Effect of Duddingtonia flagrans against Ostertagia ostertagi in cattle grazing at different stocking rates

Trapping Behaviour of Duddingtonia flagrans against Gastrointestinal Nematodes of Cattle under Year-Round Grazing Conditions

The purpose of using nematophagous fungi as biological control agents of gastrointestinal nematodes of livestock is to reduce the build-up of infective larvae on pasture and thus avoid clinical and subclinical disease. As the interaction of fungus-larval stages takes place in the environment, it is crucial to know how useful the fungal agents are throughout the seasons in areas where livestock graze all year-round. This study was designed to determine the predatory ability of the nematophagous fungus Duddingtonia flagrans against gastrointestinal nematodes of cattle during four experiments set up in different seasons. In each experiment, faeces containing eggs of gastrointestinal nematodes were mixed with 11,000 chlamydospores/g and deposited on pasture plots. A comparison between fungal-added faeces and control faeces without fungus were made with regard to pasture infectivity, larval presence in faecal pats, faecal cultures, faecal pat weight, and temperature inside the faecal mass. In three of the four experiments, Duddingtonia flagrans significantly reduced the population of infective larvae in cultures (68 to 97%), on herbage (80 to 100%), and inside the faecal pats (70 to 95%). The study demonstrated the possibility of counting on a biological control tool throughout most of the year in cattle regions with extensive grazing seasons.

In vitro efficacy of different concentrations of Duddingtonia flagrans on varying egg densities of gastrointestinal nematodes of cattle

The nematophagous fungus Duddingtonia flagrans, used for the biological control of gastrointestinal nematodes in livestock, is fed to infected animals so its chlamydospores and the parasite eggs are voided together with faeces where the fungus preys on nematode larvae, thus reducing pasture infectivity. The number of chlamydospores needed for the fungus to be efficient in the presence of a wide range in numbers of parasitic eggs is largely unknown and a matter of discussion. The aim of this study was to determine the fungal efficacy of four different chlamydospore concentrations against three different levels of cattle faecal egg counts. Fungal concentrations of 11000, 6250, 3000 and 1000 chlamydospores/gram of faeces (cpg) were added to cultures containing 840, 480 or 100 eggs/gram of faeces (epg). After 14 days of incubation, the efficacy of D. flagrans, in decreasing order of chlamydospore concentrations, ranged from 100% (P < 0.0001) to 77% (P > 0.0999) in the 100 epg groups; 100% (P < 0.0001) to 92% (P = 0.4625) in the 480 epg groups and 100% (P < 0.0001) to 96% (P = 0.7081) in the 840 epg groups. The results indicate that the numbers of eggs in cattle faeces were not a determining factor on the fungal efficacy against gastrointestinal nematodes.

Antiparasitics in Animal Health: Quo Vadis?

Antiparasitics acting on endo- or ectoparasites represent the second largest segment of the global animal health market, accounting for 23% of market share. However, relatively few novel antiparasitic agents have been introduced into the market during recent decades. One exception, and a groundbreaking 21st century success story, are the isoxazolines, whose full potential has not yet been entirely explored. Unfortunately, resistance issues are present across most parasitic diseases, which generates a clear market need for novel resistance-breaking antiparasitics with new modes/mechanisms of action. Recent advances in science and technologies strongly suggest that the time is right to invest in new modalities such as parasitic vaccines or in environmentally friendly interventions.

Safety and efficacy of BioWorma® (Duddingtonia flagrans NCIMB 30336) as a feed additive for all grazing animals

Following a request from the European Commission, the EFSA Panel on Additives and products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of BioWorma® (Duddingtonia flagrans NCIMB 30336) when used as a zootechnical feed additive for all grazing animals. Duddingtonia flagrans belongs to a group of nematophagous fungi that physically entrap nematodes through an adhesive hyphal net. The additive contains the fungus in the form of chlamydospores and is intended to control pathogenic nematodes on pasture, with subsequent benefits for grazing animals. No conclusions could be drawn on the safety for the target species due to lack of data. ■■■■■ As it is not possible to exclude the presence of secondary metabolites (other than flagranones) produced during fermentation and their potential carry-over into animal products, safety for the consumer could not be established. The Panel concluded that the additive is not irritant to skin and eyes but is irritant to the respiratory tract and a respiratory sensitiser. No conclusion could be drawn on its skin sensitisation potential. Since D. flagrans is a naturally inhabiting soil organism of world-wide distribution, the Panel considered that use of an additive based on this organism does not pose a risk for the environment under the intended conditions of use. The strain under application reduced the number of parasitic nematodes on pasture to the benefit of grazing animals when used at the recommended application rate of 3 × 104 chlamydospores/kg bodyweight and day.

