P-glycoprotein gene expression analysis of ivermectin resistance in sheep naturally infected with Haemonchus contortus

Abstract

The upregulation of P-glycoprotein genes in Haemonchus contortus suspected of ivermectin resistance (IVM-Res) was studied in sheep farms. A faecal egg count reduction test (FECRT) was used to evaluate IVM-Res on four farms (from A to D). Faecal samples positive to gastrointestinal nematodes (GINs) were used to identify infective larval stages (L3) pre- and post-IVM treatment by Polymerase Chain Reaction (PCR) test. Ten P-glycoprotein (pgp) genes were analysed to estimate the over expression level in H. contortus L3. Genes were quantified using the Retro Transcription-real time PCR technique. FECRT indicated low IVM efficacy on the four farms from zero to 33% of eggs per gram and Haemonchus, Cooperia and Trichostrongylus were the GINs identified after IVM treatment. H. contortus isolates displayed different pgp gene upregulation levels (p < 0.05): pgp4 from 19.03 to 25.96-fold on four farms; 3 and 16 pgp from 32.19 to 134.21-fold on three farms; 1, 2 and 12 pgp from 7.14 to 56.43-fold on two farms; 10 and 11 pgp from 6.82 to 32.86-fold on one farm. In conclusion, the examination of FECRT showed low IVM efficacy against GINs. Additionally, pgp3, 4 and 16 were the most frequent genes involved in sheep farms with IVM-Res problems in relation to IVM resistant H. contortus.