Evaluation of plant commercial feed additives for equine cyathostomin control.

The increasing emergence of anthelmintic-resistant parasitic isolates prompts us to reassess the management of intestinal strongylosis in horses. Additionally, societal demand is shifting toward reducing the use of chemical treatments, aligning with environmentally-friendly practices and the exploration of natural alternatives. In this context, we provide an initial view of the antiparasitic activity and the effect on immune circulating blood cells of three commercialized plant-based feed additives in ponies. Three treatments, based either on mugwort (Artemisia vulgaris), echinacea (Echinacea purpurea) or curcumin (Curcuma longa) were administrated to 18 (six per treatment) Welsh female ponies naturally infected with cyathostomins to mimic their practical use in farming conditions. Another group of six untreated ponies was used as a control. Fecal egg count (FEC), the larval development percentage and the number of red blood cells, lymphocytes, monocytes, neutrophils, eosinophils and basophils were measured the first and the last day of each treatment, and compared with those characterizing the control group. None of the three treatments showed a significant effect on the studied parameters. Moreover, the efficacy of treatments, measured from the FEC reduction compared to the control group, was weak (≤ 38.6 %). Therefore, these results do not support the practical use of these additives in equine farming, even if the determination of Cohen's d values associated with the three treatments revealed some incidences on FEC and blood immune cell counts, as well as on larval development for mugwort.

Lupin (Lupinus spp.) seeds exert anthelmintic activity associated with their alkaloid content.

The growing range of drug resistant parasitic nematode populations threatens the sustainability of ruminant farming worldwide. In this context, nutraceuticals, animal feed that provides necessary dietary requirements while ensuring parasite control, could contribute to increase farming sustainability in developed and low resource settings. In this study, we evaluated the anthelmintic potential of lupin seed extracts against the major ruminant trichostrongylids, Haemonchus contortus and Teladorsagia circumcincta. In vitro observations showed that seed extracts from commercially available lupin varieties could significantly but moderately inhibit larval migration. This anthelmintic effect was mediated by the seed alkaloid content and was potent against both fully susceptible and multidrug resistant H. contortus isolates as well as a susceptible T. circumcincta isolate. Analytical chemistry revealed a set of four lupanine and sparteine-derivatives with anthelmintic activity, and electrophysiology assays on recombinant nematode acetylcholine receptors suggested an antagonistic mode of action for lupin alkaloids. An in vivo trial in H. contortus infected lupin-fed ewes and goats failed to demonstrate any direct anthelmintic effect of crude lupin seeds but infected lupin-fed goats suffered significantly less parasite-mediated blood losses. Altogether, our findings suggest that the anthelmintic potential of lupin remains limited. However, the potent alkaloids identified could lead to the development of novel drugs or may be used in combination with current anthelmintics to improve their efficacy.

Risk factor analysis of equine strongyle resistance to anthelmintics.

Intestinal strongyles are the most problematic endoparasites of equids as a result of their wide distribution and the spread of resistant isolates throughout the world. While abundant literature can be found on the extent of anthelmintic resistance across continents, empirical knowledge about associated risk factors is missing. This study brought together results from anthelmintic efficacy testing and risk factor analysis to provide evidence-based guidelines in the field. It involved 688 horses from 39 French horse farms and riding schools to both estimate Faecal Egg Count Reduction (FECR) after anthelmintic treatment and to interview farm and riding school managers about their practices. Risk factors associated with reduced anthelmintic efficacy in equine strongyles were estimated across drugs using a marginal modelling approach. Results demonstrated ivermectin efficacy (96.3% ± 14.5% FECR), the inefficacy of fenbendazole (42.8% ± 33.4% FECR) and an intermediate profile for pyrantel (90.3% ± 19.6% FECR). Risk factor analysis provided support to advocate for FEC-based treatment regimens combined with individual anthelmintic dosage and the enforcement of tighter biosecurity around horse introduction. The combination of these measures resulted in a decreased risk of drug resistance (relative risk of 0.57, p = 0.02). Premises falling under this typology also relied more on their veterinarians suggesting practitionners play an important role in the sustainability of anthelmintic usage. Similarly, drug resistance risk was halved in premises with frequent pasture rotation and with stocking rate below five horses/ha (relative risk of 0.53, p < 0.01). This is the first empirical risk factor analysis for anthelmintic resistance in equids. Our findings should guide the implementation of more sustained strongyle management in the field.

Flavonoids and related compounds in parasitic disease control.

Flavonoids are natural plant compounds increasingly used in therapeutic applications. Their large spectrum of activities depends on their structures and cellular targets. Most recent research shows they are promising drugs for controlling human and animal parasitic diseases. Their multiple effects make it difficult to understand their modes of action, but some of them have been elucidated. This review also deals with their toxicity in mammals.

Detection of P-glycoprotein-mediated multidrug resistance against anthelmintics in Haemonchus contortus using anti-human mdr1 monoclonal antibodies.

The "multidrug resistance" (MDR) system involves the action of transmembrane P-glycoproteins (Pgp) which may be responsible for failure of chemotherapy in both invertebrates and vertebrates. We previously obtained partial reversion of anthelmintic resistance in nematodes subjected to both anthelmintics and inhibitors of this system. The results presented here are able to describe more accurately the presence of Pgp in nematodes because of the use of C219 and UIC2 monoclonal antibodies, which are used for the detection of human and mouse mdr1 gene products. These antibodies demonstrated the presence of Pgp in eggshells. Their role in these structures, which are considered to be passive barriers, remains to be determined. Flow cytometry analyses of the UIC2 staining allowed determination of the resistance of individuals, which varied within the parasite population. UIC2 demonstrated both the presence and activity of Pgp in nematodes as has previously been shown in tumour cells. Resistance seems to be due to an increase in both the number of Pgp sites and parasites with high levels of Pgp.

Analysis and partial reversal of multidrug resistance to anthelmintics due to P-glycoprotein in Haemonchus contortus eggs using Lens culinaris lectin.

Our previous work has shown that drug efflux pumps close to MDR1 P-glycoprotein (Pgp) can regulate anthelmintic efflux in nematodes in a way similar to that of the mutidrug resistance system (MDR) in vertebrate cancer cells. In the present study, the role of the glycosylation of Pgp was studied using a lectin specific for the alpha-mannosyl residues ( Lens culinaris agglutinin, LCA). Highly significant reversion (up to 50%) in the resistance to thiabendazole of eggs pre-treated with the lectin was obtained. Flow cytometric examinations were performed using FITC-labelled lectin. The results demonstrated that: (1) the number of Pgp sites was higher in resistant H aemonchus contortus, (2) resistance can also be associated with a decreased affinity of LCA for these sites, (3) eggs stained with LCA were also stained with specific MDR1 monoclonal antibodies. The implication of the glycosylation of Pgp in the activity and/or degradation of these pumps in eukaryotic cells is discussed.