A new study released this past week has revealed the presence of two parasites, previously found in cats and opossums, in marine mammals that died in the Pacific Northwest. Toxoplasma gondii enters water through infected cat feces and sarcocystis neurona is believed to be carried by opossum feces. The research concludes that marine mammals infected with both were more likely to have severe brain swelling (protozoal encephalitis) and die than just one of the parasites. Tissue samples from 161 animals that died in Washington, Oregon and British Columbia between 2004 and 2009 were tested and the parasites were found in the majority of them. The study suggested that animals with lowered immunity, such as pregnant seals, pups or yearlings, were more likely to have worse symptoms when infected with both parasites. Seal Sitters responded to three of the animals included in the study that tested positive: an adult seal in June of 2009 which tested positive for protozoal encephalitis, pup at Lincoln Park in December of 2008, and another Lincoln Park pup in January of 2009. Seal Sitters responded to a report of seal pup with seizures at Don Armeni boat ramp in January of 2011. The weaned male pup died enroute to PAWS. Initial tests were positive for protozoals in the seal’s brain. However, the cause of death for this pup is believed to have been broncho-pneumonia due to lungworm.

This study has rather disturbing implications since control of marine mammals’ exposure to foreign parasites due to storm runoff is essentially impossible to control on a large scale. It is truly the responsibility of each individual to control what materials and chemicals he or she allows in the soil/sidewalk/sewer and street drains that end up in our marine waters. As researcher Dr. Michael Grigg says in the report, “Identifying the threads that connect these parasites from wild and domestic land animals to marine mammals helps us to see ways that those threads might be cut by, for example, managing feral cat and opossum populations, reducing run-off from urban areas near the coast...and controlling erosion to prevent parasites from entering the marine food chain.” Additionally, domestic cat feces deposited in house toilets ultimately wind up in marine waters. It is obvious that there are many challenges in managing this dangerous situation.

Dyanna Lambourn, WDFW marine mammal research biologist (and SS mentor), and Jessie Huggins of Cascadia Research co-authored the study with Dr. Grigg and other esteemed researchers. Read the complete study here.

Read the National Institute of Allergy and Infectious Diseases news release here. Read the related Associated Press article here.