Cat feces also contaminate livestock. A study of pig farms on O`ahu found that nearly half of more than 500 pigs tested positive for toxoplasmosis. Most rivers that flow to the ocean traverse through an agricultural site, according to a 2006 EcoHealth article by Littnan and researchers from NOAA and the Hubbs-SeaWorld Research Institute.
Although the state doesn’t test for toxoplasmosis, the Natural Resources Defense Council’s Testing the Waters 2010 report provides some insight into the role runoff plays in pathogen transmission in Hawai`i. Storm water was responsible for 99 percent of beach closures/advisories in 2009. Sewage spills accounted for the remaining one percent. Kaua`i beaches exceeded daily maximum bacterial standards most often.
According to the EcoHealth article, nearly 30 million gallons of sewage were spilled between 2000 and 2004. That number was exceeded in a matter of days in 2005, when a broken main caused the city of Honolulu to divert 48 million gallons of raw sewage into Waikiki’s Ala Wai canal.
In addition to toxoplasmosis, other pathogens have infected monk seals.
A few years ago, Littnan, NOAA contract veterinarian Robert Braun, and Brent Stewart and Pamela Yochem of the Hubbs-SeaWorld Research Institute tested seals for pathogens while trying to assess the disease threat.Their results, published in EcoHealth, suggest that seals encounter a variety of pathogens, including Sarcocystis neurona and Neospora caninum, as well as T. gondii. S. neurona causes equine protozoal myeloencephalitis, which creates lesions on the spinal cord and brain stem. Neosporosis can cause abortions in cattle and neuromuscular degeneration in dogs.
Leptospirosis is among the biggest concerns. Suspected in the death of two pups born near a stream mouth on the island of Hawai`I, it is mainly transmitted through contact with surface water contaminated with infected rodent or mongoose urine.
Although there is limited data on leptospirosis prevalence in Hawai`i, it’s considered ubiquitous. The reported incidence rate among people in Hawai`i (1.29 cases per 100,000 persons) is about 30 times the national rate, with the highest rates on Kaua`i and Hawai`i islands.
In another effort to gauge threats, Hawai`i Pacific University graduate student Jessica Lopez is evaluating 77 industrial chemicals and pesticides found in about 60 monk seals over the past decade.
“We don't know anything about what levels can cause an effect in monk seals, whether lethal or sub-lethal, so it will be difficult to speak to whether the levels measured are ‘safe’ or not,” she says.
Lopez also plans to evaluate seal movements and locations of sewage outflows and agricultural and industrial complexes to determine high risk areas that may factor into decisions on managing the seals.
For Littnan, filling data gaps is his top priority, such as tracking the mother of January’s stillborn pup to see if she has signs of infection.
“It would be very interesting to learn more about seals that [test positive for toxoplasmosis] but are not showing any clinical signs,” he said.
If the mother tests positive, drugs might be available for treatment. NOAA is partnering with California’s Marine Mammal Center to build a monk seal hospital in Kona.
To raise public awareness about toxoplasmosis and cat feces, NOAA has begun talking with the Hawai`i Humane Society, various interest groups and the health department.
But given his experience with Hawaiian birds, Work of the U.S. Geological Survey says generating the political will to control cats is “very difficult.”
“The `alala is a classic case in point,” Work says. Ten years ago, toxoplasmosis was identified as a threat at a national wildlife refuge in Kona that was created for the birds. Yet today, the cats remain at the refuge, while the `alala have been extirpated from the area.