Listeriosis is a whole group of infectious diseases that have the same causative agent – bacterium known as Listeria monocytogenes. The diseases have an extremely variable course from banal to life-threatening with a special risk for pregnant women.
Listeria is rod-shaped bacterium living in the digestive tract of many animals and thereby causing a variety of animal diseases. However, listeria can quite easily contaminate food, particularly those of animal origin such as milk, cheese, meat products, etc. Listeria is present in animal feces and so it can contaminate plants and vegetables. Human infection occurs when the bacterium is ingested. As animals are the typical sources of infection, we refer listeria infections to as anthropozoonoses (i.e. animal-human transmitted infections).
Listeria penetrates the wall of the digestive tube, get into the bloodstream and spreads throughout the body. The symptoms depend on the affected system. Infection of the digestive tract manifests with fever, nausea, vomiting and diarrhea. Affection of other organs may cause inflammation of heart muscle, liver abscesses or meningitis. Meningitis is especially dangerous. It progresses slowly and manifests with fever, fatigue, headache, muscle cramps, epileptic seizures and in the worse cases with unconsciousness and death.
Particularly dangerous is the infection in pregnant women. Listeria affects the placenta and subsequently even the fetal tissue usually resulting in a miscarriage. In this way, listeria probably influenced the English history as the Queen Anna's repeated miscarriages were expected to be caused by Listeria infections. After her death in 1714, the absence of an heir resulted in reign of the Hanoverian dynasty.
It is important to prevent the transmission of bacteria from contaminated food. Meat and diary products should undergo proper thermal processing to minimize the threat of infection and raw vegetables should be at least washed before eating them. A major milestone in the fight against the infection has been the pasteurization of milk.
The listeriosis is very rare in developed countries and therefore, it is difficult to think about it. The diagnosis can be confirmed serologically (antibodies against bacteria) from a blood sample or by a positive microbiological examination.