Enhancing chlamydospore production in Duddingtonia flagrans on solid substrate: The impact of mannitol and varied cultivation conditions

Duddingtonia flagrans is a nematophagous fungus which has shown promising results as a non-chemical parasitic control tool. The fungus disrupts the parasite's life cycle by trapping larvae in the environment through the networks generated from chlamydospores, thus preventing the reinfection of animals. One barrier to the development of a commercial product using this tool is the need to increase chlamydospore production in the laboratory for its administration to livestock. The purpose of this study was to evaluate the addition of mannitol to an enriched culture medium and the effect of adverse cultivation conditions on chlamydospore production. D. flagrans was cultivated on Petri dishes with corn agar for 4 weeks at 27 °C and 70% relative humidity (RH). Four groups were then formed, all with Sabouraud agar as a base, to which different growth inducers were added: GSA (glucose Sabouraud agar), GSA-MI (glucose Sabouraud agar + meso inositol), GSA-E (enriched glucose Sabouraud agar), and AE-M (enriched agar + mannitol). After 4 weeks, chlamydospores were recovered by washing the surface of each plate with distilled water and then quantified. The medium that yielded the highest amount of chlamydospores was subjected to different cultivation conditions: NC (normal conditions): 70% RH and 27 °C, AC (adverse conditions) 1: 20% RH and 40 °C, CA2: 60% RH and 27 °C, and CA3: 55% RH and 24 °C. It was determined that mannitol increases chlamydospore production (65x106 chlamydospores/plate), and when reducing humidity by 10% under cultivation conditions it resulted in an approximately 10% increase in chlamydospore production compared to the control group. These results suggest that the addition of polyols, as well as its cultivation under certain environmental conditions, can improve chlamydospore production on a laboratory scale.

Formulating Parasiticidal Fungi in Dried Edible Gelatins to Reduce the Risk of Infection by Trichuris sp. among Continuous Grazing Bison

Control of infection by gastrointestinal nematodes remains a big problem in ruminants under continuous grazing. For the purpose of decreasing the risk of infection by Trichuris sp. in captive bison (Bison bison) always maintained in the same plot, dried gelatins having ≥106 chlamydospores of both Mucor circinelloides and Duddingtonia flagrans were given to them for one week, and at the end, fecal samples (FF) collected each week for four weeks were analyzed immediately. Feces taken one week prior to gelatin administration served as controls (CF). Eggs of Trichuris sp. were sorted into non-viable and viable, then classified into viable undeveloped (VU), viable with cellular development (VCD), or viable infective (VI). Ovistatic and ovicidal effects were determined throughout the study. In FF, viability of Trichuris eggs decreased between 9% (first week) and 57% (fourth week), egg development was delayed during the first two weeks, and VI percentages were significantly lower than in CF (p = 0.001). It is concluded that the preparation of gelatins with chlamydospores of parasiticidal fungi and their subsequent dehydration offer an edible formulation that is ready to use, stress-free to supply, and easy to store, as well as being well-accepted by ruminants and highly efficient to reduce the risk of Trichuris sp. infection among animals under continuous grazing regimes.

Safety of a feed additive consisting of Duddingtonia flagrans NCIMB 30336 (BioWorma®) for all grazing animals (International Animal Health Products Pty Ltd)

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety of a feed additive consisting of Duddingtonia flagrans NCIMB 30336 (BioWorma®) for all grazing animals. The safety and efficacy of the additive have been already assessed previously, however the FEEDAP Panel could not conclude on the safety of the additive for the target species and the consumers due to the limitations in the dataset provided. For the current assessment, the applicant submitted a new tolerance trial in dairy cows and new toxicological studies. After the assessment of the new data submitted, the FEEDAP Panel concluded that the use of the feed additive in animal nutrition under the conditions of use proposed is of no concern for dairy cows. This conclusion can be extrapolated to all dairy bovines, ovines and caprines, but not to fattening and rearing animals of those species. Due to the lack of data, the FEEDAP Panel cannot conclude on the safety of the additive for other grazing species/categories. The FEEDAP Panel concluded that the additive is safe for the consumers.

