Dietborne Toxicity of Tebuconazole to a Benthic Crustacean, Heterocypris incongruens and Its Relative Contribution to the Overall Effects under Food-Water Equilibrium Partitioning.

Tebuconazole (TEB), a widely used and persistent pesticide, has garnered attention due to its frequent detection in sediments worldwide. This widespread occurrence has raised concerns about potential dietborne toxicity to benthic crustaceans, as they may ingest contaminated particles in their habitat. While bioaccumulation studies indicate the importance of TEB ingestion for benthic crustaceans, limited data exist on direct dietborne toxicity testing. This study investigated the diet-related toxicity of TEB by subjecting a benthic ostracod, Heterocypris incongruens, to a 6 day toxicity test under dietary and combined exposures. Subsequently, the importance of dietary exposure for TEB toxicity was uncovered, followed by quantification of relative dietborne toxicity contributions using a modified concentration-additive model. Results revealed that the dietary route was more toxicologically significant than the aqueous route in equilibrium. The dietborne lethal concentration (LC50) for TEB on H. incongruens was 200 (170-250) mg/kg, with an 80% relative dietborne toxicity contribution. To gain comprehensive insights into dietborne significance, toxicity data were collected from previous studies involving different pollutants to calculate relative contributions. Finally, the correlation between dietborne toxicity and the partitioning coefficient was analyzed to understand the pollutant behavior and its toxic impact when ingested through the diet.

Uncertainty in the results from oral repeated dose toxicity tests: Impact on regulatory classifications.

The Lowest Observed (Adverse) Effect Level (LO(A)EL) values are point-of-departure (PoD) values that quantify repeat dose toxicity (RDT). Here, the uncertainty in the regulatory classification of these PoDs is investigated. In the application stage, the dose-response was approximated for a large set of series, giving an account of the possible presence of a hormesis zone. The minimal effect dose (MED) or dose was computed, and the ratio MED/LO(A)EL was used to represent the two components of the experimental uncertainty. The uncertainty estimations were calculated for any combination of gender and reported examination item. Subsequently, how this uncertainty affects the possible classifications was analyzed, and the percentage of the chemicals receiving ambiguous classification was determined. It was shown that more than 40% of the investigated chemicals cannot be classified unambiguously in the Globally Harmonized System (GHS) classification scheme and bear a potential for misclassification when a regulatory decision is based on a single LO(A)EL value. A table containing grey zones for different risk levels and a table with GHS classification distributions for various LO(A)EL values were prepared to facilitate the use of the RDT uncertainty in the practice.

False positive findings associated with adenoviral vector-based vaccine underscore the regulatory necessity to eliminate abnormal toxicity test.

Accumulating evidence has shown that the abnormal toxicity test (ATT) is not suitable as a quality control batch release test for biologics and vaccines. The purpose of the current study was to explore the optimal ATT experimental design for an adenoviral vector-based vaccine product to avoid false positive results following the standard test conditions stipulated in the Pharmacopoeias. ATT were conducted in both mice and guinea pigs based on methods in Pharmacopeias, with modifications to assess effects of dose volume and amount of virus particles (VPs). The results showed intraperitoneal (IP) dosing at human relevant dose and volume (i.e., VPs), as required by pharmacopeia study design, resulted in false positive findings not associated with extraneous contaminants of a product. Considering many gene therapy products use adeno associated virus as the platform for transgene delivery, data from this study are highly relevant in providing convincing evidence to show the ATT is inappropriate as batch release test for biologics, vaccine and gene therapy products. In conclusion, ATT, which requires unnecessary animal usage and competes for resources which otherwise can be spent on innovative medicine research, should be deleted permanently as batch release test by regulatory authorities around the world.

Sulfate sensitivity of early life stages of freshwater mussels Unio crassus and Margaritifera margaritifera.

