Brote de abortos por listeria ivanovii en un rebaño ovino durante dos años consecutivos

Résumé

Listeria monocytogenes and Listeria ivanovii are the most pathogenic Listeria species forruminants. L. monocytogenes is associated with neurological symptoms whereas L. ivanoviicauses abortion. Here we present the laboratory results and epidemiological investigation ofan outbreak of L. ivanovii abortion in a dairy sheep flock. Abortions lasted two consecutivebreeding seasons; the first season, ewes older than 2 years were affected (9.4%), whereasthe second season, abortions occurred in all age-groups (6.8%), including yearlings. Inboth breeding seasons L. ivanovii was isolated from placentae, liver and abomasal contentof most foetuses and placentae. During the second year, forage samples and water fromdrinkers were also analysed for the presence of Listeria, but all were negative. Bulk-tankmilk samples collected at the beginning of milking from ewes and yearlings were negative,ruling out the presence of milk shedders in the flock. Conversely, L. ivanovii was isolatedfrom faeces collected from yearlings demonstrating shedding of the bacteria through faeces.Forage of bad quality, contaminated with L. ivanovii, was identified as the most probablecause of the abortion outbreak. L. ivanovii infection has to be considered in the differentialdiagnosis of ovine abortions.