In Vitro Effect of Aqueous Extract of Fresh Cassava Leaves (Manihot Esculenta, Crantz) on The Larvae of Haemonchus Contortus as an Intestinal Parasite of Sheep

Abstract

Cassava is frequently fed to animals. In the case of sheep, the producer relates consumption to a reduction in the parasite load. The literature has proven the effect of phenolic compounds as an anthelmintic in vivo, but no evidence for cyanogenic compounds, also present in all parts of the cassava plant, was found. A controlled in vitro bioassay was used to evaluate the aqueous extract of fresh cassava leaves. The efficiency parameter was the immobility of Haemonchus contortus larvae at the L3 stage, also used to evaluate commercial anthelmintics. Cell culture plates with 100 active L3-stage larvae per well were used, being each replicate constituted by three wells. Aqueous extract of fresh cassava leaves (FCL), Ivomec® 0.01% (PCI) as the positive control, and distilled water as negative control (NCW), were placed in the culture plate wells. Considering the immobility of the larvae as a positive anthelmintic effect, the results showed that in NCW treatments all larvae were mobile, while in PCI all 300 larvae were immobile. FCL produced a gradient of larval inactivation correlation (R2 0.996). The best-fit equation was y = -33.39ln(x) + 40.517, a logarithmic equation, which allowed the calculation of the Lethal Concentration (CL) of 3.44 µg CN- ml, or 80.0 mg of fresh cassava leaves per milliliter of water, with a performance equivalent to ivermectin. This concentration of free cyanide is compatible with the safe consumption of fresh leaves by live weight of sheep. The exact amount of cassava roots, leaves, or shoots, consumed to provide an effective dose for controlling H. contort should be established in vivo. Although phenolic compounds must also be present in the extract, the immobility was attributed to cyanogenic compounds since the correlation was proportional to the increase in the cyanide concentration. It can be concluded that the consumption of fresh cassava leaves has the potential as an anthelmintic agent to be evaluated in vivo by feeding sheep and goats. Local use could also add value to the production of fresh cassava leaves, with an average potential production of 2.5 tonnes ha-1, available throughout the year, with greater production at the beginning of cultivation and in the summer months. These leaves could be used after the roots harvesting or even after pruning for this purpose. Currently, this amount of good quality protein material remains without use in the field.