Orcas and PCBs

The dramatic population decline which has been predicted to affect killer whales (Orcinus orca) on a global scale by the end of this century is of concern, with the levels of polychlorinated biphenyls (PCBs) in tissues from free-ranging orcas having been estimated to be among the highest in the animal kingdom (1). As in other cetacean and non-cetacean “top predators”, in fact, lipophilic PCBs may heavily accumulate in killer whales’ subcutaneous blubber, thereafter undergoing ad hoc “biomagnification” processes. Since these bioaccumulation and biomagnification dynamics are shared by many other persistent environmental pollutants - either “classical” (i.e. DDTs, dioxins, heavy metals, etc.) or “emerging” (i.e. PBDEs, PFAS, micro- and nanoplastics, etc.) -, that almost unvariably form “mixtures” to which aquatic organisms are chronically exposed via the marine food web(s) (2), one could wonder how the biological effects of PCBs may be effectively “dissected” from those of the other contaminants present in the aforementioned mixtures. Furthermore, the “endocrine disrupting” and the additional pathogenic activities of PCBs on host’s reproductive and immune functions are also known to be exerted by other organochlorine (OC) pollutants, the entry of which into exposed animals’ cells is mediated by aryl hydrocarbon receptors (AHRs) (3). This implies that the susceptibility of a given species to PCBs and, more in general, to OC contaminants could “ideally” result from the “sum” of its trophic position and tissue expression level(s) of AHRs. Alternatively, if not complementarily, such an increased tendency to accumulate high PCB tissue burdens might depend upon a metabolic capacity toward OC xenobiotics that is less efficient in orcas as compared to other odontocete cetacean species. The prominent PCB immunotoxicity (3) has been also linked to an increased sensitivity toward infectious pathogens, as in the case of the dramatic Cetacean Morbillivirus (CeMV) epidemic which affected, between 1990 and 1992, the population of Western Mediterranean striped dolphins (Stenella coeruleoalba) (4). To the best of our knowledge, however, neither morbilliviral epidemics nor overt cases of morbilliviral infection have been hitherto reported in orcas, the susceptibility of which to CeMV is currently unknown. In this respect, should PCBs represent the major factor underlying the predicted killer whales’ population decline (1), one could reasonably expect a prevalence of “opportunistic” infections and/or neoplastic disease conditions (significantly) higher than in other cetacean and aquatic mammal species occupying a lower trophic level. Is this really the case? We are afraid that not enough, sufficiently reliable and robust data are available, thus far, to provide an affirmative or negative answer to the above query, considering also the “intrinsic” limitation due to the fact that an undefined number of orcas, similarly to their cetacean “heterospecifics”, will die in the open sea, with no possibility to perform a post mortem examination on them. Finally, the dramatically increasing pollution of global oceans and seas by plastics, micro- and nanoplastics would also deserve special concern, given that micro- and nanoplastics may act as “attractors and concentrators” for many chemical pollutants (including PCBs) (5), coupled with their long distance transfer across marine waters, as it has been recently described following the catastrophic tsunami in March 2011 along the Eastern coast of Japan (6). In conclusion, the herein dealt PCB-related alert (1), albeit of remarkable concern, appears to be influenced by a number of “environment”-dependent and “host”-related variables which should be carefully taken into account for an accurate evaluation of the effects of chronic PCB ingestion - and, more in general, exposure to OCs and other toxic pollutants - on killer whales’ health and conservation

Dolphin Morbillivirus Associated with a Mass Stranding of Sperm Whales, Italy

In September 2014, 7 sperm whales stranded along the Adriatic Italian coastlines. Postmortem investigations on 3 dead females dead and in 1 fetus harbored by the largest one revealed molecular and immunoistochemical evidences of dolphin morbillivirus infection. A possible role of the virus in the stranding event was considered

