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Analytical Chemistry Project Accomplishments

Analytical Chemistry Project: Chemical and Metabolic Approaches for Minimizing Human-Wildlife Conflicts

PROJECT GOAL: Development of new and improved wildlife management tools through research in the application of biomarkers, chemical perception, and pharmacology as well as continued delivery of high-quality analytical support for Wildlife Services research and operational activities.

Project Accomplishments 2010

Chemistry-Based Tools
To help meet the increasing need for new, federally approved chemical tools to manage wildlife damage, National Wildlife Research center (NWRC) scientists design and test methodologies to identify, analyze, and develop new drugs, repellents, toxicants, DNA markers, and other chemistry-based wildlife damage management tools. These methodologies support U.S. Environmental Protection Agency (EPA) and U.S. Department of Health and Human Services, Food and Drug Administration (FDA) registration requirements. The NWRC chemistry unit also conducts research to develop improved techniques for modeling, tracking, monitoring, and censusing wildlife populations.

Rodenticide Toxicity to Nontarget Bird Species—Diphacinone is a first-generation anticoagulant rodenticide used to manage rats, mice, and other rodent pests. Nontarget species, such as birds, are potentially exposed to anticoagulant rodenticides through a variety of pathways during field rodent control operations.

In laboratory studies, NWRC scientists and colleagues at the USGS Patuxent Wildlife Research Center investigated sublethal responses (blood clotting time) and lethality to diphacinone in northern bobwhite quail ( Colinus virginianus), a species traditionally used in wildlife pesticide risk assessments, and American kestrels ( Falco sparverius), a model for studying toxicology in predatory birds. The scientists adapted several precise and sensitive clotting assays for measuring prothrombin time, Russell's viper venom time (RVVT), and thrombin clotting time in these species. The oral administration of diphacinone over a range of doses (sublethal to low lethal dose) prolonged prothrombin time and RVVT within 24 to 48 hours after exposure. The oral toxicity of dipahacinone was about 20 times greater to American kestrels (Falco sparverius) than to northern bobwhite quail (Colinus virginianus). Prolonged in vitro clotting times reflect impaired coagulation abilities; scientists detected these prolonged times before or at the onset of overt signs of toxicity and lethality in both bobwhite quail and American kestrels. They also tested tissues from these animals for diphacinone, enabling the scientists to correlate tissue residue levels of diphacinone to prolonged clotting times and overt signs of toxicity.

This information will aid in the development of a physiologically based, pharmacokinetic model to assess and predict rodenticide toxicity to a variety of nontarget avian species.

Detecting Disease Using Volatile Compounds—Wildlife can transmit various diseases (e.g, rabies, avian influenza, bovine tuberculosis, salmonella) to human and livestock. Thus, early detection in wildlife can be important for controlling the spread of such diseases. There is evidence that animals can detect disease through odors and that trained animals might be used to identify the presence of AI in wild birds. NWRC partnered with the Monell Chemical Senses Center to develop diagnostic tools that use odor as a means to detect disease.

Researchers trained mice to identify odors in feces collected from ducks infected with low-pathogenic AI. Mice correctly distinguished between infected feces and uninfected feces more than 90% of the time. These results indicate that yet-to-be-identified volatile compound(s) are indicators of infection. Furthermore, the results suggest that animal and instrumental tools could be developed for identifying infected animals or populations. For example, the same behavioral system used for training mice as sensor animals could be used to train dogs for environmental screening, and the same photo of mouse in mazeodorants used by the mice for discrimination could be monitored by advanced analytical chemistry techniques.

Taste Receptors and Implications for Oral Baits— Animals use taste, smell, and nervous system senses to identify beneficial nutrients, non-edible items, and toxins. For example, bitterness is thought to prompt an avoidance response in animals to toxic items. Recently, taste receptors were identified in the gastrointestinal (GI) mucosa of mammals. It is unclear, however, if chemosensory input from GI taste receptors can modify the taste response to a substance infused directly into the gut (i.e., stomach or small intestine).

In a series of experiments with mice, NWRC scientists and colleagues from the Monell Chemical Senses Center demonstrated that, despite the presence of taste receptors in the mammalian gut, information regarding food taste is not transmitted directly from the gut to the brain. However, tastes delivered directly to the gut can be detected in the oral cavity, likely via the circulatory system. These results suggest that microencapsulation of active ingredients in orally delivered baits may not prevent animals from tasting bitter toxicants. Although such coatings may prevent oral detection of bitter toxicants during ingestion, the circulatory system may be a source of taste information that could be involved in bait shyness.

Evaluation of Natural Compounds as Snake Repellents— A repellent that could deter snakes from entering into areas of human activity would be a valuable wildlife management product for military, commercial , and private users. To help address this need, NWRC scientists collaborated with a private company to evaluate 10 natural compounds for use as snake repellents.

The scientists used Y-mazes to test responses of individual garter snakes (Thamnophis sirtalis) and rattlesnakes ( Crotalis atrox) to formulations that included one or more of the following: butanethiol, butric acid, elemental sulfer, naphthalene, oleoresin of capsaicin, Colgin Liquid Smoke™, cassia oil, cornmint oil, cedar oil, and synthetic fermented egg (SFE). Each Y-maze consisted of a base arm into which a test snake was placed at the beginning of a trial, along with a right and left arm. An 8-inch-wide “strip” of test formulation was placed across the width of one arm near the Y-juncture, and a strip of control material was placed in the other arm. A trial was complete when the test snake crossed completely over either test strip. The test was repeated the following day using the same individual, but switching the placement of test and control formulations in maze arms.

Only one formulation yielded a statistically significant repellency (80 percent, 0.8% SFE, 0.2% butyric acid, 0.1% capsaicin, 0.9% cassia oil), but that result only occurred on the first day of testing. Three of the compounds tested (cassia oil, cedar oil, and cornmint oil) are listed as minimum-risk pesticide products exempted under section 25(b) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and were previously shown to be highly repellent to snakes when sprayed directly on them. These results indicate that few to none of the agents currently under FIFRA are repellent to snakes when granularly formulated and broadcast.

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