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Virginia Cooperative Extension - Knowledge for the CommonWealth

Presence of Listeria in Bulk Tank Milk

Dairy Pipeline: December 2000

Gerald M. Jones
Extension Dairy Scientist
Milk Quality & Milking Management

Listeriosis, a disease of cattle and humans, is caused by the bacterium, Listeria monocytogenes. It can cause abortion and severe neonatal infection in pregnant women and meningitis and septicemia in immunosuppressed people. Cattle may show "circling disease". The bacteria can be found in raw milk and unpasteurized or improperly pasteurized milk. Milk filters were collected from 348 New York dairy farms out of the 2,624 farms who consulted the NY Quality Milk program because of mastitis-related problems. The average somatic cell count was 500,000 for these 348 herds. There were 51 herds (12.6%) that tested positive for Listeria monocytogenes and 1.5% were positive for Salmonella. Some of the things that dairy producers can do to minimize listeria infections include: keeping cows' bedding and environment clean and dry, milking clean and dry teats by predipping and drying with single-service cloth or paper towels, sanitize milking equipment before each milking, treating every cow at drying off with an approved dry cow mastitis antibiotic, maintaining milking equipment on recommended service schedule, feeding high quality forage that has been properly cured and fermented, storing silage to minimize molding, keeping birds out of the milking parlor, and establish and effective insect control program

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