Compatibility study of Duddingtonia flagrans conidia and its crude proteolytic extract

This study aimed to evaluate the concomitant use of the nematophagous fungus Duddingtonia flagrans (AC001) and its protease-rich crude extract for the in vitro control of Panagrellus sp., Haemonchus spp., and Trichostrongylus spp. The nematicidal tests were carried out on larvae of the free-living nematode Panagrellus sp. and infective larvae of the gastrointestinal parasitic nematodes of domestic ruminants (Haemonchus spp. and Trichostrongylus spp). Five experimental groups were set: (1) one control group (G1) and (4) four treated groups -G2 - active crude extract; G3 - denatured crude extract; G4 - fungus, and G5 - fungus + active extract. Plates were incubated at 28 ºC for 24 h followed by the recovery of the larvae using the Baermann technique. The results showed a lower recovery of Panagrellus sp. larvae in the experimental groups compared to the control group, as follows: 52 % (G2), 16 % (G3), 46 % (G4), and 77 % (G5). An even greater reduction (77 ± 5 %) occurred in the group (G5). In addition, the authors observed lower averages of L3 of Haemonchus spp. and Trichostrongylus spp. in the experimental groups compared to the control group, as follows: 59 % (G2), 0 % (G3), 86 % (G4), and 76 % (G5). In turn, there was a difference (p < 0.01) between (G5) and (G2). The results this study indicate a positive effect from the compatible use of the D. flagrans fungus and its enzymatic crude extract (protease), which has been demonstrated here for the first time and with potential field applications for further designs.

The STRIPAK component SipC is involved in morphology and cell-fate determination in the nematode-trapping fungus Duddingtonia flagrans

The striatin-interacting phosphatase and kinase (STRIPAK) complex is a highly conserved eukaryotic signaling hub involved in the regulation of many cellular processes. In filamentous fungi, STRIPAK controls multicellular development, hyphal fusion, septation, and pathogenicity. In this study, we analyzed the role of the STRIPAK complex in the nematode-trapping fungus Duddingtonia flagrans which forms three-dimensional, adhesive trapping networks to capture Caenorhabditis elegans. Trap networks consist of several hyphal loops which are morphologically and functionally different from vegetative hyphae. We show that lack of the STRIPAK component SipC (STRIP1/2/HAM-2/PRO22) results in incomplete loop formation and column-like trap structures with elongated compartments. The misshapen or incomplete traps lost their trap identity and continued growth as vegetative hyphae. The same effect was observed in the presence of the actin cytoskeleton drug cytochalasin A. These results could suggest a link between actin and STRIPAK complex functions.

Survival of the nematophagous fungus Duddingtonia flagrans to in vitro segments of sheep gastrointestinal tract

The nematophagous fungus Duddingtonia flagrans is used in integrated management of gastrointestinal nematodes in ruminants. The chlamydospores of the fungus, orally administered, pass through the segments of the ruminant digestive tract and, in the feces, capture the nematodes preventing their migration to grasslands. The drastic conditions of the gastrointestinal segments can negatively affect the fungus' biocontrol activity. The aim of this study was to assess the effect of in vitro conditions of the sheep's main gastrointestinal segments on the concentration, viability and nematode predatory ability of D. flagrans chlamydospores. The segments evaluated separately in vitro were the oral cavity, rumen, abomasum, and small intestine. The results showed that chlamydospores concentration was not affected by exposure to the different segments. The viability of the chlamydospores after exposure to the oral cavity (2.53 × 10⁶ CFU/mL) and small intestine (1.24 × 10⁵ CFU/mL) was significantly lower than its control treatment, with values of 6.67 × 10⁶ CFU/mL and 2.31 × 10⁵ CFU/mL respectively. Nematode predatory ability after rumen exposure was reduced by 7% compared to the control treatment, by 25% after abomasum exposure and by 17% after small intestine. This study revealed the individual in vitro effect of each segment of ovine gastrointestinal tract on the integrity of this strain of the fungus D. flagrans affecting its viability and nematode predatory ability under the evaluated conditions. Delivery systems could be designed to protect chlamydospores considering the impact of each gastrointestinal segment.

