Predatory capability of the nematophagous fungus Arthrobotrys robusta preserved in silica gel on infecting larvae of Haemonchus contortus

Biological control of gastrointestinal nematodiasis in ruminants is an alternative to reduce the number of infective larvae. The fungal isolates predatory activity preservation is a basic requirement for the success of this control type. The aim of this work is to evaluate the predatory capacity of the fungus Arthrobotrys robusta (isolate I-31), preserved on silica gel on infective larvae of Haemonchus contortus under laboratory conditions on 2 % water agar (2 % WA). In this essay, A. robusta storage on silica gel showed successful predatory activity on H. contortus L₃ larvae (p?<?0.01) compared to the control group. Nematophagous fungi were not observed in the control group during the experiment. There was a significant reduction (p?<?0.01) of 73.84 % in the means of H. contortus (L₃) recovered from treatment with isolate I-31 compared to the control without fungi. Results indicate that A. robusta (I-31) could survive stored on silica gel for at least 7 years and keep its predatory activity on H. contortus (L₃).     

Interaction between the nematode-destroying fungus Arthrobotrys robusta (Hyphomycetales) and Haemonchus contortus infective larvae in vitro.

In an in vitro trial, the effect of the nematode-destroying fungus Arthrobotrys robusta on Haemonchus contortus infective larvae was evaluated in petri dishes containing corn meal agar. After seven days incubation at 25 degrees C, 92.33% (+/- 4.1) predation was recorded.     

Induction of nematode-trapping organs in the predacious fungus Arthrobotrys oligospora (Hyphomycetales) by infective larvae of Ostertagia ostertagi (Trichostrongylidae)

Laboratory experiments were designed to study the influence of temperature, concentrations of nematodes, oxygen tension, light, and nutrient levels, on the induction of nematode-trapping hyphal nets in the predacious fungus Arthrobotrys oligospora. When induced by infective Ostertagia ostertagi larvae, a maximum number of nets was produced at 20 degrees C, at which temperature nets in surplus were produced at larval concentrations up to 1,000 larvae per cm2. A. oligospora did not produce nets in an anaerobic atmosphere containing 21% CO2 (v/v), and net induction was suppressed to a certain degree by exposure to light. The composition of the medium had an important influence on the saprophytic growth and the net-forming capability of A. oligospora as a maximum number of nets was induced at a relatively low concentration of corn meal supporting the relatively sparse mycelium. It was shown that a proportion of trapping nets in A. oligospora maintained their trapping potential for more than 7 weeks when the temperature was below 25 degrees C. Induction of nematode-trapping organs in A. oligospora is discussed in relation to control of infective nematode parasite larvae in cow pats.     

Predatory activity of the nematophagous fungus <Emphasis Type="Italic">Duddingtonia flagrans</Emphasis> on horse cyathostomin infective larvae

This work was performed to determine the predatory capacity in vitro of the nematophagous fungus Duddingtonia flagrans (isolate AC001) on cyathostomin infective larvae of horse (L₃). The experimental assay was carried out on plates with 2% water-agar (2% WA). In the treated group, each plate contained 1.000 L₃ and 1.000 conidia of the fungus. The control group without fungus only contained 1.000 L₃ in the plates. Ten random fields (4 mm diameter) were examined per plate of treated and control groups, every 24 h for seven days under an optical microscope (10× and 40× objective lens) for non-predated L₃ counts. After 7 days, the non-predated L₃ were recovered from the Petri dishes using the Baermann method. The interaction there was a significant reduction (p < 0.01) of 93.64% in the cyathostomin L₃ recovered. The results showed that the D. flagrans is a potential candidate to the biological control of horse cyathostomin L₃.     

