SPI: The Deadly Disease That's Killing Off North America's Frogs

Posted by TF Oren
tree frog

SPI. Three little letters. One big problem.

Those three little letters stand for "severe Perkinsea infections," and they are responsible for a staggering number of mortalities among North America's frogs.

Scientists with the U.S. Geological Survey (USGS) studied 247 large-scale frog die-offs in 43 states over a 16-year period (1999-2015).

Their research revealed that SPI was responsible for 21 of those die-offs in 10 states, ranging from Alaska all the way to Florida. According to the study, SPI is the third most common infectious disease among frogs, right behind chytridiomycosis and ranavirus.

According to USGS scientist and lead author of the study, Marcos Isidoro Ayza, frogs are important indicators of environmental health.

"Like the proverbial canary in a coal mine, amphibians let us know when something in our environment is going awry," said Ayza.


Eleven species of frog, including the critically endangered dusky gopherfrog, experienced SPI mass mortality events. The bulk of the SPI die-offs happened in states along the Atlantic coast and the Gulf of Mexico. However, Alaska, Oregon, and Minnesota were also plagued by SPI.

A one-celled parasitic organism called Perkinsea is what causes SPI. The organism is stubbornly resistant to disinfectants such as bleach and is nearly impossible to prevent from reoccurring at known locations and spreading to new ones.

SPI attacks tadpoles, causing failure of multiple organ systems. There is no existing treatment or cure for the disease, which is not known to affect humans or pets.


According to Ayza:

"SPI in frogs may be under-diagnosed because it is not a disease for which they are typically screened...Incorporating routine screening of critical habitats for infected frogs is crucial to help understand the distribution of this destructive disease."

The study was published in Scientific Reports and can be found here.

What do you think of this disturbing new research? Let us know in the comments section.

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SPI: The Deadly Disease That's Killing Off North America's Frogs