A sick Hawaiian monk seal that officials were trying to save has died at The Marine Mammal Center’s hospital in Kailua-Kona after a five-week battle against a parasitic disease and other ailments.

The center announced today that the monk seal RW22, nicknamed Kolohe, died at its hospital, Ke Kai Ola, last Wednesday.

Kolohe, age 13, suffered not only from toxoplasmosis — a disease caused by infection with Toxoplasma gondii, a parasite spread into the environment through cat feces — but had ingested several fish hooks.

“Toxoplasmosis is a complex and deadly disease that requires intensive daily treatment and management for an affected Hawaiian monk seal like RW22,” says Dr. Sophie Whoriskey, the center’s monk seal conservation veterinarian in a news release. “All of us are deeply saddened about this unfortunate outcome but we find hope in knowing the valuable insights gained about how this deadly disease affects monk seals will have a positive impact on future patients.”

Despite those treatments, the center said Kolohe continued to lose weight and did not have much of an appetitie.

NOAA first received a report of a seal with a fishing line come out of its mouth on Oct. 4. A team rescued RW22 two days later, where an X-ray revealed he had swallowed fishing gear.

NOAA said he regurgitated the fishing gear while in the hospital, a very unusual occurrence that allowed him to avoid needing surgery. Upon examining this gear, officials said it appeared that he had swallowed not just one fishing line, but likely multiple hooks and part of a lay net.

The center said a post-mortem examination is planned in collaboration with the National Oceanic and Atmospheric Administration Fisheries to confirm the exact cause of death.

Angela Amlin, Hawaiian Monk Seal Recovery Coordinator at NOAA Fisheries, said toxoplasmosis is the No. 1 disease threat to recovery of the endangered seals. Interactions with fishing gear pose another top threat to monk seals.

“The more partners and local communities can work to address this issue, the better for monk seals and other native species in Hawaii affected by this disease,” said Amlin in a news release. “We applaud our partners at the Center for their incredible efforts and are very grateful for their partnership and dedication to RW22 and the species.”

With no vaccine available for toxoplasmosis, NOAA urges the general public to help by taking preventative measures such as disposing of cat litter in the trash and keeping cats indoors.