November 24, 2005

What are veterinary medicines used for?

Just as physicians who treat human infections use drugs to treat, control and prevent disease in humans, veterinarians use medicines to treat and prevent illness in food animals.  Healthy animals are essential for a safe food supply.  Commercially produced veterinary drugs have been used safely for food animal production for over 50 years.  The main benefits are to ensure a safer food supply through improved animal health and to reduce production costs by limiting illness which may slow growth and increase costs of livestock and poultry production.

Usage of veterinary medicines is tightly controlled and monitored., For example, there are restrictions defining which medicines may be used in a particular food animal species and the interval required between administration and harvesting of milk, eggs or meat. There are requirements for veterinary involvement to prescribe or use antibiotics. The quality, safety and efficacy of each drug product is reviewed by government regulatory authorities.  

What are antimicrobial agents?

Antimicrobial agents: a general term that refers to a group of drugs that includes antibiotics, antifungals, antiprotozoals, and antivirals, are powerful weapons against disease-causing microorganisms in veterinary and human medicine.  

Why are there concerns about veterinary drug use and bacterial resistance?

The long-term use of animal feed supplemented with low doses of antimicrobials has come under the greatest scrutiny. The main concern has focused on potential emergence of antimicrobial resistance. Scientists have determined that the potential for antibiotic resistance to occur in food borne bacteria exists, but using science-based risk analysis, assess the human medical consequence as low.  

It is thought that the growing problem of human infections that are difficult to treat due to antimicrobial resistance is rooted in antimicrobial overuse and inappropriate use of antibiotics in human medicine with antimicrobial resistance in food borne bacteria being only a smaller contributor. 

The World Health Organistion (WHO) with the participation of the Office Internationale des Epizootes and the Food and Agriculture Organisation, have developed global guidelines for the containment of antimicrobial resistance in animals intended for food. These principles include “Prudent or Judicious Use” for feed additive antibiotics in food producing animals. This approach, to ensure veterinary products are used in an appropriate manner is supported by all industry sectors.   

Experts recommend, and best practice is based on the principle, that veterinary drugs that are similar to human medicines may be used for animal health treatment, if science-based risk analysis indicates their use poses little or no risk of compromising future human health treatments.   

What are animal drug residues?

Meat products and animal products, such as milk and eggs, intended for human consumption may have some residual amounts of veterinary drugs which remain in edible tissues after harvest. In those animals where the manufacturers and national legislative directions are followed by the farmer/producer, drug residue levels will be within safe limits. In the relatively few cases where levels of residue levels exceed permitted maximum limits, the cause is nearly always improper use and as such are not legally allowed into the food system.  

What are the safety assessment tests that are currently required?

The toxicity studies required by regulatory authorities for a range of chemical types, including human medicines and veterinary medicines, use similar methods. They include studies to examine acute (single dose) effects and repeated long-term exposure, as well as those designed to examine specific effects e.g. adverse effects on pregnancy, fertility, reproductive performance, or ability of the substance to induce cancer. These are combined with careful clinical observations of the animals involved, both external observations and internal organ function. 

When is a veterinary medicine considered safe for use?

Veterinary medicines generally have to satisfy three major criteria before they can be authorised, licensed or approved for use. These are safety, quality and efficacy. Most countries have in place a regulatory system for the approval and safe use of veterinary medicines. 

Before the safety of residues can be assessed, appropriate studies in the food-producing animal are required to identify and quantify the residues. The studies would simulate the recommended conditions of commercial use of the veterinary drug in animal production.

In addition, acute toxicity studies, with rigorous observations of the experimental animals, are conducted to provide indications of effects on physiological systems.  

Longer term studies are also designed to investigate the effects of repeat dosing. These studies usually last 28 days (short term repeat dose studies) or 90 days (sub-chronic studies) and occasionally they may be of life-time durations. In these studies, effects (if any) of the medicine on internal organs such as the heart, kidney and lungs is determined either directly by examination of tissues or indirectly through clinical assessment such as blood and urine samples.  

