Listeria (L.) monocytogenes is occasionally involved in food borne disease outbreaks in humans. Sometimes the L. monocytogenes get hung up in some meat processing equipment and can be a bit pesky when it comes to completely cleaning the equipment. The organism can survive in a wide range of environments as well as in the gut and manure of healthy pigs. On occasion L. monocytogenes can cause septicaemia and bloody
diarrhea in growing pigs. Austrian veterinarians described an outbreak of listeriosis in a 450 head finishing pig site where the mortality rate reached 7.8%. Clinical signs included off feed, bloody diarrhoea and increased body temperature. L. monocytogenes was isolated from internal tissue of the pigs and was present in high numbers in the digestive tract lymphatic drainage system. Interestingly, L. monocytogenes was also isolated in
the maize silage that was being fed on the farm. One animal was also positive for Brachyspira hyodysenteriae, and this disease agent may have also been involved in the development of bloody diarrhea. The L. monocytogenes isolates from pigs and maize silage showed an identical DNA-fingerprint assigned to sequence type (ST) 21. The plot further thickened with additional diagnostics that showed a very high content of vomitoxin or deoxynivalenol DON (3000 parts per billion) in the maize silage.
Take Home Message
- monocytogenes can cause clinical disease in finishing pigs.
- monocytogenes is rarely seen as a clinical issue in finishing pigs. In this case you would have to be very suspicious that the high levels of vomitoxin in the face of infectious challenge from the maize silage was enough of a “tipping point” to allow clinical expression of the disease.
In a year with increased vomitoxin contamination of feed in Ontario any number of otherwise usually rare health issues can start to bubble up to the surface.
Submitted by Clint Lichty, DVM
Ref: Stein H, Stessl B, Brunthaler R, Loncaric I, Weissenböck H, Ruczizka U, Ladinig A, Schwarz L. Listeriosis in fattening pigs caused by poor quality silage – a case report. BMC Vet Res. 2018 Nov 21;14(1):362. doi: 10.1186/