how does the parasite transform in humans?

THE ESSENTIAL

• Cats are the main carriers of the parasite which can be transmitted to humans
• Transformation of the parasite in humans can lead to complications
• The disease is asymptomatic in 80% of cases

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Cats are the main targets of the parasite Toxoplasma gondii, but when a human consumes food contaminated by feline droppings, he can in turn ingest the infectious agent. In humans, toxoplasmosis can take different cellular forms: tachyzoite, which causes acute infections and bradyzoite, responsible for chronic infections. In the review Cell, American researchers show how the parasite changes shape in the cellular organism thanks to a protein called BFD1.

Multiple transformations of the parasite

The scientific community has already found that stressful conditions, such as thermal shock or basic pH, can lead to a change in Toxoplasma gondii : it goes from a tachyzoite to bradyzoite form. To understand the molecular phenomena associated with these transformations, the researchers analyzed the expression profiles of the genes of the tachyzoite pathogen, then of the tachyzoite transformed into bradyzoite. With the “DNA scissors”, CRISPR-Cas9, the research team inactivated several genes in order to determine which one or which were linked to the transformation of the parasite. They found that only one gene is responsible for it: BFD1.

Sometimes serious complications

These discoveries will certainly make it possible to better manage the complications linked to the parasite. This is transformed several times during its life cycle, when ingested by a human, the parasite releases tachyzoites, capable of infiltrating tissues such as the retina or the brain. Then, they transform into bradyzoites and remain in these parts of the body for a long time without any medication being able to act on them. They can remain inactive for long periods and then be reactivated in the event of an immune deficiency. Some patients may have a serious brain infection called encephalitis. These cases are rare, according to the Health Insurance website, toxoplasmosis is generally mild and asymptomatic. 80% of people affected do not experience any symptoms.

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