Microbiology
Summary
Toxoplasma gondii (aka toxo) is an intracellular parasitic protozoan that can infect almost any warm-blooded animal. Toxo can be transmitted in several ways, the main three of which include: consumption of raw or undercooked meat containing toxo tissue cysts; ingestion of water or vegetables contaminated with oocytes shed in the feces of infected animals (particularly cats); and vertically from mother to fetus if the mother is exposed to toxoplasma during pregnancy. Populations most at risk include pregnant women and the immunocompromised, specifically those with HIV.
In immunocompetent patients, toxoplasmosis may cause flu-like symptoms a couple weeks after exposure, but is typically asymptomatic. However, in the immunocompromised and in cases of congenital toxoplasmosis, the disease can be devastating, causing serious conditions such as brain abscesses and toxoplasma encephalitis. Congenital toxoplasmosis is characterized by the classic triad of chorioretinitis, hydrocephalus, and intracranial calcifications. Deafness is another potential symptom of congenital toxoplasmosis. Diagnosis of toxo is typically done via serology or biopsy, and treatment is with sulfadiazine and pyrimethamine. Prophylaxis is recommended for HIV patients with CD4 counts less than 100 and positive for IgG against toxo.
Lesson Outline
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FAQs
T. gondii, also known as toxo, is commonly transmitted through three main routes. The first is through the ingestion of raw or inadequately cooked meat harboring tissue cysts. Secondly, it can be transmitted through accidental ingestion of oocysts, which can be shed in cat feces. The last way is through transplacental transmission from a pregnant woman to her fetus.
Pregnant women who contract a new infection with T. gondii pose a risk of transmitting the parasite to the fetus, a transmission route known as transplacental. This might lead to several complications including congenital toxoplasmosis, characterized by chorioretinitis, intracranial calcifications, and hydrocephalus in the newborn.
Immunocompromised individuals, such as patients with HIV, are vulnerable to severe manifestations of T. gondii infection. This intracellular parasitic protozoan can cause a severe form of the disease known as toxoplasma encephalitis in HIV patients when their CD4 count drops below 200. It can also lead to the formation of brain abscesses and CNS toxoplasmosis, which may involve neurologic symptoms such as seizures and disability.
T. gondii is an intracellular parasitic protozoan that can cross the blood-brain barrier. Once in the brain, the organisms form tissue cysts leading to brain abscesses or inflammations in the nervous system known as CNS toxoplasmosis. The severity of these conditions largely depends on the host's immune status. Immune competent individuals are usually asymptomatic or display mild symptoms while immunocompromised individuals may experience severe neurological symptoms.
The standard treatment for T. gondii infections typically involves a combination of medications, most commonly sulfadiazine and pyrimethamine, which act by inhibiting parasite replication. This combination is widely used for the treatment of acute toxoplasmosis in adults, congenital toxoplasmosis in newborns and for the treatment of toxoplasma encephalitis in HIV patients.
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