Predatory activity of Pochonia chlamydosporia fungus on Toxocara (syn. Neoascaris) vitulorum eggs

Effect of Selected Entomopathogenic Fungal Species on Embryonic Development of Ascaris suum (Nematoda)

The aim of the study was to evaluate the potential of using five selected species of entomopathogenic fungi (Beauveria bassiana, B. brongniartii, Conidiobolus coronatus, Isaria fumosorosea, and Metarhizium robertsii) in the bioregulation of the dispersive stages of the parasitic nematode-Ascaris suum. Experimental cultures of each of the selected entomopathogenic fungi, as well as a control culture without fungi, were incubated with A. suum eggs at 26 °C for 28 days. Development of the A. suum eggs was observed using a light microscope on the 7th, 14th, 21st, and 28th days of incubation. The API-ZYM® test was used to determine, semiquantitatively, the activity of 19 hydrolytic enzymes from the entomopathogenic fungi. The cytotoxicity of the fungi was determined using tetrazole salt MTT. It was found that none of the five tested strains of entomopathogenic fungi showed an ovicidal effect, and none of them colonized the A. suum egg shells. However, ovistatic activity was observed mainly until the 14th day of incubation by I. fumosorosea, M. robertsii, and B. bassiana. In the MTT test, M. robertsii showed moderate cytotoxicity, while the other species showed low cytotoxicity. Among the strains tested, I. fumosorosea showed the highest spectrum of hydrolase production (13 out of 19 enzymes gave a positive reaction from 3 to 5; 20-40 nM or more). The absence of morphological changes in the A. suum egg shells suggests that the antagonistic effect of the studied entomopathogenic fungi may be due to their cytotoxicity, associated with the production of secondary metabolites-toxins (M. robertsii) and enzymatic activity (I. fumosorosea).

Human Toxocariasis: 2010 to 2020 Contributions from Brazilian Researchers

This is a review of the published contributions made by Brazilian researchers between 2010 and 2020 on the natural history of human toxocariasis and the effects of human toxocariasis on nonhuman paratenic hosts.

[Toxocara canis eggs as bait for soil fungus in a subtropical city]

BACKGROUND

The use of different isolation techniques allows the recovery of fungi based on their ability to use selective substrates. The sprinkle method is a technique for the recovery of nematophagous fungi in the soil. These fungi are natural predators of nematodes and are widely distributed in nature.

AIMS

To detect possible fungi with nematophagous ability in the soil of city parks in Corrientes (Argentina).

METHODS

The soil samples were taken from an area of ground between two trees and to no more than 2cm deep. The isolation was performed according to the sprinkle method with Toxocara canis eggs as bait.

RESULTS

Eighteen soil samples were collected, and 6 genera and 8 species of fungi were isolated. The sprinkle method, simple and efficient, has the advantage of using a small amount of untreated soil for the isolation of fungi that can grow on the eggs of geohelminths. The genera Bipolaris, Fusarium, Purpureocillium, Curvularia, Phoma and Scytalidium were isolated in this study.

CONCLUSIONS

No other studies describing the interaction between the genera Curvularia, Phoma and Scytalidium with nematode eggs have been found in the literature, thus more studies are required to determine what is their real action on these eggs.

In vitro evaluation of the ovistatic and ovicidal effect of the cosmopolitan filamentous fungi isolated from soil on Ascaris suum eggs

The ovicidal activity of seven fungal strains: Acremonium alabamense, Alternaria chlamydospora, Cladosporium herbarum, Fusarium solani, Paecilomyces variotii, Paecilomyces viridis and Penicillium verruculosum isolated from urban soil samples from Poland was determined in vitro. The fungal mycelium was co-cultured with Ascaris suum eggs on plates with 2% water-agar for 28 days. Eggs exposed and unexposed (control) to fungal mycelium were observed weekly by light microscopy and the percentage of malformed eggs were determined. The eggs were classified according to following parameters: type 1 - biochemical and physiological effect without morphological damage to the eggshell; type 2 - lytic effect with morphological alteration of the eggshell and embryo; type 3 - lytic effect with morphological alteration of eggshell and embryo with hyphal penetration and internal egg colonization. All examined species of fungi extended embryogenesis, but the retardation of embryonic development was varied and depended on the species. A. alabamense, A. chlamydospora and P. verruculosum exhibited very high inhibitory activity on A. suum egg development. The fungus-exposed eggs revealed morphological alternations in all stages of embryogenesis. Isolates of F. solani, P. variotii and P. viridis showed hyphal penetration and internal colonization of A. suum eggs (type 3 effect). No appressoria were produced and simple hyphal penetrations were most commonly observed. A. alabamense and P. verruculosum demonstrated morphological destruction, with eggshell destruction. The remaining fungi showed type 1 effect. The results demonstrated that examined strains of F. solani, P. variotii and P. viridis may be considered to be potential limiting factors of parasitic geohelminth populations.