Pathogenicity and Volatile Nematicidal Metabolites from Duddingtonia flagrans against Meloidogyne incognita

Plant parasitic nematodes, especially parasitic root-knot nematodes, are one of the most destructive plant pathogens worldwide. The control of plant root-knot nematodes is extremely challenging. Duddingtonia flagrans is a type of nematode-trapping fungi (NTF), which produces three-dimensional adhesive networks to trap nematodes. In this study, the pathogenicity and volatile organic compounds (VOCs) of the NTF D. flagrans against the plant root-knot nematode, Meloidogyne incognita, were investigated. The predatory process of D. flagrans trapping M. incognita was observed using scanning electron microscopy. Gas chromatography-mass spectrometry analysis of the VOCs from D. flagrans led to the identification of 52 metabolites, of which 11 main compounds were tested individually for their activity against M. incognita. Three compounds, cyclohexanamine, cyclohexanone, and cyclohexanol, were toxic to M. incognita. Furthermore, these three VOCs inhibited egg hatching of M. incognita. Cyclohexanamine showed the highest nematicidal activity, which can cause 97.93% mortality of M. incognita at 8.71 µM within 12 h. The number of hatched juveniles per egg mass after 3 days was just 8.44 when treated with 26.14 µM cyclohexanamine. This study is the first to demonstrate the nematicidal activity of VOCs produced by D. flagrans against M. incognita, which indicates that D. flagrans has the potential to biocontrol plant root-knot nematodes.

Control of Strongyles in First-Season Grazing Ewe Lambs by Integrating Deworming and Thrice-Weekly Administration of Parasiticidal Fungal Spores

Parasiticidal fungi have been used in several in vivo experiments in livestock farms worldwide, constituting an effective tool for the biocontrol of gastrointestinal parasites in grazing animals. In the first year of study, two groups of eight first-season pasturing ewe lambs infected by strongyles were dewormed with albendazole, and then, the test group received an oral dose of 10⁶ chlamydospores of Mucor circinelloides and 10⁶ Duddingtonia flagrans individually and thrice a week from mid-September to May (FS1), while the control group remained without fungi (CT1). In the second year, two new groups of first-season grazing ewe lambs were treated with ivermectin and subjected to the same experimental design (FS2 and CT2, respectively). The anthelmintic efficacy was 96.6% (CT1), 95.6% (FS1), 96.1% (CT2), and 95.1% (FS2). The counts of strongyle egg output increased in the control groups (CT1 and CT2) throughout the study and reached numbers higher than 600 eggs per gram of feces (EPG), while in FS1 and FS2, they were <250 EPG. The values of red blood cell parameters registered for CT1 and CT2 were lower than those of the reference standards, while a significant increment was recorded in FS1 and FS2, and values within the physiological range were attained. It is concluded that integrating efficient anthelminthic deworming with rotational pasturing and the regular intake of chlamydospores of M. circinelloides and D. flagrans provides a helpful strategy for maintaining low levels of strongyle egg output in first-season grazing ewe lambs and improves their health status.

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.

Bioverm® in the Control of Nematodes in Beef Cattle Raised in the Central-West Region of Brazil

Cooperia, Haemonchus and Oesophagostomum are the genera of gastrointestinal parasitic nematodes most prevalent in cattle and constitute a serious problem in cattle breeding due to the impact they have on meat and milk production and the high costs of control measures. The objective of the present work was to evaluate the efficiency of Bioverm^® (Duddingtonia flagrans) in the control of gastrointestinal parasitism of young cattle raised in the field, in the Central-West region of Brazil. The experiment was conducted on a farm located in the municipality of Jangada, MT, where 18 cattle, Nelore and Aberdeen Angus breeds, aged six to ten months, were randomly divided into two groups (treated group and control group) and distributed in paddocks of Brachiaria decumbens, naturally infested by larvae of gastrointestinal nematodes. The animals in the treated group received 1g of Bioverm^® for each 10 kg of body weight, administered daily with commercial feed, throughout a period of six months. In the control group, each animal received 1 g of rice bran for each 10 kg of body weight, without Bioverm^®, added to the feed. Stool and pasture samples were collected every two weeks. The treated group showed a significant reduction (p < 0.05) in values of eggs per gram of feces (EPG) and a significant gain of body weight (p < 0.05) when compared to the control group. The fungal formulation Bioverm^® was effective in pasture decontamination and consequently in reducing the occurrence of reinfection by nematodes. The animals treated with Bioverm^® showed a lower parasitic load and greater weight gain.

