Toxoplasma gondii from terrestrial sources is infecting and killing southern sea otters — a welfare and conservation problem at the land-sea interface of human activity.
Sea otter Toxoplasma welfare is a cross-system problem that illustrates how human land management decisions create distant wildlife welfare consequences. Domestic and feral cat management near California's coast directly affects sea otter mortality rates through the fecal oocyst runoff pathway. Individual sea otters with neurological toxoplasmosis experience significant suffering — disorientation, seizures, and progressive neurological decline before death. Wildlife rehabilitation for toxoplasma cases is largely unsuccessful; the disease is fatal once neurological symptoms appear. Prevention at the source — responsible domestic cat ownership, trap-neuter-return programs near coastal areas, and improved stormwater management that reduces runoff pathways — is the welfare intervention that can reduce mortality rates.