The predatory capability of Arthrobotrys cladodes var. macroides in the control of Haemonchus contortus infective larvae

One hundred compost samples were examined for the presence of nematophagous fungi on the sheep farms of Mazanderan, province, Iran. Arthrobotrys cladodes var. macroides (IRAN 677C = CBS 143565) was isolated from 3% of the samples examined. Nematophagous activity of this fungus which was shown for the first time in this study, revealed the addition of 1000, 8000, 20 000 and 100 000 conidia per gram of feces of sheep reduced significantly (P < 0.001) the number of Haemonchus contortus infective larvae in the feces by 41.71%, 63, 27%, 73.49% and 94.96%, respectively. These results show that A. cladodes var. macroides is a promising candidate for biological control of H. contortus.     

Efficacy of milbemycin oxime against naturally acquired or experimentally induced Ancylostoma spp and Trichuris vulpis infections in dogs.

The efficacy of milbemycin oxime was evaluated at dosages of 0.25, 0.50, and 0.75 mg/kg of body weight in dogs naturally infected with mature Ancylostoma spp, at a dosage of 0.50 mg/kg in dogs with experimentally induced immature and mature A caninum, and at dosages of 0.55 to 0.86 mg/kg in dogs naturally infected with mature Trichuris vulpis. Milbemycin oxime was 95 and 99% effective against mature Ancylostoma spp at dosages of 0.50 and 0.75 mg/kg, respectively, but only 49% effective at a dosage of 0.25 mg/kg. Efficacy was 49% against pulmonary L3-L4 stages of A caninum (36 hours after inoculation), greater than 80% against L4 (120 hours after inoculation) and early L5 stages (216 hours after inoculation), and greater than 90% against experimentally induced mature stages (360 hours after inoculation). Milbemycin oxime was also 97% effective in the removal of mature Tr vulpis from naturally infected dogs. Adverse reactions were not observed following treatment in any of the dogs.     

A new isolate of the nematophagous fungus Duddingtonia flagrans a biological control agent against free-living larvae of horse strongyles

An experiment was carried out in 1997 to test the efficacy of an isolate of the microfungus Duddingtonia flagrans against free-living stages of horse strongyles under conditions in the field and to assess the eventual effect of the fungus on the normal degradation of faeces. Faecal pats were made from faeces of a naturally strongyle infected horse, which had been fed fungal material at a dose level of 106 fungal unit/kg bwt. Control pats without fungi were made from faeces collected from the same animal just before being fed fungi. Faecal cultures set up for both groups of faeces to monitor the activity of the fungus under laboratory conditions showed that the fungus significantly reduced the number of infective third-stage larvae (L3) by an average of 98.4%. Five faecal pats from each batch of faeces were deposited on pasture plots at 3 times during spring-summer. The herbage around each pat was sampled fortnightly to recover L3 transmitted from faeces. The results showed that the herbage infectivity around fungus-treated pats was reduced by 85.8-99.4%. The remaining faecal material at the end of each sampling period was collected, and the surviving L3 were extracted. Significantly fewer larvae were recovered from the fungus-treated pats. Analysis of wet and dry weight of the collected pats, as well as their organic matter content, were performed to compare the degradation of faeces of both groups. The results indicated that the presence of the fungus did not alter the degradation of the faeces.     

Impact of the nematophagous fungus Duddingtonia flagrans on Muellerius capillaris larvae in goat faeces

