Licun (Hebei Yongnian Handan Agricultural College 057 150
With the modernization, intensification and large-scale production of animal husbandry. Veterinary drugs (including veterinary drug additives) play a very significant role in reducing morbidity and mortality, improving feed utilization rate, promoting growth and improving product quality, and have become an indispensable material basis for modern animal husbandry. However, due to the lack of scientific knowledge and economic benefits, the abuse and overuse of veterinary drugs are widespread in animal husbandry. Its consequences, on the one hand, lead to veterinary drug residues in animal foods, which will affect human health after eating; On the other hand, a large amount of excrement (including feces, urine, etc. ) into the surrounding environment, veterinary drugs become environmental pollutants, bringing adverse effects on the ecological environment.
① Veterinary drug residues and their types
Animaldrugresidues refer to drug prototypes, metabolites and drug impurities accumulated and stored in cells, tissues and organs after animal administration. In recent years, veterinary drug residues have become a public health problem at home and abroad, which is closely related to human health. Veterinary drug residues include veterinary drug residues in ecological environment and veterinary drug residues in animal food. Animal food refers to meat (including liver, kidney and other internal organs), eggs, milk and its products. With the development of economy, the proportion of animal food in people's total food is increasing, and its health and safety have attracted much attention.
Veterinary drugs with great toxicological significance are classified according to their uses, including antibiotics, chemically synthesized antibiotics, antiparasitic drugs, growth promoters and pesticides. Antibiotics and chemically synthesized antibiotics are collectively called antibacterial drugs, which are the most important veterinary drug additives and veterinary drug residues, accounting for about 60% of pharmaceutical additives.
② Causes of veterinary drug residues
Non-compliance with the withdrawal period, illegal use of illegal drugs and irrational use of drugs are the main reasons for the excessive veterinary drug residues. Drug withdrawal period (WDT) refers to the interval from stopping drug administration to allowing animals or their products to go on the market. According to the investigation of the US Food and Drug Administration (FDA), the failure to correctly observe the withdrawal period is the main reason for the excessive veterinary drug residues. For example, the proportions of 1970, 1985, 1990 and199/year are 76%, 5 1%, 46% and 54% respectively. Illegal use of illegal drugs means: driven by economic interests, making livestock and poultry gain weight and improving lean meat rate? Stimulants such as clenbuterol hydrochloride, namely "clenbuterol"; Anabolic steroid is a sex hormone, which is used to promote the growth of domestic animals and poultry. In order to reduce the activity of livestock and poultry and achieve the purpose of gaining weight, sleeping and calming drugs were used. Irrational drug use refers to: abusing drugs and veterinary drug additives; Once symptoms appear, in the case of undiagnosed, repeated and excessive use of veterinary drugs, the preparation is invalid and the raw materials are used directly; No matter what medicine you take, it will be used as a drug additive for a long time; Change the route and object of administration of veterinary drugs at will.
③ Harm of veterinary drug residues
3.l Toxicological effects
3. 1.l Acute poisoning? 2- adrenergic receptor agonist (hereinafter referred to as? -Stimulants can strengthen cardiac contraction, dilate skeletal muscle blood vessels and bronchial smooth muscle, and are used in veterinary and medical clinic to treat shock and bronchospasm. When the therapeutic dose is more than 5 ~ 10 times, it can improve the feed conversion rate and increase the lean meat rate of most animals (cattle, sheep, pigs and poultry), commonly known as "lean meat". Clenbuterol and Mabbutt have high oral bioavailability and are widely used. -Stimulants remain in liver, lung and eye tissues at a high concentration of 100-500 g/t, and people may have toxic reactions if they eat 100-200 g once. At home and abroad, there are many reasons for eating foods containing food. -Reports of liver and lung tissue poisoning in animals with doping residues, including headache, tachycardia, mania and blood pressure drop. For example, 1997, several people in Hong Kong ate pig lungs containing clenbuterol and suffered acute poisoning.
3. 1.2 The residual concentration of veterinary drugs in chronic poisoning is usually very low, and the possibility of acute poisoning is very small. Long-term consumption often causes chronic poisoning and cumulative toxicity.
Chloramphenicol can cause severe aplastic anemia, which has nothing to do with dose and frequency. The human body is more sensitive to chloramphenicol than animals, and the metabolism and excretion functions of infants are not perfect. They are the most sensitive to chloramphenicol, so why is there a fatal "gray baby syndrome"? The residual concentration of chloramphenicol in tissues can reach more than 1mg/kg, which is a great threat to consumers. There have been reports that 1 child died after taking 2mg chloramphenicol and that elderly women used chloramphenicol eye ointment. Therefore, chloramphenicol has been banned from eating animals.
