Understanding the mechanism of anticoccidial drug resistance is of great significance for selecting appropriate drugs and methods.
Tolerance to high concentrations of anticoccidial drugs
For most anticoccidial drugs, when preventing and treating chicken coccidiosis, once the coccidia develop resistance to a certain drug, they can tolerate 4 to 8 times or even higher concentrations of its continuous use; at this time, if the drug concentration is increased, it can tolerate 4 to 8 times or even higher concentrations of this concentration, and in actual production, this concentration is enough to cause toxic effects on the chickens themselves.
Quinoline drugs were once excellent drugs for preventing and treating chicken coccidiosis. Any quinoline compound can completely inhibit the proliferation of coccidia when used continuously at a dose of 40 mg/kg. However, after acquiring resistance, even a dose of more than 1000 mg/kg is completely ineffective.
Possessing multi-drug resistance
Chicken coccidia have the ability to develop resistance to two or more anticoccidial drugs with different chemical properties and different modes of action simultaneously or successively. This multi-drug resistance can not only be obtained in the laboratory by hybridizing between insect strains resistant to different single drugs, but also insect strains isolated from the field also have resistance to 2 to 4 drugs at the same time.
Insect strains resistant to amprolium, clopidol, decoquinate, and nicarbazine have been reported.
Cross-resistance
Cross-resistance of chicken coccidia is mainly manifested in that when coccidia develop resistance to a certain anticoccidial drug, they also develop resistance to similar drugs that they have never been exposed to. This resistance often occurs between drugs with similar chemical structures and similar mechanisms of action.
It has been reported that strains that have lost sensitivity to monovalent ion carrier anticoccidial drugs are also tolerant to other monovalent ion carrier anticoccidial drugs except maduramycin, and are sensitive to divalent lasalocid.
It has been confirmed that there is no cross-resistance between the chemical drugs diclazuril and toltrazuril with different mechanisms of action.
Hereditary and relatively stable
The emergence of drug resistance is the result of repeated selection of mutant individuals in the coccidia population. The coccidia reproduce sexually in the later stage of their life cycle, forming oocysts, and drug resistance is also passed down from generation to generation.
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