Effect of temperature, pH, physical and chemical factors on germination rate of the chlamydospores of the nematophagous fungus Duddingtonia flagrans

This study mainly investigated the effects of environmental factors on the germination/dormancy, sporulation and resistance of Duddingtonia flagrans chlamydospores. Results showed that the germination temperature of chlamydospores was >10°C and ≤35°C. After the chlamydospores were treated at -20, -40 and -80°C for 12-24 h, they still had the ability to germinate. The chlamydospores germinated at pH 3-13 but did not germinate at pH 1-2 and pH 14. The chlamydospores could tolerate ultraviolet rays for 720 min, but visible light irradiation for 24 h significantly reduced their germination rate. The chlamydospores did not germinate under anaerobic conditions. After the chlamydospores were cultured on water agar (WA) containing 5, 10 and 20% NaCl, their germination rate was significantly inhibited. Once NaCl was removed, the chlamydospores almost completely recovered their germination ability. Among the nine kinds of additives used in the study, 0.3% arginine significantly promoted spore germination (P < 0.05) but 1% trehalose and 1% glycerine significantly inhibited spore germination during incubation from 24 h to 48 h (P < 0.05). This work indicated that D. flagrans chlamydospores are highly resistant to environmental variations and so could be used for biocontrol of animal parasites.

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.

The efficacy of predatory fungi on the control of gastrointestinal parasites in domestic and wild animals-A systematic review

BACKGROUND

Gastrointestinal parasites like nematodes are associated with significant impacts on animal health, causing poor growth rates, diseases and even death. Traditional parasite control includes the use of anthelmintic drugs, albeit being associated with drug resistance and ecotoxicity. In the last decade, biological control of parasites using nematophagous or predatory fungi has been increasingly studied, although systematic evidence of its efficacy is still lacking. The aim of this work was to assess the evidence of efficacy of nematophagous fungi in the control of nematodes and other gastrointestinal parasites in different animal species.

METHODS

Using the PICO method (Population, Intervention, Comparison and Outcomes), we performed a systematic review on the subject to search for original papers published between January 2006 and October 2019, written in English, and indexed in PubMed/Medline. Medical Subject Headings (MeSH) terms were used in the syntax. Papers were selected for detailed review based on title and abstract. Inclusion and exclusion criteria were applied, and relevant data were collected from the remaining papers.

RESULTS

The literature search retrieved 616 papers. Eighty-nine were submitted to a detailed review. In the end, 53 papers were included in the analysis. The studies were very heterogeneous, using different fungi, doses, frequency of administration, duration of treatment, host animals, and target parasites. Considering the 53 papers, 44 studies (83 % of the interventions) showed efficacy, with only 9 studies (17 %) showing no significant differences when compared to control.

CONCLUSION

With the increasing hazards of drug resistance and ecotoxicity, biological control with predatory fungi stands out as a good tool for future parasite management, whether as a complementary treatment or as an alternative to standard parasite control.

Sustainable Approaches to Parasite Control in Ruminant Livestock

It is increasingly difficult to manage and control gastrointestinal nematode parasites in pasture-based ruminant livestock operations because of the high prevalence of anthelmintic resistance. Anthelmintics should be combined with alternative forms of control. Sustainable tools include copper oxide wire particles and condensed tannin-rich plants, which target primarily Haemonchus contortus in small ruminants. Nematophagous fungi reduce larvae on pasture and target nematode larvae in feces of most livestock species. In addition, and perhaps most importantly, genetic selection focuses on parasite resistance. Producers should use as many tools as possible to minimize the need for pharmaceutical interventions and optimize animal production.

