Editorial: Animal Poisoning and Biomarkers of Toxicity

Abstract

The worldwide incidence of animal poisoning is unknown. Despite reports pieced together by networks of veterinary clinics and poison control centers, their coverage is usually limited due to widespread under-reporting of cases (1–3). There are several reasons for this reality, being one of the major the wide gaps of knowledge regarding toxicosis agents and their profile (particularly in terms of toxicity mechanisms), since these encompass an extensive variety of synthetic chemicals, molecules of plant and animal origin, as well as drugs (both of use and abuse) (1–3). Together with the lack of specific and sensitive analytical techniques for their detection and quantification, this reality leads to reports being usually submitted in incomplete form, and presented in a case-by case manner (4–6). This situation has created uncertainty when comparing poisoning with other types of clinical findings, such as infectious diseases, traumatic injuries or malignant neoplasms, since toxicosis would come out, at least apparently, as an uncommon cause of disease (3). This has led to appeals for more cooperation and information sharing between countries and institutions (1, 3), even inside “data-rich regions” (7), which typically include North America and Europe. The disproportionately higher volumes of available information in these areas also contribute to introduce geographic biases in available information (2). This reality is perfectly illustrated by European and North American floras, that, despite their disparity in the number of hazardous species (Europe has a much lower number), are both fairly well characterized. Contrastingly, African flora, which is at least as rich in hazardous species as the North American, has been reduced to seemingly anecdotal reports (8, 9). Even in Europe, despite the already mentioned lower number of hazardous species, the number of poisonings (affecting livestock and companion animals) attributed to wild, illicit drug or houseplants (mostly by ingestion) is considerable, since they contain chemical substances in sufficient quantities to cause toxic effects. In the particular case of companion animals, the majority of reported cases refers ingestion of ornamental plants (as opposed to wild), as the source of toxicity, particularly at certain times of the year (8). In addition to plant toxicity, available information indicates that the incidence of animal toxicosis from all causes does not seem to be declining. In the 2010's, a series of reports (10–12) detailed the prevalent toxicants affecting different groups of animals. The authors identified toxic plants and mycotoxins as the most common toxic agents involved in livestock and poultry poisoning, with additional cases being reported for metals (Cu, Pb), pesticides (endosulfan, lindane), and industrial chemicals (e.g., dioxins, polychlorinated biphenyls, dibenzofurans) (11). Regarding companion animals, frequent causes of poisoning include the exposure to anticoagulant rodenticides (coumarins), herbicides (paraquat), and insecticides (organophosphates, carbamate, strychnine, metaldehyde). Also, the inadequate use of human and veterinary pharmaceuticals, and the exposure to household products accounted for a noteworthy part of registered toxicosis reports (10).

Wildlife species are frequently victims of primary (deliberate), but also of secondary poisonings (typically top predators). Metals and metalloids (Pb, Zn, As, Cu, Tl, Cd, and Hg) and pesticides (mostly anticholinergics and anticoagulants) were identified as frequent, often fatal, poisoning agents. In aquatic ecosystems, point or diffuse sources of chemicals and/or from industrial, agricultural, and urban runoff contribute to poisoning incidents. Additionally, chemicals released during environmental catastrophes (which could include any of the previous categories) are a significant cause of poisoning. The type of toxicants described more than two decades ago are, in a large number of cases, not the same, since, at least in the case of synthetic chemicals (including pharmaceuticals) many of them, were banned by legislation. However, new molecules (whose harmlessness is still to be entirely proven) were developed, manufactured in large scales, and started being used in their place. Despite this (partial) change of agents, current reports indicate the continuity of poisoning events toward animals (4, 6, 13–17). Consequently, researchers in this area face the paramount task of unraveling the underlying mechanisms (such as the toxicokinetics and toxicodynamics models and the adverse outcome pathways-AOPs) of new toxicants created by the continuous outpouring of new synthetic chemicals developed for the industry, the agrobusiness and household products market, as well as the growing sector of natural extracts.

Biomarkers can act as indicators or signallers of events occurring in biological systems (18). By permitting the measurement of changes in molecules, biochemical processes, cells, tissues, organs and entire organisms (encompassing physiology, pathology, or behavior) in response to external insult, they provide nuclear knowledge in order to deliver accurate diagnosis under the form of biomarkers of exposure, effects and susceptibility, as well as enabling to delineate therapeutic interventions, and the improvement of key aspects of the drug development process (19). Additionally, they can be noninvasive and can translate between species. In fact, some authors consider that the most valuable are those that can be simultaneously used in animals and humans (19).

In this Research Topic of Frontiers in Veterinary Science/Veterinary Pharmacology and Toxicology, 7 manuscripts were published: 1 Review, 5 original Research Articles and 1 Brief Research Report, whose main results and contributions are briefly presented below.