Isolation and characterization of the nematophagous fungus Arthrobotrys conoides

The spread of organic farming and the development of resistance to anthelmintics by parasites, especially in small ruminants, have necessitated the search for alternative methods of nematode control. Biological control using nematophagous fungi is one option; however, few studies have been conducted with native strains. The present study was divided into two phases. In the first phase, we aimed to isolate, identify, and assess the in vitro predatory activity of nematophagous fungi that had been isolated on Trichostrongylidae third-instar larvae. In the second phase, the isolate with superior predatory activity in vitro was molecularly characterized, and its morphological plasticity was observed using scanning electron microscopy (SEM) on Haemonchus third-instar larvae. Of the 56 soil samples from different regions of Paraná State, Brazil, 57 fungal strains were recovered, of which four exhibited predatory activity. Two pure isolates were obtained: the CED and LIN strains. After demonstrating 96.35 % predatory activity for the CED strain, this strain was selected and characterized using molecular criteria by sequencing the rDNA internal transcribed spacer and was identified as Arthrobotrys conoides (GenBank ID: JN191309). Morphological patterns in this strain during the interaction between the fungus and the nematode were revealed by SEM, in which two extensions of the infection bulb that was used to pierce the nematode's cuticle were clearly visible.

Failure of Duddingtonia flagrans to reduce gastrointestinal nematode infections in dairy ewes

A field study was conducted on three Swiss farms to investigate the efficacy of Duddingtonia flagrans against naturally acquired infections of gastrointestinal nematodes in adult dairy sheep. On each farm the ewes were divided into two equal groups. One group received Duddingtonia during a period of 4 months at a daily dose rate of 10(6) chlamydospores per kilogram body weight, the second group acted as controls. At an overall moderate infection level in all farms D. flagrans did not have a significant effect on the observed parasitological parameters with the exception of a significantly reduced herbage infectivity in one farm. In contrast, the results from faecal cultures indicated a mean suppression of larval development during the fungus-feeding period between 82, 89 and 93% on the three farms, respectively. The discrepancy observed between the fungus efficacy in coprocultures and on pasture, which was also observed in several other studies deserves further research.

Efficiency of feeding Duddingtonia flagrans chlamydospores to control nematode parasites of first-season grazing goats in France

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 x 10(5) spores/kg body weight was given to the fungus-group animals, while in 2004 a daily dose rate of 10(6) 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.

Gastrointestinal Nematode Control Programs with an Emphasis on Cattle

Control strategies for nematode parasites rely on knowledge of the relationships between the parasites and their hosts. Specifically, these programs are based on identifying crucial points of interaction in the environment provided by the host, including genetics and the immune response, and critical periods in the physical environment in which the eggs and larval stages must develop. When these targets are identified and the interactions understood, cost-effective sustainable programs can be developed using currently available antiparasitic compounds. Resistance to the major classes of anthelmintic compounds requires consideration of new approaches, such as immunity or genetics of the host. Additionally, the efficacy of these compounds can be expanded with combined or concomitant use. Increased study of the use of novel approaches, including fungi, elements such as copper, and plant products, has also occurred. This article explores each of these areas to allow readers to appreciate how various approaches may be developed and incorporated into an effective parasite control program.

Evaluation of efficacy expectations for novel and non-chemical helminth control strategies in ruminants

The interest in novel methods of controlling helminth infections in ruminants is driven primarily by the development of parasite resistance to currently available anthelmintics. While the purpose of anthelmintics is to achieve high efficacy, i.e. >90% reduction of adult and/or larval parasites in the target host animal, the purpose of novel parasite control methods is rather to assist in maintaining parasite infections below the economic threshold. The ability to maintain parasite levels below the economic threshold is related not only to the efficacy of the control method, but also to the epidemiology of the parasites, climatic conditions, the livestock management program, and integration in a sustainable parasite control program. Because of this fundamental difference, novel parasite control methods need to be evaluated using efficacy criteria different from that adopted for anthelmintics. Although the efficacy of novel parasite control methods may be demonstrated in classic dose-confirmation studies, the impact on livestock production parameters can only be evaluated when tested on-farm. In this paper, the rationale for evaluating novel methods differently from anthelmintics is reviewed, potential performance expectations are presented, and four novel parasite control methods (vaccines, nematophagous fungi, condensed tannins, and immunonutrition) are assessed based on the potential performance criteria.

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 x 10(5), (2) 2.5 x 10(5), (3) 10(5), and (4) 5 x 10(4) 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 x 10(5) 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.