Efficiency of the Bioverm ® (Duddingtonia flagrans) fungal formulation to control in vivo and in vitro of Haemonchus contortus and Strongyloides papillosus in sheep

The objective of the present work was to evaluate the efficiency of Bioverm^® fungal formulation (Duddingtonia flagrans-AC001) in controlling Haemonchus contortus and Strongyloides papillosus in sheep. In vitro predation tests were carried out in Petri dishes containing agar culture medium 2%. Four experimental groups were formed, with five replicates each: Group 1: 1 g of Bioverm ^® and 1000 third-stage larvae (L₃) of H. contortus; Group 2: 1000 L₃ of H. contortus; Group 3: 1 g of Bioverm ^® and 1000 L₃ of S. papillosus; and Group 4: 1000 L₃ of S. papillosus. In the in vivo tests, twelve 11-month-old sheep males positive for H. contortus were used. The animals were sorted in two groups (treatment and control), based on fecal egg counts (eggs per gram, EPG). Each group comprised six animals: treatment group-each animal received orally 100 g of Bioverm ^® ; and control group-each animal received orally 100 g of rice. Subsequently, feces from these animals were collected at 12, 24, 36, 48, 60, 72, 84, and 96 h after Bioverm ^® administration. In vitro results demonstrate that D. flagrans kept its predatory activity with 91.5% of mean reduction percentage of L₃. After the passage test, Bioverm ^® presented efficacy already after 12 h of its administration and kept similar results for 60 h. Bioverm^® fungal formulation (D. flagrans-AC001) was efficient in reducing the population of H. contortus and S. papillosus under laboratory conditions in sheep feces. However, further studies are needed under natural conditions of ruminant grazing to prove the efficiency of this product.

Integrating the control of helminths in dairy cattle: Deworming, rotational grazing and nutritional pellets with parasiticide fungi

Thirty-two Friesian cattle under a leaders/followers four-day rotation and passing eggs of trematodes and gastrointestinal nematodes (GIN) were studied in two trials for the integrated control of these helminths over two years. In the first trial, the effect of rotational pasturing was assessed on a group of leaders (milking cows, G-L1) and followers (dried-off cows and heifers, G-F1) supplemented daily with commercial nutritional pellets. In the second trial, leaders (G-L2) and followers (G-F2) were maintained under a rotational pasturing regime; the cows received daily commercial pelleted feed and heifers pellets manufactured with a blend of parasiticide fungi (3 × 10⁵ chlamydospores of both Mucor circinelloides and Duddingtonia flagrans/kg pellet). Deworming via closantel and albendazole was performed in cows in each trial at the beginning of their drying periods, and fourteen days later, the fecal egg-count reductions (FECR) of Calicophoron daubneyi and GIN were from 94 to 100% (average 98 %), while the percentages of reduction of cattle shedding eggs (CPCR) were from 50 to 100% (average 77 % and 82 %, respectively). The heifers were dewormed one time only, at the beginning of each trial, and the values of FECR and CPCR were 100 % against C. daubneyi and 96 % and 83 %, respectively, against GIN. Over a period of 24 months, significantly higher numbers of helminth egg-output were observed in G-L1, with the lowest numbers in G-F2. C. daubneyi egg output was reduced by 5 % (G-L1) and 42 % (G-F1) at the end of trial 1 and by 83 % (G-L2) and 100 % (G-F2) at the end of trial 2; the numbers of GIN egg-output decreased by 13 % (G-L1) and 18 % (G-F1) at the end of trial 1, and by 72 % (G-L2) and 85 % (G-F2) at the end of trial 2. No adverse effects were detected in cattle taking pellets enriched with fungal spores (G-F2). It is concluded that long-term ingestion of spores of M. circinelloides and D. flagrans provides a valuable tool to improve the effect of rotational grazing and to lessen the risk of infection by C. daubneyi and GIN in dairy cattle, and accordingly, the performance of integrated control programs.