Tetracyclines can bind to calcium in bones and inhibit the development of bones and teeth. Macrolide erythromycin. Tylosin is easy to cause liver injury and hearing damage. Aminoglycoside drugs such as streptomycin, gentamicin and kanamycin mainly damage vestibular and cochlear nerves, leading to dizziness and hearing loss. Sulfonamides can destroy the hematopoietic function of human body. Long-term contact with animal food containing these drug residues may be harmful to health and cause chronic poisoning.
3. 1.3 "three causes" action, that is, carcinogenic, teratogenic and mutagenic action. Dibazole is a broad-spectrum antiparasitic drug, which kills worms and eggs by inhibiting cell activity. These drugs interfere with cell mitosis and have obvious teratogenic effect and potential carcinogenic and mutagenic effects. Estrogen, arsenic preparation, quinoxaline, nitrofuran and nitroimidazole drugs have been proved to have the "three-cause" effect, and many countries prohibit their use in edible animals, so it is generally required that they should not be detected in food. Quinolones are a new class of broad-spectrum antibacterial drugs with high efficiency and low toxicity, which are widely used in aquaculture in China. These drugs mainly affect the DNA synthesis of prokaryotic cells, but some varieties show mutagenic effect in eukaryotic cells. Some sulfonamides, such as sulfadiazine, can induce thyroid hyperplasia in rodents and have a tendency to induce tumors. Streptomycin has potential inducing effect. Excessive residues of these drugs will seriously affect human health.
3.2 Allergy
Some antibacterial drugs such as penicillin, sulfonamides, aminoglycosides and tetracycline can cause allergic reactions. Penicillins are widely used, and their metabolites and degradation products have strong sensitization effect. Quinolones can also cause allergic reactions and photosensitive reactions. Mild allergic reactions only cause measles and dermatitis. Have a fever, etc. , serious can lead to shock, and even life-threatening.
3.3 Effects on Gastrointestinal Microbes
Under normal circumstances, there are a large number of flora in human gastrointestinal tract, which are antagonistic and restrictive to each other to maintain balance. If you are exposed to animal food with antibiotic residues for a long time, some sensitive flora will be inhibited or killed, drug-resistant bacteria or conditional pathogenic bacteria will multiply in large numbers, and the balance of microorganisms will be destroyed, causing diseases and damaging human health.
3.4 Inducing drug-resistant strains
The widespread use of antimicrobial agents, especially long-term sub-therapeutic doses of antimicrobial agents in feed, is easy to induce drug-resistant strains. Bacterial drug resistance gene is located on R plasmid, which can replicate autonomously in cytoplasm and can be genetically transferred and spread among bacteria through transduction. The transfer of drug-resistant plasmids between humans and animals has been controversial, but experiments have confirmed that drug-resistant genes can be transferred between humans and animals, that is, drug-resistant strains from animals can be transmitted to humans.
In addition, people's long-term exposure to animal food with antibacterial drug residues will also directly induce drug-resistant strains in the human body.
3.5 Hormone-like effect
Sex hormones and their analogues mainly include steroid anabolic steroids and nonsteroidal anabolic steroids, which were used as growth promoters for livestock and poultry in many countries before 1970s. Anabolic steroids often exist in liver, kidney and injection or implantation sites, which can produce a series of hormone-like effects after human consumption. Potential carcinogenicity, developmental toxicity (precocious puberty in children), feminization and feminization. In recent years, children's precocious puberty is often reported in China, which is related to the illegal use of sex hormones as growth promoters in aquaculture, resulting in their residues in animal foods. In addition, the hormone-like effects of sulfadiazine are also under study.
3.6 Eco-environmental toxicity
Veterinary drugs and their metabolites enter the environment through feces and urine. Because of its biological activity, it is potentially toxic to the surrounding environment and will have an impact on soil microorganisms, aquatic organisms and insects, which has become a hot research topic at home and abroad in recent years.
Avermectin is highly toxic to lower aquatic animals, nematodes in soil and insects in the environment. Anabolic steroids enter the environment with excreta and become environmental hormone pollutants. For example, the estradiol of lng/L in sewage can induce the feminization of male fish. Haloperidone is an anticoccidial drug, which is very toxic to aquatic animals (such as fish and shrimp). Organoarsenic preparations are widely used as additives, which can inhibit soil nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and cellulose-decomposing bacteria when they enter the environment with excreta.
In addition, veterinary drugs entering the environment are passive, enriched by plants and then enter the food chain, which is also harmful to human health. Organophosphorus pesticides and organochlorine pesticides are often used to repel parasites in animals and in vitro. Organophosphorus pesticides in excreta do great harm to the ecological environment, while organochlorine pesticides can exist in the environment for a long time, and are passive, rich in plants and have the "three causes" effect. Diethylstilbestrol and chlorohydroxypyridine degrade slowly in the environment and can be highly enriched in the food chain, which affects human health.
