Devinn Sinnott

UC Davis

“Does parasite genotype influence Sarcocystis neurona infection outcome in southern sea otters in California?”

Infection with the parasite Sarcocystis neurona is an important cause of death in southern sea otters. In addition to sporadic deaths that occur every year, outbreaks due to S. neurona infection occurred in 2004 and 2021, hindering recovery efforts for this threatened species. We still do not understand why some S. neurona-infected otters die quickly after exposure while others appear to experience little to no disease. The goal of this study is to examine if different genotypes of S. neurona lead to different disease outcomes in sea otters, including the occurrence of outbreaks. To do this, we evaluated pathology data to identify fatal and non-fatal S. neurona infections, then characterized the genotype of S. neurona infecting each case. One group of closely related genotypes was significantly associated with fatal infections and was responsible for the deaths of all otters tested from the 2004 outbreak. Two other genotypes were associated with non-fatal infections. Our results suggest that parasite genotype, likely alongside other host and environmental factors, may contribute to disease outcome in S. neurona-infected sea otters.


The protozoal parasite Sarcocystis neurona is an important pathogen infecting southern sea otters in California. Many infected sea otters die from this parasitic infection, while others survive and develop chronic, asymptomatic infections. The goal of our study is to determine if the genotype of S. neurona affects whether a sea otter is more likely to die from this infection or become incidentally infected.

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