In vitro predatory activity of nematophagous fungi and after passing through gastrointestinal tract of equine on infective larvae of Strongyloides westeri

Determination of cyclic adenosine phosphate and protein content in dormant chlamydospore and nondormant chlamydospore of Arthrobotrys flagrans

Arthrobotrys flagrans, a nematode-eating fungus, is an effective component of animal parasitic nematode biocontrol agents. In the dried formulation, the majority of spores are in an endogenous dormant state. This study focuses on dormant chlamydospore and nondormant chlamydospore of A. flagrans to investigate the differences in cyclic adenosine monophosphate (cAMP) and protein content between the two types of spores. cAMP and soluble proteins were extracted from the nondormant chlamydospore and dormant chlamydospore of two isolates of A. flagrans. The cAMP Direct Immunoassay Kit and Bradford protein concentration assay kit (Coomassie brilliant blue method) were used to detect the cAMP and protein content in two types of spores. Results showed that the content of cAMP in dormant spores of both isolates was significantly higher than that in nondormant spores (p < 0.05). The protein content of dormant spores in DH055 bacteria was significantly higher than that of nondormant spores (p < 0.05). In addition, the protein content of dormant spores of the SDH035 strain was slightly higher than that of nondormant spores, but the difference was not significant (p > 0.05). The results obtained in this study provide evidence for the biochemical mechanism of chlamydospore dormancy or the germination of the nematophagous fungus A. flagrans.

Chlamydospore dormancy and predatory activity of nematophagous fungus Duddingtonia flagrans

The chlamydospores of Duddingtonia flagrans are an essential survival and reproductive structure and also an effective ingredient for the biocontrol of parasitic nematodes in livestock. In this study, entering and exiting dormancy conditions and predatory activity of the fungal chlamydospores were conducted. During this fungal growth process, the cultivation time is negatively correlated with spore germination rates. After the spores were processed by vacuum drying for 168 h, their germination rate dropped to 0.94%. In contrast, the percentage of living spores remained 54.82%, suggesting that the spores entered structural dormancy in the arid environment. Meanwhile, the efficacies of the spore against Haemonchus contortus larvae were 93.05% (0 h), 92.19% (16 h), 92.77% (96 h), and 86.45% (168 h), respectively. After dormant spores were stored at 4°C, -20°C, and 28°C (RH90 ~ 95%) for 7 days, their germination rate began to increase significantly (p < 0.05). For in vitro predation assay under the condition of 28°C (RH90 ~ 95%), the predation rate was significantly higher on the 7th day after incubation than that on the 3rd day (p < 0.05). During the period when spores were stored at room temperature for 8 months, their germination rate decreased in the first 5 months and then increased slowly to reach a peak in the 7th month. However, the reduction rate of H. contortus L3 in feces captured by spores remained above 71% for the first 7 months. These results will help us increase the end products yield and the quality of biological control of parasitic nematodes in livestock.

Efficacy Evaluation of a Commercial Formulation With Duddingtonia Flagrans in Equine Gastrointestinal Nematodes

The indiscriminate use of antiparasitics for the treatment of helminths in horses has caused the ineffectiveness of commonly used chemical active principles, therefore, new alternatives such as the use of helminthophagous fungi have been studied. In this context, this study aimed to evaluate the in vitro efficacy of the commercial formulation Bioverm, composed of the fungus Duddingtonia flagrans strain AC001, in the reduction of gastrointestinal nematode larvae in equine feces. In coproculture, the genus Cyathostomum sp. was the most prevalent in the analyzed samples. The commercial formulation with D. flagrans demonstrated effectiveness in the predation of Cyathostomum sp. in tests. The recommended dose of 0.4 g, containing 105 chlamydospores per gram of product, reduced larvae by 44.23%, while the extrapolated dose of 1.0 g with the same concentrations of chlamydospores (105/g) resulted in a reduction of 57.20%, indicating the effectiveness of the product in controlling infective larvae.

