East Hawaii News

Hawaiian monk seal dies after battling toxoplasmosis

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The Marine Mammal Center is mourning following the death of adult male Hawaiian monk seal RW22. The seal died Nov. 17 after a battle of more than five weeks with the parasitic disease toxoplasmosis. RW22 also suffered from the effects of ingested fishing gear and malnutrition.

“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,” said Dr. Sophie Whoriskey with Hawaiian Monk Seal Conservation at the center.

For the past four weeks, experts at The Marine Mammal Center administered a series of intensive medical treatments to RW22 to try to slow the rate of infection. During that time, RW22 regained some stamina and movement but minimal appetite caused the animal to continue losing weight and deteriorate in body condition.

“Toxoplasmosis is the No. 1 disease threat to recovery of these endangered animals,” said Angela Amlin, Hawaiian monk seal recovery coordinator at the National Oceanic and Atmospheric Administration’s Fisheries. “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. 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.”


Center experts plan to conduct a post-mortem examination. The team will send tissue and blood samples to NOAA Fisheries for further examination to confirm an exact cause of death. Those results could take weeks to months to process.

Only three other seals impacted by toxoplasmosis have been rescued prior to death. RW22 is the second patient the center has admitted to its Kona hospital with the disease.

Toxoplasmosis is one of the main threats facing the endangered Hawaiian monk seal population, in part because of the infection being difficult to detect. Other threats to monk seals include negative human interaction and fisheries interaction via hooking and entanglements.


On Oct. 4, NOAA received a report of RW22 with a fishing line in his mouth off the Oʻahu coast. NOAA experts worked with Hawaiʻi Marine Animal Response and community members to locate the seal and were able to successfully rescue RW22 on Oct. 6. The team initially transported the seal to NOAA’s Inouye Regional Center where an X-ray revealed the ingested fishing gear.

Because of RW22’s deteriorated condition, NOAA determined additional care was necessary. RW22 was airlifted and transferred the same day to Ke Kai Ola, The Marine Mammal Center’s Kailua-Kona hospital for Hawaiian monk seals.

After suffering partial facial nerve paralysis and a corneal ulcer to his left eye, a suspected symptom of toxoplasmosis, RW22 underwent a successful eye procedure on Nov. 11 to provide short-term comfort in hopes of increasing his appetite and general well-being.


Previously in rehabilitation, RW22 regurgitated the ingested fishing gear avoiding surgery. Examination of the gear suggests that he swallowed multiple lines with hooks that appear to be part of a lay net.

With no vaccine available for toxoplasmosis, preventative measures must be taken by the general public. This disease is spread into the environment exclusively via cat feces. To help protect endangered Hawaiian monk seals such as RW22 from toxoplasmosis, dispose of cat litter in the trash, keep your cats indoors and help your community members learn how they, too, can prevent this disease from harming more marine mammals.

For more information about The Marine Mammal Center, visit MarineMammalCenter.org. You can also follow the center on Facebook, Instagram and Twitter.

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