Calibration and validation of a dynamic water model in agricultural scenarios

A dynamic aquatic model (DynA model) was previously developed to predict the fate of a chemical in aquatic scenarios characterized by daily or periodic changes in several input parameters. DynA model is here calibrated with data obtained from the literature in specific unsteady state scenarios, such as those of rice fields. The results obtained for two herbicides (cinosulfuron and pretilachlor) in rice paddy scenarios revealed the capability of the model to accurately predict water and sediment concentrations, as shown by some statistical indicators. Modelling efficiency (EF) values of 0.86–0.99 for the water compartment and of 0.77–0.84 for sediment show the good agreement between predicted and measured concentrations. An ‘‘external validation’’ was performed using measured data for a different herbicide (molinate) applied in a Portuguese paddy rice scenario. A sensitivity analysis for this volatile chemical revealed the influence of some climatic parameters (e.g. temperature) to the model outcomes, such as water and sediment concentrations. This confirmed the capability of DynA model as an efficient tool for the pesticide risk assessment in dynamic scenario

Mediterranean Fin Whales (Balaenoptera physalus) Threatened by Dolphin MorbilliVirus

During 2011-2013, dolphin morbillivirus was molecularly identified in 4 stranded fin whales from the Mediterranean Sea. Nucleoprotein, phosphoprotein, and hemagglutinin gene sequences of the identified strain were highly homologous with those of a morbillivirus that caused a 2006-2007 epidemic in the Mediterranean. Dolphin morbillivirus represents a serious threat for fin whales

Dolphin Morbillivirus in Eurasian Otters, Italy

We report biomolecular evidence of dolphin morbillivirus in 4 wild Eurasian otters (Lutra lutra) from southern Italy; 2 animals showed simultaneous immunohistochemical reactivity against morbilliviral antigen. These cases add further concern and support to the progressively expanding host range of dolphin morbillivirus in the western Mediterranean Sea

Cellular Prion Protein Expression in the Brain Tissue from Brucella ceti-Infected Striped Dolphins (Stenella coeruleoalba)

Brucella ceti, a zoonotic pathogen of major concern to cetacean health and conservation, is responsible for severe meningo-encephalitic/myelitic lesions in striped dolphins (Stenella coeruleoalba), often leading to their stranding and death. This study investigated, for the first time, the cellular prion protein (PrPc) expression in the brain tissue from B. ceti-infected, neurobrucellosis-affected striped dolphins. Seven B. ceti-infected, neurobrucellosis-affected striped dolphins, found stranded along the Italian coastline (6) and in the Canary Islands (1), were investigated, along with five B. ceti-uninfected striped dolphins from the coast of Italy, carrying no brain lesions, which served as negative controls. Western Blot (WB) and immunohistochemistry (IHC) with an anti-PrP murine monoclonal antibody were carried out on the brain parenchyma of these dolphins. While PrPc IHC yielded inconclusive results, a clear-cut PrPc expression of different intensity was found by means of WB analyses in the brain tissue of all the seven herein investigated, B. ceti-infected and neurobrucellosis-affected cetacean specimens, with two dolphins stranded along the Italian coastline and one dolphin beached in Canary Islands also exhibiting a statistically significant increase in cerebral PrPc expression as compared to the five Brucella spp.-negative control specimens. The significantly increased PrPc expression found in three out of seven B. ceti-infected, neurobrucellosis-affected striped dolphins does not allow us to draw any firm conclusion(s) about the putative role of PrPc as a host cell receptor for B. ceti. Should this be the case, an upregulation of PrPc mRNA in the brain tissue of neurobrucellosis-affected striped dolphins could be hypothesized during the different stages of B. ceti infection, as previously shown in murine bone marrow cells challenged with Escherichia coli. Noteworthy, the inflammatory infiltrates seen in the brain and in the cervico-thoracic spinal cord segments from the herein investigated, B. ceti-infected and neurobrucellosis-affected striped dolphins were densely populated by macrophage/histiocyte cells, often harboring Brucella spp. antigen in their cytoplasm, similarly to what was reported in macrophages from mice experimentally challenged with B. abortus. Notwithstanding the above, much more work is needed in order to properly assess the role of PrPc, if any, as a host cell receptor for B. ceti in striped dolphins