Studies On Resistance To Anticoccidial Drugs And Its Mechanisms In Eimeria Tenella

Eimeria tenella is one of pathogens of avain coccidia which damaged chicken seriously in the world. The main methods of controlling avain coccidia depend on chemotherapy of anticoccidial drugs at present. But the development of drug-resistance of coccidia affected critically on the prevention and treatment effect of anticoccidial drugs. Demonstration of the drug-resistant mechanism of coccidian was an important basic work for finding the more effective prevention and treatment methods.The sensitive strain of Eimeria tenella was induced into the drug-resistant stains by using alone one of four anticoccidial drugs or combining anticoccidial drugs with other drugs, drug-drinking and drug-feeding, stopping drinking drug solution at the right moment during early experiment induced stage, in order to find out more suitable methods of inducing the resistant strains. The sensitive strain was compared with the resistant stains in the ultrastructure test by transmittance electron microscope, genomic DNA difference test by RAPD (Random Amplified Polymorphic DNA), the Na~+ and K~+ concentration of different strains test by flame photometer, ATP enzyme activity test by the testing box, the membrane fluidity of sporozoites test by fluorescence polarization technique, in order to find out the resistant mechanism of E. tenella. The main results were as follows:1. The strains of resistance to 1.25mg/L diclazuril solution were induced after 12 passages by means of stopping drinking the drug at rightmoment in the early induced stage of the single diclazuril-drinking , which indicated that drug-drinking and stopping drinking the drug at right moment in the early induced stage could speed up the development of strains of resistance to diclazuril.2. The strains of resistance to 1.25mg/kg diclazuril-feeding were induced after only 2 passages by combining enronfloxacin-drinking with diclazuril-feeding. The strains of maduramysin-resistance and of salinomycin-resistance were induced respectively after only 3 passages by combining the solution of LiCl ( ATP enzyme inhibitor ) with maduramysin-feeding or salinomycin-feeding. The strains of maduramysin-resistance and of salinomycin-resistance were induced respectively after only 3 passages by combining the solution of Lidocaiunm (Na+ channel blocking agent) with maduramysin-feeding or salinomycin-feeding. The results indicated that the development of the drug-resistant strains was accelerated evidently by combining anticoccidial drugs with other drugs.3. One strain induced of diclazuril-resistance was only resistant to diclazuril, but sensitive to toltrazuril. The result suggested that not all drug-resistant strains existed cross drug-resistance to diclazuril and toltrazuril.4. The glucose content of sporulated oocysts was higher in the induced diclazuril-resistant strains than in the sensitive strain. The more starch granules were observed in the induced diclazuril-resistant strains than in the sensitive strain under transmittance electron microscope.5. The genomic DNA polymorphism between the drug-sensitive strain and the induced diclazuril-resistant strains was analyzed by using RAPD and cutting genomic DNA with EcoR I ,which indicated that the induced diclazuril-resistant strains maybe came from the gene mutation of the drug-sensitive strain.6. The Na+ and K+ concentration and the ATP enzyme activity were higher in the drug-sensitive strain than in the induced maduramysin-resistant strain and in the induced salinomycin-resistant strain, which wasprobably the cause that brought about resistance to maduramysin or salinomycin.7. The membrane fluidity of sporozoites was decreased evidently in the induced strains of maduramysin-resistance or of salinomycin-resistance. The result suggested that the change of the membrane fluidity of sporozoites was probably one of the mechanisms of resistance to maduramysin or salinomycin.8. Glutamate sodium had some effect on restoring the sensitivity to maduramysin in the field maduramysin-resistant strain. The result could explain indirectly that the blocked Na' channel of the maduramysin-resistant strain was the mechanism of its resistance to maduramysin.The above results were reported first on the methods of inducing the drug-resistant strains experimentally and the resistant mechanisms of E.tenella.