Stimulating Duddingtonia flagrans chlamydospore production through dehydration

Duddingtonia flagrans is a nematode-trapping fungus that has shown promising results as a tool to combat parasitic nematode infections in livestock. The fungus interrupts the parasitic lifecycle by trapping and killing larval stages on pasture to prevent re-infection of animals. One barrier to the fungus' commercial use is scaling up production of the fungus, and specifically of chlamydospores, which survive the digestive tract to grow in fecal pats on pasture, thus have potential as a feed through anthelmintic. The purpose of this study was to evaluate the effect of dehydration on sporulation of the fungus. Disks of Duddingtonia flagrans type strain (ATCC® 13423™) were grown on 17% cornmeal agar for 26 days at 30 °C, then split into three groups; dried quickly at 38 °C and 37% humidity over 48 h ("incubated"), dried more slowly at 24 °C and 55% humidity over 10 days ("air-dried"), or kept at 30 °C and sealed with parafilm to prevent loss of moisture as a control ("wet"). Half of each dried culture was resuspended in water, then heated to liquify and homogenized through vortexing. Spores were then counted in a Neubauer hematocytometer. Both the "air-dried" and "incubated" drying techniques yielded significantly more spores than the "wet" control (Welch's two sample t test p values of .0359 and .0411, respectively). The difference in average chlamydospores per milliliter was insignificant between the two drying techniques, although a visual representation of the data shows less spore count variability in the "air-dried" technique.

Synthesis and role of melanin for tolerating in vitro rumen digestion in Duddingtonia flagrans, a nematode-trapping fungus

We describe the synthesis and a function of melanin in Duddingtonia flagrans, a nematode-trapping fungus. We tested various culture media treated with L-DOPA, glucose and tricyclazole on fungal growth and melanin distribution using infrared spectroscopy (IS), electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM). In vitro rumen digestion was used to test the environmental stress and then to evaluate the capacity of this fungus to trap nematode larvae. The growth and melanization of the fungus after 21 days of incubation at 30°C were best in Sabouraud dextrose medium. IS indicated the presence of melanin in D. flagrans, with similar bands for commercial melanin used as a control, and assigned the values obtained by EPR (g of 2.0051 ± 0.0001) to the production of melanin by the fungus. TEM indicated that melanin was produced in melanosomes but was not totally inhibited by tricyclazole. Within the limits of experimental error, the predatory activity of fungus treated with tricyclazole was drastically affected after 27 h of in vitro anaerobic stress with rumen inoculum. The deposition of melanin particles on the fungal cell wall contributed to the maintenance of D. flagrans predatory abilities after in vitro anaerobic ruminal stress.

Morphological variability, molecular phylogeny, and biological characteristics of the nematophagous fungus Duddingtonia flagrans

This study aims to investigate the molecular phylogenetic analysis, morphological variability, nematode-capturing ability, and other biological properties of Chinese Duddingtonia flagrans isolates. We isolated 13 isolates of D. flagrans and found features that have never been reported before, such as two to three septa incluing club-shaped conidia. Meanwhile, we conducted molecular phylogenetic analysis of the seven isolates and tested the radical growth of the isolates under different pH values, temperatures, and media. The capturing ability against infective larvae (L3) of Cooperia spp. in yak was detected in vitro. Finally, one isolate was selected for scanning electron microscopy (SEM) to investigate the trap formation process. The fungal sequence was obtained and submitted to GenBank (Accession no. KY288614.1, KU881774.1, KP257593.1, KY419119.1, MF488979.1, MF488980.1, and MF488981.1), and the tested isolates were identified as D. flagrans. Except for three isolates, the radial growth of the other isolates on 2% corn meal agar and 2% water agar exhibited faster growth than on other media. The fungus could not grow at 10 and 40°C but grew within 11 to 30°C. Moreover, it did not grow at pH 1-3 and 13-14, but instead at pH 4-12. In the in vitro experimental, L3s were reduced by 94.36%, 88.15%, and 91.04% for SDH035, DH055, and F088, respectively. SEM results showed that at 8 hr post addition of nematodes, some of the latter were captured. In the later stages of the interaction of the fungus with nematodes, a large number of chlamydospores were produced, especially on the predation trap. Results of the present study provided information about the molecular phylogenetic analysis, morphological variability, nematode-capturing ability, and other biological properties of Chinese Arthrobotrys flagrans isolates before administering them for biocontrol.

