Development of a high performance liquid chromatography/mass spectroscopy method for the determination of strychnine concentrations in insects used to assess potential risks to insectivores

A high performance liquid chromatography/mass spectrometry (HPLC/MS) method was developed in support of a study to assess potential tertiary risks posed to insectivores by strychnine baited pocket gophers (Thomomys sp.). Necropholous insects are primary consumers of pocket gopher carcasses. A field study was conducted to collect insects from strychnine-baited and control pocket gopher carcasses. The majority of the insects collected were from the orders Diptera (flies, assayed separately as adults and larvae), Coleoptera (beetles), and Hymenoptera (ants and wasps, assayed separately). Samples (0.5 g) were extracted in acetic acid (2%) and analyzed with the mass spectrometer configured for tandem mass spectrometry. For most of the samples the strychnine concentrations were less than the method limit of detection. However, strychnine concentrations as high as 0.338, 0.341, 0.698, and 0.034 μg/g were detected in ants, fly adults, fly larvae, and beetles, respectively. This information collected with the HPLC/MS method is critical for assessing potential non-target hazards for insectivores

EVALUATION AND SIGNIFICANCE OF TETRACYCLINE STABILITY IN RABIES VACCINE BAITS

Tetracycline is widely used as a biomarker for bait consumption by wildlife; tetracycline is incorporated into bones and teeth and can be detected by fluorescence microscopy several weeks postconsumption. During 2003, the United States Department of Agriculture distributed more than 10 million tetracycline-containing rabies-vaccine baits to control the spread of wildlife vectored rabies to humans, pets, and livestock. To estimate the percentage of target species consuming the baits, raccoons and skunks were collected in baited areas and teeth were analyzed for the presence of the biomarker. Several incidents of low biomarker detection rates prompted an investigation of the stability of the biomarker in the baits. Baits were collected at several points along the manufacturing and distribution chain. Baits were analyzed for free and polymer-bound tetracycline and the less active isomer epitetracycline. Results indicated that a portion of the tetracycline was converted to epitetracycline. Additionally, significant quantities of both compounds were trapped in the polymer, which is homogeneously distributed throughout the bait. The results of this study suggest that approximately 40% of the target quantity of tetracycline was unavailable for absorption. This situation could contribute to low biomarker detection rates and suggests that formulation modification should be considered