3.7 Affect the export trade of livestock and poultry products
A few years ago, China's livestock and poultry products began to enter the international market. However, due to the excessive veterinary drug residues being returned, destroyed, claimed or even terminated by some countries, China not only suffered huge economic losses, but also lost its good reputation, which seriously affected the export trade of livestock and poultry products. 1990 10000 tons of chicken exported to Japan, because the residue of chlorohydroxypyridine exceeded the standard, all the products were destroyed, causing huge economic losses. Since 1996, when the EU suspended the export of livestock and poultry products from China, the EU Veterinary Committee sent representatives to China for inspection every year. 200 1, the export of livestock and poultry products of some enterprises in Shanghai and Shandong temporarily resumed, and the export of livestock and poultry products in China was completely banned on June 2, 2002. One of the main reasons is the residue of veterinary drugs in livestock and poultry products.
After joining WTO, the phenomenon of non-trade technical barriers in international trade makes the export of livestock and poultry products in China face a more intense competitive environment. If veterinary drug residues cannot be well controlled, the export trade of livestock and poultry products will be very difficult.
④ Control measures of veterinary drug residues
The monitoring of veterinary drug residues in China started late, but the relevant departments have begun to pay attention to the problem of veterinary drug residues in animal food, and have formulated various laws and regulations to monitor veterinary drug residues, which is a powerful measure to ensure the safety of animal food in China. However, the monitoring of veterinary drug residues is a long-term and arduous task, which needs the great attention of the government and management departments and the support of the general public. The following control measures are recommended.
4.l Accelerate the legislation of veterinary drug residues and formulate corresponding laws and regulations.
Formulate laws and regulations on penalties for the safe use and illegal use of veterinary drugs as soon as possible, formulate national laws and regulations on animal food safety and a series of operational supporting management regulations, bring the monitoring of veterinary drug residues into the legal management track, so that there are laws to follow and rules to follow, and at the same time increase penalties to promote and promote the monitoring of veterinary drug residues.
4.2 Strictly regulate the safe production and use of veterinary drugs.
Supervise enterprises to produce, manage and use veterinary drugs according to law, prohibit veterinary drugs with unknown ingredients and inconsistent with the labeled ingredients from entering the market, increase the investigation and punishment of prohibited veterinary drugs, and crack down on them once found; Strictly stipulate and abide by the object, duration, dosage and withdrawal period of veterinary drugs. Strengthen the monitoring of feed production enterprises and prohibit the use of veterinary drugs other than those stipulated by the Ministry of Agriculture as feed additives.
4.3 Strengthen feeding management and change the concept of feeding.
Learn foreign advanced breeding management technology, create a good breeding environment, enhance animal immunity, implement comprehensive health and epidemic prevention measures, reduce the incidence of livestock and poultry, and reduce the use of veterinary drugs. At the same time, make full use of traditional Chinese medicine preparations, microecological preparations, enzyme preparations, polysaccharides and other high-efficiency, low-toxicity and low-residue preparations to prevent diseases and reduce veterinary drug residues.
4.4 Increase publicity efforts
Make full use of the publicity of various media to make the whole society fully aware of the harm of veterinary drug residues to human health and ecological environment, widely publicize and introduce the knowledge of scientific and rational use of veterinary drugs, comprehensively improve the scientific and technological level of farmers, and make them consciously use veterinary drugs according to regulations and consciously abide by the withdrawal period.
4.5 Strengthen the monitoring of veterinary drug residues and improve the monitoring system of veterinary drug residues.
Accelerate the establishment of national, ministerial and provincial monitoring institutions for veterinary drug residues, implement the national residue monitoring plan, increase monitoring efforts, strictly inspect and quarantine, prevent products with veterinary drug residues exceeding the standard from entering the market, destroy and punish those who exceed the standard, promote the transformation of livestock and poultry products from quantity to quality, make products with veterinary drug residues exceeding the standard have no market, and force farmers to use veterinary drugs scientifically and rationally and abide by the provisions of drug withdrawal period, so as to control veterinary drug residues.
4.6 Accelerate the establishment of detection methods for veterinary drug residues, and actively carry out international exchanges and cooperation in veterinary drug residue control technology.
Improve the detection methods of veterinary drug residues, especially the rapid screening and confirmation methods, and increase the research and efforts of veterinary drug residue screening kits. Actively carry out international exchanges and cooperation in the standardization of veterinary drug residue legislation and methods, so as to make China's veterinary drug residue monitoring in line with international standards.