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The faecal egg count reduction test (FECRT) remains the method of choice for establishing the efficacy of anthelmintic compounds in the field, including the diagnosis of anthelmintic resistance. We present a guideline for improving the standardization and performance of the FECRT that has four sections. In the first section, we address the major issues relevant to experimental design, choice of faecal egg count (FEC) method, statistical analysis, and interpretation of the FECRT results. In the second section, we make a series of general recommendations that are applicable across all animals addressed in this guideline. In the third section, we provide separate guidance details for cattle, small ruminants (sheep and goats), horses and pigs to address the issues that are specific to the different animal types. Finally, we provide overviews of the specific details required to conduct an FECRT for each of the different host species. To address the issues of statistical power vs. practicality, we also provide two separate options for each animal species; (i) a version designed to detect small changes in efficacy that is intended for use in scientific studies, and (ii) a less resource-intensive version intended for routine use by veterinarians and livestock owners to detect larger changes in efficacy. Compared to the previous FECRT recommendations, four important differences are noted. First, it is now generally recommended to perform the FECRT based on pre- and post-treatment FEC of the same animals (paired study design), rather than on post-treatment FEC of both treated and untreated (control) animals (unpaired study design). Second, instead of requiring a minimum mean FEC (expressed in eggs per gram (EPG)) of the group to be tested, the new requirement is for a minimum total number of eggs to be counted under the microscope (cumulative number of eggs counted before the application of a conversion factor). Third, we provide flexibility in the required size of the treatment group by presenting three separate options that depend on the (expected) number of eggs counted. Finally, these guidelines address all major livestock species, and the thresholds for defining reduced efficacy are adapted and aligned to host species, anthelmintic drug and parasite species. In conclusion, these new guidelines provide improved methodology and standardization of the FECRT for all major livestock species.

The antiparasitic drug ivermectin plays an essential role in human and animal health globally. However, ivermectin resistance is widespread in veterinary helminths and there are growing concerns of sub-optimal responses to treatment in related helminths of humans. Despite decades of research, the genetic mechanisms underlying ivermectin resistance are poorly understood in parasitic helminths. This reflects significant uncertainty regarding the mode of action of ivermectin in parasitic helminths, and the genetic complexity of these organisms; parasitic helminths have large, rapidly evolving genomes and differences in evolutionary history and genetic background can confound comparisons between resistant and susceptible populations. We undertook a controlled genetic cross of a multi-drug resistant and a susceptible reference isolate of Haemonchus contortus, an economically important gastrointestinal nematode of sheep, and ivermectin-selected the F2 population for comparison with an untreated F2 control. RNA-seq analyses of male and female adults of all populations identified high transcriptomic differentiation between parental isolates, which was significantly reduced in the F2, allowing differences associated specifically with ivermectin resistance to be identified. In all resistant populations, there was constitutive upregulation of a single gene, HCON_00155390:cky-1, a putative pharyngeal-expressed transcription factor, in a narrow locus on chromosome V previously shown to be under ivermectin selection. In addition, we detected sex-specific differences in gene expression between resistant and susceptible populations, including constitutive upregulation of a P-glycoprotein, HCON_00162780:pgp-11, in resistant males only. After ivermectin selection, we identified differential expression of genes with roles in neuronal function and chloride homeostasis, which is consistent with an adaptive response to ivermectin-induced hyperpolarisation of neuromuscular cells. Overall, we show the utility of a genetic cross to identify differences in gene expression that are specific to ivermectin selection and provide a framework to better understand ivermectin resistance and response to treatment in parasitic helminths.

For years, livestock farmers have relied on the use of anthelmintics as their sole means for controlling helminth infections; however, this strategy has proven to be unsustainable. The current high levels of anthelmintic resistance to multiple drug classes makes it difficult to control parasites using chemical means alone. Furthermore, the lack of new classes of anthelmintic drugs means that the drugs we have now will be all we have for quite a long time. Thus, parasite control needs to be viewed more holistically within an ecological context and practiced in a multi-pronged integrated manner. Here, we review some of the recent literature on parasite control in small ruminants that addresses these issues., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2020

Anthelmintic resistance in gastrointestinal nematodes of cattle has been worsening over the past 2 decades and is now a global problem. Though the problem was originally seen primarily in Cooperia, which is not a highly pathogenic species, we now know that other more pathogenic species have become drug resistant as well. With no new classes of anthelmintics in the cattle product pipeline, we will need to be better stewards of the drugs we have now, as they will need to last us for a long time. Thus, there is a need to use our anthelmintics differently and smarter than in the past. In this paper we present several strategies for improving the sustainability of parasite control in cattle that will both reduce the development of resistance while maintaining good productivity. Furthermore, we should not just assume a drug works or does not work; testing using the fecal egg count reduction test (FECRT) should be performed on every farm. This is the only way to make evidence-based decisions on optimal drug choices. Optimally, the strategies promoted here should have been instituted years ago. However, it is not too late, and the sooner these strategies are implemented widely, the more successful the beef industry will be in controlling parasites both now and in the future., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2020

Control of gastrointestinal (GIN) parasites is of primary concern in any small ruminant health management program, and is critical to profitability of the farm. For many years, GIN were controlled by the frequent use of anthelmintics, and this approach was quite effective. However, we now know that this strategy is shortsighted and unsustainable. Anthelmintic resistance is bounding out of control, and many of the drugs relied upon for decades no longer are effective on many farms. Furthermore, despite the occasional development of new anthelmintic classes, history clearly demonstrates that the development of resistance is almost certain to outpace the introduction of new drug classes. Thus, anthelmintics can no longer be viewed as inexpensive management tools, but instead must be viewed as extremely valuable and limited resources. Furthermore, parasite control must no longer be equated with a deworming program. Rather, parasite control will only be sustainable if it is approached as an integrated parasite management program, where anthelmintics are only 1 of several components. Additionally, there are new strategies for how we need to use our anthelmintics, the most important of which are that treatment is given selectively to animals based on need, and multiple anthelmintics are administered as a combination treatment., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2020