Symptoms of Listeriosis
It is believed that the ingestion of fewer than 1,000 Listeria bacteria can cause human illness. The incubation period (time between ingestion the onset of symptoms) for Listeria monocytogenes infection, known as listeriosis, ranges from three to seventy days, and averages 21 days (Bryan, 1999).
A person with listeriosis usually experiences fever, muscle aches, and gastrointestinal symptoms such as nausea or diarrhea. Five days to three weeks after ingestion of the bacterium, Listeria can access all body areas, including the central nervous system, heart, and eyes (FDA/CFSAN, 2003). If the infection spreads to the nervous system, symptoms such as headache, stiff neck, loss of balance, confusion, obtundation, or convulsions can occur. With brain involvement, listeriosis may mimic a stroke.
For unknown reasons, in immune-deficient hosts Listeria invades and grows best in the central nervous system, causing meningitis and/or encephalitis (brain infection). In pregnant women, the fetus is most heavily infected, leading to spontaneous abortion, stillbirths, or sepsis in infancy.
Pregnant women are the most at-risk population for contracting Listeria infection, and are about 20 times more likely than other healthy adults to become ill with listeriosis. About one-third of Listeria cases occur during pregnancy. Infected pregnant women ordinarily experience only a mild, flu-like illness; however, infection during pregnancy can lead to miscarriage, infection of the newborn or even stillbirth (Cossart & Bierne, 2001). In most cases, the fetus or newborn is more likely than the mother to experience severe listeriosis associated with pregnancy (Silver, 1998); the perinatal and neonatal mortality rate is 80 percent (FDA/CFSAN 2003).
Symptoms of Listeria infection in newborns (Mayo Clinic, 2007):
- Loss of appetite
- Lethargy
- Yellowing of the skin and whites of the eyes (jaundice)
- Vomiting
- Skin rash
- Breathing difficulty
Others more at-risk for contracting listeriosis than the general population include: people with weakened or compromised immune systems, cancer patients, transplant recipients, diabetics, and persons with AIDS. (CDC, 2005a)
Human cases of Listeria are, for the most part, sporadic and treatable. Nonetheless, Listeria remains an important threat to public health, especially among those most susceptible to this disease. With an increasing immunocompromised population, the risk multiplies. The fact that Listeria is a disease easily transmitted from mother to fetus through the placenta is worrisome to an expectant mother, especially since pregnant women themselves rarely show outward signs of such a devastating infection.
Many physicians overlook the possibility of Listeria food poisoning because they do not know how easily it can survive and grow in refrigerated foods. For example, recent large outbreaks of Listeria poisoning have been caused by contaminated hot dogs and lunchmeat - foods that had not previously been considered dangerous. More research needs to be done, so that all of the mechanisms and intricacies of this bacterial strain can be understood. Above all, common myths about “proper” food storage need to be updated, so that contamination can be kept at a minimum.