High frequency of benzimidazole resistance polymorphisms and age-class differences in trichostrongyle nematodes of ranched bison from the south-central United States

Article

Author: Verocai, Guilherme G ; Kipp, Kaylee R ; Redman, Elizabeth M ; Claussen, Dani ; Gilleard, John S ; Luksovsky, Joe L

Bison production is a growing sector of the United States agriculture, with more consumers choosing bison products. Commercial bison are kept on smaller pastures and treated with anthelmintics for gastrointestinal nematodes (GIN) to maintain production. However, there is a lack of information regarding the GIN parasite communities in ranched bison or the extent of their resistance to anthelmintics. Our objectives were: i) to determine the GIN species present and the extent of resistance to the benzimidazole drug class in commercial bison herds in the southern US and ii) to assess age class differences in GIN species composition and BZ resistance. Composite coprocultures from bison in Texas (n = 14) and Oklahoma (n = 2), and individual bison of different age classes from a single ranch in central Texas (n = 43) were analyzed using ITS2 rDNA nemabiome metabarcoding to determine the trichostrongylid species composition. For both the composite and individual samples, the most common trichostrongylid species found were Haemonchus contortus, Haemonchus placei, and Ostertagia ostertagi. Among the known canonical isotype-1 β-tubulin BZ resistance polymorphisms (at codons 200, 198, 167), the 200Y (TTC > TAC) substitution was the most widespread across the two southern states, with a prevalence of 81.3 %. Other polymorphisms, such as 167Y (TTC > TAC) and 198L (GAA > TTA), were also detected, and both had prevalences of 62.5 %. Ostertagia ostertagi was found to have very high frequencies (overall mean frequency = 62.6 %; range = 28.3-100 %) of the 200Y (TTC > TAC) polymorphism in all age classes sampled. Overall, benzimidazole resistance polymorphisms were found at moderate to high frequency in the three major economically important GIN species in ranched bison in Texas and Oklahoma, suggesting a potential widespread distribution of benzimidazole resistance polymorphisms in the southern United States. This work has important implications for all other grazing livestock and illustrates the importance of early detection of anthelmintic resistance and the need for mitigation strategies.

01 Apr 2025·Veterinary Parasitology: Regional Studies and Reports

Albendazole resistance in naturally infected sheep with gastrointestinal nematodes in two northwest municipalities of Sinaloa, Mexico

Article

Author: López-Arellano, Ma Eugenia ; Enríquez-Verdugo, Idalia ; Solis-Carrasco, Jesús Daniel ; Reyes-Guerrero, David E ; Gaxiola-Camacho, Soila Maribel ; Barraza-Tizoc, Claudia Leonor ; Rodríguez-Gaxiola, Miguel Ángel ; Pérez-Anzures, Gustavo ; Castro-Del-Campo, Nohemí

The main aim of this study was to evaluate the anthelmintic resistance to albendazole (ABZ) (from the benzimidazole [BZ] family) in sheep farms located in the northeast of Sinaloa, Mexico. The study was conducted on four sheep farms in the northwest of Sinaloa, Mexico. The faecal egg count reduction test (FECRT), along with endpoint and allele-specific polymerase chain reaction techniques, were used to determine the percentage and proportion of BZ resistance in gastrointestinal nematode (GIN) species before and after ABZ treatment. Genomic DNA (gDNA) from infective larvae (L₃) was processed to identify GIN species and detect nucleotide changes at codons 167 and 200 of the β-tubulin gene. Results from the FECRT showed low ABZ efficacy, ranging from 0 % to 83 % across the four sheep farms. Haemonchus was the most prevalent nematode identified, with a high number of gDNA copies detected both before and after ABZ treatment, followed by Cooperia, Trichostrongylus, and Oesophagostomum, but only before ABZ treatment. Additionally, ABZ BZ] polymorphisms were confirmed at codon 200 (TTC/TAC) in Haemonchus contortus (H. contortus) across all four farms, with both gDNA fragments detected: a 550-bp fragment indicating susceptibility and a 250-bp fragment indicating a heterozygous population for BZ resistance. No BZ polymorphism was observed at codon 167 (TTC/TAC) in any population. In conclusion, sheep farms in the northwest of Sinaloa demonstrated resistance to BZ, with H. contortus being the main GIN species involved. These findings highlight the importance of conducting parasitological and molecular diagnostics for anthelmintic resistance, as detecting heterozygous populations may help improve control methods and preserve ABZ efficacy.

07 Jan 2025·The Journal of Chemical Physics

Molecular orientation of dielectric layers at indigo/dielectric interfaces impacts the ordering of indigo films in organic field-effect transistors

Article

Author: Tanoue, Koki ; Miyamae, Takayuki ; Roberts, Sean T. ; Marsters, Celena L. ; Ishii, Hisao

Organic multilayer systems, which are stacked layers of different organic materials, are used in various organic electronic devices such as organic light-emitting diodes (OLEDs) and organic field-effect transistors (OFETs). In particular, OFETs are promising as key components in flexible electronic devices. In this study, we investigated how the inclusion of an insulating tetratetracontane (TTC) interlayer in ambipolar indigo-based OFETs can be used to alter the crystallinity and electrical properties of the indigo charge transport layer. We find that the inclusion of a 20-nm-thick TTC film thermally annealed at a low temperature of 70 °C acts to significantly increase the ambipolar electrical transport of the indigo layer. X-ray diffraction, atomic force microscopy, and vibrational sum frequency generation measurements showed that annealing the TTC film significantly improved its ordering. The electronic sum-frequency generation spectra of TTC/indigo bilayers show that this improved ordering of TTC films promotes the growth of crystalline indigo films that exhibit charge mobilities in OFET that are nearly an order of magnitude larger than those measured for devices grown on unannealed TTC layers. Furthermore, using vibrational sum-frequency generation spectroscopy, we found that pre-annealing the TTC layer prior to indigo deposition can suppress the formation of defects within the TTC layer during indigo film growth, which also contributes to enhanced charge transport. Our results highlight the importance of controlling the molecular ordering within the interlayer contacts in OFET structures to achieve an enhanced performance.

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Acute Kidney Injury	Preclinical	China	Cheng Du Yun Hai Si Mian Ti Sheng Wu Ke Ji You Xian Gong Si	26 Jun 2024

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