A case report of sporadic ovine listerial menigoencephalitis in Iowa with an overview of livestock and human cases

Pre-Harvest Food Safety and Enteric Diseases Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, Ames, IA 50010, USA.

A case of ovine listeriosis was examined in a flock of sheep. The index case was a male lamb, which was part of a flock of 85 sheep located in central Iowa. Because the sheep were raised on a premise where soybean sprouts were also cultivated for the organic foods market, the potential of a public health concern was addressed. To identify the source of contaminations, clinical and environmental samples were cultured for Listeria monocytogenes. Isolates were serotyped and analyzed using pulsed-field gel electrophoresis (PFGE). Listeria monocytogenes (serotype 1) was recovered from the brain of a male lamb with clinical signs of listerial encephalitis. Isolates of serotypes 1 and 4 were also cultured from feces of clinically healthy lambs, compost piles, and soybean cleanings. By PFGE, the clinical isolate was distinctly different from the other isolates. Environmental isolates were identified as L. monocytogenes serotypes 1 and 4. However, by PFGE, none matched the profile of the single clinical isolate. Thus, the ultimate source of contamination is unknown.