01967naa a2200277 a 450000100080000000500110000800800410001910000170006024500760007726000090015352012220016265000310138465000140141565000170142965000140144665000210146065000130148165000180149465000170151265000140152965300130154365300140155665300320157070000160160277300710161815220552023-06-12       1979    bl uuuu     u00u1 u    #d1 aKELLY, J. D.  aResistance of animal helminths to anthelmintics.h[electronic resource]  c1979  aThis chapter discusses the resistance of animal helminths to anthelmintics. Resistance is defined as a significant increase in the ability of individuals within a strain to tolerate doses of a compound, which would prove lethal to the majority of individuals in a normal population of the same species. The introduction of phenothiazine and the benzimidazole broad-spectrum anthelmintics, has unfortunately led to the selection of drug-resistant strains of important parasitic helminths. The emergence of an increasing number of resistant helminths is associated with the widespread use and misuse of anthelmintics, and poses important problems for the helminth chemotherapist. Several species of ovine nematodes have developed resistance to anthelmintics after repeated exposures. Field strains of Haemonchus contortus resistant to phenothiazine (coarse particle) were first reported in the United States by Drudge et al. Benzimidazole-resistant strains of H. contortus have now been reported from the United States, Chile, Australia, South Africa, and West Malaysia. Other species of helminths known to have developed resistance to this group of drugs are Trichostrongylus colubriformis and Ostertagia circumcincta.  aAnimal parasitic nematodes  aHelminths  aParasitology  aRuminants  aAnti-Helmíntico  aHelminto  aParasitologia  aResistência  aRuminante  aControle  aNematodeo  aResistance to anthelmintics1 aHALL, C. A.  tAdvances in Pharmacology and Chemotherapygv. 16, p. 89-128, 1979.