Sulfate is increasingly found in elevated concentrations in freshwater ecosystems due to anthropogenic activities. Chronic exposure to sulfate has been reported to cause sublethal effects on freshwater invertebrates. Previous sulfate toxicity tests have mostly been conducted in hard or moderately hard waters, and research on species inhabiting soft water is needed, given that freshwater organisms face heightened sensitivity to toxicants in water of lower hardness. In the present study, we examined sulfate sensitivity of two endangered freshwater mussel species, Unio crassus, and Margaritifera margaritifera. Glochidia and juveniles of both species were subjected to acute and/or chronic sulfate exposures in soft water to compare sulfate sensitivity across age groups, and effective concentrations (EC)/lethal concentrations (LC) values were estimated. Mussels were individually exposed to allow relatively larger numbers of replicates per treatment. Chronic sulfate exposure significantly reduced growth, foot movement, and relative water content (RWC) in juvenile mussels of M. margaritifera. Mussels at younger stages were not necessarily more sensitive to sulfate. In the acute tests, LC50 of glochidia of M. margaritifera and U. crassus was 1301 and 857 mg/L, respectively. Chronic LC10 was 843 mg/L for 3-week-old U. crassus juveniles, 1051 mg/L for 7-week-old M. margaritifera juveniles, and 683 mg/L for 2-year-old M. margaritifera juveniles. True chronic Lowest Effective Concentration for 7-week-old M. margaritifera may be within the 95% interval of EC10 based on RWC (EC10 = 446 mg/L, 95%CI = 265-626 mg/L). Our study contributed to the understanding of sulfate toxicity to endangered freshwater mussel species in soft water.

The use of integrative tools and multiple models for aquatic environmental quality assessment: a case study of the Mirim Lagoon, Southern Brazil.

This study performed toxicity assays with microalgae, microcrustaceans, and fish as well as evaluated biochemical and behavioral biomarkers in fish and microcrustaceans to assess the quality of the surface water of Mirim Lagoon, which belongs to one of the largest hydrographic basins in the world, located in southern Brazil. Three distinct sampling periods were chosen (January, March, and June 2022) based on the rice plantation dynamics which is the main activity surrounding the lagoon. In January, the plantation is irrigated; in March, the water is drained into the Mirim Lagoon, and July is the off-season. Concerning toxicity tests, there was significant inhibition in microalgae growth when exposed to water collected in March, but no mortality was observed for Ceriodaphia dubia, Daphnia magna, and Danio rerio. Regarding biomarkers, behavioral variables contributed more to the higher values of the Integrated Biomarker Response (IBR) index for both D. magna and D. rerio, in March. The Redundancy Analysis (RDA) indicated a correlation between the biomarkers for both organisms and abiotic parameters, mainly nutrients (total phosphorus and total nitrogen), thermotolerant coliforms, total solids, and turbidity. Spatially, there was no difference during monitoring, but the most significant ecotoxicological effects were observed in March. Multivariate analysis and the IBR index proved to be useful tools for monitoring of water bodies such as Mirim Lagoon.

Synthesis of C12-C18 Fatty Acid Isobornyl Esters.

Camphene, C12-C18 fatty acids, and titanium sulfate were used as raw materials to study the synthesis of long-chain fatty acid isobornyl esters. Products were analyzed quantitatively by gas chromatography (GC), characterized by nuclear magnetic resonance spectroscopy (hydrogen and carbon), and evaluated using toxicity tests. The optimum reaction conditions were as follows: n(lauric acid):n(camphene) = 2.5:1, m(titanium sulfate):m(camphene) = 0.25:1, reaction temperature of 80 °C, and reaction time of 25 h. Under these conditions, the content of isobornyl laurate in the product was 74.49%, and the content of purified product was 95.02%. The reaction kinetics for isobornyl laurate showed an apparent first-order reaction in the first 9 h with an activation energy of 31.01 kJ/mol. The reaction conditions of myristic acid, palmitic acid, and stearic acid were similar to those of lauric acid, but the reaction time had to be increased as the molecular weight of the fatty acid increased. Toxicity tests for four types of long-chain fatty acid isobornyl esters showed that the samples had low toxicity.

In Silico and In Vitro Methods in the Characterization of Beta-Carotene as Pharmaceutical Material via Acetylcholine Esterase Inhibitory Actions.

Molecular docking is widely used in the assessment of the therapeutic potential of pharmaceutical agents. The binding properties of beta-carotene (BC) to acetylcholine esterase (AChE) proteins were characterized using the molecular docking method. The mechanism of AChE inhibition was assessed by an experimental in vitro kinetic study. In addition, the role of BC action was tested by the zebrafish embryo toxicity test (ZFET). The results of the docking ability of BC to AChE showed significant ligand binding mode. The kinetic parameter, i.e., the low AICc value shown as the compound was the competitive type of inhibition of AChE. Further, BC also showed mild toxicity at a higher dose (2200 mg/L) in ZFET assessment with changes in biomarkers. The LC50 value of BC is 1811.94 mg/L. Acetylcholine esterase (AChE) plays a pivotal role in the hydrolysis of acetylcholine, which leads to the development of cognitive dysfunction. BC possesses the regulation of acetylcholine esterase (AChE) and acid phosphatase (AP) activity to prevent neurovascular dysfunction. Therefore, the characterization of BC could be used as a pharmaceutical agent for the treatment of cholinergic neurotoxicity-associated neurovascular disorders such as developmental toxicity, vascular dementia, and Alzheimer's disease due to its AChE and AP inhibitory actions.

