Agriculture Business Week

Antimicrobial agents, or a group of drugs like antibiotics, antifungals, antiprotozoals, and antivirals, are potent weapons’ against pathogenic microorganisms in veterinary and human medicine, the long term use of animal feed supplemented with low or “sub-therapeutic” doses of antimicrobials has come under the greatest scrutiny.

The main concern is focused on the 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 mounting problem on human infections are difficult to treat due to antimicrobial resistance rooted in antimicrobial overuse and inappropriate use of antibiotics, with antimicrobial resistance in food borne bacteria being only a smaller contributor.

The World Health Organization (WHO) with the participation of the World Organisation for Animal Health [a.k.a. Office Internationale des Epizootes (OIE)] and the Food and Agriculture Organization (FAO), 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. The approach to ensure veterinary drugs 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 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 ANIMAL DRUG RESIDUES ARE
Meat products and animal products such as milk and eggs, may have some residual amounts of veterinary drugs which remain in edible tissues after harvest. In those food animals; where the manufacturers and national legislative directions are followed by the farmer, producer, drug residue levels will b;: 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.

REQUIRED SAFETY ASSESSMENT TESTS
The toxicity studies required by regulatory authorities like the Bureau of Animal Industry (BAI), National Meat Inspection Service (NMIS), Bureau of Fisheries and Aquatic Resources (BFAR), and the Bureau of Food and Drugs (BFAD) – 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 like adverse effects in pregnancy, fertility, reproductive performance, or ability of the substance to induce cancer (carcinogenicity) or chromosomal aberration. These are combined with careful clinical observations of the animals involved, both external observations and internal organ function.

WHEN IS A VETERINARY DRUG CONSIDERED SAFE FOR USE?
Veterinary drugs/pharmaceuticals generally have to satisfy three major criteria which are safety, quality, and efficacy before they can be authorized, licensed or approved for use.

Most countries, like the Philippines, have in place a regulatory system for the approval and safe use of veterinary medicines.

To upgrade the quality of medicated and commercial feeds, the BAI has been mandated to implement the following laws and regulations :
1. R.A. 1556, as amended, otherwise known as the “Livestock and Poultry Feeds Act,” and its implementing rules and regulations (Animal Industry Administrative Order Nos. 35, 35-A and 40; and General Memorandum Order No. 1);
2. R.A. 3720, as amended by Executive Order No. 175, otherwise known as “Food, Drugs and Devises and Cosmetics Act,” and its implementing rules and regulations; and
3. R.A. 6675, otherwise known as “Generic Acts of 1988.”

The above-mentioned laws and regulations are administered and implemented by the secretary of agriculture through the director of animal industry. The BAI, through its Animal Feed Standards Division (AFSD), oversees the manufacture, importation, distribution, advertisement and sale of livestock, poultry, aqua and specialty feeds, veterinary drugs, and chemical feed additives.

The DA and the DoH signed a Memorandum of Agreement (MOA) to delineate the responsibilities regarding registration of veterinary drugs and products.

Before the safety residues can be assessed, appropriate studies in the food producing animal are required to identify and quantify the residues. The studies would stimulate 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 lifetime durations. In these studies, effects (if any) of the medicine in internal organs such as the heart, kidney, and lungs are determined either directly by the examination of tissues or indirectly through clinical assessment such as blood and urine samples.

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 sale. It is set by scientific experts following a review of the safety data for national governments when approval is given for the commercial use of veterinary medicines. It is also a trading standard that is rigorously adhered through monitoring and surveillance testing programs for both domestically produced and imported foods. MR-Ls 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 (ADI) is a measure expressed in relation to body weight and to 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 take into account variations in the sensitivity level of different groups of people (e.g. pregnant women or children), has a safety margin added to the NOEL as determined by laboratory, safety studies to allow for such variations within population.

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 with JEFCA is responsible for the toxicological evaluation and acceptance of an 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 (CAC) 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.

CAC is an intergovernmental body with over 170 members, within the framework of the Joint Food Standards Programme established by the FAO of the United Nations and the WHO in 1963, with the purpose of protecting the health of consumers and ensuring fair practices in the food trade. The Commission also promotes coordination of all food standards work undertaken by international governmental and nongovernmental organizations. About 99 percent of the world’s population is represented in the CAC.

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 CAC to be the legally permitted maximum concentrations in a food.

CAC, on its 32nd Session held at the FAO Headquarters in Rome, Italy last July, approved the adoption of the Design and Implementation of the National Regulatory Food Safety Assurance Programme Associated with the use of Veterinary Drugs in Food Producing Animals.

to be continued…