THE MISSISSIPPI Department of Agriculture and Commerce has obtained an emergency exemption from EPA for the use of niclosamide — a pesticide used to control the parasite-hosting ram's horn snail. The one-year exemption was given after concerns that the parasite (a species of yellow grub trematode) could cause major problems for Delta catfish producers.

“This parasite has the potential to cause million of dollars in economic loss if we don't control it. The devastation experienced by the industry could lead to a total economic hardship on our state economy of at least $350 million a year,” said Lester Spell, Mississippi agriculture commissioner.

It's estimated that more than half of Mississippi's 113,500 acres of catfish ponds are threatened by the parasite.

A profound challenge to control, the parasite uses three pond-loving hosts during its life cycle: pelicans, snails and fish. The parasite reproduces while living in a pelican's gut and its eggs exit with the bird's feces. As pelicans often congregate around catfish ponds, their “deposits” have easy access their next host, the ram's horn snail. Once inside the snail, the eggs mature into larvae and then leave the snail to look for a fish. After the fish are infected (fingerlings suffer liver and kidney damage due to the parasite) pelicans will eat them and the cycle continues.

By using niclosamide — a product manufactured by Bayer AG and commercially known as Bayluscide — to control snails and interrupt the parasite's life cycle, it's hoped the threat to aquaculture will be lessened.