Effects of four tanniferous plant extracts on thein vitroexsheathment of third-stage larvae of parasitic nematodes

Abstract

The anthelmintic properties of tanniferous plants and of their secondary metabolites represent one possible alternative to chemotherapy that is currently being explored as a means of achieving sustainable control of gastrointestinal nematodes in ruminants. Previous in vivo and in vitro results suggest that tanniferous plants can have direct anti-parasitic effect against different stages of nematodes. However, the mode of action of the bioactive plant compounds remains obscure. The objectives of the current study were (1) to examine the hypothesis that extracts of tanniferous plants might interfere with the exsheathment of third-stage infective larvae (L3); (2) to assess the role of tannins in the process by examining the consequence of adding an inhibitor of tannins (polyethylene glycol: PEG) to extracts. The effects of 4 tanniferous plant extracts on exsheathment have been examined on L3 of Haemonchus contortus and Trichostrongylus colubriformis. Artificial exsheathment was induced in vitro by adding hypochloride solution to larval suspension. The evolution of exsheathment with time was measured by repeated observations at 10-min interval for 60 min. The selected plants were: genista (Sarothamnus scoparius), heather (Erica erigena), pine tree (Pinus sylvestris), and chestnut tree (Castanea sativa), with tannin contents ranging from 1.5 to 24.7% of DM. Extracts of a non-tanniferous plant (rye grass, tannin content: 0.3% of DM) were included in the assay as negative controls. The extracts were tested at the concentration of 600 microg/ml and the effects were compared to the rate of exsheathment of control larvae in PBS. No statistical differences in the pattern of exsheathment was observed after addition of rye grass or genista extracts for both nematode species and with heather extracts for T. colubriformis. In contrast, pine tree extracts on larvae of both species and heather extracts with H. contortus induced a significant delay in exsheathment. Last, contact with chest nut extracts led to a total inhibition of the process for both nematodes. These results suggest that extracts of tanniferous plants might affect a key process in the very early stages of larval invasion of the host. In most cases, the addition of PEG led to a total or partial restoration towards control values. This suggests that tannins are largely involved in the inhibitory process. However, other secondary metabolites may also interfere with the process that would help to explain some of the differences in response observed between the two nematode species.

Effect of six tropical tanniferous plant extracts on larval exsheathment of Haemonchus contortus

“…The assay conducted in this study has been routinely used in other experiments. Bahuaud et al (2006), Brunet et al (2007), Alonso-Díaz et al (2008a, 2008b found retardation or inhibition of H. contortus and Trichostrongylus colubriformis larval exsheathment after incubation with tanniferous plant extracts. The assumption is that condensed tannins complex with the sheath proteins of nematodes, which have high proline content and prevent exsheathment (BRUNET et al, 2007).…”

“…The test was performed according to Bahuaud et al (2006). The extracts were diluted in phosphate buffer solution (PBS), and the concentration evaluated was 300 µg.mL -1…”

The effects of condensed tannins extracted from different plant species on egg hatching and larval development of Teladorsagia circumcincta (Nematoda: Trichostrongylidae)

“…Studies in New Zealand (Niezen et al 1995, 1998, United Kingdom (Athanasiadou et al 2000a, b, Marley et al 2003, France (Paolini et al 2003, Bahuaud et al 2006 and United States (Min and Hart 2003) have shown that some plant species that contain CTs may reduce the degree of parasite infections and improve sheep and goat performance. Although the underlying mechanisms for such beneficial effects have not been determined, both direct (Athanasiadou et al 2000a, b) and indirect (Aerts et al 1999, Waghorn andMolan 2001) effects of CTs on parasites in the gut were suggested to be behind these effects.…”

Obtaining the Minimum Lethal Dose against <i>Fasciola hepatica in Vitro</i> Using Plant Extract Hexanes with Fasciolicide Activity and Toxicity Evaluation on CD1 Male Mice

“…Artemisia absinthium, Chenopodiumgraveolens, Gymnospermaglutinosum, Limpiacritridora, Populusalba and Thymus vulgaris, have an activity of 500 mg/L respectively (Tables 1, 2). These results were obtained by means of different repeated tests in the vitro model [17,18].…”