Biodegradation and Detoxification of Low-Density Polyethylene (LDPE) by Stenotrophomonas sp. and Alcaligenaceae bacterium.

Every year, human activities introduce large amounts of synthetic plastics into the environment. Decomposition of the plastic derivatives is very difficult and time consuming, so it is essential to eliminate these pollutants using different methods. Bioremediation, is suitable option, because of the low cost and environmentally safe. In this research, degradation of low-density polyethylene (LDPE) was investigated by two strains, isolated from Hamadan province (Iran) landfill soil. After identification by 16sr DNA primers, their abilities of polyethylene biodegradation were examined by Fourier transform infrared (FTIR), SEM and Gas Chromatography-Mass Spectrometry (GC-MS). Using media contain polyethylene) after and before addition of bacteria), toxicity test was conducted by measuring the germination index, root and hypocotyl length of Lactuca sativa seed. After three months, 10.15% ± 1.04 weight loss of LDPE achieved through strain Stenotrophomonas sp. degradation. Both strains had high biofilm formation capacity, confirmed by Electron microscope images and FTIR analysis. GC-MS confirmed the presence of the end-product of LDPE degradation (Pentacosane, Hexacosane, and Octadecane). Both, Stenotrophomonas sp. and Alcaligenaceae bacterium had significant detoxification ability. In media contain LDPE (without bacteria), decrease in the germination of lettuce seeds was observed.

In Vivo Toxicity of Industrial Biocide Containing 2,2-Dibromo-3-nitrilopropionamide in Adult and Zebrafish Larvae.

2,2-Dibromo-3-nitrilopropionamide (DBNPA) is a widely used biocide with potential environmental implications due to its toxicity. This study aimed to investigate the in vivo toxicity of DBNPA in zebrafish (Danio rerio), a model organism in environmental toxicology. Both adult and larval zebrafish were exposed to varying concentrations of DBNPA, and significant morphological changes and mortality rates were observed. The study found that even relatively low concentrations of DBNPA can have detrimental effects on zebrafish embryonic development, and high concentrations resulted in rapid mortality in adult zebrafish and larvae. The LC50 values calculated from this study were 9.3 ppm for adults and 9.1 ppm for larvae, indicating the high toxicity of DBNPA to these organisms. These findings underscore the potential environmental impact of DBNPA and highlight the need for further research into its effects on aquatic ecosystems.

Treatment of electropolishing industrial wastewater and its impact on the immobilisation of Daphnia magna.

The amount of industrial pollution entering the environment and its impact on living organisms is an ongoing concern. At the same time, due to an increasing awareness, new methods of wastewater treatment are being explored that are not only effective but also environmentally acceptable. Meeting environmental standards for permitted concentrations is a necessity, but investigating the effects of wastewater on living organisms is also an important issue. In this paper, the influence of metal ions (Fe(III), Cr(III), Ni(II), Cu(II)) in industrial wastewater from electropolishing of stainless steel on Daphnia magna has been investigated. Daphnids have been exposed to wastewater both before and after treatment (Ca(OH)2 precipitation, sorption with peat). Immobilisation in a 48-h acute toxicity test and EC50 has been determined. In the case of studied industrial wastewater, the organic content (expressed as total organic carbon) of the effluent has a positive impact in terms of the survival of D. magna and increases the range of heavy metal concentrations tolerated by them. The application of a two-stage process with Ca(OH)2 neutralisation followed by sorption with peat allows for the removal of almost 100% of metal ions from the wastewater. The reduction obtained ensured a limited impact on D. magna and a decrease in immobilisation to less than 10%. Proper execution of the wastewater treatment process ensures a reduction of its negative impact on living organisms.

Embryotoxicity of polystyrene microplastics in zebrafish Daniorerio.