The small lungworm Muellerius capillaris is very prevalent in goats and causes production losses. Its control is particularly difficult. The nematophagous fungus Duddingtonia flagrans has been shown to be effective in trapping a large range of gastro-intestinal nematode larvae but its trapping activity against small lungworm remains to be assessed. The purpose of this work was firstly, to evaluate the ability of first-stage larvae of M. capillaris (L1) to induce trap formation in in vitro conditions and secondly, to determine the effect of D. flagrans on the L1 infectivity to snails. In experiments on agar, the presence of L1 failed to induce any D. flagrans traps whereas in the same conditions, gastro-intestinal third-stage larvae induced 44-135 traps/cm(2) depending on the species. Moreover, when the traps were pre-induced by Haemonchus contortus larvae, the L1 of M. capillaris were not trapped. For the in vivo trial, two goats naturally infected with M. capillaris received D. flagrans chlamydospores at the daily dose rate of 5x10(5) spores/kg BW for 8 days. Faeces were collected individually before, during and 11 days after spore administration. On each day of harvest, the initial larval output was determined. The remaining faeces were subjected to coproculture at 21 degrees C for 7 days. At the end of this period, L1 were collected and used to infect snails (30 snails per goat isolate each snail given 40 L1 by direct deposit of the larvae on the foot of the snail). These snails were artificially challenged in contrast to others that were exposed to natural infection by exposure to faeces carrying first-stage M. capillaris larvae. The natural infection used the same number of snails, i.e. 30 snails deposited on the faeces of each goat. After 3 weeks at room temperature, the infective larvae present in the snail foot were counted. There was no difference in the survival of the L1 in faeces after coproculture whether the faeces contained D. flagrans or not. The infectivity of the extracted larvae from the two goats before and after fungal administration was the same. The number of infective larvae per snail obtained after "natural" infection showed variations that were not related to the presence of D. flagrans mycelium in faeces. These trials clearly indicate that D. flagrans was unable to trap or to alter the infectivity of M. capillaris first-stage larvae and thus cannot be considered as a non-chemotherapeutic alternative approach to the control of the small lungworm in goats.     

Interactions between the predacious fungus Arthrobotrys oligospora and third-stage larvae of a series of animal-parasitic nematodes

Interactions between the predacious hyphomycete Arthrobotrys oligospora and third-stage larvae of nine animal-parasitic nematodes were tested in vitro. The trap-inducing capabilities of the ruminant trichostrongylus Cooperia oncophora, C. curticei, Haemonchus contortus and Ostertagia ostertagi and of equine cyathostomes were almost comparable to those of free-living soil nematodes, and significantly higher than those of the porcine Oesophagostomum dentatum and Oe. quadrispinulatum and of the murine Nematospiroides dubius. The trap-forming potential of Dictyocaulus viviparus was poor. All animal-parasitic nematodes were rapidly captured when fungal traps had been pre-induced in high numbers. The possible influence of predacious fungi on animal-parasitic nematode populations under natural conditions in the field is discussed.     

Efficacy of the nematophagous fungus Duddingtonia flagrans in reducing equine cyathostome larvae on pasture in south Louisiana

The effectiveness of Duddingtonia flagrans in reducing the free living third stage larvae (L(3)) of equine cyathostomes on pasture when fed to horses has been demonstrated in cold temperate climates. The objective of this experiment was to assess the efficacy of D. flagrans against equine cyathostomes in the subtropical environment of southern Louisiana. Fecal pats were prepared by mixing feces obtained from a parasite-free horse fed D. flagrans at a dose of approximately 2 x 10(6) spores kg(-1), with feces containing cyathostome eggs from a parasitized horse. Control pats contained feces from a parasite-free horse mixed with feces containing cyathostome eggs. The fecal pats were placed on pasture in six replicates at 4-week intervals from March 1997 until January 1998. Comparison of recoveries of L(3) from non-treated control pats in the field with non-treated coprocultures maintained in the laboratory indicated that L(3) survival on pasture was reduced during the months of May, June, July, August and September. The efficacy of the fungus was determined by L(3) recovery from grass surrounding the fecal pats of treated and control groups. D. flagrans significantly reduced L(3) during the months of April, May, and October 1997 to January 1998 (range 66-99% reduction, p=0.0001), and for the year as a whole (p=0.0001).     

Viability and pattern of emergence of Dictyocaulus viviparus larvae in sporangia of the fungus Pilobolus kleinii

Recoveries of third stage Dicytocaulus viviparus larvae (L3) from Pilobolus species sporangia ranged from 23 per cent at 21 days to 3 per cent after 90 days for sporangia attached to polythene discs positioned on pasture. There was a continuous release of L3 for up to 16 days from sporangia which were placed under conditions simulating those occurring on pasture.     

Arrested development of bovine Ostertagia spp. and Cooperia spp. in New Zealand. Effect of temperature and duration of storage on infective larvae

Infective larvae of Ostertagia spp. and Cooperia spp. derived from naturally infected dairy calves were subjected to periods of storage of up to 16 weeks at 4 degrees C or 15 degrees C to determine if this treatment would influence their propensity for arrested development in previously worm-free calves. Results showed no significant increase in the propensity of Ostertagia spp. for arrested development in response to the treatments, but a small increase in the case of Cooperia spp.     

