Listeria

Most of us take precautions to avoid contracting infections from sick people. But you may be surprised to hear that humans can acquire many infections from animals as well. These are typically called zoonotic diseases. Infectious organisms from animals can reach humans through direct contact, food, water or insect bites. Now we will be discussing one such organism which can prove deleterious to humans especially if they have a weak immune system. Listeria and its species are commonly found bacteria in many animals, especially cattle that can carry the bacteria without appearing sick.

Humans get infected by consuming food contaminated with Listeria. Unpasteurized milk and milk products such as cheese, meat and vegetables are the most likely sources. Pregnant women infected by Listeria can pass the bacteria to their baby.

The most common manifestation of listeriosis in humans is meningitis, which is an infection and inflammation of the covering over the brain. The manifestations of listeriosis are really devastating in neonates. Neonatologists commonly see newborn babies with sudden onset of fever, loose motions and altered sensorium raising the suspicion of meningitis and encephalitis.

Adults with Listeria meningitis present with rigid neck, severe headache and unconsciousness. Convulsions are also reported in both babies and adults.  The most common manifestation of Listeria infection in people with a normal immune system is an upset stomach with fever which is self-limited in most cases.

The treatment of listeriosis is simple and effective if detected early. Penicillin group of antibiotics are the antibiotics of choice to treat listeriosis. Treatment requires a two week long course which may be extended by one more week if the symptoms do not regress. In Listeria meningitis CSF analysis and microscopy are required.  The good news about Listeria is that there is no report of person to person transmission yet and hence there is no need of prophylaxis for other family members.

There are ways to prevent Listeria transmission; they are simple and easy to follow. Cook all raw food thoroughly. Do not consume raw milk and milk products. Use pasteurized milk. Wash kitchen knives thoroughly after use. Pregnant women, elderly and immunocompromised people should take extra precautions for ensuring safety from Listeria because the disease has most serious consequences in these groups.