Figure 6.

Schematic representation of transmission, pathophysiology (right side) and clinical signs (left side) of listeriosis in humans (a) and ruminants (b). Listeria, via contaminated food products, reaches intestine. In immunocompetent humans, Listeria produces febrile gastroenteritis; in immunocompromised individuals it traverses intestinal barrier, produces septicemia, can cross blood–brain barrier and cause meningoencephalitis. Newborn infection occurs as consequence of maternal chorioamnitis (“early-onset” sepsis) or by contamination from birth canal colonized with Listeria from digestive tract (“late-onset” meningitis). Listeria localized infections occur in multiple organs. In ruminants, Listeria vehiculated through contaminated silage crosses oral epithelium (facilitated by small breaches of the oral mucosa), ascends to brain stem via trigeminal nerve, leading to unilateral cranial nerve paralysis and circling disease syndrome. In ruminants, Listeria also causes septicemia, abortion and, less frequently reported, mastitis and eye infections