Effect of the consumption of heather on incoming larvae and established population of Teladorsagia circumcincta in experimentally infected Cashmere goats

The feeding of heather (Calluna vulgaris) to Teladorsagia circumcincta infected lambs reduces parasitism but can detrimentally impact performance

Gastrointestinal nematode (GIN) infections impact small ruminant health, welfare, and production across farming systems. Rising anthelmintic resistance and regulation of synthetic drug use in organic farming is driving research and development of sustainable alternatives for GIN control. One alternative is the feeding of plants that contain secondary metabolites (PSMs) e.g., proanthocyanidins (PA, syn. condensed tannins) that have shown anthelmintic potential. However, PSMs can potentially impair performance, arising from reduced palatability and thus intake, digestibility or even toxicity effects. In this study, we tested the trade-off between the antiparasitic and anti-nutritional effects of heather consumption by lambs. The impact of additional feeding of a nematophagous fungus (Duddingtonia flagrans) on larval development was also explored. Lambs infected with Teladorsagia circumcincta or uninfected controls, were offered ad libitum heather, or a control chopped hay for 22 days during the infection patent period. Eight days into the patent period, parasitised lambs were supplemented (or remained unsupplemented) with D. flagrans for a 5-day period. Performance and infection metrics were recorded, and polyphenol levels in the heather and control hay were measured to investigate their association with activity. The lambs consumed heather at approximately 20% of their dry matter intake, which was sufficient to exhibit significant anthelmintic effects via a reduction in total egg output (P = 0.007), compared to hay-fed lambs; the magnitude of the reduction over time in heather fed lambs was almost 10-fold compared to control lambs. Negative effects on production were shown, as heather-fed lambs weighed 6% less than hay-fed lambs (P < 0.001), even though dry matter intake (DMI) of heather increased over time. D. flagrans supplementation lowered larval recovery in the faeces of infected lambs by 31.8% (P = 0.003), although no interactions between feeding heather and D. flagrans were observed (P = 0.337). There was no significant correlation between PA, or other polyphenol subgroups in the diet and egg output, which suggests that any association between heather feeding and anthelmintic effect is not simply and directly attributable to the measured polyphenols. The level of heather intake in this study showed no antagonistic effects on D. flagrans, demonstrating the methods can be used in combination, but provide no additive effect on overall anthelmintic efficacies. In conclusion, heather feeding can assist to reduce egg outputs in infected sheep, but at 20% of DMI negative effects on lamb performance can be expected which may outweigh any antiparasitic benefits.

Antiparasitic Tannin-Rich Plants from the South of Europe for Grazing Livestock: A Review

Internal parasites are one of the main causes of health threats in livestock production, especially in extensive livestock farming. Despite the environmental toxic effects (loss of dung beetles, biodiversity, and other issues) and resistance phenomenon derived from their prolonged use, anti-parasitic chemical pharmaceuticals are frequently used, even in organic farming. Such a situation within the context of climate change requires urgent exploration of alternative compounds to solve these problems and apparent conflicts between organic farming objectives regarding the environment, public health, and animal health. This review is focused on some plants (Artemisia spp., Cichorium intybus L., Ericaceae family, Hedysarum coronarium L., Lotus spp., Onobrychis viciifolia Scop.) that are well known for their antiparasitic effect, are voluntarily grazed and ingested, and can be spontaneously found or cultivated in southern Europe and other regions with a Mediterranean climate. The differences found between effectiveness, parasite species affected, in vitro/in vivo experiments, and active compounds are explored. A total of 87 papers where antiparasitic activity of those plants have been studied are included in this review; 75% studied the effect on ruminant parasites, where gastrointestinal nematodes were the parasite group most studied (70%), and these included natural (31%) and experimental (37%) infections.

Anthelmintic activity of plants against gastrointestinal nematodes of goats: a review

The gastrointestinal nematodes (GIN) stand out as an important cause of disease in small ruminant, especially on goat farm. Widespread resistance to synthetic anthelminthics has stimulated the research for alternative strategies of parasite control, including the use of medicinal plants. The present work summarizes the in vitro and in vivo studies of plants with activity against GIN of goats, focusing on the description of chemical constituents related to this effect. This review retrieved 56 scientific articles from 2008 to 2018 describing more than 100 different plant species. The most frequently investigated family was Fabaceae (30.7%). Most in vitro studies on the activity of plant extracts and fractions were carried out with of free-living stages nematodes. In vivo studies were conducted mainly with the use of plants in animal feed and generally showed lower effectiveness compared to in vitro assays. The main plant secondary metabolites associated with anthelmintic effect are condensed tannins, saponin and flavonoids. However, the studies with compounds isolated from plants and elucidation of their mechanisms of action are scarce. Herbal medicines are thought to be promising sources for the development of effective anthelmintic agents.

