Anthelmintic Effect ofBacillus thuringiensisStrains against the Gill Fish TrematodeCentrocestus formosanus

Abstract

Parasitic agents, such as helminths, are the most important biotic factors affecting aquaculture, and the fluke Centrocestus formosanus is considered to be highly pathogenic in various fish species. There have been efforts to control this parasite with chemical helminthicides, but these efforts have had unsuccessful results. We evaluated the anthelmintic effect of 37 strains of Bacillus thuringiensis against C. formosanus metacercariae in vitro using two concentrations of total protein, and only six strains produced high mortality. The virulence (CL50) on matacercariae of three strains was obtained: the GP308, GP526, and ME1 strains exhibited a LC50 of 146.2 μg/mL, 289.2 μg/mL, and 1721.9 μg/mL, respectively. Additionally, these six B. thuringiensis strains were evaluated against the cercariae of C. formosanus; the LC50 obtained from the GP526 strain with solubilized protein was 83.8 μg/mL, and it could be considered as an alternative control of the metacercariae and cercariae of this parasite in the productivity systems of ornamental fishes.

Impact of the “Bacteria-Parasite Interaction” in Animal Health and their Participation in the Control of Parasites

“…colubriformis and Ostertagia circumcincta, nematodes of livestock [61] Within the group of Cry proteins that possess nematicide action we have the following; Cry 5A, 5B, 6A, 6B, 12A, 13A, 14A and 21A [62]. So far there are few reports of activity of B. thuringiensis against platyhelminths, GP526 strain is presumed to be highly toxic against Centrocestus formosanus [63], so it also acts on the egg and the tegument of the Dipylidium caninum cestode of dogs [64]. The ovicidal activity of B. thuringiensis can be used in the treatment of wastewater, the contamination for helminths eggs is a problem because the wastewater is using for the vegetal culture in agriculture.…”

Repertoire of the Bacillus thuringiensis Virulence Factors Unrelated to Major Classes of Protein Toxins and Its Role in Specificity of Host-Pathogen Interactions

“…δ-endotoxins include two families of non-selective pore-forming proteins, namely Cry (crystal) and Cyt (cytotoxic) [14], and demonstrate a wide range of affected hosts, including insects of Coleoptera, Lepidoptera, Diptera, Hymenoptera, Hemiptera and Orthoptera orders, as well as phytopathogenic nematodes and terrestrial gastropods. For most of the known δ-endotoxins, however, no suitable natural targets have been discovered so far, though some of these cryptic toxins show toxicity against species, which are unlikely to be encountered by Bt in natural conditions, such as parasitic nematodes [15] and trematodes [16] and a flagellar protist Trichomonas vaginalis [5]. Regardless of their structure and mode of action, to fulfill their cytotoxic properties all Bt toxins need to bind specific receptors exposed on membranes of host midgut cells.…”

Physiological parameters of Piaractus mesopotamicus (Osteichthyes: Characidae) exposed to a biopesticide based on Bacillus thuringiensis

“…Spores of Bt have advantages over vegetative cells because they remain stable for long periods, have the ability to grow rapidly, tolerate a wide range of physiological conditions, involve simple production processes, and are inexpensive. They can be used in commercial products because they are naturally suitable for ingestion by animals (Mendoza-estrada et al 2016).…”

“…Studies reported that Bt has no toxicity to non-target species, including fish (Jackson et al 2002, Meher et al 2002, Ahmad et al 2011, but it produces toxic and highly specific proteins against protozoans, insects, helminths and mites of agricultural and veterinary importance (Mendozaestrada et al 2016). Thus, Bt has been recommended for control of trematodes Centrocestus formosanus in ornamental fish (Mendoza-Estrada et al 2016). However, for Oreochromis niloticus, exposure to Bt increased erythrocyte apoptosis (grisolia et al 2009) and in Colossoma macropomum, it decreased the number of total erythrocytes (Mariano et al 2017).…”