Science at CVM
CVM places strong emphasis on its scientific capacity, because without supporting research the ability of CVM to effectively protect the health of humans and animals would be diminished. Current and evolving regulatory issues related to the safety of animal-derived food and animal health products are addressed at the CVM Office of Research in Laurel, MD. Three divisions compose the Office of Research: the Division of Animal Food Microbiology, the Division of Applied Veterinary Research, and the Division of Residue Chemistry. Scientists at the Office of Research work together to conduct basic and applied research, using animals and animal systems. This research focuses on veterinary compounds as well as veterinary pathogens that pose potential health risks to both animal health and human food safety. The following is an overview of some achievements of CVM’s scientists during FY 2011.
Several ongoing studies support CVM’s mission to provide and improve methods for the detection of unsafe veterinary drug residues in animal-derived food products.
Hormone detection. In the United States, several hormones (testosterone, trenbolone, progesterone, estradiol, melengestrol acetate, zeranol) are approved for use in beef cattle at very low concentrations for the purpose of enhancing muscle growth and improving feed efficiency. The use of hormones in the animal meat production industry, however, is strictly prohibited by the European Union. As such, the use of hormones in food-producing animals has been grounds for discussion between the European Union and the United States for many years. In addition, there is the potential for hormones to be used illegally in food-producing animals, which could lead to the detection of residues in meat products. Because of the associated food safety risks, CVM has a great need for the development of specific and accurate assays for the detection of multiple hormone residues.
The Division of Residue Chemistry previously validated single-analyte methods for the detection and quantification of diethylstilbestrol and methyltestosterone in muscle tissue. With the growing need of better and faster methods for monitoring the illegal use of veterinary drugs in food-producing animals, the Division of Residue Chemistry is expanding its existing methodology to include development of sensitive multi-residue methods for the determination of multiple hormone residues in beef muscle.
In order to evaluate and validate new analytical methods, beef tissues containing incurred residues of hormones are required. To this end, individual steers were dosed parenterally (i.e., by intravenous or intramuscular injection) with 1–3 of 14 hormones to achieve the desired levels (1–5 parts-per-billion) of each hormone in muscle. Serial muscle biopsies were performed and analyzed to define target levels. At least two levels of each hormone in muscle tissue were harvested from the dosed animals. In FY 2011, we accomplished our objective of generating beef muscle tissues containing incurred hormone levels suitable for method validation. Assessment of the incurred samples and validation of the multi-residue hormone detection method will continue in FY 2012.
Ceftiofur bridging study in bovine kidney. A new and much more efficient and reliable liquid chromatography tandem mass spectrometry method has been developed and validated within the Division of Residue Chemistry for the determination and confirmation of the ceftiofur metabolite desfuroylceftiofur cysteine disulfide (DCCD) in bovine kidney. The new method, if correlated—or bridged—successfully to the existing method, could replace the high performance liquid chromatography method currently used in regulatory activities. The new liquid chromatography tandem mass spectrometry method uses current laboratory methodology and equipment, and may have the potential to be expanded into a multiclass determinative and confirmatory method for β lactams, sulfonamides, fluoroquinolones, and macrolides. In 2011, Phases 1 and 2 of the ceftiofur methods bridging study were completed and Phase 3 initiated. In Phase 1, eight animals (bovine steers) were dosed with ceftiofur, and the drug depletion profile in plasma was investigated. After a washout period (Phase 2), four of the eight animals were dosed again with ceftiofur, and tissue samples were harvested at different time points (guided by the information gathered in Phase 1) in order to achieve desired drug concentration levels in the tissue. Analysis of the incurred tissue by both the existing high performance liquid chromatography method and the newly developed liquid chromatography tandem mass spectrometry method was underway at the end of FY 2011.
Pharmacokinetics/efficacy – therapeutics for goats. Currently, only a limited number of drugs are approved by FDA for specific use in goats raised for meat and dairy products. However, the number of goats and volume of goat products entering the food supply in the United States is rapidly increasing. Accordingly, criteria are needed to evaluate the pharmacokinetics and efficacy of therapeutics intended for use in goats in order to establish guidelines to facilitate the approval of drugs intended for use in small ruminants under the Minor Use Minor Species program.
To this end, scientists within the Division of Applied Veterinary Research have initiated studies designed to determine the pharmacokinetics of several drugs used to treat intestinal worms (anthelmintic) that are approved for use in ruminant species. These drugs include levamisole, fenbendazole, albendazole, ivermectin, doramectin, and moxidectin. At present, approval of drugs for minor ruminant species (sheep and goats) relies on data generated in cattle. Comparisons of the in vivo pharmacokinetic behavior of the approved anthelmintics are thus being made across multiple ruminant species, including cows, sheep, and goats in order to determine potential species-specific differences in pharmacokinetic parameters. Investigations to characterize potential differences in the depletion of anthelmintic drugs in plasma collected from cattle, sheep, and goats were ongoing in 2011, and the data had not been finalized at the end of the year.
Biomarkers of drug efficacy in small ruminants. Office of Research scientists are working to identify potential biomarkers of drug efficacy in small ruminants to aid in the approval of new and existing veterinary therapeutics for specific use in minor species. In the small ruminant biomarker research program, comparative protein characterization (proteomic) methodologies are being applied to the assessment of changes in milk protein expression in goats with both experimentally induced endotoxin and coliform mastitis.
The goals of the separate challenge studies were to identify biomarkers of local and systemic inflammation for use in evaluating the effectiveness of non-steroidal anti-inflammatory drugs (NSAIDs) for use in minor species, and to determine if goats could be used as surrogates for dairy cattle in biomarker discovery analyses. Preliminary data indicate that the sensitivity of goats to Gram-negative bacterial toxins differs significantly from cattle. The families of proteins that exhibit altered expression in goat milk following intra-mammary challenge with lipopolysaccharide are similar to those identified in cattle, including plasma and acute-phase proteins, as well as proteins with anti-microbial properties. However, the data indicate that species-specific biomarkers will be required in order to accurately assess the efficacy of drugs that are currently approved for lactating dairy cattle for use in lactating dairy goats. Additional analyses are underway to assess changes in goat milk protein expression as a result of the administration of NSAIDs.
Nanotechnology refers to the creation, use, and manipulation of materials that are measured in nanometers (billionths of a meter). Scientists at the Office of Research are currently engaged in studies to address concerns regarding the potential toxicity and distribution of nanomaterials. Two nanotechnology projects are currently underway, one that focuses on the investigation of the in vitro effects of nanoparticles on genomic (real-time PCR and microarray) data, and the other an in vivo study aimed at the determination of the biodistribution of various nanoparticles in edible animal tissues and byproducts (milk and eggs). The goals of both studies are to increase our current understanding on how nanoparticles distribute within edible tissue in food animals and whether these particles have the potential to reach the nation’s food supply. Data from the in vitro experiments were being analyzed at the end of the year, and results of the study will be available in 2012.