Potential of Haemonchus contortus first-stage larvae to characterize anthelmintic resistance through P-glycoprotein gene expression

Authors: GIGLIOTI, RODRIGO - Instituto De Zootecnia; Ferreira, Jorge; LUCIANI, GUILHERME - Instituto De Zootecnia; LOUVANDINI, HELDER - Universidade De Sao Paulo; OKINO, CINTIA - Embrapa Southeast Livestock; NICIURA, SIMONE - Embrapa Southeast Livestock; OLIVEIRA, MÁRCIA - Embrapa Southeast Livestock; AMARANTE, ALESSANDRO - Universidade Estadual Paulista (UNESP); KATIKI, LUCIANA - Instituto De Zootecnia

Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2022
Publication Date: 11/9/2022
Citation: Giglioti, R., Ferreira, J.F., Luciani, G., Louvandini, H., Okino, C., Niciura, S., Oliveira, M., Amarante, A., Katiki, L. 2022. Potential of Haemonchus contortus first-stage larvae to characterize anthelmintic resistance through P-glycoprotein gene expression. Small Ruminant Research. 217. Article 106864. https://doi.org/10.1016/j.smallrumres.2022.106864.
DOI: https://doi.org/10.1016/j.smallrumres.2022.106864

Interpretive Summary: The barber pole worm is a hurdle for meat production, is deadly when present in high loads (especially in goats), and is the most economically significant gastrointestinal parasite in small ruminant systems worldwide. The high genetic diversity among different geographic isolates is considered a major impediment for the elucidation of the mechanisms responsible for the parasite’s multidrug resistance to commercial anthelmintics. This work evaluated the levels of gene expression of nine parasitic genes encoding for proteins (named glycoproteins or Pgp) responsible for removing anthelmintic drugs from inside parasitic cells. These genes were evaluated in male and female parasites that were susceptible or resistant to anthelmintic drugs at different stages of the parasitic cycle (from eggs to adults). From the nine genes evaluated, the gene “Pgp-9” was the most expressed in all the life cycles of the barber pole worm. Our findings suggest that Pgp-9 can be a useful genetic marker that can be used to identify anthelmintic resistance at any stage of the parasitic life cycle, not only the adult stage. As the adult stage can only be obtained by sacrificing infected animals, the use of Pgp-9 can simplify the search for anthelmintic resistance and prevent the sacrifice of animal subjects harboring the parasite. The results are of major value for understanding and mitigating multidrug resistance to commercial anthelmintics in small-ruminant meat and milk production systems.

Technical Abstract: The high genetic diversity among different geographic isolates of Haemonchus contortus is considered a major hurdle to elucidating the mechanisms responsible for parasite multidrug resistance to commercial anthelmintics. Anthelmintic resistance can be assessed by the expression of resistance-related genes. Among them, Pglycoproteins (Pgp) have been extensively associated with anthelmintic resistance due to their role in drug efflux.Therefore, this study aimed to evaluate gene expression levels of nine Pgp (Pgp-1, Pgp-2, Pgp-3, Pgp-4, Pgp-9, Pgp-10, Pgp-11, Pgp-12, and Pgp-16) in eggs, first-stage larvae (L1), third-stage infective larvae (L3), adult female, and adult male of H. contortus from two isolates characterized as anthelmintic-resistant (R) and -susceptible (S). Four worm-free sheep were experimentally infected with approximately 4000 L3 larvae of H. contortus: two animals received L3 from the R isolate and two animals received L3 from the S isolate. Pgp-9 gene expression in all developmental stages of H. contortus was significantly higher (P < 0.05) in R isolate compared to S isolate. Higher expression(P < 0.05) of Pgp genes, except Pgp-4, was observed in L1 stage larvae from the R isolate. Our findings suggest that the L1 stage can be potentially used for anthelmintic resistance characterization through monitoring of different P-glycoproteins gene expression. These results may be useful in subsequent research to unveil anthelmintic resistance mechanisms in H. contortus without slaughtering sheep hosts, because L1 stages can be directly produced from eggs collected from feces.