Efficiency of feeding Duddingtonia flagrans chlamydospores to grazing ewes on reducing availability of parasitic nematode larvae on pasture

Gastrointestinal nematodes are of concern in sheep production because of production and economic losses. Control of these nematodes is primarily based on the use of anthelmintic treatment and pasture management. The almost exclusive use of anthelmintic treatment has resulted in development of anthelmintic resistance which has led to the need for other parasite control options to be explored. The blood sucking abomasal parasitic nematode Haemonchus contortus causes severe losses in small ruminant production in the warm, humid sub-tropic and tropics. This study evaluated the effectiveness of a nematode trapping fungus, Duddingtonia flagrans, in reducing availability of parasitic nematode larvae, specifically H. contortus, on pasture. Chlamydospores of D. flagrans were mixed with a supplement feed which was fed daily to a group of crossbred ewes for the duration of the summer grazing season. A control group was fed the same supplement feed without chlamydospores. A reduction in infective larval numbers was observed in fecal cultures of the fungus-fed group. Herbage samples from the pasture grazed by the fungus-fed group also showed a reduction in infective larvae. There were no significant (P > 0.05) differences in overall fecal egg count, packed cell volume or animal weight between fungus-fed and control groups. Tracer animals were placed on the study pastures at the end of the study to assess pasture infectivity. Although tracer animals were only two per group, those that grazed with the fungus-fed group had substantially reduced (96.8%) nematode burdens as compared to those from the control group pasture. Results demonstrated that the fungus did have activity against nematode larvae in the feces which reduced pasture infectivity and subsequently nematode burdens in tracer animals. This study showed that D. flagrans, fed daily to grazing ewes, was an effective biological control agent in reducing a predominantly H. contortus larval population on pasture.

Biological control of trichostrongylid infections in calves on pasture in Lithuania using Duddingtonia flagrans, a nematode-trapping fungus

The effect on the pasture contamination level with infective trichostrongylid larvae by feeding the nematode-trapping fungus, Duddingtonia flagrans at two dose levels to first time grazing calves was examined in Lithuania. Thirty heifer-calves, aged 3-6 months, were divided into three comparable groups, A, B and C. Each group was turned out on a 1.07 ha paddock (a, b and c). The paddocks were naturally contaminated with infective trichostrongylid larvae from infected cattle grazing the previous year. Fungal material was fed to the animals daily during a two month period starting 3 weeks after turnout. Groups A and B were given 10(6) and 2.5x10(5) chlamydospores per kg of live weight per day, respectively, while group C served as a non-dosed control group. Every two weeks the heifers were weighed and clinically inspected. On the same dates, faeces, blood and grass samples were collected. From mid-July onwards, the number of infective larvae in grass samples increased markedly (P<0.05)on paddock c, whereas low numbers of infective larvae were observed on paddocks a and b grazed by the fungus treated groups. However, the results indicate that administering fungal spores at a dose of 2.5x10(6)chlamydospores per kg live weight per day did not significantly prevent parasitism in calves, presumably due to insufficient suppression of developing infective larvae in the faeces. In contrast, a dose of 10(6) chlamydospores per kg lowered the parasite larval population on the pasture, reduced pepsinogen levels (P<0.05), and prevented calves from developing parasitosis.

The impact of internal parasites on the productivity of young cattle organically reared on semi-natural pastures in Sweden

A grazing experiment with young cattle was conducted over two consecutive (1997, 1998) grazing seasons on semi-natural pasturelands in central-eastern Sweden. Comparisons were made between groups of animals that were either untreated and set-stocked, ivermectin bolus treated and set-stocked or untreated but moved in mid-summer (mid-July) to ungrazed pasture. The whole experimental area had remained virtually free of cattle during the previous two seasons and the cattle had been raised indoors since birth. To introduce low-levels of parasite infection into the experimental system, each animal received a 'priming dose' of approximately 10, 000 infective trichostrongylid larvae at the time of turnout for both years. Results of the first year study showed that the level of parasitism was so low that it failed to induce any productivity losses in both groups of untreated cattle, which grew as well as those given boluses at turnout. In contrast, in 1998 both groups of untreated cattle suffered varying degrees of sub-clinical and clinical parasitism to result in an average of 30kg liveweight depression, compared with the bolus treated cattle, at the end of the season. The only major departure between the two years was that in the latter, the cattle in the untreated groups were exposed to infective larval pickup, which had overwintered on pasture. Cattle in the move treatment grazed in the same sequence on pastures used by similar classes of animals during the previous year. That is, their pastures at turnout had not been grazed since mid-summer of the previous year. Clearly this early season (1997) grazing by young cattle resulted in sufficient overwintered larvae at the start of the following year (1998) to cause productivity losses of the same magnitude as those recorded for young cattle grazing on pastures contaminated for the entire grazing season of the previous year. This was confirmed by tracer tests that were carried out on all treatments, at the time of turnout and the mid-summer move in 1999. These results have major significance to organic cattle producers in Sweden who have a much higher tendency to practice a variety of grazing management techniques aimed at controlling nematode parasite infections in young cattle, than their conventional farming colleagues. It has been identified that one of these strategies is to simply use summer/autumn saved pastures for young stock at turnout, which if grazed by young stock prior to this, could prove to be counter-productive.

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).