Progress and significance of monitoring drug residues in livestock and poultry products

Introduction: with the rapid development of animal husbandry and the growing demand for livestock and poultry products, the variety and quantity of animal health products are increasing and widely used At present, although we strive to produce green livestock and poultry products, the large dosage and wide range application of veterinary drugs and drug feed additives are still inevitable under the current production conditions in our country, and even some cases of abuse of illegal drugs occur frequently Drug residues in livestock and poultry products have become more and more serious and become a hidden scourge of people's health 1 The harm of drug residues in livestock and poultry products 1.1 The export of livestock and poultry products was blocked in 1999 China exported 402277 tons of meat, 339109 tons of eggs, 133628 tons of milk and 776102 tons of aquatic products The export of meat accounted for 0.8% of the total output of meat, 1.8% of eggs, 1.8% of milk and 0.4% of aquatic products In the early 1990s, China's livestock and poultry products began to enter the international market, but due to the drug residues were returned or destroyed by the relevant countries one after another The chicken exported to Japan was rejected one after another due to the excessive residue of "keqiu powder" in the chicken, resulting in the export blocked; the honey exported to France was also returned due to the excessive pesticide "Chlordimeform", and then it was refused to import, followed by the European community, the United States and Japan; the European Union refused to import honey from China due to the excessive use of drugs in Chinese feed and the excessive residue in livestock and poultry products, etc., in August 1996 The import of livestock and poultry products in China was stopped in May Subsequently, the export of livestock and poultry products in Japan, South Korea, South Africa and other countries was curbed; in 1998, EU countries decided to continue to impose trade embargo on livestock and poultry products in China, and the drug residue is still one of the main problems 1.2 Harm to human health In 1998, 17 residents in Hong Kong were poisoned by eating pig viscera from mainland China, which contained clenbuterol residues Diving athletes in China were found to be positive in urine test due to eating pig liver containing the same drugs, their performance was cancelled, and they were suspended from competition In the 1990s, some European countries also successively took the bovine liver with β - dope residue and other poisoning events Recently, dioxin in Belgian livestock and poultry products seriously exceeded the standard, which shocked the world even more Generally speaking, the harm of drug residues to human health does not always show acute toxicity If the human body often takes the same residues of low dose, after a certain period of time, they gradually accumulate in the body and lead to various organ diseases or even canceration The effects of drug residues on human body are mainly manifested in allergy, anaphylaxis, teratogenesis, mutagenesis, carcinogenesis and hormone (like) effects 2 The negative effect of antibiotic additive 2.1 The long-term use of antibiotics leads to antibiotic resistance of bacteria The emergence of antibiotic resistance is due to the existence of antibiotic resistant bacteria The development of antibiotic resistant bacteria is quite rapid For example, penicillin has been produced in large quantities since 1939, drug-resistant bacteria have appeared since 1943, and new penicillin resistant bacteria have appeared in 1967, 1976 and 1983 In 1994, the British reported the presence of bacteria in patient samples that could resist all existing antibiotics It can be said that since the 1990s, terrible things have happened constantly Drug resistant bacteria can not only tolerate one or a few antibiotics, but also tolerate many kinds of antibiotics, and the drug resistance spectrum is more and more wide So far, at least three kinds of disease bacteria that can cause serious life-threatening have been found, Enterococcus faecalis, Mycobacterium pneumoniae and Pseudomonas aeruginosa can tolerate more than 100 kinds of antibiotics The harm of antibiotic resistance is very serious It not only weakens the efficacy of antibiotics, but also results in the increase of drug dosage, the prolongation of treatment course, the increase of recurrence rate, and sometimes causes complications In some cases, it even makes antibiotics lose efficacy, leading to the increase of mortality This problem has aroused widespread attention from all walks of life, so it is imperative to provide "green food" to the market and strictly control the drug residues in food As a developing country, the quality of science and culture of the masses is relatively low, the systems are not perfect, and the wrong practices such as unilateral pursuit of high efficiency, efficacy of broad-spectrum antibiotics "treating all diseases" and unilateral pursuit of benefits and massive addition of antibiotics lead to the problem of drug resistance of pathogenic bacteria in China becoming more and more serious, and all kinds of pathogenic bacteria have different degrees of drug resistance Almost 100% of Shigella are resistant to antibiotics, especially tetracycline antibiotics In animal husbandry, bacterial diseases, such as Escherichia coli, Staphylococcus and Salmonella, which were not serious or rarely occurred in the past, have risen to be the main infectious diseases of poultry, which is directly related to the long-term abuse of antibiotics 2.2 the long-term use of antibiotics results in the decline of animal immunity A large number of antibiotics will be distributed to lymph nodes, kidneys, liver, spleen, thymus, lungs, bones and other tissues and organs with blood circulation after they are ingested into the body The immune ability of animal body will be gradually weakened, the number of chronic cases of human and animal will increase, and some diseases that can form lifelong strong immune will recur frequently Antibiotics can also lead to the reduction of antigen quality, directly affect the immune process, and thus have adverse effects on vaccination 2.3 the long-term use of antibiotics can cause endogenous infection and double infection in livestock and poultry Although antibiotics have their own antibacterial spectrum, it is basically difficult to avoid that they will affect the growth of beneficial bacteria in the body when they act on pathogenic bacteria, especially the long-term and large-scale use, which will cause the imbalance of bacteria in the body and damage the