The Hawaiian monk seal population continues to grow, but researchers are increasingly concerned about a deadly disease that threatens the seals. Toxoplasmosis, a parasitic disease that is solely transmitted from cat feces, killed a seal last month and infected another.
While other animals and humans can get infected, the parasite only reproduces in digestive system of felines. Runoff carries the waste to the ocean, contaminating the water and the seals' food.
Researchers with the National Oceanic and Atmospheric Administration say they know of 12 monk seals that have died since the late 1990s, although they believe the number is much higher.
"We don't recover every body of a monk seal that passes away, and we're not able to examine them," said Angela Amlin, a NOAA monk seal recovery coordinator.
A male monk seal named Sole died last month from toxoplasmosis. Another, a female, called Pohaku is infected. She is being treated at the Ke Kai Ola Mammal Center on Hawaiʻi Island, and is improving.
Pohaku is one of the few seals that has been treated for toxoplasmosis. Charles Littnan, a protected species division director at NOAA, says two out of the three seals brought in with the disease pass away within the first 48 hours of treatment.
"Toxoplasmosis is by far the number one threat for the species -- there's nothing even remotely close," Littnan said.
"It moves through them like wildfire. It affects a whole range of organs, neurological tissues, brain, spinal cord, even into their fat layer. And it is incredibly debilitating and the animal responds with this terrible inflammation," he said.
Amlin and Littnan say they're both cautiously optimistic about Pohaku's condition, but treatment does not solve the problem.
"Really, where this problem needs to be treated is at the source, which is cats on the landscape," Amlin said. "And a very simple thing that folks can do is, if you have cats, keep them indoors. If they're not on the landscape, then they're not able to shed this parasite into the environment."
Amlin says NOAA is working with other agencies and groups to develop a plan to address toxoplasmosis. She acknowledged it's a complicated matter, but says a meaningful discussion needs to happen among officials to protect the monk seals.