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Germs that infect humans


Toxoplasma gondii

Toxoplasma gondii

© Dennis Kunkel Microscopy, Inc.

Microorganism: the protozoan Toxoplasma gondii

Disease: toxoplasmosis. Toxoplasmosis is also known by other names: litter box disease and sandbox disease.

Occurrence of the disease

History: this disease attracted public attention when it became known that some severe congenital malformations, and even fetal death, were associated with it.

Current situation: today, toxoplasmosis is often involved in the death of persons suffering from AIDS.

Mechanism of action of the microorganism: the microbe enters the host through the oral or fecal route. It eventually attacks several organs, such as the lungs, heart, liver, and the retina of the eye. The immune system normally overcomes this infection.

However, the organism may form resistant cysts in some organs. When an infected individual's immune system weakens, the organism may start to multiply again and cause illness.

Symptoms of the disease: except in cases of congenital malformations or fetal death, most affected people do not have symptoms (they are asymptomatic). Symptoms that may eventually appear are swelling of lymph nodes or symptoms associated with mononucleosis.

Incubation period: ten to 20 days following consumption of undercooked meat; five to 20 days in the case of contamination by an infected cat.

Contagious period: this disease does not spread from person to person, except from a mother to her child. However, the organisms excreted by an affected cat are infectious for one to five days following excretion. Moreover, the microorganism can survive in water for more than one year.

Hosts: cats, dogs, cattle, sheep, and humans.

Transmission: transmission is generally through the fecal or oral route. However, the disease can also be spread through ingestion of raw meat, by blood transfusion, by organ transplantation, or from mother to child.

Treatment: there are medications for treating toxoplasmosis, such as pyrimethamine and sulfadiazine.

Geographical distribution of the microorganism: worldwide

Prevention: avoid consumption of raw meat; wash hands after gardening; clean cat litter boxes regularly and wash hands afterwards; keep pet cats indoors, and feed them commercial cat food.

Vaccine: no vaccine available