Current studies indicate that parasites, environmental pollutants, and other pathogens interact with each other in aquatic organisms. Parasites impact host’s growth, reproduction, immunity, and behavior, while some metals are endocrine disruptors. Some metals are chelated by the herbicide Glyphosate (N-phosphonomethyl-glycine). Metal bioaccumulation and parasitic diseases could vary in different species depending on some environmental factors, such as temperature changes or contaminants. Little is known about the interactions of metals, Glyphosate-based herbicides (GBHs), parasites, and epigenetics in aquaculture species. GBHs can modify toxicity and epigenetic marks in shellfish and fish. Recent findings of portions of the SARS-Cov-2 coronavirus RNA in bivalve mollusks and in wild carp of Wuhan, China, as well as the potential association of parasite co-infection with a reduced risk of severe COVID-19 in African patients, suggest the need for a more holistic approach to studying interactions of metals and other contaminants in parasites and their hosts.
A review of the interactions of metals, GBHs, parasites, and epigenetic marks in shellfish and fish is presented. The glyphosate-associated Shikimate pathway was first reported in apicomplexan parasites in 1999. Cadmium (Cd) is highly toxic to earthworm Eisenia fetida, and the presence of glyphosate markedly reduced the acute toxicity of Cd to earthworm. GBHs impact the gut microbiome of earthworm species (Alma millsoni, Eudrilus eugeniae, and Libyodrilus violaceus) - a major shift reported in bacterial populations in exposed earthworms with Proteobacteria becoming the dominant phylum. Affected bacteria were mostly from the genus Enterobacter, Pantoea and Pseudomonas, while they were present at a minor abundance in unexposed earthworms. Mortality rate and accumulation of Cd in the earthworms decreased with the increase of the glyphosate/Cd molar ratio; longer exposure glyphosate alleviated the weight loss of earthworm and the total Cd absorption. Glyphosate can generate oxidative stress in Danio rerio by interfering with mitochondrial metabolism, impairing mitochondria in oocytes, and adversely affecting ovarian maturation. Arsenic affects resistance to cestodes in brine shrimp. GBH Roundup® Biactive modifies Cd toxicity to Daphnia carinata. Exposure to GBH Roundup® Original on hemocytes of the snail Biomphalaria glabrata infected by the platyhelminth Echinostoma paraensei showed that the frequencies of dead hemocytes were lower in the infected group and higher in pesticide treated groups, suggesting impairment of the internal defense system of B. glabrata making the snails more vulnerable to parasitic infections.
Studies are needed to understand the synergistic interactions between metals, pesticides, parasites, and epigenetics in shellfish and fish using the tools of One Health.