Evidence for genes controlling resistance to Heligmosomoides bakeri on mouse chromosome 1

Resistance to infections with Heligmosomoides bakeri is associated with a significant quantitative trait locus (QTL–Hbnr1) on mouse chromosome 1 (MMU1). We exploited recombinant mice, with a segment of MMU1 from susceptible C57Bl/10 mice introgressed onto MMU1 in intermediate responder NOD mice (strains 1094 and 6109). BALB/c (intermediate responder) and C57Bl/6 mice (poor responder) were included as control strains and strain 1098 (B10 alleles on MMU3) as NOD controls. BALB/c mice resisted infection rapidly and C57Bl/6 accumulated heavy worm burdens. Fecal egg counts dropped by weeks 10–11 in strain 1098, but strains 1094 and 6109 continued to produce eggs, harbouring more worms when autopsied (day 77). PubMed search identified 3 genes (Ctla4, Cd28, Icos) as associated with ‘Heligmosomoides’ in the B10 insert. Single nucleotide polymorphism (SNP) differences in Ctla4 could be responsible for regulatory changes in gene function, and a SNP within a splice site in Cd28 could have an impact on function, but no polymorphisms with predicted effects on function were found in Icos. Therefore, one or more genes encoded in the B10 insert into NOD mice contribute to the response phenotype, narrowing down the search for genes underlying the H. bakeri resistance QTL, and suggest Cd28 and Ctla4 as candidate genes

Evaluation of anthelmintic properties of ethnoveterinary plant preparations used as livestock dewormers by pastoralists and small holder farmers in Kenya

Parasitic nematodes, especially Haemonchus contortus, are among the most common and economically important causes of infectious diseases of sheep and goats owned by pastoralists and small holder farmers in East Africa. In Kenya, control of these infections mainly relies on the use of anthelmintic drugs. However, ethnoveterinary medicine (EVM) preparations are widely used by pastoralists and small holder farmers (SHF) for treatment of their livestock against helminth parasites. This thesis covers the evaluation of the anthelmintic efficacy of some EVM preparations used by pastoralists and SHF in Kenya. The plant species selected, and prepared for animal dosing with the help of traditional healers (THs) were: Aframomum sanguineum, Albizia anthelmintica, Ananas comosus, Annona squamosa, Azadirachta indica, Dodonaea angustifolia, Hagenia abyssinica, Hildebrandtia sepalosa, Myrsine africana, Olea europaea var. africana, and Rapanea melanophloeos. Evaluation was carried out in two in vivo infection models, namely H. contortus in sheep and Heligmosomoides polygyrus in mice. The anthelmintic efficacy of the EVM preparations was monitored through faecal egg count (FEC) reduction, at regular intervals for a period of 2 – 3 weeks post treatment in sheep. Monitoring in mice was done through FEC and total worm counts (TWC) one week after treatment. An a priori cut-off value of 70% reduction of FEC and TWC, to denote useful anthelmintic efficacy, was used for both sheep and mice. Of the ten plant species tested in sheep, the largest decrease of 34% in FEC was measured from a bark preparation of A. anthelmintica collected from the Samburu District. None of the other plant species had a significant effect on FEC. Similarly, the seven plant species and some of their related active constituents evaluated in mice did not significantly reduce FEC or remove parasites. Preparations of A. anthelmintica at doses above 0.5 g per mouse were toxic. In conclusion, no reduction of FEC or TWC greater than the a priori value of 70% was observed in sheep or in mice. Therefore, the plants evaluated were ineffective as anthelmintics in the preparations and forms that were used

Use of plants in novel approaches to 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 mainly performed with the free-living rather than the 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 with in vivo studies when used to validate the anthelmintic properties of plant remedies. In vivo controlled studies have showed that plant remedies have in most instances caused reductions in the level of parasitism less pronounced than that of anthelmintic drugs, and only rarely has reductions similar to that caused by synthetic anthelmintics been achieved. Whether it is necessary or not to achieve the latter in order for plant remedies to have a role in the control of parasitism depends on determination of biologically important levels of reduction of parasitism. This is 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 done. Although in many cases the active compounds in the herbal remedies have not been identified yet, 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 against the parasitised herbivores, 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

In vitro organic matter disappearance of tanniferous browse using rumen liquid from goats ingesting grass versus browse

In vitro organic matter disappearance (IVOMD) of African browse species often indicates artificially low nutritive value due to the presence of condensed tannins (CT). Diet of the rumen liquor donor may change this if it contains CT. Leaves from 11 browse species were evaluated for their IVOMD of nitrogen, fibre fractions and CT concentrations. Crude protein (CP) ranged from 14% to 25%, whereas neutral detergent fibre (NDF) varied from 20% to 40%. The CT fractions differed (P ≤ 0.05) among the browse species with most CT either soluble or bound to protein. Acacia brevispica and Berchemia discolor had the greatest concentrations of total CT, whereas Balanites aegyptiaca and Prosopis juliflora had the least. Rumen liquid from goats on grass diet (no CT) or browsing species with CT resulted in differences in IVOMD of NDF (P ≤ 0.05); 37% less (P = 0.11) fibre-bound CT IVOMD resulted when rumen liquid donors consumed browse containing CT. This indicates that (1) during IVOMD assays, rumen fluid donor diets should reflect, as closely as possible, those of the target animals and their diets, and (2) rumen liquid donor diet composition, especially forage CT concentrations, should be documented when evaluating results of IVOMD trials that use rumen liquor donors consuming CT.Keywords: condensed tannins, IVOMD, NDF, nitrogen, phenolic compounds, rumen liquidAfrican Journal of Range & Forage Science 2013, 30(3): 155–16