In vivo and in vitro effects of the herbicide Roundup(®) on developmental stages of the trematode Echinostoma paraensei

A new cryptic species of Echinostoma (Trematoda: Echinostomatidae) closely related to Echinostoma paraensei found in Brazil

Echinostoma paraensei, described in Brazil at the end of the 1960s and used as a biological model for a range of studies, belongs to the ‘revolutum’ complex of Echinostoma comprising species with 37 collar spines. However, molecular data are available only for a few isolates maintained under laboratory conditions, with molecular prospecting based on specimens originating from naturally infected hosts virtually lacking. The present study describes Echinostoma maldonadoi Valadão, Alves & Pinto n. sp., a species cryptically related to E. paraensei found in Brazil. Larval stages (cercariae, metacercariae and rediae) of the new species were found in the physid snail Stenophysa marmorata in the State of Minas Gerais, Brazil, the same geographical area where E. paraensei was originally described. Adult parasites obtained experimentally in Meriones unguiculatus were used for morphological (optical microscopy) and molecular [28S, internal transcribed spacer (ITS), nad1 and cox1] characterization. The morphology of larval and adult parasites (most notable the small-sized dorsal spines in the head collar), associated with low (0–0.1%) molecular divergence for 28S gene or ITS region, and only moderate divergence for the mitochondrial cox1 gene (3.83%), might suggest that the newly collected specimens should be assigned to E. paraensei. However, higher genetic divergence (6.16–6.39%) was found in the mitochondrial nad1, revealing that it is a genetically distinct, cryptic lineage. In the most informative phylogenetic reconstruction, based on nad1, E. maldonadoi n. sp. exhibited a strongly supported sister relationship with E. paraensei, which may indicate a very recent speciation event giving rise to these 2 species.

Effect of Agrochemical Exposure on Schistosoma mansoni Cercariae Survival and Activity

Singular use of activity assays or staining dyes to assess pathogen agrochemical tolerance can underestimate tolerance if pesticides cause sublethal effects. We exposed Schistosoma mansoni cercariae, the aquatic life stage of this trematode that infects humans, to 4 insecticides at 5 concentrations using a 24-h time-to-death assay. We used Trypan blue dye, which stains dead tissue, and activity assays simultaneously to discriminate dead from live but paralyzed individuals. Whereas cypermethrin, deltamethrin, and dimethoate exposure did not affect cercariae at any ecologically relevant concentrations, methamidophos exposure increased survival of cercariae compared with those in the controls. This was because methamidophos-induced paralysis reduced cercarial activity and thus energy expenditures, extending the lifespan of this short-lived parasite that causes human schistosomiasis. These findings highlight that sublethal effects should be considered when pesticide effects on disease are under investigation. Environ Toxicol Chem 2020;39:1421-1428. © 2020 SETAC.

Changes in hemocytes of Biomphalaria glabrata infected with Echinostoma paraensei and exposed to glyphosate-based herbicide

The immune system of snails is highly sensitive to pollutants, which can suppress its immune response. We investigated the effects of exposure to the glyphosate-based herbicide Roundup® Original on the snail Biomphalaria glabrata infected by the platyhelminth Echinostoma paraensei by evaluating changes in the snail's internal defense system. Four cohorts were studied: control group, infected snails, snails treated with Roundup®, and snails infected and treated with Roundup®. The hemocyte viability was assessed, morphological differentiation of cells was observed and flow cytometry was performed to determine the morphology, viability and the lectin expression profiles. The frequencies of dead hemocytes were lower in the infected group and higher in both pesticide treated groups. Three cell types were identified: blast-like cells, hyalinocytes and granulocytes. The highest number of all types of hemocytes, as well as the highest number of dead cells, were observed in the infected, pesticide-treated group. The association between infection and herbicide exposure greatly increased the frequency of dead hemocytes, suggesting that this condition impairs the internal defense system of B. glabrata making the snails more vulnerable to parasitic infections.

Morphological effects on helminth parasites caused by herbicide under experimental conditions

Helminth parasites have been studied as potential accumulators for different pollutants. Echinostoma paraensei is a foodborne trematode whose vertebrate host, the rodent Nectomys squamipes, is naturally exposed to environmental pesticides. However, little information exists regarding the pesticide's effects on helminths. This study investigated the morphological effects on the trematode, E. paraensei, after experimental Roundup® herbicide exposure, in concentrations below those recommended for agricultural use. After two hours of exposure, scanning electron microscopy (SEM) showed changes to the tegument, such as furrowing, shrinkage, peeling, spines loss on the peristomic collar, and histopathological evidence of altered cells in the cecum and acinus vitelline glands with vacuoles and structural changes to the muscular layers. Glycidic content was decreased, primarily in the connective tissue. As E. paraensei is an intestinal parasite of the semi-aquatic wild rodent, N. squamipes, it is predisposed to pesticide exposure resulting from agricultural practices. Therefore, we emphasize the need to evaluate its impact on helminth parasites, due to their pivotal role in regulating host populations.