Anthelmintic Drug Resistance of Gastrointestinal Nematodes of Naturally Infected Goats in Haramaya, Ethiopia

First evaluation and detection of ivermectin resistance in gastrointestinal nematodes of sheep and goats in South Darfur, Sudan

In Sudan, resistance to benzimidazoles has been reported recently in cattle and goats from South Darfur. Herein, ivermectin efficacy against gastrointestinal nematodes (GINs) was evaluated in sheep and goats in three study areas in South Darfur. The faecal egg count reduction test (FECRT) was used to evaluate the efficacy of ivermectin in sheep and goats naturally infected with GINs in the region of Bulbul (goats: n = 106), Kass (goats: n = 40) and Nyala (Domaia (sheep: n = 47, goats: n = 77) and the University farm (goats: n = 52)), using different treatment plans, and the efficacy was evaluated 12 days after treatment. Ivermectin efficacy was also evaluated in goats experimentally infected using local Haemonchus contortus isolates from Kass and Nyala. Nematodes surviving ivermectin treatment in goats in Bulbul and Nyala were harvested and larvae used to infect worm-free male sheep (n = 6, ≤6 months old). Infected sheep were dosed subcutaneously with ivermectin every eight days with increasing doses from 0.2 mg/kg to 1.6 mg/kg bodyweight (bw). Reduced ivermectin efficacy was identified in sheep and goats in the four study locations. Using a paired statistic, the efficacy of a therapeutic dose in sheep was 75.6% (90% upper credible limit (UCrL): 77.5%), while twice the recommended dose led to a reduction of 92.6% (90% UCrL: 93.3%). In goats, the FECRs of a therapeutic dose were 72.9-95.3% (90% UCrL range: 73.6-95.7%) in Bulbul, Nyala Domaia, Nyala University farm and Kass. Twice the dose recommended for goats in Bulbul revealed a 90% UCrL of 87.6%. All post-treatment faecal cultures contained only Haemonchus spp. larvae. The experimental infection trials in sheep and goats supported our findings from field trials and calculated upper 90% CrL of below 98.9%. For the first time highly ivermectin resistant H. contortus populations have been identified in sheep and goats in Sudan, and resistance was experimentally confirmed.

The identification of small molecule inhibitors with anthelmintic activities that target conserved proteins among ruminant gastrointestinal nematodes

Gastrointestinal nematode (GIN) infections are a major concern for the ruminant industry worldwide and result in significant production losses. Naturally occurring polyparasitism and increasing drug resistance that potentiate disease outcomes are observed among the most prevalent GINs of veterinary importance. Within the five major taxonomic clades, clade Va represents a group of GINs that predominantly affect the abomasum or small intestine of ruminants. However, the development of effective broad-spectrum anthelmintics against ruminant clade Va GINs has been challenged by a lack of comprehensive druggable genome resources. Here, we first assembled draft genomes for three clade Va species (Cooperia oncophora, Trichostrongylus colubriformis, and Ostertagia ostertagi) and compared them with closely related ruminant GINs. Genome-wide phylogenetic reconstruction showed a relationship among ruminant GINs structured by taxonomic classification. Orthogroup (OG) inference and functional enrichment analyses identified 220 clade Va-specific and Va-conserved OGs, enriched for functions related to cell cycle and cellular senescence. Further transcriptomic analysis identified 61 taxonomically and functionally conserved clade Va OGs that may function as drug targets for new broad-spectrum anthelmintics. Chemogenomic screening identified 11 compounds targeting homologs of these OGs, thus having potential anthelmintic activity. In in vitro phenotypic assays, three kinase inhibitors (digitoxigenin, K-252a, and staurosporine) exhibited broad-spectrum anthelmintic activities against clade Va GINs by obstructing the motility of exsheathed L3 (xL3) or molting of xL3 to L4. These results demonstrate valuable applications of the new ruminant GIN genomes in gaining better insights into their life cycles and offer a contemporary approach to discovering the next generation of anthelmintics.IMPORTANCEGastrointestinal nematode (GIN) infections in ruminants are caused by parasites that inhibit normal function in the digestive tract of cattle, sheep, and goats, thereby causing morbidity and mortality. Coinfection and increasing drug resistance to current therapeutic agents will continue to worsen disease outcomes and impose significant production losses on domestic livestock producers worldwide. In combination with ongoing therapeutic efforts, advancing the discovery of new drugs with novel modes of action is critical for better controlling GIN infections. The significance of this study is in assembling and characterizing new GIN genomes of Cooperia oncophora, Ostertagia ostertagi, and Trichostrongylus colubriformis for facilitating a multi-omics approach to identify novel, biologically conserved drug targets for five major GINs of veterinary importance. With this information, we were then able to demonstrate the potential of commercially available compounds as new anthelmintics.

Understanding anthelmintic resistance in livestock using "omics" approaches

Widespread and improper use of various anthelmintics, genetic, and epidemiological factors has resulted in anthelmintic-resistant (AR) helminth populations in livestock. This is currently quite common globally in different livestock animals including sheep, goats, and cattle to gastrointestinal nematode (GIN) infections. Therefore, the mechanisms underlying AR in parasitic worm species have been the subject of ample research to tackle this challenge. Current and emerging technologies in the disciplines of genomics, transcriptomics, metabolomics, and proteomics in livestock species have advanced the understanding of the intricate molecular AR mechanisms in many major parasites. The technologies have improved the identification of possible biomarkers of resistant parasites, the ability to find actual causative genes, regulatory networks, and pathways of parasites governing the AR development including the dynamics of helminth infection and host-parasite infections. In this review, various "omics"-driven technologies including genome scan, candidate gene, quantitative trait loci, transcriptomic, proteomic, and metabolomic approaches have been described to understand AR of parasites of veterinary importance. Also, challenges and future prospects of these "omics" approaches are also discussed.