Comparison of the in vitro anthelmintic effects of Acacia nilotica and Acacia raddiana

Gastrointestinal nematodes are a major threat to small ruminant rearing in the Sahel area, where farmers traditionally use bioactive plants to control these worms, including Acacia nilotica and Acacia raddiana. The main aim of this study was to screen the potential anthelmintic properties of aqueous and acetone extracts of leaves of these two plants based on three in vitro assays: (1) the egg hatch inhibition assay (EHA); (2) the larvae exsheathment inhibition assay (LEIA) using Haemonchus contortus as a model; and (3) an adult mortality test (AMT) applied on Caenorhabditis elegans. For the EHA, only A. raddiana was effective with IC₅₀ = 1.58 mg/mL for aqueous extract, and IC₅₀ = 0.58 mg/mL for acetonic extract. For the LEIA, all extracts inhibited the exsheathment of larvae compared to the controls, and the aqueous extract of A. nilotica was more larvicidal with IC₅₀ = 0.195 mg/mL. In general, all responses to the substances were dose-dependent and were significantly different from the control group (p < 0.05). For the AMT, the extracts of the two Acacia species were effective but A. raddiana showed greater efficacy with 100% mortality at 2.5 mg/mL and LC₅₀ = 0.84 mg/mL (acetonic extract). The addition of polyvinyl polypyrrolidone (PVPP) to the extracts suggested that tannins were responsible for blocking egg eclosion and inducing adult mortality but were not responsible for exsheathment inhibition. These results suggest that the leaves of these Acacia species possess ovicidal and larvicidal activities in vitro against H. contortus, and adulticidal effects against C. elegans.

Anthelmintic activity of acetone-water extracts against Haemonchus contortus eggs: interactions between tannins and other plant secondary compounds

This study aimed at (i) describing the effects of acetone-water extracts obtained from a range of different plant materials, on the hatching process of Haemonchus contortus eggs under in vitro conditions and (ii) identifying the role of tannins and other plant secondary compounds (PSC), on these AH effects by using polyvinylpolypyrrolidone (PVPP), an inhibitor of tannins and other polyphenols. An egg hatch assay (EHA) was used to determine the AH effect. Acetone-water (70:30) extracts from different foliages (Lysiloma latisiliquum, Laguncularia racemosa, Rizophora mangle, Avicennia germinans) and plant by-products (Theobroma cacao seed husk and pulp, and percolated Coffea arabica) were obtained. Fresh H. contortus eggs were incubated in PBS with increasing concentrations of each extract (0, 600, 1200, 2400 and 3600 μg/ml PBS). A general linear model was used to determine the dose effect of each extract. A mild ovicidal activity was only recorded for T. cacao extracts (seed husk and pulp). The main anthelmintic (AH) effect for all the extracts, except for C. arabica, was to block the eclosion of larvated eggs. The use of PVPP at 3600 μg/ml PBS showed that tannins of the L. racemosa extract were responsible for blocking eclosion of larvated eggs. Extracts of L. latisiliquum, A. germinans, T. cacao seed husk and pulp also blocked eclosion of larvated eggs but the addition of PVPP indicated that tannins were not responsible for that activity. In contrast, it suggested unfavorable interactions between polyphenols and other PSC contained in those extracts, limiting the AH effect on the egg hatching process. The present results suggest that the interactions between tannins and other PSC are complex and may reduce the AH effects against H. contortus eggs.

In vitro effect of heather (Ericaceae) extracts on different development stages of Teladorsagia circumcincta and Haemonchus contortus

The aim of the present study was to evaluate the in vitro effects of heather (Ericaceae) phenolic extracts on the abomasal nematodes Teladorsagia circumcincta and Haemonchus contortus. Extracts of three heather species (Calluna vulgaris, Erica cinerea, Erica umbellata and a balanced mixture of all three) were tested in vitro on different development stages of T. circumcincta (eggs, infective larvae and adult worms) and H. contortus (eggs and infective larvae) using an egg hatching assay (EHA), a larval exsheathment inhibition assay (LEIA) and an adult motility inhibition assay (AMIA). The egg hatching rate was measured after incubation with heather extracts for 48 h at 25 °C. Ensheathed infective larvae were incubated for 3h at 20 °C with heather extracts. Artificial exsheathment was induced in vitro by adding hypochloride solution to the larval suspension. The progress of exsheathment over time was measured by repeated observations at 10-min (T. circumcincta) and 20-min (H. contortus) intervals for 60 min. Adult T. circumcincta worms were obtained from two donor goats and incubated with the extracts at 37 °C for 3 days in 48-well multiwell plates. Worm motility was measured at 0, 19, 24, 43, 48, 67 and 72 h. The extracts were tested at concentrations of 75, 150, 300, 600 and 1200 μg/mL. Incubation with E. cinerea, E. umbellata and mixed heather extracts had a significant (P<0.01) dose-dependent effect on T. circumcincta egg hatching. H. contortus egg hatching was significantly (P<0.01) inhibited only by the E. cinerea extract. All extracts had a significant (P<0.01) dose-dependent effect on the exsheathment of T. circumcincta and H. contortus infective larvae. The incubation with all heather extracts induced a reduction in adult T. circumcincta motility compared to the control, although significant (P<0.05) differences were only found at the highest concentration (1200 μg/mL). The effect of the mixed extract was significant at all concentrations and significant effects were also observed for C. vulgaris and E. umbellata at 600 μg/mL. These results show anthelmintic properties of heather phenolic extracts against T. circumcincta and H. contort, thus confirming observations from previous in vivo studies.