Ressource pédagogique : Dr Behdad Tarbiat -Allele frequency shift in the ?-tubulin gene of Ascaridia galli in response to repeated exposure to fenbendazole

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Despite global spread of anthelmintic resistance in livestock, there has been little discussion about the development of AR in poultry. Ascaridia galli has become ubiquitous in layers due to the ban on battery cages which has led to increase in anthelmintic use. Rapid changes in the pattern of anthelmintic use in poultry may impose strong selective pressures on A. galli. This study was set out to investigate the genetic changes of the ?-tubulin gene upon repeated exposure to BZ. Worm population with 0-, 1- and 3-times exposure (TT) to BZ was acquired. Parasite DNA was extracted, and three ?-tubulin candidate genes (2, 4 and 5) were amplified and sequenced. Each of the pools were then demultiplexed and allele frequencies were analysed, and Hardy-Weinberg test was performed. A total of 4, 4 and 2 alleles were identified for candidate 2, 4 and 5 respectively. The Hardy-Weinberg equilibrium test showed no significant difference (P> 0.05) between treatments for candidate 2 and 5. However, the HW test result was significant for TT treatment group in candidate 4 indicating selection pressure on one of the Alleles. The appearance of drug resistance reflects changes in the composition of a parasite population gene pool. We have quantified changes in allele frequencies in beta tubulin gene after multiple exposure to BZ. Even though substitution in the amino acid sequence of the ?-tubulin seems to mediate BZ resistance, this may not be the only mechanism. Shift in allele frequencies or deletion may play a role in development of AR in ascarids in poultry.<br>

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• Sciences de la vie. Biologie (570)

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