Top Dressing of Feed with Desiccated Chlamydospores of Duddingtonia flagrans for Biological Control of the Pre-Parasitic Stages of Ovine Haemonchus contortus

Feeding trials were conducted with stall-fed sheep parasitized with Haemonchus contortus. For 10 days they were offered 250 g of a concentrate feed that had been top-dressed with desiccated chlamydospores of Duddingtonia flagrans at 1×10⁵, 5×10⁵, 1×10⁶ or 2×10⁶ chlamydospores/kg body weight. Pooled faeces from each group on day 7 of spore feeding were spread on different pasture plots. On day 28 after the start of spore feeding, further pooled faeces from each group were spread on the same plots. The larval burdens on the plots were monitored for 2 months and the larval harvest from in vitro faecal cultures were monitored regularly. The application of 1×10⁶ or more spores/kg body weight virtually eliminated larvae from both the pasture and the faecal cultures. The application of as few as 1×10⁵ spores/kg body weight had a profound impact on larval recovery. The effect persisted while the spores were being fed but not for more than 4 days following discontinuation of spore feeding. Top dressing supplementary feed with dried chlamydospores offers a potential way of using D. flagrans for biological control of the pre-parasitic stages of H. contortus.     

Biological control of trichostrongyles in calves by the fungus Duddingtonia flagrans fed to animals under natural grazing conditions

The present study was conducted in the 1993 grazing season with yearling calves exposed to a pasture with a natural mixed trichostrongyle larval infection. It was shown that daily feeding with the microfungus Duddingtonia flagrans during the first 2 months of the season led to a lowered herbage infectivity and a reduced acquisition of Ostertagia sp. and Cooperia sp. later in the season. In addition, the procedure delayed the onset of clinical disease. This was due to the nematode-destroying effects of the fungi in the dung excreted by the fungus-treated calves, as evidenced by results from a parallel in vitro assay on faecal larval cultures. The paper discusses future research needs before practical biological control can be implemented.     

捕食性真菌Duddingtonia flagrans原生质体的快速制备与再生

为快速获得大量捕食性真菌Duddingtonia flagrans原生质体并使其再生,本试验研究了酶质量浓度、酶解温度、菌龄、酶解时间对D.flagrans原生质体产生的影响,以确定D.flagrans原生质体最佳快速制备条件。结果表明,在溶壁酶2mL/L、蜗牛酶8g/L、纤维素酶8g/L时,35℃恒温条件下,酶解菌龄为2d的菌丝7h,捕食性真菌D.flagrans产生原生质体数量最多且能够再生。这为下一步转化并标记和克隆捕食性相关基因奠定了重要基础。     

Soil Nematode Populations Beneath Faecal Pats from Grazing Cattle Treated with the Ivermectin Sustained-release Bolus or Fed the Nematophagous Fungus Duddingtonia flagrans to Control Nematode Parasites

The size and composition of the nematode assemblage in soil under faecal pats derived from young cattle treated or untreated with either ivermectin sustained-release boluses, or the nematophagous fungus Duddingtonia flagrans, were studied in each of three years. Soil samples taken 4, 6, 8 and 10 weeks after four deposition dates in 1998 showed significant temporal effects in many taxa and treatment effects in a few genera. In 2000, soil samples taken 10 weeks after deposition in July, August and September showed treatment effects in the plant-associated Tylenchus and Cephalenchus, and the bacterial-feeding Cephalobus 1 and Cephalobus 2 taxa. However, overall it was found that the nematode assemblages were similar below all three types of pat, and the assemblages varied with the season of deposition. D. flagrans, the novel biological control agent being tested against the free-living stages of nematode parasites of cattle, had no detectable impact on the size or the structure of the soil nematode communities under the faecal pats.     

Screening for Indian Isolates of Predacious Fungi for Use in Biological Control against Nematode Parasites of Ruminants

Four isolates of predacious fungi, two each of Arthrobotrys oligospora isolated from a sheep and a male crossbred calf and of Duddingtonia flagrans isolated from a sheep and a female buffalo in western India, were studied for their suitability as biocontrol agents against parasitic nematodes of ruminants, using growth assay, predatory activity, germination potential and ability to survive passing through the ruminants gut as criteria. The study showed that isolates of D. flagrans grew well in artificial media, had encouraging predatory activity, produced profuse chlamydospores that germinated easily at 25°C and could survive passage through the ruminant gut. The ovine isolate of D. flagrans was superior in all respects to the isolate from buffalo and was the most promising candidate for biological control of nematode parasites of ruminants.     

嗜线虫真菌中Duddingtonia flagrans培养性状的初步研究

研究嗜线虫真菌中Duddingtonia flagrans在不同生长环境中的培养特性.选择普通琼脂培养基(WA)、玉米琼脂培养基(CMA)、马铃薯琼脂培养基(PA)和面粉琼脂培养基(FA)4种不同培养基培养,结果表明,在WA中真菌生长速度最快,在PA中产孢量最多.从应用的角度考虑,PA为最佳培养基;以10～35 C每隔5℃设置7种不同温度组培养,结果表明,10℃和35℃时不生长,25℃和30℃时菌丝生长率较高,产孢量较多,其中以30℃培养效果最好.     