A review of the use of Duddingtonia flagrans as a biological controller of strongylid nematodes in horses

In horses, the nematodes of the Strongylidae family are the most important due to their prevalence and pathogenicity. Sanitary plans include parasite control based on chemical anthelmintics. Among these, the benzimidazole compounds have been used since the 1960s to control the nematode Strongylus vulgaris. Its inappropriate use resulted in the development of resistance in parasites with a shorter biological cycle, such as the small strongyles. Currently, the genera that make up this group show widespread resistance to all chemical treatments available in veterinary medicine, except for macrocyclic lactones, where less effective action has been detected. The need to find alternative routes for its control is recognized. International organizations and markets are increasingly restrictive in the allowed levels of drugs in products of animal origin, so one of the drawbacks is the permanence of chemical compounds in tissues. Therefore, other tools not chemically based are proposed, such as the biological control of gastrointestinal nematodes. Various research groups around the world have carried out tests on the control capacity of the nematophagous fungus Duddingtonia flagrans against this group of parasites. The objective of this review is to compile the different tests that are available on biological control in this species, in in vivo and in vitro tests, and the possible incorporation of this tool as an alternative method of antiparasitic control in an integrated control scheme of parasites.

Biological methods for the control of gastrointestinal nematodes

Gastrointestinal nematodes (GIN) are a cause of significant losses in animal production worldwide. In recent years, there have been important advances in the biological control of GIN of ruminants and horses. While these measures are still relatively under-utilised in practice, interest will undoubtedly grow due to the emergence of drug resistant parasite populations, the rise in demand for organically farmed products (which does not allow prophylactic use of drugs, including anthelmintics) and legislation, which regulates and restricts the use of anthelmintics. This review provides an overview of the most promising biocontrol agents of GIN of grazing animals including nematophagous fungi, dung beetles, earthworms, predacious nematodes and nematophagous mites. Recent advancements in these fields are evaluated, and the potential reasons for the delayed development and slow uptake of biocontrol agents are discussed. It is now widely believed that no method of GIN control is sustainable alone, and a combination of strategies (i.e. integrated pest management) is required for long term, effective parasite control. This review shows that, although their efficacies are lower than those of conventional anthelmintics, biological control agents are an important adjunct to traditional GIN control.

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.

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.

Control of sheep gastrointestinal nematodes using the combination of Duddingtonia flagrans and Levamisole Hydrochloride 5

The objective was to evaluate the action of D. flagrans pellets in association with Levamisole Hydrochloride 5% for controlling sheep gastrointestinal nematodes in the northeastern Brazil. Three groups of six sheep each were formed: group 1 received 3 g of the pellets (0.6 g of D. flagrans mycelium) for each 10 kg b.w., twice a week for six months, and deworming with Levamisole Hydrochloride 5% when EPG ≥ 1500; group 2 received a dosage of Levamisole Hydrochloride 5% when EPG ≥ 1500; and group 3 received 3 g of pellets without fungi for each 10 kg b.w., twice a week for six months. EPG counts, larval cultures, packed cell volume (PCV) and weighing were performed every 15 days; monthly, samples of grass from each paddock were collected. The mean EPG of the groups began to statistically differ from day 30 (p < 0.05). Group 1 required less deworming with Levamisole Hydrochloride 5% and showed superiority of PCV values ​​throughout the experiment (p < 0.05). There was a significant reduction (p < 0.05) in L3 recovery in the group 1 paddock from day 30 onwards. The use of D. flagrans pellets in association with Levamisole Hydrochloride 5% was effective for controlling gastrointestinal nematodes.

In vitro and in vivo studies of nematophagous fungi Arthrobotrys musiformis and Arthrobotrys robusta against the larvae of the trichostrongylides

