Search

A specific and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the determination of the anticoagulant rodenticide diphacinone (DPN) in mouse and rat liver. Tissue samples were extracted with a mixture of water and acetonitrile containing ammonium hydroxide. The extracted sample was cleaned up with a combination of liquid-liquid partitioning and dispersive solid phase extraction. Chromatographic separation was achieved using a Waters X-Bridge BEH C-18 LC column (50 mm, 2.1 mm ID, 2.5 μm particle size) with detection on a triple quadrupole mass spectrometer in multiple reaction monitoring (MRM) mode. The monitored transition for DPN was m/z 339.0 → 167.0 for quantitation and 339.0 → 172.0 and 339.0 → 116.0 for confirmation. The linear range was 0.5 to 375 ng/mL. The average precision of DPN, represented by the relative standard deviation of the observed concentrations, was 7.2% (range = 0.97% - 20.4%) and the average accuracy, represented by the relative error, was 5.8% (range = 1.06% - 14.7%). The recovery of DPN fortified at 3 different levels averaged 106% in rat liver and 101% in mouse liver. The established method was successfully used to determine DPN residue levels in Polynesian rats (Rattus exulans) and mice (Mus musculus) fed two different formulated baits containing DPN. The observed residue levels were consistent with values observed in other rodent studies. However, the amount of bait consumed was lower for the novel baits evaluated in this study., Competing Interests: The authors have no competing interests to the publication of this work., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

We tested the efficacy and palatability of nine commercial rodenticide bait formulations on Polynesian rats (Rattus exulans), roof rats (R. rattus), and house mice (Mus musculus). Efficacy varied by rodenticide tested and rodent species. Generally, rodenticides were more effective against mice than for either of the rat species, and mice tended to consume more rodenticide bait than the laboratory chow alternative food. Efficacy was generally highest for the second-generation anticoagulants tested; however, this varied across products and one-first-generation rodenticide had similar effectiveness. Bait acceptance (palatability) also varied both by rodenticide and by rodent species. Acceptance was the lowest for the acute rodenticides. Bait acceptance appeared to substantially affect the efficacy of rodenticides; materials that were not well accepted produced lower mortality rates. Rodenticide products currently registered for use in Hawaii performed less effectively in this study than other available products not yet registered. Although markets for rodent control products for use on islands are limited, there are advantages to having additional products registered for island use in agriculture, conservation, and public health., (© US Government 2010)

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%.

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.

The eradication or control of invasive small Indian mongooses from islands likely requires toxic baiting when removal by trapping proves insufficient. The one toxic bait currently registered for mongooses in the United States has relatively low palatability and efficacy for mongooses. Developing and registering a new pesticide can be very expensive, while funding for developing toxicants for mongooses is limited. Once registered, use of a toxic bait may be hindered by other factors, such as public opposition to an inhumane toxicant, poorer efficacy than expected, or if the toxic bait is difficult for applicators to apply or store. Therefore, we conducted a product feasibility assessment comparing the registration and use potential of toxic baits for mongooses containing either bromethalin, diphacinone, para-aminopropiophenone (PAPP), or sodium nitrite (SN). We estimated that a diphacinone bait would be the cheapest and fastest to register, and more application methods may be allowed compared to the others. On the negative side, we ranked diphacinone as the least humane toxicant of the four, largely due to a prolonged time to death following exposure and onset of symptoms. However, this interval also increases the probability that the antidote can be administered following an accidental exposure. If an alternative toxicant is required, use of a bromethalin, PAPP, or SN bait would likely be limited to bait stations or burrow baiting due to primary risks to non-target species. A bromethalin bait would be the cheapest and fastest to register of the three, particularly if a bait that is already commercially available proved efficacious for mongoose. However, we ranked bromethalin lower than PAPP or SN for overall humaneness. A PAPP bait would be slow and the most expensive to register. An SN bait would be challenging to formulate into a palatable bait with a reasonable shelf life. Although we focused on the U.S., mongooses are invasive in many parts of the world and the regulatory and use requirements for pesticides in other countries are generally comparable. In addition, our feasibility assessment can serve as a template or starting point for managers considering development of toxicant products for vertebrate pests. [ABSTRACT FROM AUTHOR]