Predatory effect of Duddingtonia flagrans on infective larvae of gastro-intestinal parasites under sunny and shaded conditions

Duddingtonia flagrans is a natural strain of Nematophagous-Fungi isolated around the world. It has demonstrated efficacy and ease of use in laboratory as well as in field conditions. The fungus contributes to the prophylactic control of the worms by reducing the number of L₃ on pasture. The aims of this study were to test and analyze the predatory effect of D. flagrans under sunny and shaded conditions on the L₃ in the faeces, and to verify the reduction of translation to pasture during summer and winter seasons. Faecal Mass Units (FMUs) were assigned to two treated groups (groups treated with D. flagrans chlamydospores, TG) and two untreated groups (without D. flagrans chlamydospores, UG), in summer and winter, under sunny and shaded conditions. FMUs and herbage samples were taken for parasitological workup. Predatory activity of D. flagrans was evident under both conditions for the summer experiment but was not manifest for the winter experiment. In summer, an interaction between sunny and shaded conditions and predatory activity of D. flagrans was found. Environmental conditions on predatory activity should be considered when designing strategies for the implementation of D. flagrans in grazing systems to smooth the infectivity curve of L₃.

A combined effort to avoid strongyle infection in horses in an oceanic climate region: rotational grazing and parasiticidal fungi

Background

An approach to preventing strongyle infection in horses was tested, comprising rotational pasturing and the administration of spores of two parasiticidal fungi, Mucor circinelloides and Duddingtonia flagrans.

Methods

Twenty-two adult Spanish Sport Horses were dewormed with ivermectin (1 mg pour-on/kg body weight) and then randomly divided into three groups. G-1 was maintained with continuous grazing, and G-2 and G-3 were kept on a four-paddock rotation system. Commercial pelleted feed (2.5 kg/horse) was supplied to G-1 and G-2 twice a week; horses in G-3 received pellets containing 2 × 10⁶ spores/kg of each fungus. Fecal samples were analyzed by the flotation method to estimate the reduction in the fecal egg counts (FECR), the percentage of horses shedding eggs (PHR), and the egg reappearance period (ERP).

Results

Third-stage larvae were identified in fecal pats as Cyathostomum (sensu lato) types A, C and D, Gyalocephalus capitatus, Triodontophorus serratus, Poteriosthomum spp., Strongylus vulgaris and S. edentatus. Two weeks after treatment, the FECR values were 100% in G-1, 96% in G-2 and 99% in G-3; the PHR values were 100% in G-1, 75% in G-2 and 88% in G-3. A strongyle ERP of 6 weeks was observed in G-1, ERP of 10 weeks was observed in G-2, and ERP of 16 weeks was observed in G-3. The counts of eggs per gram of feces (EPG) were > 300 EPG in G-1 and G-2 but remained below 250 EPG in G-3 throughout the observation period of 12 months.

Conclusions

These results suggest that horse strongyle infection could be decreased by combining rotational pasturing with feeding pellets containing the spores of parasiticidal fungi.

Extracellular biosynthesis of silver nanoparticles using the cell-free filtrate of nematophagous fungus Duddingtonia flagrans

The biosynthesis of metallic nanoparticles (NPs) using biological systems such as fungi has evolved to become an important area of nanobiotechnology. Herein, we report for the first time the extracellular synthesis of highly stable silver NPs (AgNPs) using the nematophagous fungus Duddingtonia flagrans (AC001). The fungal cell-free filtrate was analyzed by the Bradford method and 3,5-dinitrosalicylic acid assay and used to synthesize the AgNPs in the presence of a 1 mM AgNO₃ solution. They have been characterized by UV-Vis spectroscopy, X-ray diffraction, transmission electron microscopy, dynamic light scattering, Zeta potential measurements, Fourier-transform infrared, and Raman spectroscopes. UV-Vis spectroscopy confirmed bioreduction, while X-ray diffractometry established the crystalline nature of the AgNPs. Dynamic light scattering and transmission electron microscopy images showed approximately 11, 38 nm monodisperse and quasispherical AgNPs. Zeta potential analysis was able to show a considerable stability of AgNPs. The N-H stretches in Fourier-transform infrared spectroscopy indicate the presence of protein molecules. The Raman bands suggest that chitinase was involved in the growth and stabilization of AgNPs, through the coating of the particles. Our results show that the NPs we synthesized have good stability, high yield, and monodispersion.

