How is coccidiosis caused? Where is the possibility of onset? Come on, everybody, 3Q.

Coccidiosis is a widely distributed protozoan disease. Because of the important influence of the disease on poultry industry, for decades, the majority of scientific workers have been looking for effective prevention and control methods. At present, drug therapy, immunization and combination therapy have been widely used. This paper briefly summarizes the following, for the majority of poultry farmers to learn from when choosing prevention and control strategies. 1 drug therapy drug therapy is currently recognized as an effective method to prevent and treat coccidiosis, that is, using anticoccidial drugs as feed additives [1 ~ 4]. 1. 1 currently widely used anticoccidial drugs and their modes of action 1. 1. 1 polyether antibiotics acting on cell membrane are a kind of anticoccidial drugs that have been put on the market since 1970s. China began to popularize and apply 1985, mainly including monensin, salinomycin, methylsalinomycin, lasalin and maduramycin. Polyether antibiotics can cross the cell membrane and affect ion transport. These drugs are absorbed before spores or merozoites penetrate the host cells, and combine with ions in coccidia to form complexes, which destroy the normal ion balance of cells and lead to metabolic disorder and even death of coccidia. At the same time, activating Na+-K+-ATPase increases ATP consumption, lactic acid production and amylopectin consumption [5]. The peak of its action is in the invasion period of coccidia, that is, it is effective on extracellular spores and 1 generation merozoites. 1. 1.2 drugs affecting the absorption and synthesis of coenzyme As preventive drugs for preventing and treating coccidiosis, sulfanilamide and aminopyrine have been widely used. Sulfonamides inhibit the normal development of coccidia by competing with p-aminobenzoic acid for dihydrofolate synthase, which is the most effective for all the second generation merozoites of coccidia. Amino proline replaces thiamine in the metabolism of coccidia, which prevents many carbohydrate metabolic reactions involving thiamine, thus inhibiting the development of coccidia. Its highest activity is on the third day of the cycle, and it is most effective for 1 generation merozoites. In addition, it also has certain influence on sexual cycle and sporozoites. 1. 1.3 Quinoline and pyridine anticoccidial drugs affecting mitochondrial function were used to control coccidiosis in 1970s, but their application declined due to the rapid development of drug resistance. They all inhibit the respiration of coccidia by blocking the transmission of mitochondria electrons, making them unable to develop, but in different ways. The highest activity period of these two compounds is 1 day in the life cycle of coccidia, that is, the sporozoite stage. They only inhibit the development of sporozoites and cannot kill coccidia. The active components of chlorpheniramine and nicarbazine have the ability to bind to protein, preventing mitochondrial coupling and inhibiting oxidative phosphorylation. However, the real mechanism of their action on coccidia is still unclear. The highest activity period of chlorpheniramine against Eimeria tenella is on the second day of its life cycle, and the anticoccidial activity period of nicarbazine is the second generation merozoite of its life cycle, and its killing effect on coccidia is greater than its inhibiting effect. Triazinone, a drug acting on plastids, is a new broad-spectrum anticoccidial drug, which can inhibit the function of D 1 protein, thus affecting the electron transfer or the invasion of coccidia to host cells at low oxygen concentration. Studies have shown that triazinone can swell the endoplasmic reticulum, mitochondria and other membrane structures of coccidia at different development stages without affecting the concentration of host cells, resulting in serious vacuolation, and its activity cycle is longer. 1. 1.5 haloperidone, another anticoccidial drug, also known as Sudan red, has high coccidiosis activity and has effects on all three stages of coccidiosis development. Dinitrotomide, also known as Qiuliling, mainly inhibits the asexual reproduction stage of coccidia life cycle, that is, the third day of the cycle. Qiuqiuling is a new anticoccidial drug with high efficiency, broad spectrum and low toxicity. However, there are few reports about the mechanism of action of these drugs. Great progress has also been made in the application of artemisinin, artemisinin -TMP mixture, "Quqiu Powder", "Modi Decoction" and other Chinese herbal medicines and preparations to prevent and treat this disease. Studies have shown that the use of Chinese herbal medicines and their preparations to control coccidiosis is safe and reliable, with high curative effect and no drug residue, and can regulate the immune function of the body, which is a potential method. 1.2 problems and countermeasures in drug treatment in the process of using drugs to control coccidiosis, some drug-resistant strains appear constantly. Some data show that [6 ~ 8], almost all anticoccidial drugs are threatened by drug-resistant strains to varying degrees, and show a certain degree of cross-resistance. The emergence of drug-resistant strains often leads to the failure of prevention and treatment of coccidiosis. In severe cases, coccidiosis will still erupt, accompanied by bloody stool and death. In fact, more often than not, the weight gain decreases and the feed conversion rate decreases after the drug effect decreases, which causes considerable losses to poultry farmers economically. In order to reduce or delay the emergence of drug resistance and maintain the effectiveness of anticoccidial drugs, people often adopt drug schemes such as rotation, shuttle and cooperation. Rotation is to use one drug continuously for a certain period of time, and then switch to another drug to avoid drug resistance after long-term use. Shuttle medication refers to giving different anticoccidial drugs at different growth stages of chickens. Nicabazine is a commonly used drug in this scheme 1 period. Combined medication refers to the use of two or more anticoccidial drugs with different activities, and the synergistic effect between them is used to expand the anticoccidial spectrum and improve the curative effect. Increasing drug concentration may be effective for a certain period of time, but it is not ideal from the perspective of economics and drug residue. Another problem of chemotherapy is immunosuppression. The development of coccidia is obvious in stages, and only when it develops to the second generation division and reproduction stage will it release functional antigens and induce immunity. However, the peak activity of most anticoccidial drugs is in the asexual reproductive period of coccidia development, which may prevent coccidia from developing to the reproductive period of the second generation schizont, thus inducing immunity. Therefore, it is necessary to limit the amount of feed, so that chicks can maintain a certain degree of infection without getting sick, and some oocysts can be developed under the encirclement of drugs to induce immunity. This method is more suitable for laying hens and breeders. 