Efficacy of milbemycin oxime against experimentally induced Ancylostoma caninum and Uncinaria stenocephala infections in dogs.

Twenty-eight helminth-naive Beagles, 16 to 26 weeks old, were inoculated with 200 third-stage larvae each of Ancylostoma caninum and Uncinaria stenocephala 5 times at weekly intervals. Dogs were randomly allocated to 4 groups of 7 on the basis of fecal egg counts, and treatments were randomly assigned. Groups 1 and 3 were given milbemycin oxime at a dosage of 500 micrograms/kg of body weight, PO, on day 0 and on days 0 and 30, respectively; groups 2 and 4 were nontreated controls. Fecal egg counts were evaluated before and after treatments. Feces were collected daily for 7 days after the final treatment for recovery of worms passed, and all dogs were euthanatized 7 days after the final treatment for recovery of worms retained. A 65.7% reduction from the pretreatment value for geometric mean hookworm egg count was found 7 days after the first treatment, and a 97.1% reduction 7 days after the second treatment. Although milbemycin oxime had 96.5% and 99.5% controlled efficacy against A caninum after 1 or 2 treatments, respectively, it lacked efficacy against U stenocephala. The geometric mean number of U stenocephala and the total number of hookworms retained after 1 or 2 treatments were not significantly different from the numbers retained by the corresponding control groups.     

嗜线虫真菌Duddingtonia flagrans减少绵羊粪便中线虫感染性幼虫剂量测定

嗜线虫真菌Duddingtonia flagrans是目前发现的一种最具有动物胃肠道线虫病生物防治应用潜力的真菌。为了解该菌捕杀绵羊粪便中感染性幼虫效果与剂量的关系,为今后该制剂应用和质量检验标准的制定提供依据,用不同剂量的厚垣孢子,分别以不经消化道直接加入感染羊粪便,或作添加剂通过饲喂进入消化道后采集直肠粪便,经培养检测感染性幼虫数量的变化。结果表明,嗜线虫真菌Duddingtonia flagrans具有良好的捕杀胃肠道线虫感染性幼虫的生物学特性。以制剂厚垣孢子4&#215;103/g剂量加入感染羊粪便,或以每天5&#215;105/kg体质量的剂量饲喂绵羊,可使粪便培养物中线虫感染性幼虫数减少83.6%~87.5%。     

Effect of milbemycin oxime against Ancylostoma caninum in dogs with naturally acquired infection

Twenty-six mixed-breed (14 males, 12 females) dogs were used in a double-blind study to evaluate the effect of milbemycin oxime against naturally acquired infection with Ancylostoma caninum. Dogs were ranked and paired, on the basis of number of hookworm eggs/g of feces, and treatment was randomly assigned. Each dog was given either the study drug or placebo (1 tablet/11.4 kg [0.5 mg/kg] of body weight). Eggs per gram of feces enumeration was done on days 3 and 7 after treatment, and dogs were euthanatized on day 7. On day 3, 5 of the 13 dogs in the milbemycin-treated group had hookworm eggs in the feces (results of the McMaster test). In these dogs, mean number of eggs per gram of feces had decreased markedly (from 5,289 to 452) and, by day 7, was 114. At necropsy, 16 A caninum adults were recovered from 2 of the milbemycin-treated dogs. On day 3, 12 of the 13 dogs in the placebo-treated group had hookworm eggs in the feces. Mean number of eggs per gram of feces in these dogs decreased slightly (from 5,243 to 2,646), but did not decrease further by day 7. A mean number of 54.4 A caninum adults was recovered from 12 of the 13 placebo-treated dogs at necropsy. Milbemycin oxime had 97.8% efficacy against A caninum. Results also indicated that milbemycin oxime may be effective against Trichuris vulpis, but not against Dipylidium caninum.