micro ecological balance Latent harmful bacteria take the opportunity to multiply in large numbers and cause endogenous infection In another case, antibiotics will destroy the sensitive bacteria in the body, causing a large number of vacancies on the attachment points of these microorganisms in the body, providing opportunities for the external drug-resistant bacteria to enter, thus causing exogenous infection Double infection is also caused by the destruction of microecological balance when a large number of antibiotics are used to kill a certain bacteria, and another or more endogenous or exogenous bacteria then infect the body again 2.4 after long-term use of antibiotics in livestock and poultry products and environment, residual antibiotics are absorbed into the body and distributed to almost all organs of the body, but most antibiotics are difficult to pass through several "natural barriers" of the body, such as blood-brain barrier, blood testis barrier, etc Antibiotics are more distributed in internal organs, especially in liver, but less in muscle and fat Antibiotics are metabolized in many ways, but most of them are mainly metabolized by liver and excreted by excrement through bile They also remain in milk and egg through the process of lactation and egg production Some stable antibiotics can still exist for a long time after being excreted into the environment, resulting in drug residues in the environment These residual drugs slowly accumulate in human body and other plants through livestock and poultry products and environment, and finally gather in human body in various ways, resulting in a large number of drug-resistant strains, loss of resistance to certain diseases, or toxic effects on the body due to a large amount of accumulation 3 Thinking about the prohibition of antibiotics as growth promoting additives in EU countries 3.1 The World Health Organization (who) conference held in Berlin in 1997 proposed the cautious use of antibiotics in animal feed to reduce the spread of antibiotic resistance of pathogenic bacteria In March of the same year, the FAO held a meeting in Paris, at which it was determined to control the threat of using antibiotics in feed to public health through "risk analysis, risk management, careful use of antibiotics and drug resistance testing" The meeting proposed the establishment of a European bacterial resistance testing system to identify pathogens resistant to antibiotics At the end of 1998, the European Commission issued a ban on the use of bacitracin zinc, spiramycin, virginiamycin and tylosin as growth promoters in animal feed, which came into effect on July 1, 1999 These four antibiotics account for 80% of the total market share of animal antibiotics At the same time, the EU's permission to use some anticoccidial drugs will not be extended after it expires in 1999 In addition to several widely used anticoccidial agents, only monensin, salinomycin, Flavomycin and pycnomycin are allowed to continue to be used in feed The EU believes that these four drugs are not important in the current human drug system and will not lead to resistance of human pathogens The European Union has begun a series of programs to study the relationship between antibiotic growth promoters and drug-resistant microorganisms The EU will eventually evaluate and re register all existing antibiotics, using the standards of the US FDA and relevant EU agencies to evaluate the potency and safety of each drug 3.2 Countermeasures of China's ban on the EU since the implementation of the EU ban, it has a huge negative impact on the export of livestock and poultry products in China After China's accession to the WTO, non-tariff trade barriers such as drug residues and drug use procedures will also become the biggest obstacle to the export of livestock and poultry products How to solve this practical problem will become one of the most important problems in China's breeding industry and feed industry The prerequisite for the EU to lift the ban on the import of livestock and poultry products from China is that China's breeding industry should conform to the EU's production procedures and regulations on livestock and poultry products In addition to the health quarantine of products (including Salmonella, Escherichia coli and other microbial indicators), drug residues and other general indicators are qualified, the EU regulations on the use of antibiotics in feed should also be implemented China is a vast country with different breeding bases To implement it comprehensively, on the one hand, it is not in line with the national conditions, and it is difficult to implement it; on the other hand, the EU's ban on the use of antibiotics is still a temporary measure Whether it can work or not can be determined only through evaluation It is difficult to estimate the advantages and disadvantages of blind follow-up in China The most feasible measure is to establish a special breeding base according to the scale of export to the EU, and produce livestock and poultry products suitable for export to the EU according to the production procedures and requirements of the EU This supply mode of livestock and poultry products has a precedent in Hong Kong, and it is less difficult to implement In the case of mature opportunity and conditions, gradually promote, and finally establish an efficient, high-quality, safe export-oriented breeding industry 4 The progress and significance of drug residues monitoring in livestock and poultry products 4.1 The progress of drug residues monitoring in livestock and poultry products abroad In view of that drug residues in livestock products have become a potential risk for human survival, the management and monitoring of animal health products has been paid more and more attention by governments of all countries The problem of veterinary drug residues in food has attracted great attention of the food Legislative Committee (CAC), the food additive legislative committee and other international organizations In order to prevent the possible drug residues in animal food from damaging human health, in 1984, under the advocacy of CAC, FAO and who jointly organized the "CCRVDF" Its main purpose is to control the residues of veterinary drugs in food, select and establish analytical methods and sampling methods applicable to the global veterinary drugs and other chemical residues, carry out toxicological evaluation on the residues of veterinary drugs, and formulate the regulations on the maximum residues of veterinary drugs in animal tissues and products and the regulations on the off drug period according to the eight steps of formulating the world or regional "regulations and standards" CCRVDF was officially established in October 1986