A parasite affecting a portion of the feral cat population is responsible for the death of a monk seal in Hawaii.

Scientists determined the seal died last week due toxoplasma gondii, which reproduces in the digestive tract and is excreted through feces, Hawaii News Now reported.

The parasite lives in the tissue of rodents and small birds.

Hawaii Veterinary Medical Association executive vice president Dr. Eric Ako says about 30 percent of Oahu’s estimated 330,000 feral cats could have the disease.

There are about 100 monk seals that reside in the main Hawaiian Islands. Ako said the parasite also poses a risk to a monk seal’s "unborn fetus if she contracts the disease during pregnancy, which would then lead to serious birth defects in the fetus."

Michelle Barbieri of the National Oceanic and Atmospheric Administration’s Hawaiian Monk Seal Research Program says in a short period of time, cats could put millions of parasite eggs into the environment.

"It’s washed mauka to makai in the environment," she said.

Barbieri, her colleagues and animal welfare officials are looking at ways of controlling the number of feral cats.

"Right now, we think the best mitigation strategy for these animals is to stop this at the source," she said.