Biological control of horse cyathostomin (Nematoda: Cyathostominae) using the nematophagous fungus Duddingtonia flagrans in tropical southeastern Brazil

The viability of a fungal formulation using the nematode-trapping fungus Duddingtonia flagrans was assessed for the biological control of horse cyathostomin. Two groups (fungus-treated and control without fungus treatment), consisting of eight crossbred mares (3–18 years of age) were fed on Cynodon sp. pasture naturally infected with equine cyathostome larvae. Each animal of the treated group received oral doses of sodium alginate mycelial pellets (1 g/(10 kg live weight week)), during 6 months. Significant reduction (p < 0.01) in the number of eggs per gram of feces and coprocultures was found for animals of the fungus-treated group compared with the control group. There was difference (p < 0.01) of 78.5% reduction in herbage samples collected up to (0–20 cm) between the fungus-treated group and the control group, during the experimental period (May–October). Difference of 82.5% (p < 0.01) was found between the fungus-treated group and the control group in the sampling distance (20–40 cm) from fecal pats. During the last 3 months of the experimental period (August, September and October), fungus-treated mares had significant weight gain (p < 0.01) compared with the control group, an increment of 38 kg. The treatment with sodium alginate pellets containing the nematode-trapping fungus D. flagrans reduced cyathostomin in tropical southeastern Brazil and could be an effective tool for biological control of this parasitic nematode in horses.     

Capability of the nematode-trapping fungus Duddingtonia flagrans to reduce infective larvae of gastrointestinal nematodes in goat feces in the southeastern United States: dose titration and dose time interval studies

Infection with gastrointestinal nematodes, particularly Haemonchus contortus, is a major constraint to goat production in the southeastern United States. Non-anthelmintic control alternatives are needed due to increasing resistance of these nematodes to available anthelmintics. Two studies were completed in Central Georgia in August 1999, and April–May 2000, using Spanish does naturally infected with Haemonchus contortus, Trichostongylus colubriformis, and Cooperia spp. to evaluate effectiveness of nematode-trapping fungi as a biological control agent. In the first experiment, five levels of Duddingtonia flagrans spores were mixed with a complete diet and fed once daily to the does (three per treatment) in metabolism crates. The treatment concentrations were (1) 5×10⁵, (2) 2.5×10⁵, (3) 10⁵, and (4) 5×10⁴ spores per kilogram body weight (BW), and (5) no spores. Fungal spores were fed for the first 7 days of the 14-day trial, and fecal samples were collected daily from individual animals for analysis of fecal egg count and establishment of fecal cultures. Efficacy of the fungus at reducing development of infective larvae (L3) in the fecal cultures was evaluated. The mean reduction in L3 from day 2 of the treatment period until the day after treatment stopped (days 2–8) was 93.6, 80.2, 84.1, and 60.8% for animals given the highest to lowest spore doses, respectively. Within 3–6 days after termination of fungal spore feedings, reduction in L3 development was no longer apparent in any of the treated animals. In a second experiment, effectiveness of 2.5×10⁵ spores of D. flagrans per kilogram BW fed to does every day, every second day, and every third day was evaluated. Reduction in L3 development by daily feeding was less in the second experiment than in the first experiment. Daily fungal spore feeding provided more consistent larval reduction than intermittant feeding (every second or third day). When fed daily under controlled conditions, D. flagrans was effective in significantly reducing development of L3 and appears to be an effective tool for biocontrol of parasitic nematodes in goats.     

Predacious activity of the nematode-trapping fungus Duddingtonia flagrans against cyathostome larvae in faeces after passage through the gastrointestinal tract of horses

This study was undertaken to examine the potential of the nematode-trapping microfungus Duddingtonia flagrans to survive passage through the gastrointestinal tract of horses and subsequently to destroy free-living stages of cyathostomes in faecal cultures. Three different oral dose levels were tested, two horses being used for each level. Faeces were collected twice daily and the number of parasite eggs per gram of faeces were determined. The numbers of infective third stage larvae which developed in faecal cultures were determined after the cultures had been incubated for 2 weeks at 24°C. Results showed a positive relationship between dose level and reduction in the number of infective larvae. Fungi were recovered in faeces at times which corresponded to high larval reduction.     

用嗜线虫真菌防治家畜胃肠道线虫病的研究进展

简要论述了嗜线虫真菌种类及其捕捉器官和国内外生物防治家畜胃肠道线虫病的研究进展。国内外防治该病主要是用各种驱虫药物定期驱虫，由此造成寄生虫抗药性、动物组织残留药物、环境污染、线虫反复感染等诸多负作用。用线虫天敌嗜线虫真菌生物防治家畜胃肠道线虫病成为该领域研究的重点课题之一。实验室和野外的大量研究结果证明，嗜线虫真菌在通过动物胃肠道时能不被消化，从而保持活性，在粪便中能有效捕食营自由生活阶段的线虫幼虫，使放牧草场中感染性线虫幼虫明显减少，呈现出良好的生物防治效果。文章重点介绍了嗜线虫真菌Duddingtonia flagrans，对用嗜线虫真菌生物防治家畜胃肠道线虫病的前景充满信心。