title: Analysis of the beta-tubulin codon 200 genotype distribution in a benzimidazole-susceptible and -resistant cyathostome population.
abstract: To study the prevalence of the polymorphism in position 200 of the beta-tubulin gene in the mechanism of benzimidazole (BZ) resistance in cyathostomes of horses, an allele-specific PCR was used to detect the genotype of individuals of BZ-susceptible and BZ-resistant populations. The molecular analysis of 100 adults recovered from an anthelmintic-naïve horse revealed 80% homozygous TTC/TTC individuals, 17% heterozygous TTC/TAC and 3% homozygous TAC/TAC. A naturally infected horse was treated with increasing fenbendazole (FBZ) dosages to select a BZ-resistant population of cyathostomes. The PCR based analysis of 3rd-stage larvae (L3) during the experiment revealed a decrease of the homozygous TTC/TTC genotype and an increase in heterozygous TTC/TAC and homozygous TAC/TAC individuals. After treatment 42.3% of the adults (n=104) were homozygous TTC/TTC, 55.8% were heterozygous TTC/TAC and only 1.9% showed the homozygous genotype TAC/TAC. The results of the molecular analysis lead to the proposal that polymorphism within codon 200 is not the only reason for the development of BZ resistance in small strongyles.
authors.affiliation: Institute of Parasitology, School of Veterinary Medicine Hannover, Buenteweg 17, D-30559 Hannover, Germany. Michaela.Pape@tiho-hannover.de
authors.forename: M
authors.initials: M
authors.lastname: Pape
authors.forename: J
authors.initials: J
authors.lastname: Posedi
authors.forename: K
authors.initials: K
authors.lastname: Failing
authors.forename: T
authors.initials: T
authors.lastname: Schnieder
authors.forename: G
authors.initials: G
authors.lastname: von Samson-Himmelstjerna
mesh_terms: D000483:Alleles; D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology*; D001562:Benzimidazoles / Q000494:pharmacology*; D003062:Codon / Q000032:analysis; D018509:DNA, Helminth / Q000235:genetics; D004351:Drug Resistance; D005838:Genotype; D006736:Horses; D008970:Molecular Weight; D013319:Strongyle Infections, Equine / Q000175:diagnosis / Q000453:epidemiology / Q000469:parasitology*; D013320:Strongyloidea / Q000235:genetics* / Q000302:isolation & purification; D014404:Tubulin / Q000032:analysis / Q000235:genetics*
chemical_list: D000871:Anthelmintics; D001562:Benzimidazoles; D003062:Codon; D018509:DNA, Helminth; D014404:Tubulin; C031000:benzimidazole