Ovicidal potential of Pochonia chlamydosporia isolate Pc-10 (Ascomycota: Sordariomycetes) on egg masses of the snail Pseudosuccinea columella (Mollusca: Gastropoda)

Metabolic disruptions in Biomphalaria glabrata induced by Heterorhabditis bacteriophora HP88: Implications for entomopathogenic nematodes in biological control

Research on the use of entomopathogenic nematodes (EPNs) as a potential tool for the biological control of invertebrates has been growing in recent years, including studies involving snails with One Health importance. In this study, the effect of exposure time (24 or 48 h) of Heterorhabditis bacteriophora HP88 on the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the concentration of total proteins, uric acid, and urea in the hemolymph of Biomphalaria glabrata, were investigated. The concentrations of these metabolic markers were measured weekly until the end of the third week after exposure. Along with a significant reduction in total protein levels, a significant increase (p < 0.01) in uric acid and urea contents in the hemolymph of B. glabrata exposed to H. bacteriophora was observed. The accumulation of urea in these mollusks could lead to deleterious effects due to its high toxicity, inducing significant cell damage. Variations in transaminase activities were also observed, with snails exposed to EPNs showing significantly higher values (p < 0.01) than individuals in the control group, both for ALT and AST. These results indicate that experimental exposure to infective juveniles of H. bacteriophora causes significant alterations in the metabolic pattern of B. glabrata, compromising the maintenance of its homeostasis. Finally, exposure for 48 h caused more damage to the planorbid in question compared to snails exposed for 24 h, suggesting that the exposure time may influence the intensity of the host's response.

Alterations in the metabolism of Pseudosuccinea columella (Mollusca: Gastropoda) caused by Heterorhabditis bacteriophora HP88 (Rhabditida: Heterorhabditidae)

The gastropod Pseudosuccinea columella participates in the dissemination of Fasciola hepatica in the environment, acting as the main intermediate host of this parasite in Brazil. The present study sought to elucidate the possible pathogenic effects of the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora on P. columella, by evaluating the influence of infection on alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the concentrations of total protein, uric acid, and urea in the snail's hemolymph. For this, the snails were exposed to EPNs for 24 and 48 h, and for each exposure time, 20 snails were dissected after 7, 14 and 21 days for hemolymph collection. The primary findings suggest a significant proteolysis alongside elevated levels of uric acid and urea in P. columella infected individuals. These findings reveal that H. bacteriophora HP88 infection induced serious changes in the snail's metabolism, triggering important deleterious effects.

Nematophagous fungus Pochonia chlamydosporia to control parasitic diseases in animals

The control of gastrointestinal parasites in animals has become more challenging every year due to parasite resistance to conventional chemical control, which has been observed worldwide. Ovicidal or opportunistic fungi do not form traps to capture larvae. Their mechanism of action is based on a mechanical/enzymatic process, which enables the penetration of their hyphae into helminth eggs, with subsequent internal colonization of these. The biological control with the Pochonia chlamydosporia fungus has been very promising in the treatment of environments and prevention. When used in intermediate hosts of Schistosoma mansoni, the fungus promoted a high percentage decrease in the population density of aquatic snails. Secondary metabolites were also found in P. chlamydosporia. Many of these compounds can be used by the chemical industry in the direction of a commercial product. This review aims to provide a description of P. chlamydosporia and its possible use as a biological parasitic controller. The ovicidal fungus P. chlamydosporia is effective in the control of parasites and goes far beyond the control of verminosis, intermediate hosts, and coccidia. It can also be used not only as biological controllers in natura but also as their metabolites and molecules can have chemical action against these organisms. KEY POINTS: • The use of the fungus P. chlamydosporia is promising in the control of helminths. • Metabolites and molecules of P. chlamydosporia may have chemical action in control.

Susceptibility of embryos of Biomphalaria tenagophila (Mollusca: Gastropoda) to infection by Pochonia chlamydosporia (Ascomycota: Sordariomycetes)

Schistosoma mansoni is a heteroxenous parasite, meaning that during its life cycle needs the participation of obligatory intermediate and definitive hosts. The larval development occurs in aquatic molluscs belonging to the Biomphalaria genus, leading to the formation of cercariae, which emerge to infect the final vertebrate host. For this reason, studies for control of the diseases caused by digenetic trematodes often focus on combating the snail hosts. Thus, the objective of this study was to evaluate the susceptibility of Biomphalaria tenagophila embryos to the fungus Pochonia chlamydosporia (isolate Pc-10). The entire experiment was conducted in duplicate, with five replicates for each repetition (five egg masses/replicate), utilizing a total of 100 egg masses, with 20-30 eggs/egg mass. At the end of 15 days, the egg masses were evaluated under a stereomicroscope to analyze the hatching of B. tenagophila embryos in both experimental groups. After days of interaction, the exposure to the fungal hyphae bodies significantly impaired the viability of the B. tenagophila eggs, inhibiting the embryogenesis process by 83.7% in relation to the control group. Transmission and scanning electron microscopic images revealed relevant structural alterations in the egg masses exposed to the hyphae action of the fungus, interfering in the development and hatching of the young snails under analysis. These results indicate the susceptibility of B. tenagophila embryos to the fungus P. chlamydosporia (isolate Pc-10) and suggest the potential of Pc-10 to be used in the control of intermediate host, for its ovicidal capacity and for being an ecologically viable option, but in vivo experiments become necessary.