What is Listeriosis?
Each year, particularly during late fall and winter, we see cases of acute listeriosis in sheep, goats, camelids, and cattle. Listeriosis is caused by a bacteria known as listeria monocytogenes. Listeriosis in animals typically presents in one of two forms: abortions or acute encephalitis. It also has the potential to cause sepsis. Listeria can infect cattle as well, and typically causes a number of abortions in the herd. Humans can also be infected by listeria, typically through food contamination, but are always cautioned to restrict the number of people who handle affected animals, always wear gloves, and good use hand hygiene.
What are the clinical signs?
Clinical signs typically occur very quickly and can progress to death in 24-48 hours. Animals may lose the ability to blink in one eye, resulting in a cloudy eye, and have a droopy ear on one side. Affected animals may walk in a circle in one direction, lose the ability to chew, swallow, and control their tongue. Animals may drool excessively, go down and not be able to stand, lay on their side thrashing/paddling, and have a fever over 104 degrees Fahrenheit. Up to 20% of the herd may be affected.
What causes it?
Listeria monocytogenes is the bacterial cause of the disease. The bacteria grows in soil and infects sheep and goats when it is eaten, inhaled, or when it contacts a mucous membrane, such as the conjunctiva around their eyes. Listeria can be found in rotten hay bales, poorly fermented silage, in feed bunks with buildup from old feed, compost piles, wild bird droppings contaminating feed sources and housing, and rotting plant and leaf debris. The animal may shed the bacteria in the urine, manure, tears, and nasal discharge. The bacteria can survive in the environment for 5 or more years. It is readily killed with common disinfectants, but it can be difficult to thoroughly clean in dirt.
How is it treated?
Immediate treatment is critical for a favorable outcome. Animals that are not able to stand require intense nursing care to keep their eyes lubricated, prevent bloat, and to prevent sores from developing on their skin. They may also require tube feeding or fluid therapy until they regain ability to eat and swallow. High doses of antibiotics are used to cross the blood-brain barrier, as well as anti-inflammatory drugs to relieve brain swelling. There is no vaccine for listeria.
Infected animals should be quarantined away from healthy animals so that their stall, buckets, mineral feeders, and all other items within the stall can be cleaned and disinfected after treatment.
Human Health Risk
Listeria is secreted into the milk of infected animals. We strongly discourage the consumption of raw milk. Boiling or proper pasteurization kills listeria. Humans can experience mild irritation of the hands and arms from assisting with delivery of kids/lambs/calves. Listeria can also cause abortion, encephalitis, gastrointestinal upset, and sepsis in humans. Pregnant women and immunosuppressed individuals are at higher risk contracting the disease. Seek medical attention should you feel you have been exposed or are suffering from symptoms consistent with listeriosis. For more information, click here.