Ovicidal activity of seven Pochonia chlamydosporia fungal isolates on Ascaris suum eggs

The ovicidal effect of the nematophagous fungus Pochonia chlamydosporia on eggs of Ascaris suum was tested under laboratory conditions. A. suum eggs were plated on 2% water-agar with seven fungal isolates (Isol. 5, Isol. 31, Isol. 1, VC1, Isol. 12, Isol. 22 and VC4) and control without fungus. After 5, 7, 10, 14, 15 and 21 days of incubation, approximately 100 eggs were removed from the plates and classified according to the following parameters: type 1, biochemical and physiological effect without morphological damage to the eggshell, type 2, lytic effect with morphological alteration of the eggshell and embryo and type 3, lytic effect with morphological alteration of eggshell and embryo showing hyphal penetration and internal egg colonization. The isolates effectively destroyed A. suum eggs and all types of effects were observed during the experiment. There was no variation in ovicidal capacity (type 3 effect) among the isolates (p>0.05) throughout the experiment. After 21 days, isolate 5 showed the highest percentages of type 3 effect (58.33%). The results indicated that P. chlamydosporia (Isol. 5, Isol. 31, Isol. 1, VC1, Isol. 12, Isol. 22 and VC4) can destroy A. suum eggs and is, therefore, a potential biological control agent of nematodes.

In vitro ovicidal activity of the nematophagous fungi Duddingtonia flagrans, Monacrosporium thaumasium and Pochonia chlamydosporia on Trichuris vulpis eggs

The in vitro effect of four isolates of the nematophagous fungi Duddingtonia flagrans (AC001), Monacrosporium thaumasium (NF34a) and Pochonia chlamydosporia (VC1 and VC4) on the eggs of Trichuris vulpis was evaluated. One thousand eggs of T. vulpis were plated on Petri dishes with 2% water-agar with the fungal isolates grown and without fungus as control. After 7, 14 and 21 days 100 eggs were removed from each plate and classified according to the following parameters: type 1, lytic effect without morphological damage to eggshell; type 2, lytic effect with morphological alteration of embryo and eggshell; and type 3, lytic effect with morphological alteration of embryo and eggshell, besides hyphal penetration and internal egg colonization. P. chlamydosporia demonstrated ovicidal activity (p<0.05) on the eggs of T. vulpis in the studied intervals presenting type 3 effect of 29.5% (VC1) and 36.5% (VC4), 59.5% (VC1) and 2.5% (VC4), 94.8% (VC1) and 2.95% (VC4) at 7, 14 and 21 days, respectively. The other fungi showed no type 3 effect. P. chlamydosporia should be a potential biological control agent of T. vulpis eggs.

Ovicidal activity of different concentrations of Pochonia chlamydosporia chlamydospores on Taenia taeniaeformis eggs

Three concentrations of chlamydospores of the nematophagous fungus Pochonia chlamydosporia (1000, 10,000 and 20,000 per Petri dish) were evaluated in vitro on Taenia taeniaeformis eggs. Chlamydospores at each concentration were cultured in two different media: 2% water-agar (2%WA) and 2% corn-meal-agar (2%CMA). Taenia taeniaeformis eggs were plated in each chlamydospore concentration in 2%WA and 2%CMA (treated groups) and without fungus (control group). Eggs were removed from each Petri dish at intervals of 7, 14 and 21 days and classified according to ovicidal activity (type 1, type 2 and type 3 effects). Plates containing 2%CMA showed the highest percentages for type 3 effect (81.3%) on the 21st day of observation. A difference (P < 0.01) between the media 2%WA and 2%CMA for type 1 effect was observed only at a concentration of 1000 chlamydospores on the 7th day. There were differences (P < 0.01) between 2%WA and 2%CMA on the 14th and 21st days, at the concentration of 20,000 chlamydospores, for type 1 and type 3 effects. Regression curves for type 3 effect in 2%WA and 2%CMA at the tested concentrations showed higher ovicidal activity with increasing chlamydospore concentrations. Results indicate that, at concentrations of 1000, 10,000 and 20,000 per Petri dish, chlamydospores of P. chlamydosporia effectively destroyed T. taeniaeformis eggs and can be considered a potential biological control agent for this cestode.