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.The principal governmental agencies involved in regulating the use of veterinary drugs, biologics, and insecticides are:
FDA administers the Food Drug and Cosmetic Act (FD&C Act). Under this Act the FDA’s Center for Veterinary Medicine is responsible for regulating animal foods/feed and chemotherapeutic drugs. Veterinary drugs, medicated animal feeds and pet foods are examples of specific items subject to the FD&C Act.
The Environmental Protection Agency (EPA) administers the Federal Insecticide, Fungicide and Rodenticide Act. EPA has regulatory authority over the preparation and use of rodenticides, insecticides, and germicidal preparations for topical application on animals. If a product is to be administered systemically such as cythioate or fenthion for fleas, FDA has jurisdiction.
USDA Food Safety and Inspection Service administers a comprehensive system of inspection to insure that meat and poultry products moving in interstate commerce are safe, wholesome and accurately labeled. Their authority comes from the Federal Meat Inspection Act of 1906 and subsequent amendments.
USDA Animal and Plant Health Inspection Service through its Veterinary Biologics staff has regulatory jurisdiction over all veterinary biologics: viruses, serums, toxins and analogous products. Their authority comes from the Virus-Serum Toxin Act of 1913 .
USDA regulates such products as antitoxins, vaccines and the antigenic or immunizing component of microorganisms intended for use in diagnosis, treatment or prevention of disease in animals.
The Drug Enforcement Agency (DEA) administers the Federal Controlled Substance Act of 1970. This is the major federal law regulating the manufacture, distribution, dispensing and delivery of certain drugs that have potential for abuse, physical dependence or psychological dependence.
It is important to avoid antibiotic residues in all tissues and animal products because:
According to a report in the Journal of Dairy Science, Kaneene and Ahl reported that the following management factors relative to drug residues were causes for concern among surveyed Michigan dairy farmers:
A food is adulterated whenever it contains any chemical that may render it injurious to health or otherwise unfit for human consumption. Meat and poultry may become adulterated by unacceptable concentrations of chemicals during production of the animals before slaughter, or during processing, packaging, or storage of the meat after slaughter. During their growth, animals may be intentionally or inadvertently exposed to antibiotics, sulfonamides, growth promoting substances, mycotoxins, pesticides, toxic metals, and radionuclides. All of these may persist at slaughter and are considered residues.
Health risks from residues in food are determined by the toxicity or hazard of the chemical and the likelihood of exposure (i.e. consuming it in a given food).
Average daily intake is another important factor in determining exposure related risks. This is especially true for milk-borne residues in infants inasmuch as milk represents a much higher-than-average portion of their diet.
In the United States the maximum acceptable residue concentrations in foods are established by the Environmental Protection Agency (EPA) for pesticides and by the FDA for animal drugs and unavoidable environmental contaminants. The concentrations, designated in parts per million (ppm) or parts per billion (ppb), are referred to as tolerances. International standards, available for use by all countries, have been developed for more than 2000 compounds by the joint Food and Agricultural Organization (FAO)/World Health Organization (WHO) Codex Alimentarius Commission and are referred to as maximum residue limits (MRLs).
Several types of residue are found in foods of animal origin: industrial chemicals, agricultural chemicals, and veterinary therapeutic agents. The former two categories are of occasional clinical concern to veterinarians, usually manifested as herd problems. The latter, the therapeutic agents, are of constant concern to veterinarians involved in the production of food animals.
Agricultural and industrial chemicals which are responsible for only occasional clinical episodes in food animals, are more important as causes of adulteration. When heptachlor-treated seed grains were used as feed for dairy cattle, poultry and swine, extensive losses resulted from condemnation of adulterated meat and milk. Heptachlor persists for long periods in body fat. Polybrominated and polychlorinated biphenyls are industrialized meat and milk. Heptachlor persists for long periods in body fat. Polybrominated and polyclorinated biphenyls are industrial chemicals that persist in fat, cause clinical signs in animals, have been noted as residue producers, and have caused problems resulting from feed contamination.
Hormones. Use of diethylstilbestrol (DES) will produce a l000 pound beef animal 30 days sooner than is required for growth of a non-treated animal and will save about 500 lb of feed. In the United States this 10 to 12 percent increase in efficiency could save about 7.7 billion lb. of feed annually.
Concern about the causal association between sex hormones and neoplasia, however, resulted in the passage in 1958 of the Delaney Amendment to the Food, Drug and Cosmetic Act prohibiting the use of potential carcinogens. This was modified in 1962 to permit carcinogens to be used in animals if none was found in edible portions of the carcass. At that time, the minimum amount detectable was 100 ppm. Anything less than this equaled zero. At the present time, techniques exist for detecting levels as low as a few ppb. During the late 1970s, several actions were taken by FDA to eliminate all use of DES in cattle.
More than 40 percent of antibacterial agents produced in the United States are for animals. Nearly 100 percent of poultry, 90 percent of swine, and 60 percent of cattle agents produced in the United States are for animals. Nearly 100 percent of poultry, 90 percent of swine, and 60 percent of cattle received by carcass weight, have received growth-promoting supplementation. Most often, antibiotic residues appear in meat or meat products because of failure to observe proper withdrawal periods after therapy. This therapy may be in response to clinical disease or may be preventive in nature, such as in dry-cow therapy or feed additives.
In 1970 a special task force was appointed by the FDA to study the use of antibiotics in animal feed. The group concluded:
Veterinarians may be held legally responsible for utilizing antibiotics in such a manner that illegal concentrations of medications are found in carcasses of food animals. Veterinarians also may be held responsible for failure to advise clients of potential residue problems. Many producers, for example, do not realize that veal calves can have measurable residue concentrations when nursing dams are treated with antibiotics. Even pooled colostrum fed to calves may produce residues.
