WASHINGTON (AP) – Botulism poisoning from commercially canned foods has been virtually eliminated in the United States, making the new cases linked to hot dog chili sauce all the more striking.

On Thursday, the Food and Drug Administration, Agriculture Department and Centers for Disease Control and Prevention were investigating a Castleberry’s Food Co. plant in Augusta, Ga., where the suspect product was canned. Four people have been hospitalized; they are expected to survive.

Botulism is a muscle-paralyzing disease caused by a toxin made by a bacterium, Clostridium botulinum. Such bacteria are commonly found in soil.

Typically, commercially canned foods are heated long enough and to high enough temperatures to kill the spores that otherwise can grow and produce the toxin. If canned foods are underprocessed, the bacteria can thrive in the oxygen-poor environment inside the sealed containers.

Food packaged in defective cans, including those with leaky seams, also can become contaminated because the bacteria can be sucked into the containers as the product cools.

, according to health officials. Contamination with the bacteria can sometimes cause lids to bulge.

Each year, the CDC records roughly 25 cases of foodborne botulism poisoning. Most involve home-canned foods. Some fermented whale and other traditional foods prepared by Alaska natives also have been implicated in outbreaks.

CDC medical epidemiologist Dr. Michael Lynch said the last U.S. case of botulism linked to commercially sold canned food dates to the 1970s.

One food safety expert said the new outbreak was disturbing.

“It raises concerns that the existing food safety programs that have been functioning are losing ground because of gaps in FDA oversight,” said Caroline Smith DeWaal, director of food safety for consumer group Center for Science in the Public Interest.

Symptoms of botulism include double or blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth and muscle weakness that moves down the body. Eventually, paralysis can cause a person to stop breathing and die, unless supported by a ventilator. Botulism is fatal in about 8 percent of cases; most victims eventually recover after weeks to months of care.

Botulinum toxin is extremely potent. Even opening a contaminated can may expose consumers to the toxin if it is inhaled, swallowed or absorbed through the eye or breaks in the skin, health officials said.

Yet small doses of an FDA-approved product made from the toxin are routinely used to paralyze or weaken the muscles that can cause facial wrinkles. The product is best known by its trade name: Botox.

The FDA warned consumers to throw away 10-ounce cans of Castleberry’s, Austex and Kroger brands of hot dog chili sauce with “best by” dates from April 30, 2009, through May 22, 2009. Castleberry’s, owned by Bumble Bee Seafoods LLC, has recalled the products flagged by the FDA, as well as seven others.

On the Net:

Castleberry’s Food Co. recall information: http://www.castleberrys.com/

CDC botulism information: http://www.bt.cdc.gov/agent/botulism/index.asp

AP-ES-07-19-07 1549EDT