Use of plants in novel approaches for control of gastrointestinal helminths in livestock with emphasis on small ruminants.

Helminth infections are a major cause for reduced productivity in livestock, particularly those owned by the poor worldwide. Phytomedicine has been used for eons by farmers and traditional healers to treat parasitism and improve performance of livestock, and many modern commercial medicines are derived from plants. However, scientific evidence on the anti-parasitic efficacy of most plant products is limited, regardless of their wide ethnoveterinary usage. Scientific validation of the anti-parasitic effects and possible side-effects of plant products in ruminants is necessary prior to their adoption as a novel method for parasite control. A variety of methods has been explored to validate the anthelmintic properties of such plant remedies, both in vivo and in vitro. In vitro assays are useful as pre-screens of activity and are mainly performed with the free-living rather than parasitic stages of nematodes. Concentrations of potentially active substances used in vitro do not always correspond to in vivo bioavailability. Therefore, in vitro assays should always be accompanied by in vivo studies when used to validate the anthelmintic properties of plant remedies. In vivo controlled studies have shown that plant remedies have in most instances resulted in reductions in the level of parasitism much lower than those observed with anthelmintic drugs. Whether it is necessary or not to achieve very high efficacy in order for plant remedies to have a role in the control of parasitism depends on the determination of biologically important levels of reduction of parasitism and it will be required prior to the wide-scale use of plant products for parasite control. Similarly, standardisation of validation studies in reference to the numbers of animals required for in vivo studies to measure direct anthelmintic effects of a plant needs to be established. Although in many cases the active compounds in the herbal remedies have not been fully identified, plant enzymes, such as cysteine proteinases, or secondary metabolites, such as alkaloids, glycosides and tannins have shown dose-dependent anti-parasitic properties. However, as some of the active compounds may also have anti-nutritional effects, such as reduced food intake and performance, it is essential to validate the anti-parasitic effects of plant products in relation to their potential anti-nutritional and other side effects. A concerted effort on isolation, development, and validation of the effects of these herbal remedies will have to be undertaken before their wider acceptance.

Ethnoveterinary plant preparations as livestock dewormers: practices, popular beliefs, pitfalls and prospects for the future.

Ethnomedicine is an integral part of traditional medical practices in many countries of the developing world. A large proportion of the population uses this form of treatment for primary health care and for the treatment of ailments in their livestock. Livestock is a major asset for resource-poor smallholder farmers and pastoralists throughout the world and internal parasites are recognized by these communities as having an impact on livestock health. Parasitic infections are among those infections that traditional healers confidently treat and against which an enormous variety of remedies exist. Many of these are based on the use of plant preparations. Although various methods have been used for the validation of traditional phytomedical preparations, there is a lack of standardization of these procedures. The present study is aimed at providing an overview of ethnoveterinary deworming preparations, the various methods that have been used in their validation and the future prospects for their use against helminth parasites of ruminant livestock in developing countries, with an emphasis on nematode parasites. Recommendations are made on the procedures that should be followed to conduct in vivo and in vitro assays. Fostering better interaction between traditional healers and scientists is advocated to prevent harmful overexploitation, both of local knowledge and of plant species that may have effects against nematode parasites.

The anthelmintic efficacy of the plant, Albizia anthelmintica, against the nematode parasites Haemonchus contortus of sheep and Heligmosomoides polygyrus of mice.

Albizia anthelmintica Brong., belongs to the plant family Mimosaceae. The plant is widely used in East Africa by poor smallholder farmers and pastoralists to treat their livestock against internal parasites. The anthelmintic effects of water extracts from the bark of A. anthelmintica, obtained from three different geographic areas in Kenya and using different methods of preparation, were tested at different doses in sheep and mice infected with the nematode parasites Haemonchus contortus and Heligmosomoides polygyrus, respectively. Lambs were infected with 3000 infective larvae of H. contortus and treated with the plant preparations 28 days later, while mice were infected with 200 infective larvae of H. polygyrus and treated 18 days later. Proximate analysis established high levels of crude proteins in A. anthelmintica bark. Two sheep out of the 45 treated with the plant preparations suffered from transient bloat, which was relieved by dosing with a surfactant. Significant reductions in faecal egg counts were observed in lambs treated with A. anthelmintica in two of the three experiments undertaken, but the efficacy levels achieved were well below the 70% reduction required. Similar values of packed red cell volume and live weight gain were observed for treated and control lambs. There was no overall significant effect of treatment with A. anthelmintica on faecal egg and total worm counts in mice. A dose rate of 1000 mg/kg bodyweight of A. anthelmintica preparation resulted in death of all mice. The results show that A. anthelmintica at the doses and preparations used is not efficacious against H. contortus in sheep or against H. polygyrus in mice.

Evaluation of anthelmintic properties of extracts from some plants used as livestock dewormers by pastoralist and smallholder farmers in Kenya against Heligmosomoides polygyrus infections in mice.

Parasitic nematodes are among the most common and economically important infectious diseases of grazing livestock, especially in small ruminants in the tropics and subtropics in Kenya the control of gastrointestinal nematode infections in sheep and goats is usually made with synthetic anthelmintics but substantial levels of anthelmintic resistance have been recorded. A number of medicinal plants, that may provide possible alternatives, and are used by pastoralists and smallholder farmers in Kenya as deworming agents for their livestock and equines, namely Aframomum sanguineum, Dodonea angustifolia, Hildebrandtia sepalosa, Myrsine africana, Rapanea melanophloeos from Kenya, and Azadirachta indica from Kenya and Malaysia, together with the chemicals embelin and santonin that occur in some of these plants, were evaluated against Heligmosomoides polygyrus in mice. Commercial anthelmintics, namely ivermectin, pyrantel and piperazine, were also investigated, both to validate the mouse model system and to assess efficacy of these drugs against H. polygyrus. Pyrantel and ivermectin were highly effective in reducing the numbers of H. polygyrus worms as well as eggs in faeces of the mice, but piperazine had a lower activity. Application of santonin and M. africana significantly reduced the number of total worm counts (TWC) but not faecal egg counts (FEC). The use of embelin, R. melanophloeos and A. indica reduced FEC but not TWC. In all cases, however, reductions were well below the a priori level of 70% required for biological significance. A. sanguineum, D. angustifolia and H. sepalosa had no effect on either TWC or FEC. In conclusion, none of the plant preparations had any biologically significant anthelmintic effect in this monogastric host-parasite model system.

Anthelmintic activity of preparations derived from Myrsine africana and Rapanea melanophloeos against the nematode parasite, Haemonchus contortus, of sheep.

Myrsine africana L. and Rapanea melanophloeos L. belong to the plant family Myrsinaceae. Various rural communities in Kenya, such as smallholder farmers and pastoralists, use them to treat their livestock. The anthelmintic effects/activities of leaves and fruits of M. africana and fruits of R. melanophloeos were tested in sheep experimentally infected with the nematode parasite Haemonchus contortus. Male lambs were infected with 3000-5000 third stage larvae of H. contortus and treated 28 days after inoculation with concoctions made from leaves or fruits of the plants. No significant reduction in faecal nematode egg counts was observed with any of the concoctions at any of the doses tested. Packed red cell volume decreased and live weight increased at similar rates in treated and control groups, thus there was no significant effect of treatment. The results showed that the tested extracts of the M. africana and R. melanophloeos were not efficacious against H. contortus in sheep.