We live in a day and age when extinctions are far too commonplace. The so-called Anthropocene epoch has seen a drastic loss in diversity. The Southern sea otter (Enhydra lutris nereis) experienced a near extinction at the beginning of the last century. Though their numbers have rebounded to some degree, many sea otters are dying due to two protozoans, namely Toxoplasma gondii and Sarcocystis neurona, whose definitive host species are felids (wild or domestic) and opossums, respectively. The former parasite is zoonotic and the latter is implicated in Equine Protozoal Myeloencephalitis. Pathology in other species aside, sea otters may suffer from protozoal encephalitis with brain tissue inflammation as the protozoa divide. Though the protozoa are only shed by the aforementioned terrestrial species, their environmentally robust oocysts or sporocysts found in feces are likely deposited in the ocean via freshwater runoff, especially after precipitation. Increased water flow is just one variable that is correlated with otter infection, morbidity, and mortality. Otters that come into contact with the runoff or ingest marine invertebrates (such as marine snails and razor clams) which concentrate the protozoa in their bodies will become infected.
Now the major question remains: what do we do to combat this problem? Seeing stranded otters and carcasses is a sad sight, but we can use the information we have collected from studies in attempts to decrease these events. Since otter infection is an indicator of human toxoplasmosis, the issue is of public health relevance. Monitoring of wild and feral felid populations with an overlapping distribution with the coastline wildlife like sea otters will continue to be very important.