Six isolates of Arthrobotrys musiformis and five isolates of Arthrobotrys robusta were assessed in in vitro test regarding the capacity of prey larvae of the natural mixed trichostrongylides. In 5 isolates of A. robusta, the decrease percentage of infective larvae (L3) of trichostrongylides ranged from 97.71%-99.98% and for the isolates of A. musiformis, 5 isolates ranged from 97.99%-99.95% and only NF015 isolate 60.72%. In the following, the isolate (NPS045) of A. musiformis was selected to assess its excretion time in feces after oral administration of goats. Regarding L3 reduction rate, results demonstrated by NPS045 at each time point after fungal administration were 31.65% (12 h), 51.25% (24 h), 41.07% (48 h), 6.44% (72 h), 0% (96 h) and (120 h) (p<0.05) respectively, when compared to the control group. In the plates of the treated groups, the presence of the isolate (NPS045) was detected in samples at 12, 24 and 48 h after the fungus dose and 72 h later was not done. All native isolates of nematophagous fungi, including 6 isolates of A. musiformis and 5 isolates of A. robusta were assessed in vivo regarding the capacity of supporting the passage through goat gastrointestinal tract. The 3 isolates of A. musiformis could be able to pass through the digestive tract of goats without complete loss of ability of preying larvae of trichostrongylides in feces and their efficacies ranged from 47.60% to 55.93%. The two isolates of A. robusta survived the passage and the percentage reduction of L3 in feces were 41.96% and 66.97%, respectively. The remaining isolates were negative for both the efficacy of L3 reduction and the fungal examination in feces. In this study, the native isolates whose efficacies are good in vivo test have preliminarily demonstrated to be potential for the biological control of small ruminant parasite.

Duddingtonia flagrans no controle de nematoides gastrintestinais de equinos em fases de vida livre

RESUMO O objetivo deste estudo foi avaliar a atividade predatória do fungo Duddingtonia flagrans contra larvas infectantes (L3) de nematoides gastrintestinais na pastagem e no bolo fecal de equinos, em um período de 21 dias. O delineamento experimental foi inteiramente ao acaso, com três grupos tratados (G1, G2 e G3) e um controle (C), com oito animais/grupo. Os tratados receberam 1,5x105; 3x105 e 6x105 clamidósporos de D. flagrans/kg-1peso vivo animal, G1, G2 e G3, respectivamente, durante 21 dias, com administração a cada três dias. Foram delimitadas 36 áreas de 1m2 cada, equivalendo a repetições em triplicata para cada grupo. As fezes foram coletadas dos animais nos dias 0 (D0), 15 (D15) e 30 (D30 = sete dias após a última administração dos tratamentos) e depositadas nessas áreas de pastagem. O número de larvas presentes nos bolos fecais e na pastagem foi avaliado após 14 e 21 dias de cada etapa de deposição. A avaliação da atividade predatória de D. flagrans na pastagem e nos bolos fecais demonstrou que a redução do número de L3 nos bolos fecais foi acompanhada pelo aumento da variável na pastagem. Não se constatou diferença significativa entre os grupos avaliados em decorrência da temperatura média registrada durante o período. As avaliações realizadas em um curto período podem ser insuficientes para a avaliação do efeito do fungo.

Nematocidal activity of extracellular enzymes produced by the nematophagous fungus Duddingtonia flagrans on cyathostomin infective larvae

Duddingtonia flagrans produces chitinases, however, optimization of the production of these enzymes still needs to be explored, and its nematocidal activity should still be the subject of studies. The objective of the present study was to optimize chitinase production, and evaluate the nematocidal activity of extracellular enzymes produced by the nematophagous fungus D. flagrans on cyathostomin infective larvae. An isolate from D. flagrans (AC001) was used in this study. For the production of enzymes (protease and chitinase), two different culture media were inoculated with AC001 conidia. Both enzymes were purified. The statistical Plackett-Burman factorial design was used to investigate some variables and their effect on the production of chitinases by D. flagrans. After that, the design central composite (CCD) was used in order to determine the optimum levels and investigate the interactions of these variables previously observed. Only two variables (moisture and incubation time), in the evaluated levels, had a significant effect (p<0.05) on chitinase production. The conditions of maximum chitinase activity were calculated, with the following values: incubation time 2 days, and moisture 511%. The protease and chitinase derived from D. flagrans, individually or together (after 24h), led to a significant reduction (p<0.01) in the number of intact cyathostomin L3, when compared to the control, with following reduction percentage values: 19.4% (protease), 15.5% (chitinase), and 20.5% (protease+chitinase). Significant differences were observed (p<0.05) between the group treated with proteases in relation to the group treated with proteases+chitinases. In this study, the assay with the cyathostomins showed that chitinase had a nematocidal effect, suggesting that this enzyme acts on the "fungus versus nematodes" infection process. It is known that nematode eggs are rich in chitin, and in this case, we could think of a greater employability for this chitinase.

