Hawaiian monk seal dies after battle with parasitic disease

HONOLULU — A male Hawaiian monk seal has died at a Big Island marine mammal hospital after a five-week battle with toxoplasmosis, which is a parasitic disease spread by cat feces, officials said Monday.

Toxoplasmosis is the biggest disease threat facing the Hawaiian monk seal, a critically endangered species numbering just 1,300 animals.

The seal that died last week Wednesday was known as RW22, the Marine Mammal Center said in a news release. The center called on cat owners to keep their feline pets indoors and dispose of cat litter in the trash to protect the species.

Feral cat feces are also a concern. Stray cats have no predators in Hawaii and their numbers have ballooned. Marketing research commissioned by the Hawaiian Humane Society in 2015 estimated Oahu alone had 300,000 feral cats.

The National Oceanic and Atmospheric Administration received a report early last month that RW22 had a fishing line in his mouth off Oahu. An X-ray revealed the seal had swallowed some fishing gear. He also showed signs of partial facial nerve paralysis and a corneal ulcer to his left eye, a suspected symptom of toxoplasmosis.

The Coast Guard flew RW22 to the seal hospital in Kailua-Kona, where veterinarians treated the seal in hopes of slowing the rate of infection. He regained some stamina and movement but continued to deteriorate.

The center plans to send tissue and blood samples from RW22 to NOAA Fisheries to confirm the cause of death.

Felines are the only animals that can shed Toxoplasma gondii eggs, or oocysts. Parasites enter the digestive tract of cats through infected prey, then multiply in their small intestines and produce eggs. Cats excrete the eggs in their feces.

Researchers believe these parasite eggs wash into the ocean and accumulate in invertebrates along the sea floor. They believe monk seals become exposed by swallowing contaminated water or prey.