The larval feeding inhibition assay for the diagnosis of nematode anthelmintic resistance.
A larval feeding assay for detection of nematode anthelmintic resistance to macrocyclic lactones and imidazothiazoles is described. The estimated concentration of anthelmintic required to inhibit larval feeding in 50% of L1's (IC50) that were resistant to either macrocyclic lactones or imidazothiazoles were significantly higher (P < or = 0.05) than those of susceptible isolates. Some variations in IC50 values were observed during the patent period of infection in all strains, although the pattern of the IC50 followed the same course. IC50 values varied in larvae developing from eggs shed throughout the patent period, with low values in the earliest larvae followed by higher values as the infection progressed, before decreasing at 70-90 days post-infection, although the low values of the first part of the patent period were not reached. However, the IC50 differences between all resistant and susceptible strains were significant throughout the whole patent period for ivermectin and levamisole. These results suggest that this technique may provide an alternative in vitro to detect anthelmintic resistance.
Alvarez-Sánchez
M A
MA
Department of Patología Animal (Sanidad Animal), Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n, 24071 León, Spain.
Pérez García
J
J
Bartley
D
D
Jackson
F
F
Rojo-Vázquez
F A
FA
D000818:Animals; D000969:Antinematodal Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D004435:Eating / Q000187:drug effects; D005243:Feces / Q000469:parasitology; D020128:Inhibitory Concentration 50; D007559:Ivermectin / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D007978:Levamisole / Q000494:pharmacology*; D010270:Parasite Egg Count / Q000662:veterinary; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy / Q000469:parasitology; D014251:Trichostrongyloidea / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D014252:Trichostrongyloidiasis / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary
D000969:Antinematodal Agents; D007978:Levamisole; D007559:Ivermectin