What are safe drug residue standards?

Trace amounts of some drug residues may pass into our food through the food chain and can be detected by analysis of food products in the laboratory. It is of paramount importance that there exist safety standards by which food producers can adhere to. 

Veterinary drug residues are regulated similar to other chemical residues that may be present in a foodstuff. For each approved drug, a Maximum Residual Level (MRL) will be established. The MRL is the maximum permissible quantity of residues that may still be present in the food product at point of sale. The MRL is set by scientific experts   following a review of the safety data for national governments when approval is given for the commercial use of the veterinary medicines. The MRL is a trading standard that is rigorously adhered too through monitoring and surveillance testing programs for both domestically produced and for imported foods.  MRL’s are intentionally set to be many times lower than the level directly calculated to be safe from the laboratory animal safety studies.  The application of these additional safety factors to establish an MRL provides another “built in” precautionary measure of safety.   

The Acceptable Daily Intake or ADI is a measure expressed in relation to bodyweight, of the quantity of the drug that can be consumed daily by humans over a lifetime without any known risk to health. The ADI is usually derived from laboratory studies and diet trials observing the maximum levels of substance that can be consumed before any noticeable health effects (NOEL) are observed. The ADI standard, which takes into account variations in the sensitivity level of different groups of people (eg pregnant women or children), has a safety margin added to the NOEL as determined by laboratory, safety studies to allow for such variations within the population.  

Is there an international standard for veterinary drug residues?

The Joint FAO/WHO Expert Committee on Food Additives (JEFCA) conducts food safety assessments for residues of veterinary drugs in food. The WHO group of experts within JECFA is responsible for the toxicological evaluation and establishment of an Acceptable Daily Intake (ADI), while the FAO group of experts reviews the residue and metabolism studies relevant for establishing MRLs for veterinary drugs. 

JEFCA serves as the scientific advisory body to the FAO, WHO, their Member States, and the Codex Alimentarius Commission, primarily through the Codex Committee on Food Additives and the Codex Committee on Residues of Veterinary Drugs in Foods, regarding the safety of food additives, residues of veterinary drugs, and contaminants in food. 

The Codex Committee on Residues of Veterinary Drugs is the lead agency on veterinary drugs residues in foods and recommends MRLs for veterinary drugs. Codex MRLs for Residues of Veterinary Drugs (MRLVD) are not legally binding but are recommended by the Codex Alimentarius Commission to be the legally permitted maximum concentrations in or on a food.

What can I do to be sure my diet is safe and healthy?

Veterinary medicine is an essential part of livestock and poultry farming, and will continue to be an important part of providing safe and abundant animal products for human consumption. It is only through strict regulation and vigilance that a safe and clean environment can be provided for livestock, and the farming community, while at the same time ensuring that the final product (or derivatives) destined for human consumption remains safe, of high quality, affordable and nutritious. . 

AFIC recommends that consumers strive to maintain a balanced and varied diet, incorporating many different types of foods. This will not only ensure that consumers minimize the risk of serious illness from any particular food source, but has the added benefit of providing a more nutritionally balanced and complete diet. In general, excluding entire food groups from the daily diet increases risk that the overall diet may be nutritionally inadequate or unsafe, and major dietary change should only be made after consultation with a qualified health professional. 

Consumers who have concerns about veterinary drug residues and antimicrobial resistance can be assured that government oversight and regulation, food inspection and industry’s adherence to “Prudent Use” are designed to ensure a safe food supply.  However, consumers can exercise their right to choose by buying meat products from outlets that offer a varied product line produced using different agricultural practices. Consumers can also look for products sold under a quality assurance scheme that indicates that the producer understands and follows recommendations and restrictions on the use of veterinary drugs under the “Prudent Use” guidelines as well as meeting other standards related to animal welfare and food safety.  

Physical inspection of meat products may also be helpful, for example checking indicators like colour, smell and texture. Also check that the product for sale has not passed its expiry date. 

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