Assessing potential risk to alligators, Alligator mississippiensis, from nutria control with zinc phosphide rodenticide baits.

Nutria, Myocastor coypus, populations must be reduced when they cause substantial wetland damage. Control can include the rodenticide zinc phosphide, but the potential impacts to American alligators, Alligator mississippiensis, must be assessed. The mean amount of zinc phosphide per nutria found in nutria carcasses was 50 mg. Risk assessment determined that a conservative estimate for maximum exposure would be 173 mg zinc phosphide for a 28 kg alligator, or 6.2 mg/kg. Probit analysis found an LD(50) for alligators of 28 mg/kg. Our studies suggest that the use of zinc phosphide to manage nutria populations would pose only a small risk to alligators.

Determination of diphacinone residues in Hawaiian invertebrates.

A reversed-phase ion-pair liquid chromatographic analysis combined with a solid-phase extraction clean-up method is used to assess the quantity of diphacinone residue found in invertebrates. Three invertebrate species are exposed to commercially available diphacinone-fortified bait used for rat control. The invertebrate samples are collected, frozen, and shipped to the laboratory. The samples are homogenized after cryogenic freezing. A portion of the homogenized samples are extracted with acidified chloroform-acetone, followed by cleanup with a silica solid-phase extraction column. Diphacinone is detected by UV absorption at 325 nm after separation by the chromatographic system. The method limit of detection (MLOD) for snail and slug samples averaged 0.055 and 0.066 mg/kg, respectively. Diphacinone residues in snail tissue ranges from 0.83 to 2.5 mg/kg for Oxychilus spp. The mean recoveries from snails at 0.20 and 2.0 are 97 +/- 21% and 84 +/- 6%. Diphacinone residues in slug tissue ranges from 1.3 to 4.0 mg/kg for Deroceras laeve and < MLOD to 1.8 mg/kg for Limax maximus, respectively. The mean recoveries from slugs at 0.20 and 2.0 mg/kg are 91% +/- 15% and 86% +/- 5%.

Probabilistic risk assessment for snails, slugs, and endangered honeycreepers in diphacinone rodenticide baited areas on Hawaii, USA.

Three probabilistic models were developed for characterizing the risk of mortality and subacute coagulopathy to Poouli, an endangered nontarget avian species, in broadcast diphacinone-baited areas on Hawaii, USA. For single-day exposure, the risk of Poouli mortality approaches 0. For 5-d exposure, the mean probability of mortality increased to 3% for adult and 8% for juvenile Poouli populations. For Poouli that consume snails containing diphacinone residues for 14 d, the model predicted increased levels of coagulopathy for 0.42 and 11% of adult and juvenile Poouli populations, respectively. Worst-case deterministic risk characterizations predicted acceptable levels of risk for nonthreatened or endangered species such as northern bobwhite quail and mallards. Also, no acute toxicity was noted for snails and slugs that feed on diphacinone baits.

Stability of the tranquilizer drug propionylpromazine hydrochloride in formulated products.

An analytical method to evaluate propionylpromazine hydrochloride (PPZHCl) in tranquilizer formulations was developed using high-performance liquid chromatography (HPLC). During analysis of aged quality-control samples, a previously unreported chromatographic response was observed at a shorter retention time than PPZHCl. Further investigation of formulations stored in trap tap devices at temperatures ranging from 5 to 40 degrees C during field trials at four different locations confirmed the degradation of the active ingredient. Further investigation using HPLC/tandem mass spectrometry revealed two to five degradates, with the major degradates being oxidation products of the active ingredient, PPZHCl. As PPZHCl formulations must be stable when stored at 5 to 40 degrees C for 6 to 12 months, reformulation with the anti-oxidant ascorbic acid was utilized to achieve the required PPZHCl stability.

Determination of anthraquinone in technical material, formulations, and lettuce by high performance liquid chromatography.

Foraging on lettuce seeds and seedlings by horned larks (Eremophila alpestris) causes millions of dollars in losses to the California lettuce crop annually. Anthraquinone (AQ; 9,10-anthracenedione) has been shown to deter pest birds from consuming the seeds and seedlings of several plant species and was evaluated as a repellent to horned larks when applied to lettuce seedlings. A set of analytical methods using simple liquid extraction followed by high-performance liquid chromatography analysis were developed for the quantitation of AQ as technical material, as an active ingredient in a commercial formulation, and as a residue in lettuce plants. The methods were easy, reliable, and repeatable. AQ recoveries from control formulation fortified to concentrations of either 24 or 600 mg g(-)(1) were 99 (+/-1.2%) and 98% (+/-1.2%), respectively, with a control formulation method limit of detection (MLOD) of 0.50 mg g(-)(1). Control lettuce tissues from three growth stages were AQ-fortified to concentrations of 0.50 and 500 microg g(-)(1). The resulting AQ recoveries for the two fortification levels were 99 (+/-8.5) and 89% (+/-1.5%) for 11 day old seedlings, 95 (+/-2.6%) and 86% (2.1%) for 16 day old plants, and 92 (+/-1.4%) and 93% (+/-1.1%) for adult head lettuce cover leaves, respectively. The MLODs for the same three lettuce tissues were 0.055, 0.058, and 0.077 microg g(-)(1), respectively. These methods were used to quantify AQ residues from field-grown, treated lettuce and associated fortified quality control samples.

