Which enterotoxin causes profuse watery diarrhea and is transmitted through fecal-oral routes often from water contamination?

The enterotoxin associated with profuse watery diarrhea and transmitted through fecal-oral routes, often from contaminated water, is produced by Vibrio cholerae. This bacterium is the causative agent of cholera, a disease characterized by severe diarrhea and dehydration. The cholera toxin, which acts as the enterotoxin, works by stimulating the intestinal cells to secrete large amounts of electrolytes and water, leading to the characteristic watery stools.

The transmission of Vibrio cholerae typically occurs in areas with poor sanitation where water supplies can be contaminated with fecal matter. This makes outbreaks common in regions facing inadequate water treatment and hygiene practices. The clinical presentation may include the rapid onset of severe diarrhea, sometimes described as "rice-water" stools, and can quickly lead to dehydration and electrolyte imbalances if not treated promptly.

The other options involve different pathogens or toxins that do not produce the same specific symptoms or routes of transmission as Vibrio cholerae's toxin. Therefore, the distinct mechanism and serious effects of the cholera toxin highlight why Vibrio cholerae is the correct answer to this question.