Anthelmintic Resistance of Gastrointestinal Nematodes of Communally-Grazing Goats in Humbo District, Southern Ethiopia

Background and Aim

Anthelmintic resistance (AR) in gastrointestinal nematodes (GINs) is currently present worldwide and a major challenge to goat production. However, no updated information is available on this topic in the study area. Thus, this study evaluated the efficacy of commonly used anthelmintics on GINs in naturally-infected goats and assessed farmers' perception of anthelmintic utilization practices in Humbo district, Southern Ethiopia.

Materials and Methods

The field experiments for routinely used anthelmintics, namely, albendazole, ivermectin, and tetramisole, were conducted from September 2022 to April 2023. Sixty naturally-infected goats with nematodes were selected based on egg count (≥150 eggs per gram of feces) and allocated randomly into four groups (15 animals per group). Then, fecal samples were collected pre- and post-treatment and examined for fecal egg count reduction (FECRT) to determine the AR status of goat GINs. The modified McMaster technique using standard floatation was used for quantifying the eggs. In addition, a questionnaire survey was conducted to assess anthelmintic utilization practices among goat owners.

Results

The FECR levels for albendazole, ivermectin, and tetramisole were 94.6, 95.9, and 97.3%, respectively. By coproculture, the nematode genera identified before treatment were Haemonchus, Trichostrongylus, Teladorsagia, Oesophagostomum, Bunostomum, and Chabertia Species. However, post-treatment fecal cultures showed that some Haemonchus, Trichostrongylus, and Strongyloides spp. did not respond to the treatments. The questionnaire survey revealed that albendazole was the most commonly used anthelmintic to treat nematode infection in goats. Respondents expressed that anthelmintic treatment was utilized based on veterinarian prescription (59%), availability (32%), efficacy (4%), and affordability (5%).

Conclusion

Tetramisole should be used cautiously to prevent the development of resistant strains, as it was still effective in the study area. Additionally, regular monitoring of anthelmintic effectiveness is necessary.

Extract of Torreya nucifera Pericarps Exhibits a Parasiticidal Effect on the Nematode Parasite, Trichinella spiralis

Benzimidazole derivatives can effectively treat nematode parasitic infections; however, some derivatives demand distinct administrative strategies depending on plasma concentration and patient conditions. Numerous studies have examined the potential of natural extracts to exert parasiticidal activity with minimal side effects. Herein, we examined the potential parasiticidal effects of Torreya nucifera extract. The pericarps of T. nucifera were extracted with methanol, dried, and the pellet was dissolved in hot water (Tn-Phw). We designed four individual mouse experiments to clarify the prophylactic and therapeutic effects of Tn-Phw on Trichinella spiralis infection. Also, 100 L1 larvae were isolated and treated with Tn-Phw (10 mg/mL) in vitro to confirm the killing effect. Furthermore, we microscopically examined the morphology of L1 larvae to confirm the parasite-killing effect and analyzed the morphology using a scanning electron microscope (SEM). The expression of three molting-related genes was confirmed to determine whether Tn-Phw induced morphological changes in L1 larvae. Following treatment with Tn-Phw, L1 larvae death was observed after 16 h. Following SEM examination, the healthy muscle larvae showed striated ridges and wrinkles; this was not observed in extract-treated muscle larvae. Expression levels of the three molting-related genes did not differ between the Tn-Phw-treated and control groups. T. spiralis-infected mice pretreated with Tn-Phw showed significantly reduced muscle larva infection when compared with control mice. In all experiments, treatment with Tn-Phw afforded preventive and therapeutic effects against T. spiralis infection and parasitism. Natural substances against nematode parasites could be developed as therapeutic agents with few side effects and enhanced parasiticidal efficacy.

Oxalis tetraphylla (Class: Magnoliopsidae) Possess Flavonoid Phytoconstituents with Nematocidal Activity against Haemonchus contortus

The nematocidal activity of an Oxalis tetraphylla hydroalcoholic extract against the nematode Haemonchus contortus (Hc) was assessed in vitro and the major compounds associated with nematocidal activity were identified. One hydroalcoholic extract was obtained from O. tetraphylla stems and leaves (Ot HE-SLE). The in vitro lethal concentrations (LC50 and LC90) against both eggs and exsheathed Hc infective larvae (L3) were assessed. Ot HE-SLE showed a potent ovicidal activity (LC50 = 0.213 mg/mL; LC90 = 0.71 mg/mL) and larvicidal effect (LC50 = 28.01 mg/mL; LC90 = 69.3 mg/mL). Later on, the extract was bipartitioned to obtain an ethyl acetate phase (EtOAc-Ph) and an aqueous phase (Aq-Ph). Both phases were assessed against Hc eggs at 0.25 and 1.0 mg/mL concentrations. The results with EtOAc-Ph showed 93.6% ovicidal activity, while 96.6% was recorded with Aq-Ph at 48 h post-confrontation (PC). In the case of larvicidal activity, both phases were assessed at 28 mg/mL; Aq-Ph showed >80% larvicidal activity 24 and 72 h PC, while EtOAc-Ph did not show important activity. HPLC analysis showed the presence of coumaric acid and flavonols. Flavonol compounds were the major compounds and were associated with the nematocidal activity. Additionally, the Aq-Ph that showed the highest activity was purified, and the fraction F3 showed the highest nematocidal activity.