Quantification of plasma and egg 4,4'-dinitrocarbanilide (DNC) residues for the efficient development of a nicarbazin-based contraceptive for pest waterfowl.

Urbanization and associated landscaping has increased the abundance of year-round habitat for waterfowl, resulting in vegetation damage, loss of recreational activities, air transportation mishaps and health hazards. As part of a research program to develop socially acceptable techniques for management of pest bird populations, we are evaluating nicarbazin as a contraceptive in pest and surrogate avian species. As reproductive studies with Canada Geese (Branta canadensis) are tedious due to the difficulty of conducting controlled field studies and/or breeding geese in captivity, we evaluated the effects of oral nicarbazin administration on the production and hatchability of chicken eggs. Blood plasma and egg DNC concentrations were correlated to contraceptive efficacy. Subsequent studies are being conducted with geese to determine the diet nicarbazin concentration required to produce the desired blood and plasma DNC concentrations. This approach permits the expeditious evaluation of formulations and dosing regimes by simply monitoring blood DNC concentrations in target species.

Liquid chromatographic determination of 4,4'-dinitrocarbanilide, the active component of the infertility agent nicarbazin, in chicken, duck, goose, and snake eggs.

4,4'-Dinitrocarbanilide (DNC) was extracted from chicken, duck, goose, and snake eggs and isolated by reversed-phase liquid chromatography. DNC was detected by ultraviolet absorbance at 347 nm and quantitated by comparison with a calibration standard. Recoveries of DNC from fortified control chicken, duck, goose, and snake egg samples were determined for DNC levels of 0.16, 10, and 16 microg/g. The mean recoveries from chicken, duck, goose, and snake eggs were 92 +/- 4, 88 +/- 9, 87 +/- 7, and 95 +/- 6%, respectively. The method limits of detection for DNC in chicken, duck, goose, and snake eggs ranged from 0.015 to 0.035 microg/g. The reported method is much simpler than and equally efficient as previous methods developed for the determination of DNC residues in egg contents.

The effect of cooking on diphacinone residues related to human consumption of feral pig tissues.

We examined feral pig tissues to determine whether the potential hazard of consuming meat from pigs previously exposed to diphacinone rodenticide baits was reduced by cooking. Residue levels were measured in cooked and uncooked tissues of feral pigs exposed to sub-lethal quantities of the anticoagulant rodenticide. Pigs were provided large amounts of baits or untreated food to consume, then euthanized prior to the onset of symptoms indicative of rodenticide poisoning or sickness. For analysis, we grouped pigs into three levels of mean diphacinone consumption: 0, 3.5, and 7.4 mg/kg. None of the pigs displayed obvious signs of toxicity during the study period. The highest concentrations of diphacinone were found in liver tissue. Cooking had little effect on residual diphacinone concentrations. The hazards to humans and pets from meat from feral pigs that consumed the rodenticide diphacinone are not reduced by cooking; consumption of pig meat obtained from areas with active rodent control programs should be avoided.

Response of captive skunks to microencapsulated tetracycline.

A captive striped skunk (Mephitis mephitis) study was conducted between February and June 2004 at the United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services National Wildlife Research Center, Fort Collins, Colorado, USA. The main objective was to determine the percentage of adult striped skunks that were marked after consuming placebo oral rabies vaccine (ORV) baits containing 100 mg of an experimental microencapsulated (coated microparticle) tetracycline hydrochloride biomarker. Biomarkers were identified in the canine teeth and mandibles of five of five skunks that consumed an ORV bait. A second objective was to determine if the microencapsulated tetracycline was resistant to photochemical conversion from tetracycline to epitetracycline. After 15 days of exposure, conversion from tetracycline to epitetracycline concentration in the microencapsulated product (mean 1.9% conversion, SD=1.24) was significantly less (P=0.006) than the pure-grade tetracycline powder (mean 7.5% conversion, SD=1.37). Results support the use of microencapsulated tetracycline hydrochloride as a biomarker in circumstances where the use of conventional powdered tetracycline hydrochloride is not feasible due to ORV bait design constraints.