In the recent years, increasing scientific and societal concern has been raised over the presence and accumulation of plastic debris in the environment and the effects of microplastics (MPs) that can easily interact with biota. In order to elucidate the impact of MPs at the critical development stages of freshwater fish species, a fish embryo toxicity test was herein performed on the zebrafish Danio rerio, exposed to 10 µm polystyrene MPs at 200 particles/mL for 120 hpf. After exposure, accumulation of MPs in larvae was measured, survival, hatching and larvae development were monitored and the oxidant/anti-oxidant responses and cellular detoxification evaluated. No impact on survival of developing zebrafish was revealed, but a moderate delay in hatching was observed. Alterations in larvae development were recorded with zebrafish exhibiting serious deformities, mainly at the level of column and tail, as well as a compromised integrity of the visual structure of the eyes. Moreover, increased levels of gene transcription involved in the oxidative stress (sod1, sod2 and cat) and in cellular detoxification (gst and cyp) were also detected in MPs-exposed zebrafish larvae. Overall, this research work provides new insights on the ecotoxicological impact of polystyrene MPs on the critical developmental stages of a freshwater fish species, therefore enhancing the current knowledge of the environmental risk posed by MPs to the aquatic ecosystem.

Mechanisms and Safety of Antidepressant-Like Effect of Nutmeg in Mice.

Nutmeg, a dried seed kernel of a tall evergreen Myristicaceae tree, is widely used as a spice and herbal medicine and is known to have antidepressant-like effects. This study evaluates the mechanisms underlying this antidepressant-like effect and safety of nutmeg n-hexane extract (NNE) in mice. Tail suspension and open field tests showed that NNE (10 mg/kg, per OS (p.o.)) significantly decreased the immobility time of mice without effecting their spontaneous locomotor activity. The reduction of immobility time of mice elicited by NNE was significantly inhibited by ketanserin (5-hydroxytryptamine (5-HT)2A/2C receptor antagonist), ondansetron (5-HT3 receptor antagonist), and yohimbine (α2 receptor antagonist). WAY100635 (5-HT1A receptor antagonist) tended to inhibit the effect of NNE but without significance. Testing according to the Organisation for Economic Co-operation and Development Guidelines, no mice died due to administrated NNE (2000 mg/kg, p.o.), and behavioral and weight changes were not seen in the acute toxicity test. In the Ames test, no increase in the number of revertant colonies for each bacterial strain test strains TA98 and TA100 by nutmeg powder was observed either with or without metabolic activity by S9 mix. These results suggest that NNE shows an antidepressant-like effect involving various serotonergic and noradrenergic nervous systems and maybe a highly safe natural preparation.

Accelerating Global Deletion of the Abnormal Toxicity Test for vaccines and biologicals. Planning common next steps. A workshop Report.

This online workshop Accelerating Global Deletion of the Abnormal Toxicity Test for vaccines and biologicals. Planning common next steps was organized on October 14th, 2021, by the Animal Free Safety Assessment Collaboration (AFSA), the Humane Society International (HSI), the European Federation of Pharmaceutical Industries and Associations (EFPIA), in collaboration with the International Alliance of Biological Standardization (IABS). The workshop saw a participation of over a hundred representatives from international organizations, pharmaceutical industries and associations, and regulatory authorities of 28 countries. Participants reported on country- and region-specific regulatory requirements and, where present, on the perspectives on the waiving and elimination of the Abnormal Toxicity Test. With AFSA, HSI, EFPIA and IABS representatives as facilitators, the participants also discussed specific country/global actions to further secure the deletion of ATT from all regulatory requirements worldwide.

Correlation analysis of single- and multigenerational endpoints in Daphnia magna toxicity tests: A case-study using TiO2 nanoparticles.

Multigenerational toxicity tests provide more sensitive measures of population-level effects than conventional single-generation tests. Particularly for stressors which exhibit slow uptake rates (e.g. nanomaterials), multigenerational tests may also provide a more realistic representation of natural exposure scenarios. To date, the inherently high costs and labor intensity have however limited the use of multigenerational toxicity tests and thereby their incorporation in environmental risk assessment. The aim of the present study was therefore to determine to what extent short(er) term endpoints which are conventionally measured in Daphnia magna toxicity tests hold predictive capacity towards reproduction measured over longer timescales, including multiple generations. To assess this, a case-study was performed in which effects of TiO2 nanoparticles (0, 0.02, 0.2, 2 and 5 mg L-1) on D. magna life-history traits were assessed over five generations. Additionally, it was determined whether offspring derived from exposed parents exhibited sustained adverse effects when rearing them in clean (non-exposed) media after each generation of exposure. The present study showed that although various life-history traits correlate with the total reproductive output in the same- and subsequent generation under non-exposed conditions, these correlations were decoupled in presence of exposure to nTiO2. In addition, it was found that nTiO2 can induce adverse effects on population relevant endpoints at concentrations 1-2 orders of magnitude lower than previously found (i.e. 0.02 mg L-1), and close to the range of concentrations occurring in natural freshwater ecosystems.