Guidelines concerning drugs approved for use in food animals and appropriate withdrawal times are published by the Center for Veterinary Medicine (CVM) of the FDA. Veterinarians must inform themselves and their clients of all legal withdrawal times for drugs, hormones, pesticides, and other products, and not abet observed violations through inaction.
Drug manufacturers are required to furnish information about withdrawal times for medications they manufacture and sell. Reading the label and adhering to stated guidelines will avoid potential problems. Drugs such as sulfamethazine persist in the environment, and this factor must be considered as well in preventing residues.
Identification of treated animals and maintenance of a permanent record that documents drugs used, route and date of administration, and recommended withdrawal periods will avoid possible legal judgments against the practitioner. This is especially important when using extralabel (unapproved) drug therapy. Extra-label use involves a careful decision by a veterinarian to use a product in a species for which it has not been specifically approved. However, some drugs, such as chloramphenicol, have always been prohibited from use in food animals and any administration would be an illegal use.
Test kits are available for the veterinarian to use on the farm to detect antibiotic residue concentrations in meat and milk before shipment (example - Live Animal Swab Test).
The USDA currently is capable of testing slaughtered animals for more than 400 drugs, pesticides, herbicides, industrial chemicals and heavy metals. This detection program consists of two parts, surveillance and monitoring.
Surveillance is designed to detect components of the livestock and poultry population in which residue problems exist, to determine the extent of the problem, and to evaluate the impact of actions initiated to reduce the problem. The information obtained by surveillance is specifically intended to provide the basis for a decision on which a range of predetermined actions could be taken. One possible action would be testing animals presented for slaughter. Surveillance results in rapid awareness among the producers with the problem. It has less impact on producers without the problems.
Monitoring also answers questions regarding residues in nonproblem populations, using the same techniques as surveillance, but it is not intended to trigger action (control). The combined results of monitoring and surveillance provide a picture of the overall residue situation in a population (e.g., beef cows + dairy cows = all cattle).
The monitoring phase uses a random sample of all animals slaughtered at a federally inspected plant to determine the prevalence of residues in food animal tissue.
The surveillance phase uses a subjective sampling method. Animals are sampled when they belong to producers responsible for recent illegal residues or because there is some indication (e.g., previous record, injection sites, or suspect animals) that an animal may contain violative residues.
Current surveillance procedures require a producer found in violation to have two consecutive lots of animals (at least five animals each) sampled and found free of residues before being released from surveillance. The carcasses are retained until the test is completed. In the past, this could take 5-12 days. Now the Swab Test On Premises (STOP) is used. Muscles, kidney, or liver is swabbed and plated on a Bacillus subtilis culture and incubated for 12 hours at 29°C (84.2°F) The sensitivity of this test is 98 percent. If results are positive, samples are sent to a laboratory, as in the past, for confirmation. Using the STOP program, FSIS can test 10 times the number of animals that were tested previously. A modification of this test, the Live Animal Swab Test (LAST) can be used with urine to screen animals before slaughter.
To be most effective advising food animal producer clients, veterinarians should be prepared to develop an efficient program of residue preventive in advising food animal producer clients, veterinarians should be prepared to develop an efficient program of residue prevention. This involves examining all critical points in the client's production enterprise in which residue problems may evolve. Elements to consider include the following:
A parent drug or chemical, its metabolites, decomposition products or all three accumulated deposited or stored within the cells, tissues, or organs of an animal following use of the drugs or chemicals:
Drug, chemical, or biologic substances added directly to animal feeds in small quantities, usually in concentrations of a few ppm., for the purpose of modifying some aspect of performance or production.
Use of target animal refers to the determination of safety and efficacy of a drug directly within the target animal - Use of target animal refers to the determination of safety and efficacy of a drug directly within the target animal for which therapeutic claims are made by the drug manufacturer; i.e., claims made for a drug in treatment of bovine ketosis must have been tested and evaluated in cattle and not specifically in rats or any other species. Safety and tissue residue data for drugs approved by the FDA in food producing animals must have been obtained from the so-called target species to coincide with the therapeutic claims made by the manufacturer.
An unintentional residue is one that occurs in animal feed or food as a result of circumstances not intended to protect the feed of food against the attack of infectious or parasitic diseases. The unintentional residue also includes residue of a drug or chemical that occurs as an environmental contaminant but cannot be differentiated from residues occurring from actual use of drugs or chemicals.
Carcinogenic effect refers to an effect produced by a substance having carcinogenic or cancer producing activity.
The term mutagen is used to describe chemical agents that damage the genetic components of a cell or organism. Mutagenic effect is genetic injury of the types gene elimination chromosome breakage point mutation. Either the germinal or somatic cells may be affected. Mutations in the germinal cells are the most far-reaching because of the impact on future generations. Several chemicals including alkylating agents and analogs of DNA bases, have been shown to elicit mutagenic activity. There has been increasing concern that drugs as well as environmental chemicals may pose a potential hazard to the human population by production of gene mutation or chromosome aberrations.
The term teratogen applies to drug or chemical agents that produce a toxic effect on the embryo or fetus during a critical phase of gestation. As a consequence, a congenital malformation is produces that affects the structural and functional integrity of the organism.
An allergic of hypersensitive effect following administration of a drug (i.e., drug allergy) is quite similar to that typified by allergic responses to protein, carbohydrate, and lipid macromolecules. Allergic reactions to drugs or chemicals may include influxes, serum sickness, cutaneous reaction and delayed hypersensitive response.
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