) and black (Melichthys niger) triggerfish, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides).

Anticoagulant rodenticides (ARs) are used in rat eradication efforts on island wildlife refuges. AR bait pellets can get into coral reef areas during broadcasting and lead to exposure of non-target organisms, such as marine fishes. The objective of this study was to determine the sensitivity of representative saltwater fishes, Red-toothed triggerfish (Odonus niger) and Black triggerfish (Melichthys niger), and common freshwater fishes, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides) to first generation ARs, diphacinone (DPN) and chlorophacinone (CPN), as well as a second-generation AR, brodifacoum (BROD). Acute toxicity of ARs was evaluated by single dose, intraperitoneal injections. The median lethal dose (LD50) ranges were 137-175 µg DPN/g, 155-182 µg CPN/g, and 36-48 µg BROD/g for Red-toothed triggerfish and 90-122 µg DPN/g, 125-164 µg CPN/g, and 50-75 µg BROD/g for black triggerfish. Laboratory surrogate test fish species fathead minnow and largemouth bass were of similar sensitivity toward AR-induced toxicity compared to triggerfish based on LD50 values. Sublethal effects on elevated clotting time occurred in dose-dependent fashion in all fish tested. Fish appear to have low sensitivity to AR chemicals as compared to other taxa, in particular mammals and birds, based on across-taxa comparisons of species sensitivity distributions of whole body, single dose acute lethality (LD50 values). The sensitivity of fish to waterborne exposures of ARs has yet to be fully evaluated and indeed may prove more hazardous to fish.

Differential modulation of FXR activity by chlorophacinone and ivermectin analogs.

Chemicals that alter normal function of farnesoid X receptor (FXR) have been shown to affect the homeostasis of bile acids, glucose, and lipids. Several structural classes of environmental chemicals and drugs that modulated FXR transactivation were previously identified by quantitative high-throughput screening (qHTS) of the Tox21 10K chemical collection. In the present study, we validated the FXR antagonist activity of selected structural classes, including avermectin anthelmintics, dihydropyridine calcium channel blockers, 1,3-indandione rodenticides, and pyrethroid pesticides, using in vitro assay and quantitative structural-activity relationship (QSAR) analysis approaches. (Z)-Guggulsterone, chlorophacinone, ivermectin, and their analogs were profiled for their ability to alter CDCA-mediated FXR binding using a panel of 154 coregulator motifs and to induce or inhibit transactivation and coactivator recruitment activities of constitutive androstane receptor (CAR), liver X receptor alpha (LXRα), or pregnane X receptor (PXR). Our results showed that chlorophacinone and ivermectin had distinct modes of action (MOA) in modulating FXR-coregulator interactions and compound selectivity against the four aforementioned functionally-relevant nuclear receptors. These findings collectively provide mechanistic insights regarding compound activities against FXR and possible explanations for in vivo toxicological observations of chlorophacinone, ivermectin, and their analogs.