Commercial pesticides for urban applications induced population growth and sub-cellular alterations in Raphidocelis subcapitata (Chlorophyceae) at concerning environmental concentrations.

Information regarding the safety and environmental risks of pesticides intended for urban use remains limited. This study aimed to assess the effects of four common pesticides on the microalga Raphidocelis subcapitata: DIAZINON® 25% C. E., Roundup®, URBACIN® 20C. E., and VAPODEL® 20% C. E., which are commercial formulations of diazinon, glyphosate, dichlorvos, and cypermethrin, respectively. According to 96-h inhibition of population growth bioassays, the four pesticide toxicities exemplified the following order: DIAZINON® (diazinon) > Roundup® (glyphosate) > VAPODEL® (dichlorvos) > URBACIN® (cypermethrin). Increasing pesticide concentrations elicited alterations in the specific growth rates (µmax). The macromolecule contents and photosynthetic pigments increased in groups exposed to the highest concentrations of DIAZINON® 25%, Roundup®, and URBACIN® 20 compared to the control group, despite these treatments inducing lower population growth rates. VAPODEL® 20% induced higher growth rates and lower macromolecule content compared to the control. Since active ingredients were not quantified, certain comparisons may prove limiting, but it is important to assess the effects of the whole mixtures in the form that they enter the environment, especially for urban-intended applications or generic formulations with higher additive contents. Finally, this study demonstrated that commercial pesticide formulations designed for urban applications might pose a threat to freshwater microalgae due to their underestimated toxic potential, but further studies are required.

The Biodegradation of Indigo Carmine by Bacillus safensis HL3 Spore and Toxicity Analysis of the Degradation Products.

The aims of this article were to investigate Bacillus safensis HL3 spore for its capacity to degrade and detoxify indigo carmine and to provide an effective biological agent for the treatment of isatin dye wastewater. Bacillus safensis HL3 spore was found to decolorize indigo carmine by 97% in the presence of acetosyringone within 2 h. Significantly increased activities of spore laccase, intracellular tyrosinase, and lignin peroxidase upon exposure to indigo carmine were observed. The results of RT-qPCR also showed that the expression of laccase gene was significantly increased. The spore has the ability to degrade indigo carmine through oxidization. Furthermore, the pathway by which indigo carmine is degraded was investigated using liquid chromatography-mass spectrometry analysis to identify the biodegradation products. A detailed pathway of indigo carmine degradation by bacterial spores was proposed for the first time. Toxicity tests indicated that the biodegradation products of indigo carmine are non-toxic to Nicotiana tabacum seeds and are less hazardous to human erythrocytes than the original dye. Indigo carmine is a typical recalcitrant dye and severely jeopardizes human health. The results demonstrate the utility of the spore from Bacillus safensis HL3 for the degradation of indigo carmine and simultaneous reduction of its toxicity.

Determining the Relative Importance of Dietborne and Waterborne Toxicity of 4-tert-Butylphenol and 4-tert-Octylphenol to the Benthic Crustacean, Heterocypris incongruens.

Organic pollutants with high solid-water equilibrium partition coefficients are adsorbed into solid particles and are easily ingested by benthic organisms, potentially causing dietborne toxicity. Whether dietborne toxicity is more important than waterborne toxicity for such chemicals remains to be determined. In this study, we identify the most relevant uptake route for the toxicity of two alkylphenols, 4-tert-butylphenol (4tBP), and 4-tert-octylphenol (4tOP). To achieve this, 6-day toxicity tests under two exposure conditions, namely dietary exposure (clean water + contaminated food) and combined exposure (contaminated water + contaminated food) were conducted on a benthic ostracod, Heterocypris incongruens. The toxicologically important exposure routes were confirmed by the consistency of dietary and aqueous dose-response relationships under different exposure conditions. During the test, frequent renewal of water and food was performed to reduce variability in the exposure conditions. The results showed that, under the equilibrium condition, the dietary exposure route was toxicologically more important than the aqueous route for 4tBP, whereas the waterborne exposure route was more important than the dietary exposure route for 4tOP. This study provides a novel approach to identify the most relevant uptake pathways for chemical toxicity, which better explains the importance of exposure routes in toxicity effects.

