Alimentary Bacteriology Practice Test 2026 – Comprehensive Exam Prep

The key concept here is how enterotoxigenic E. coli (ETEC) causes disease in neonatal animals. ETEC is noninvasive and produces enterotoxins that disrupt normal ion transport in the intestinal lining, leading to a secretory form of diarrhea. In neonates like calves, lambs, and piglets, these toxins (often alongside specific fimbrial adhesins that help the bacteria attach to the gut mucosa) trigger increased secretion of chloride and water into the intestinal lumen. The result is profuse, watery diarrhea without fever, and dehydration can occur quickly in young animals.

This matches the described clinical picture: secretory diarrhea without fever in neonatal calves, lambs, and piglets. The other scenarios describe diseases more typical of invasive or chronic enteric pathogens, or involve different age groups or clinical signs that aren’t characteristic of ETEC.