Scientists at Brookhaven National Laboratory and collaborators at two other institutions have found a major piece in the botulism puzzle, revealing how the toxin that causes the paralyzing illness survives unscathed in the human digestive tract, a finding that can lead to possible treatments and vaccines.

Botulism is a rare and usually fatal condition that isn’t caused by infection per se, but by a deadly neurotoxin that immobilizes the nerves that govern muscles.

The toxin is released by Clostridium botulinum bacteria, which are ubiquitous in soil but are most often associated with improperly canned foods. In recent weeks, several botulism scares have been linked to contaminated canned tuna and other products, spawning broad public health investigations and recalls.

Brookhaven biologist Subramanyam Swaminathan led a team of researchers at his institution as well as at Stony Brook University and the Institute of Advanced Sciences in Dartmouth, Massachusetts, to discover how the bacteria do their dirty work.

When people eat contaminated food, he said, they swallow the bacteria, which in turn, release the associated toxin. But Swaminathan has found that the toxin is linked to at least one and as many as two protective “cloaking proteins,” which, with the toxin, form a complex. This cloak, he said, aids the toxin’s survival in the harsh acidic environment of the human stomach, which secretes hydrochloric acid in a slurry of digestive juices that break down foods.

“It protects the toxin for as long as it is in the gut,” Swaminathan said Tuesday. Hydrochloric acid as has a low pH — which means it’s exceptionally acidic, Swaminathan said.

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He theorizes that drugs that interfere with the cloak proteins may help disable the deadly toxin, which is impervious to antibiotics.

There are seven types of botulinum toxins and all are released from Clostridium botulinum bacteria as a protein/toxin complex capable of outlasting the digestive tract’s acid bath, Swaminathan said.

Once it escapes the digestive tract, it is capable of paralyzing the nerves involved in muscle control. The Centers for Disease Control and Prevention considers the toxin a Tier 1 poison and a potential weapon of bioterror. In minute doses, however, it is used as the wrinkle-erasing cosmetic Botox.

Dr. Brian Harper, medical director of the academic health centers at NYIT College of Osteopathic Medicine in Old Westbury, said many people are familiar with the toxin for its role in food poisoning.

“The toxin is usually a problem when people try to preserve their own foods,” said Harper, a former public health executive in Nassau and Suffolk counties, “If foods are boiled or cooked you can denature the toxin.”

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Honey can harbor botulinum bacteria and is the reason people are cautioned from giving the substance to children under age 1.

While botulism poisoning is relatively rare on the whole, Harper said, it is an extraordinarily serious illness. He said the toxin prevents the body’s chemical messenger, a neurotransmitter called acetylcholine, from being released. The toxin can paralyze muscles that control the eyes, extremities and those involved in swallowing. When the toxin attacks nerves governing the diagphram, respiration can be fatally impaired, he said.

In October, Ecola Foods in Oregon recalled cans of tuna and salmon because of contamination with botulinum bacteria. That same month, Dungeness Seaworks in Washington recalled tuna products because of the contaminant. Last month, Old Oregon Smokehouse recalled cans of albacore tuna possibly linked to the bug.

Swaminathan’s discovery, meanwhile, comes on the heels of another botulinum toxin finding last year by Rongsheng Jin, an associate professor of physiology and biophysics at the University of California, Irvine.

Jin told Newsday on Tuesday that the toxin is elusive and tricky but he figured out last year how it escapes into the blood unscathed, capable of moving on to damage neuromuscular control.

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Despite the Brookhaven discovery, Jin contends he and his California team discovered the toxin cloak proteins first. Jin said he discovered them in type A botulinum toxin; Swaminathan discovered them in type E. Both are associated with severe foodborne illnesses.