Management of nematode parasites of grazing livestock is essential, but there is concern about the potential environmental risk from agents used in their control. In this experiment, parasites in young cattle were controlled, using ivermectin boluses or the predacious fungus Duddingtonia flagrans , over 3 years. Treatment differences were sought among the soil nematodes recovered from soil samples collected from the paddocks on which treated animals grazed, and compared with similar samples taken from an untreated control paddock. Analysis of the soil nematode fauna on 21 occasions failed to demonstrate any impact of parasite management on soil nematodes. In 0-22 mm soil total nematode abundance averaged 524 000 m -2 , with 18 nominal taxa and H' diversity 2.41. There were both underlying paddock and year-to-year, climate-related, differences. The results of this trial not only confirm the lack of any adverse environmental impact of D. flagrans , a promising biological control agent, on soil nematodes, but also fail to show any impact arising from the use of ivermectin boluses. 相似文献
In 2004, an experiment was carried out to evaluate the effect of biological control through feeding spores of Duddingtonia flagrans on parasitic gastroenteritis in lambs, kept under an evasive grazing system. In total 66 lambs were used. Forty naturally infected 3-month old ram lambs were weaned in mid June, and divided into four groups of 10 lambs. On 21 June, G1–G4 were moved to four separate virtually clean plots, they were moved after 4 and 8 weeks to similar plots, and housed after 12 weeks to be necropsied 16 days later. The other 26 lambs had been raised helminth-free, and were used as pairs of tracer lambs. All but one of these pairs, were grazed during the last 2 weeks on each plot. The remaining pair (TA) was grazed during the last 2 weeks on pasture (30 August to 13 September) on the plot that had been grazed by G3 between 19 July and 16 August, to study inhibited development in Haemonchus contortus. All lambs were fed 200 g of concentrates daily throughout the whole period, and those of G1 and G2 were also fed 500,000 spores of D. flagrans/kg bodyweight daily.
The faecal cultures demonstrated a high reduction in yield as a result of fungal application. However, no differences between groups were seen in weight gain, faecal egg counts, pasture larval counts, worm counts and tracer worm counts. H. contortus was the dominant species, and it is obvious that the moves at 4-week intervals prevented the development of severe haemonchosis. This is in particular demonstrated by the much higher worm counts in the two TA tracer lambs grazed. Nevertheless, increases to high faecal egg counts 3 weeks after the first and second moves, indicated acquisition of infection before these moves and at least subclinical haemonchosis. This was supported with the worm counts of lambs and tracer lambs. A higher proportion of inhibited early L4 than in other tracers and than in the permanent lambs were found in the pair of TA tracer lambs. This indicates that moves to new pastures in late summer and autumn delays the onset of inhibition. 相似文献
An in vitro trial with carbendazim fungicide on the growth profile of the predatory fungus Duddingtonia flagrans was undertaken and in vivo trials in sheep and buffaloes, fed on chlamydospores of D. flagrans and administered albendazole anthelmintic, were conducted. Although no growth inhibition was detected at a carbendazim concentration of 0.05 ppm, growth inhibition was recorded of 50% and above at concentrations of 0.25 and 1.00 ppm (p < 0.001) and of around 90% at concentrations of 2.00 to 5.00 ppm (p <0.0001). Scanty recovery of the fungus was made from faecal culture 48 h following a single dose of albendazole both in sheep and buffaloes. However, profuse fungal recovery was made from 96 h post dosing onwards. When the drug was used as an intraruminal slow-release capsule, no faecal fungal recovery could be made from day 3 after administration of the capsule, when the albendazole sulphoxide concentration was around 1.0 microg/ml. However, profuse and scanty fungal recovery could be made on days 1 and 2, respectively, after administration of the capsule, when the plasma albendazole sulphoxide concentration was around 0.4 and 0.9 microg/ml, respectively. The implications for use of a combination of anthelmintics and biological control in sustainable parasite control programmes are discussed. 相似文献
A field trial, conducted over two consecutive years, was aimed at assessing the efficacy of the administration of spores of
the nematophagous fungus Duddingtonia flagrans to young goats for the control of nematode parasite infections on a French commercial dairy goat flock. For both years, the
first-year grazing kids were divided into two similarly managed groups (fungus and control groups): in 2003 a daily dose rate
of 5 × 105 spores/kg body weight was given to the fungus-group animals, while in 2004 a daily dose rate of 106 spores/kg body weight was used; the other half of the kids, acting as control, did not receive the spores. Parameters measured
every 3 weeks included nematode egg excretion, larval development in faecal cultures and pasture larval counts. Additionally,
at the beginning, the middle and the end of each grazing season, the goats were weighed and blood samples for pepsinogen determination
were collected. In 2003, similar results were recorded for all the measured parameters in the control and fungus groups. In
contrast, in 2004, the kids receiving the spores showed lower faecal egg counts and pepsinogen levels at the end of the season
and higher growth rate compared to kids of the control group. 相似文献
Anthelmintics, veterinary medicines for the control of endoparasites, enter into the environment largely through faeces of the treated animals. Sheep dung is a patchily distributed, ephemeral resource, with a functionally important decomposer community. The nature of this community and the pharmacokinetics of anthelmintics in sheep mean that the ecotoxic impacts of these drugs in sheep dung may differ markedly from those in cattle dung, where most research has been focussed. The period of maximum residue excretion is generally more transient in sheep than cattle dung, but low-level excretion may continue for longer, giving the potential for extended sub-lethal effects. Here, the environmental impacts of sheep anthelmintics, as well as alternative endoparasite control methods are reviewed. Impacts are discussed in terms of the potential for residues to enter into the environment, the toxicity and the impact on ecosystem functioning at an appropriate scale. Future research priorities are also discussed; these include the need for studies of the functional contributions of dung-colonising species, as well as the development of higher-tier ecotoxicological methods bridging the gap between laboratory and field experiments. Large-scale and long-term studies, including the development of appropriate models, are necessary to allow the consequences of anthelmintic administration to be assessed, particularly within the remit of sustainable animal production. 相似文献