In California, four otters have tested positive for a deadly brain disease called toxoplasmosis. Some biologists suspect domesticated cat feces could be to blame.
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Toxoplasmosis is caused by the toxoplasma parasite, which is known to infect house cats. It spreads by getting into cats’ prey—i.e., mice and rats—and taking over the rodents’ brains. The mechanism of spread is particularly sinister: Rats and mice with toxoplasmosis tend to exhibit a strange affinity for cats. Essentially, the parasite finds a new host by tricking mice into getting close enough to cats to get eaten.
Toxoplasmosis has also been detected in some humans. In a famous episode of NPR’s RadioLab podcast, experts conjecture that the toxoplasma parasite could potentially rewire human brains the same way it rewires rodent brains. In that case, it could create an affinity for cats in humans—and might therefore be a contributing factor for the “crazy cat lady” or “crazy cat guy” phenomenon.
Toxoplasmosis is also relatively common in sea otters. However, the recent deaths have been caused by a new and particularly virulent strain of the parasite that has never before been found in marine mammals, reports a press release from UC Davis.
All four of the dead otters were discovered after severe rainfall events. That has led scientists to believe that runoff from the California coast could have washed disease-bearing cat poop into the ocean. When the diseased sewage reached the waters where the otters live and play, the parasite could have infected them.
The risk to other otters and to humans remains unclear, but the scientists say people shouldn’t panic just yet. However, lead researcher Melissa Miller cautions cat owners to clean up after their pets responsibly.
“I keep my cats indoors all the time and I make sure to dispose of their litter into something that will not leak into the environment,” she told The Guardian. If you live in California—and want to keep your local sea otters safe—you should consider doing the same.