Influence of the preservation period in silica-gel on the predatory activity of the isolates of Duddingtonia flagrans on infective larvae of cyathostomins (Nematoda: Cyathostominae)

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.

Scale-Up of Duddingtonia flagrans Chlamydospores Production from Laboratory to Pilot-Scale Using a Solid-State Fermentation System

The fungus Duddingtonia flagrans is a biological control tool to reduce infective larvae of gastrointestinal nematode in pastures. To create a commercially available bioproduct based on a nematophagous fungus, an efficient mass production process should be developed that is able to guarantee a good predatory capacity and satisfactory production rates. In this work, solid-state fermentation (SSF) parameters were investigated to produce D. flagrans at pilot-scale. The results showed that the relative humidity was a critical factor to increase productivity and to reduce fermentation time. The best production conditions using a tray bioreactor were a relative humidity in the room at 90% for 2 days, and inoculation by sprinkling. The fermentation process was composed of 7 days under submerged fermentation to produce the inoculum and 7 more days of SSF in a tray bioreactor. The productivity reached was 4.96 × 10⁶ chlamydospores g^-1 of dry substrate day^-1, which is the highest productivity reported to date. The predatory capacity of the chlamydospores produced using this process was 91%. Also, a statistical control process analysis was applied, finding that the process presents stability in the biological activity, yield, and final moisture content of the substrate between batches. Finally, the operational expenses (OPEX) based on the use of the heating and humidification system were estimated, given a final cost of 0.20 USD g^-1 of the fermented substrate.

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.

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.

Mycelial mass production of fungi Duddingtonia flagrans and Monacrosporium thaumasium under different culture conditions

BACKGROUND

Duddingtonia flagrans and Monacrosporium thaumasium are promising fungus species in veterinary biological control of gastrointestinal nematodes because of their production capacity of fungal structures (conidia and/or chlamydospores), growth efficiency in laboratory solid media and especially their predatory capacity. However, their large-scale production remains a challenge. This work aimed at evaluating the mycelial mass production of D. flagrans (AC001 and CG722) and M. thaumasium (NF34A) nematophagous fungi under different culture conditions.

RESULTS

The results did not present significant differences (p > 0.05) in mycelia mass production between the isolates cultured under pH 4.0. Furthermore, after 168 hrs., the isolate CG722 presented a lower production of mycelial mass in medium CM (corn meal) (p < 0.05).

CONCLUSION

We therefore concluded the use of culture media SD (soy dextrose) and CG (corn grits) at pH values between 6.0 and 7.0 is suitable for high mycelial mass production of D. flagrans and M. thaumasium.

First report of interaction of nematophagous fungi onLibyostrongylus douglassii (Nematoda: Trichostrongylidae)

Libyostrongylus douglassii is a gastrointestinal nematode parasite of ostriches that can cause up to 50% mortality in young birds. The objective of this study was to compare the predatory capacity of two isolates of the predatory fungi Duddingtonia flagrans(AC001 and CG722 isolates) and one of Arthrobotrys cladodes (CG719) on infective larvae (L3) of L. douglassii under laboratory conditions, in 2% water-agar medium. The results showed that the fungi tested were effective in preying upon the L3 of L. douglassii (P < 0.05), compared with the control group. However, there was no difference in predatory capacity between the fungi tested (P > 0.05) during the seven days of experimental testing. In comparison with the control, without fungus, there were significant decreases (P < 0.05) of 85.2% (AC001), 81.2% (CG722) and 89.2% (CG719) in the average numbers of L3 of L. douglassii recovered from treatments with the isolates tested. In the present study, the three isolates of the predatory fungi D. flagrans (AC001 and CG722) andA. cladodes (CG719) were efficient at in vitro destruction of the L3 of L. douglassii.

Control of infective larvae of gastrointestinal nematodes in heifers using different isolates of nematophagous fungi

The effect of different nematophagous fungi [Duddingtonia flagrans (AC001 and CG722) and Monacrosporium thaumasium (NF34)] with regard to controlling infective larvae (L3) of nematodes after gastrointestinal transit in female cattle (3/4 Holstein × Zebu) was evaluated. A total of 24 pubescent female cattle were used, weighing approximately 320 kg each one. There were three treatment groups, each contained six animals that received 150 g of pellets (0.2 g of mycelium), orally in a single dose, in a sodium alginate matrix containing mycelial mass of the fungus D. flagrans (AC001 or CG722) or M. thaumasium (NF34); and one control group (without fungi). Fecal samples were collected from the animals at intervals of 12, 15, 18, 21, 24, 48, and 72 hours. At the end of 17 days, the L3 not subjected to predation were recovered by means of the Baermann method. The fungal isolates tested were capable of destroying the L3 after gastrointestinal transit. It was observed that within 72 hours, the isolates AC001, CG722, and NF34 showed a higher predatory activity (81.2%, 97.3%, and 98.3%, respectively). The results justify the need for studies in the field, and over longer intervals, in order to observe the efficiency of the fungus D. flagrans, or even M. thaumasium, for environmental control over nematodes in naturally infected cattle.

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.