1.3 the problem that should be paid attention to in drug treatment is to prolong the validity period of the drug and avoid long-term single use of certain anticoccidial drugs. According to different chickens and different feeding conditions, different medication schemes should be adopted. For example, for broilers, in order to prevent coccidiosis, continuous medication is very necessary. For laying hens and breeders, on the one hand, it is necessary to prevent the outbreak of coccidiosis, on the other hand, it is necessary to make chickens immune to coccidiosis, so drugs are generally used only before laying eggs. Moreover, it is best that these drugs do not affect the production of immunity, such as Qiu Liling and nicarbazine. Different feeding conditions have different medication methods. From flat feeding to net feeding, regular amount of anticoccidial drugs are used for flat feeding, so there is no need to use drugs online. From flat feeding to flat feeding, chicks should use appropriate level of anticoccidial drugs to reduce the number of oocysts, so that chicks can obtain a certain level of immunity. When moving to a new home, it is best to use a new pad to prevent the insect pollution in the adult chicken pad, and generally you will not get sick without medication in the later stage. Rational drug use should be based on the peak period of drug action. This includes both prevention and treatment. When choosing a preventive medication scheme, it is necessary to rationally dispense drugs according to the peak period of action. For example, ampicillin is active against Eimeria tenella and Eimeria wax, and partially active against Eimeria gigantea; Ethoxyamide phenylmethyl ester is active against Eimeria maxima and Eimeria Mivae. After the combination of the two, its anticoccidial spectrum is greatly expanded and the therapeutic effect is obviously improved. On the other hand, when coccidiosis occurs, the drugs corresponding to the peak period should be selected according to the onset time to obtain the best treatment effect. When using the scheme of rotating medication and shuttle medication, the order of medication should be determined according to the mode of action and characteristics of these drugs, so as to avoid the alternate use of two drugs with the same mode of action. For example, in the first few weeks of broilers, it is unwise to use anticoccidial drugs first and then ionophore drugs, because the endogenous development period inhibited by anticoccidial drugs can still develop without the effect of ionophore drugs used later. In addition, it is unreasonable to use anticoccidial drugs in the last stage of a batch of broilers. Because drug-inhibited coccidia may develop during the withdrawal period of 5 ~ 7 days. We must ensure that coccidiosis can be controlled at the most critical moment, which must ensure that we have the strongest anti-coccidiosis drugs at this moment. Therefore, according to the epidemiology of coccidiosis and the effectiveness of drugs, the medication scheme should be adjusted in time to make the use time of the most effective anti-coccidiosis drugs consistent with the most dangerous period when coccidiosis may occur. Attention should be paid to drug residues. Because anticoccidial drugs are generally used for a long time, it is inevitable that residues will appear in meat and eggs, which will often affect the quality of products and people's health. Therefore, the withdrawal period of anticoccidial drugs must be strictly implemented. 2 Vaccination In order to cope with the drug resistance of coccidia, a new drug must be introduced every 1 ~ 2 years in the world. With the continuous improvement of people's requirements for environment and health, the cost of new drug research and development is getting higher and higher, which makes many pharmaceutical companies give up the research and development of new drugs. Another fact that must be recognized is that almost no medicine is perfect. Many drugs not only have toxic side effects, but also their residues in meat and eggs are harmful to people's health. Therefore, a certain withdrawal period is stipulated. This makes poultry farmers and researchers face a serious problem, that is, how to avoid the outbreak of coccidiosis during drug withdrawal. Therefore, it is very necessary to develop coccidiosis vaccine [9 ~ 17]. 2. 1 breeder coccidiosis vaccine 2. 1. 1 virulent coccidiosis vaccine This is the earliest coccidiosis vaccine used by people, and the strains contained in it were directly isolated from the site without any attenuated treatment. Such as Coccivac in the United States, Immucox in Canada, and live coccidiosis vaccine developed by Chien Han in China. These vaccines are mainly inoculated to chickens aged 4 ~ 14 days by drinking water or mixing materials. After the chicken breeds, the oocysts of the offspring are scattered on the bedding grass, so that the chicken can acquire immunity through repeated infection. Because this coccidia vaccine uses a virulent strain, a large number of oocysts produced by chicken reproduction may cause diseases in chickens that have not had time to form strong immunity. Therefore, the dosage should be carefully controlled to avoid harm to chickens. 2. 1.2 attenuated coccidia seedlings, which mainly include management treatment, chicken embryo passage, early breeding, late breeding and attenuated coccidia strains. For example, Paracox in Britain, Livacox in Czech Republic, attenuated coccidia vaccine of chicken embryo developed by Yang in China, early-maturing strain vaccine developed by Duan Jiashu, EIMERICOX PLUS vaccine of early-maturing and late-maturing strains introduced by Xunxun, and mixed coccidia vaccine prepared by double attenuated coccidia strains developed by Fan, etc. These coccidia vaccines are mainly suitable for chicks aged 5 ~ 10, and they are fed with feed or drinking water, and the immune effect and immune duration are ideal.