Feeding horses with industrially manufactured pellets with fungal spores to promote nematode integrated control

The usefulness of pellets industrially manufactured with spores of parasiticide fungi as a contribution to integrated nematode control was assessed in grazing horses throughout sixteen months. Two groups of 7 Pura Raza Galega autochthonous horses (G-T and G-P) were dewormed pour-on (1mg Ivermectin/kg bw) at the beginning of the trial, and other group (G-C) remained untreated. The G-P was provided daily with commercial pellets to which was added a mixture of fungal spores during the industrial manufacturing (2×10⁶ spores of Mucor circinelloides and same dose of Duddingtonia flagrans/kg), and G-T and G-C received pellets without spores. The efficacy of the parasiticidal strategy was assessed by estimating the reduction in the faecal egg counts (FECR) and in the number of horses shedding eggs in the faeces (PHR), and also the egg reappearance periods (ERP). Blood analyses were performed to identify the changes in the red and white cell patterns. To ascertain if horses developed an IgG humoral response against the fungi, antigenic products collected from M. circinelloides and D. flagrans were exposed to the horse sera by using an ELISA. The faecal elimination of eggs of Parascaris equorum and strongyles ceased 2 weeks after treatment in G-T and G-P, thus the values of FECR and PHR were 100%. No P. equorum-eggs were detected later, and the strongyle egg reappearance period was 28 weeks in G-P, and 8 weeks in G-T. Strongyle egg-output values remained lower than 300 eggs per gram of faeces in the G-P, whereas numbers between 330 and 772 in G-C and G-T were recorded. Normal values for the erythrocytes, haemoglobin and haematocrit in horses consuming pellets with spores were recorded, and lower than normal in the other groups. Sensitization of horses to the fungal species was disproven. It is concluded that feeding horses with pellets industrially manufactured with fungal spores represents a very useful tool to implement an integrated control of helminths affecting horses. This strategy allows a decrease in their risk of infection, aids in reducing the frequency of anthelmintic treatment.

Serine proteases activity is important for the interaction of nematophagous fungus Duddingtonia flagrans with infective larvae of trichostrongylides and free-living nematodes Panagrellus spp

The nematode-trapping fungus Duddingtonia flagrans has been studied as a possible control method for gastrointestinal nematodes of livestock animals. These fungi capture and infect the nematode by cuticle penetration, immobilization, and digestion of the internal contents. It has been suggested that this sequence of events occurs by a combination of physical and enzymatical activities. The aim of this study was to investigate the participation of proteolytic enzymatic activity during the interaction of the nematophagous fungus D. flagrans with infective larvae of trichostrongylides and the free-living nematode Panagrellus spp. Protease inhibitors used interfered in the predatory activity of D. flagrans. However, only PMSF significantly reduced the mean number of Panagrellus spp. captured by D. flagrans in comparison with the control. The experiment with fluorogenic substrate showed that maximum urokinase activity during the interaction of the fungus with the infective larvae of trichostrongylides or Panagrellus spp. occurred within 7 or 1 h of incubation, respectively. The protease activity, especially of the serine class, may be important during the interaction between the fungus and nematodes.

Toward practical biological control of parasitic nematodes in domestic animals

In a series of laboratory and field experiments where the nematophagous fungus Arthrobotrys oligospora was mixed directly with feces it has been demonstrated that it is possible to use nematophagous fungi for biological control of animal parasitic nematodes. A procedure used for selection of nematophagous fungi that can pass the digestive tract of ruminants, horses, and pigs is described. The selected fungus, Duddingtonia flagrans, has been used in further field experiments, and the results have confirmed that by the addition of D. flagrans to feed supplement it is possible to reduce the parasitic burden significantly.