By MITZI BAKER

It's not often that School of Medicine researchers get to apply their expertise to creatures other than humans, but John Boothroyd, PhD, recently had the chance to collaborate with a team led by UC-Davis to search for clues about an infection that kills sea otters.

In recent years, California sea otters have been dying in increasing numbers. Part of the problem is attributed to infectious diseases such as toxoplasmosis.

Toxoplasma gondii is perhaps the most wide-spread parasite on earth, said Boothroyd, professor of microbiology and immunology, who has studied the single-celled organism for years. Almost any warm-blooded animal can be infected, including humans, but it rarely causes symptoms except in the severely immune compromised and in developing fetuses.

In sea otters, however, toxoplasmosis can result in a fatal brain infection.

The UC-Davis team found previously that many sea otters were infected with toxoplasma. They wondered what could be learned from knowing which strain infected an otter, so they turned to Boothroyd for help in the genetics and biology of toxoplasma.

“This is real-life science, which I love,” said Boothroyd. “It's where the rubber meets the road and we lose the ability to do controlled experiments.” There are no sea otters used in experiments, he said, so the studies are based on observation, much like studies with humans.

Michael Grigg, a postdoctoral scholar in Boothroyd's lab at the time, genetically analyzed toxoplasma samples from 35 California sea otters found dead on the beach between 1998 and 2002. In the March 9 issue of the International Journal for Parisitology, they and their colleagues reported that out of the three known types of toxoplasma strains, 40 percent of the otters had one type, but the other 60 percent had a previously unidentified type, which they called “type x.” They found that three-quarters of the ones that had died of toxoplasmosis had type x, which also happened to be clustered around one coastal location.

Very little was known previously about the strains that infect other animals, said Boothroyd, since most sampling in the past has been from humans and some livestock. He said they didn't have enough information to be surprised by their results and that type x may well be the dominant strain in the wild.

Studies like this may help determine how to end the devastating decline in sea otter populations. If more facts were known about which strains were causing the most severe disease, Boothroyd said, there might be interventions that could save lives, such as vaccination with a less-harmful strain that could offer protection against the lethal strain.

“I think this qualifies as translational medicine,” said Boothroyd. “I enjoy seeing our basic research on population biology lead to important clinical findings, even if the patient ends up being a sea otter. We're not the only species on Earth that matters.”