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The effects of cold storage of infective third-stage larvae (L3) of different isolates of the parasitic nematode Haemonchus contortus were studied with respect to infectivity, pre-patent period and propensity for larval arrestment. Two complementary experiments were conducted with 2 groups of lambs, each animal being inoculated with 2000 L3 of either Swedish or Kenyan origin. In a first experiment, L3s were cold treated at 5 degrees C for 9 months prior to infection, whereas in a second experiment larvae were newly hatched. Individual faecal egg counts (FECs), and worm burdens were determined for each experiment. The results showed that the greatest differences were associated with the pre-treatment of larvae. The pre-patent period and the FECs differed significantly between the experiments but not between the isolates used in each experiment. However, the extent of hypobiosis was significantly different between the two isolates when fresh larvae were used (36% Kenyan isolate and 70% Swedish). The storage of H. contortus at 5 degrees C had no apparent effect on the infectivity of L3s, as high establishment ranging from 43 to 74% were observed, irrespective of isolates used. This study showed that H. contortus exhibited similar phenotypic traits regardless of geographical origin. Thus, there was limited evidence for adaptations to temperate climatic conditions.

Gastrointestinal helminth infections remain a major constraint to livestock production globally. This study evaluated anthelmintic efficacy of 7 plants used as dewormers by farmers and pastoralists in Kenya. Thus 3 commercial anthelmintics and 7 plant preparations were tested in lambs infected with 5000 or 3000 L3 Haemonchus contortus in 4 experiments. In the first experiment, ivermectin, levamisole and albendazole were tested in 46 lambs. Seven plant preparations of Hagenia abyssinica, Olea europaea var. africana, Annona squamosa, Ananas comosus, Dodonea angustifolia, Hildebrandtia sepalosa and Azadirachta indica were tested in 151 lambs in 3 experiments. All 3 anthelminitics were highly effective in reducing faecal egg counts (FEC) and total worm counts (TWC) in lambs. Plant preparations had varying levels of crude proteins from 2.6% for O. europaea to 18.4% for A. indica. Compared with controls, no significant reductions in FEC were observed for any of the treated groups either 2 or 3 weeks post-treatment. Lambs treated with A. squamosa and A. comosus were slaughtered 4 weeks post-treatment. No significant differences were observed in mean TWC or number of eggs per female worm between treated animals and the controls. No significant improvements in weight gain were observed in treated lambs.

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.

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.

The genus Haemonchus consists of blood-sucking parasitic nematodes in the abomasum of ruminants. Members of this genus are responsible for extensive production losses, particularly of small ruminants in the tropics but are also found in temperate regions. In this study, we examined the internal transcribed spacers-1 and -2 of rRNA in Haemonchus spp. The rRNA region spanning the internal transcribed spacers-1, -2 and the 5.8S rRNA gene was amplified by PCR from each of 10 worms from Swedish sheep, a Swedish goat and Kenyan sheep. The fragments were sequenced and examined with respect to genetic differences fixed among the three isolates. These and additional worms were further analysed with Pyrosequencing technology. This technique allowed us to rapidly analyse 110 individuals in three putative polymorphic nucleotide positions that were initially identified with dideoxy sequencing. The geographical isolates could to a large extent be genetically distinguished, but none of the polymorphic positions were consistent among all individuals within each isolate. Furthermore an alignment of our sequences and a consensus sequence published for Haemonchus contortus revealed two differences in positions 123 and 196 in internal transcribed spacers-2. Although these positions were previously reported as heterogenic, no polymorphism was detected among the 30 worms sequenced in the present study. Modelling of the internal transcribed spacers-2 secondary structure based on our data also identified a new putative long-range interaction. The isolates are best described as populations. In conclusion, consistent differences were not identified and the studied isolates are therefore best described as discrete populations. This study also reveals for the first time the potential of Pyrosequencing technology as a tool in the analysis of nematode population genetics.