Slimy Molecule May Spread Disease from Cats to Sea Otters in the Ocean

Sea otters are suffering from land-based diseases and now, scientists may have found what might be aiding this spread. They've found that gelatinous, sticky polymers produced by seaweed could be helping disease-causing organisms become introduced to the marine food chain.

Contamination of coastal waters with disease-causing microorganism can pose a threat to both humans and animals. Yet the mechanism by which diseases are transmitted in marine ecosystems has, until now, remained unknown.

In order to better understand the spread of disease, the researchers examined the parasite Toxoplasma gondii. This parasite infects animals and humans worldwide, and actively reproduces in various cat species. Its egg cells pass on in cat feces and can then persist in the environment for months to years. It can also infect sea otters, so scientists set out to find out how this was occurring.

The researchers found that T. gondii infections were 10 times more common among sea otters that fed heavily on kept-grazing marine snails tan among otters that fed on abalone and other ocean food sources. In the end, they found that gelatinous polymers excreted by seaweed act in two ways to provide an environment that can help transmit infectious diseases; the polymers act like glue, binding the water-borne organic material into larger particles, in which infectious agents can embed and settle to the sea floor, and the polymers also form sticky biofilms that can trap infectious agents and coat kelp on which marine snails graze.

The findings reveal how these polymers can help transmit disease. This, in particular, is important for understanding how best to focus efforts of conservations for sea otters and other marine animals.

"Discovering the role that these invisible polymers play in disease transmission in the ocean is a tremendous step forward in helping us better understand and mitigate the impacts of coastal water pollution on the health of wildlife and humans," said Karen Shapiro, lead author of the new study, in a news release.