Comparative study of cultivation of feces in vermiculite or charcoal to obtain larvae of Strongyloides venezuelensis

INTRODUCTION

We compared feces culturing in charcoal or vermiculite to obtain Strongyloides venezuelensis larvae.

METHODS

Feces (5 g) from infected rats was mixed with vermiculite (10 g) or coal (10 g) in plastic cups and incubated at 28°C for 48 h. Larvae were recovered using Baermann-Moraes method.

RESULTS

Significantly higher number of positive larval cultures were recovered from vermiculite than from charcoal (15/17 and 4/17, respectively; p < 0.001; 990.6 ± 307.5 and 215 ± 78.1 larvae, p = 0.027).

CONCLUSIONS

Vermiculite yields more larvae and provides cleaner pellets, improving larvae identification and facilitating their use for other purposes.

Duddingtonia flagrans in the control of gastrointestinal nematodes of horses

Horses can harbor a large amount of parasites that may cause serious clinical signs even death. The aim of this study was to evaluate the predatory activity of the fungus Duddingtonia flagrans against infective larvae (L3) of gastrointestinal nematodes of horses in fecal culture. The experimental design was completely randomized with three treated groups (G1, G2 and G3) and one control (CG), using eight animals/group. The treated animals received G1: 1.5 × 10(5); G2: 3 × 10(5) and G3: 6 × 10(5) chlamydospores of D. flagrans/kg body weight during 21 days. The fungi preparation was given at every other three-day interval. Faecal samples were collected during 30 days, on the same interval, to perform the fecal egg counts (EPG) and fecal culture for each horse. All groups demonstrated similar results for the EPG (P > 0.05) counts. D. flagrans significantly reduced (P < 0.05) the number of infective larvae after 72 h-interval between treatments. The G2 and G3 promoted higher results (P < 0.05) of L3 reduction compared to the CG. The biological control with the predacious fungi D. flagrans is still a promising free-living parasite regulator alternative to be use in livestock.

In vitro biological control of infective larvae of Ancylostoma ceylanicum

The aim of this study was to evaluate the predatory activity of the fungus Duddingtonia flagrans (AC001) on infective larvae of Ancylostoma ceylanicum after gastrointestinal transit in hamsters. Twenty animals were used in the experiment, divided into two groups: a treated group (10 animals) and a control group (10 animals). In the group treated with D. flagrans, each animal received mycelium from the AC001 isolate, at an oral dose of 5 mg/25 g of live weight. To evaluate the predatory activity of the fungus, fecal samples were collected from the animals in both groups, at the times of 6, 8, 12, 24 and 36 hours after the treatment. Then, subsamples of 2 g of feces were placed in Petri dishes containing 2% water-agar (2% WA) culture medium and 1000 L3 of A. ceylanicum. Over the study period, the following percentage reductions were observed: 43.2% (6 hours), 30.8% (8 hours), 25.8% (12 hours), 30% (24 hours) and 11% (36 hours). The fungus D. flagrans presented predatory activity on the L3 of A. ceylanicum, after passing through the hamsters' gastrointestinal tract. It was therefore concluded that the fungus D. flagrans may be an alternative for biological control of the L3 of A. ceylanicum.

Control of Strongyloides westeri by nematophagous fungi after passage through the gastrointestinal tract of donkeys

Strongyloides westeri is the most prevalent nematode among equines aged up to four months and causes gastrointestinal disorders. The objective of this study was to observe the control of infective S. westeri larvae (L3) by the nematophagous fungi Duddingtonia flagrans (AC001) and Monacrosporium thaumasium (NF34) after passage through the gastrointestinal tract of female donkeys. Twelve dewormed female donkeys that were kept in stables were used. Two treatment groups each comprising four animals received orally 100 g of pellets made of sodium alginate matrix containing a mycelial mass of either D. flagrans (AC001) or M. thaumasium (NF34). The control group consisted of four animals that received pellets without fungus. Feces samples were then collected from the animal groups at different times (after 12, 24, 48 and 72 hours). These feces were placed in Petri dishes containing 2% water-agar medium and 1000 L3 of S. westeri. AC001 and NF34 isolates showed the ability to destroy the L3, after gastrointestinal transit, thus demonstrating their viability and predatory activity.