Molecular evidence on the emergence of benzimidazole resistance SNPs in field isolates of Marshallagia marshalli (Nemato
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ORIGINAL ARTICLE
Molecular evidence on the emergence of benzimidazole resistance SNPs in field isolates of Marshallagia marshalli (Nematoda: Trichostrongylidae) in sheep Fatemeh Fakhrahmad1 • Ehsan Rakhshandehroo1
•
Mehran Ghaemi1
Received: 15 July 2020 / Accepted: 10 November 2020 Ó Indian Society for Parasitology 2020
Abstract The infection with members of the Trichostrongylid nematodes has been frequently reported from sheep and goats. Because of the widespread use of Benzimidazoles (BZs), the resistance suspected to occur in some worms populations. In this study, we focused on the prevalent nematode, Marshallagia marshalli, from the abomasa of sheep. Samples were obtained from at least 10 infected farms and diagnosed with morphological and molecular methods. For resistance analysis, genomic DNA from pooled adult samples of all farms were analysed for the beta tubulin gene to detect any polymorphisms at codon positions of F167Y, E198A and F200Y. According to the results, seven farms (70%) revealed resistance (R) allele at F200Y with relatively high frequency. No other mutations were identified at the other two positions. Also, except for one homozygous (RR) occasion, the isolates with R allele had heterozygous (RS) genotype. This finding indicates that the worm populations are still affected by drugs of the BZ class. However, the genetic data also notes on developing resistance mechanisms in M. marshalli populations in sheep. Keywords Marshallagia marshalli Beta tubulin isotype 1 Sheep Internal transcribed spacer-2 (ITS-2)
& Ehsan Rakhshandehroo [email protected] 1
Department of Pathobiology, School of Veterinary Medicine, Shiraz University, P.O. Box 71441-69155, Shiraz, Iran
Introduction The increasing selection of drug-resistant nematodes in small ruminants have affected the economics of farming through decreases in productivity and reproduction (Waller 1997). Among the anthelmintic classes, the Benzimidazoles (BZs) have successfully used worldwide against nematode infections in sheep and goats (Falzon et al. 2013). In contrast, many reports have documented the development of resistance to BZ derivatives in prevalent gastrointestinal nematodes (GINs) in the trichostrongylid group (Kaplan, 2004; von Samson-Himmelstjerna et al. 2007). Therefore, a bulk of investigations have focused on the mechanisms and functional diagnosis of the resistance to BZs in those nematodes (Alvarez-Sa´nchez et al. 2005; Ghisi et al. 2007; Esteban-Ballesteros et al. 2017). The molecular techniques have demonstrated a close relation between the occurrence of single nucleotide polymorphisms (SNPs) in the beta tubulin isotype 1 gene and the resistance to BZ. The SNPs related to BZ-resistance were first found in codon position of F200Y (TTC to TAC) in Haemonchus contortus (Kwa et al. 1994). Then, mutations in two additional codons, F167Y (TTC to TAC) (Elard and Humbert 1999; Silvestre and Cabaret 2002) and E198A (GAA to GCA) (Ghisi et al. 2007) were also attributed to BZ-resistance; however, F200Y appears to be th
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