Three Hawaiian monk seals found dead on Oahu last month were caused by a disease called toxoplasmosis. It’s a disease that’s spread through cat feces. 

People are also at risk, especially pregnant women.

Officials tell us there are about 300-thousand cats in Hawaii, many of them feral. 

Pregnant women and people with weak immune systems are at risk. We learned there have been cases of these groups of people getting the disease. People typically get it through ingestion. 

Toxoplasmosis is a disease caused by parasites. Those parasites reproduce in a cat’s digestive system. We’re told a single cat can excrete 145 billion eggs per year in its feces.

“The risk is not insignificant particularly for pregnant mothers and people with immune systems that aren’t functioning properly,” said Health Department Director Bruce Anderson.

Anderson tells us the infection of the parasites can cause miscarriages or birth defects.

We learned there have been 20 cases of toxoplasmosis last year. The year before that, there were 18 but no deaths. 

We asked which beaches or areas has toxoplasmosis been detected. The Department of Health tells us it’s not practical to test for the parasite in the environment since it potentially could be anywhere where there are feral cats.

“It’s not considered a major health threat because we don’t have many cases of human illness expect in these high risk groups,” said Anderson. 

We did reach out to organizations that clean coastlines to find out where many of the feral cats live.

“We see cats in areas close to the shore primarily Kakaaako Waterfront Park, also Sand Island Boat Ramp area. So those two areas have a lot of rocks that cats like to live in and hide under,” said Fawn Liebengood of 808 Cleanups. 

However, Anderson says going to the beach where there are a lot of feral cats is not considered a high risk activity. Many don’t usually swallow enough water to get toxoplasmosis like monk seals do. People are more likely to get the disease if they come in direct contact with cats or their feces. For safe measure, those who are pregnant or have weak immune systems should stay away from cats and their litter boxes. 

Nonetheless, state officials are stressing the importance of not feeding feral cats near water to reduce the risk of the infection for people and monk seals.  

“If you don’t have cats, you don’t have the disease. So if you can control the cats better, you can control what’s happening,” said Anderson. 

NOAA says at least 11 monk seals in Hawaii have died because of toxoplasmosis since 2001. However, it’s an under-reported problem and there could be more.