Investigating the Predictive Power of Three Potential Sublethal Endpoints for the Fathead Minnow Fish Embryo Toxicity Test: Snout-Vent Length, Eye Size, and Pericardial Edema.

The fish embryo acute toxicity (FET) test is known to be less sensitive than the fish acute test for some chemicals, including neurotoxicants. Thus, there is an interest in identifying additional endpoints that can improve FET test performance. The goal of this project was to advance alternative toxicity testing methods by determining whether select developmental abnormalities-snout-vent length, eye size, and pericardial area-are linked to adverse alterations in ecologically-relevant behaviors and delayed mortality. Fathead minnow (Pimephales promelas) FET tests were conducted with 3,4-dicholoroaniline, cadmium, and perfluorooctanesulfonic acid (PFOS) and developmental abnormalities were quantified. Surviving eleutheroembryos were reared in clean water to 14 days post fertilization (dpf), during which time behaviors and mortality were evaluated. None of the abnormalities evaluated were predictive of behavioral alterations; however, embryos with ≥14% reductions in length or ≥3.54-fold increases in pericardial area had an 80% chance of mortality by 14 dpf. When these abnormalities were used as markers of mortality, the LC50s for cadmium and PFOS were less than those calculated using only standardized FET test endpoints and similar to those obtained via larval fish tests, indicating that the snout-vent length and pericardial area warrant consideration as standard FET test endpoints.

Anticancer active trifluoromethylated fused triazinones are safe for early-life stages of zebrafish (Danio rerio) and reveal a proapoptotic action.

The main purpose of this investigation was to evaluate the effect of anticancer active compounds (I-VIII) on zebrafish development in order to select the safest molecules. Larval mortality, embryo hatchability and malformations were end-points used to assess the acute toxicity among embryos and larvae from compounds-/pemetrexed-treated and control groups. LC50 and MNLC (maximal non-lethal concentration) were determined. Lipophilicity-dependent structure-toxicity relationships were established. The results clearly indicated that the majority of test molecules are safe for zebrafish individuals and simultaneously are less toxic than an anticancer agent - pemetrexed. The subsequent aim of this study was to elucidate the molecular mechanism of antiproliferative activity of the most selective compounds. Substantially increased activation of caspase-6 and -8 in cancerous cell lines confirmed the proapoptotic action of molecules examined. Considering the safety for zebrafish individuals, the title compounds as inducers of apoptosis are promising drug candidates in the preclinical phase of drug development.

Toxic effects in Aphanomyces brasiliensis and zebrafish embryos caused by oomyceticides.

In fish farming, high losses occur during egg incubation and larviculture due to diseases caused by oomycetes. This study aimed to identify the oomycete species that occurs in zebrafish Danio rerio eggs and to evaluate the oomyceticidal effect of copper sulfate, bronopol and methylene blue on the mycelial growth of this organism, as well as to determine the lethal and sublethal toxicity of these compounds in embryos of D. rerio. The isolates were cultivated in yeast-starch medium to determine the concentration necessary to inhibit mycelial growth by 50% (IC50) and 100% (minimum oomyceticidal concentration) after a 96 h exposure to these compounds. In addition, tests with D. rerio eggs were conducted to determine the lethal concentrations for 50% of the organisms (96h-LC50), and the concentrations that inhibited 17% of the eggs hatching (96h-IC17) after 96 h. The organism responsible for the mortality of D. rerio eggs was classified by classical and molecular methods as Aphanomyces brasiliensis, representing the first report of this pathogen in zebrafish eggs. IC50 values could be determined for both bronopol and copper sulfate, whereas methylene blue had low effectiveness against the oomycete. Copper showed high toxicity to D. rerio eggs at low concentrations, while methylene blue and bronopol toxicity was low and similar to each other. The use of bronopol at a concentration of 4.8 mg l-1 for the treatment of zebrafish eggs allows controlling the pathology without causing deleterious effects to the treated organisms.